The Best Car Amplifier: Buyers Guide And 5 Great Picks

September 17, 2020November 15, 2019

Image of Alpine amplifier demo car display

Building a great sounding car audio system is fun and very rewarding. I absolutely love driving good quality speakers with a great amplifier for powerful and amazingly clear sound.

I’m sure you will, too! Finding the best car amplifier can be a very time-consuming task – there are so many choices out there.

In order to help you, I’ve put together a list of 5 of the best car amplifiers worth your money. You’ll also find some helpful buying info and car amp facts below too.

Contents

Car amplifier basics

Audio amplifier technology has moved forward over the last decade and the average buyer is a winner because of it. No longer will you have to choose between the same of average types, but fortunately a newer design type has made getting far more for your money in a smaller package possible.

Class A and class AB amplifiers

Car amplifiers, just like home stereo amplifiers, are all designed with a similar fundamental “class” which just means how they fundamentally operate to generate boosted audio signals that drive speakers.

All powerful amps have to take the 12V supply in a vehicle and step it up to higher voltages in order to deliver more power with greater clarity than a standard car stereo can (as those are limited to around 14W per channel).

Class A amplifiers are rarer and are considered “audiophile” amps as they have extremely low distortion and a lot more effort (and expense) is put into the design to get the best sound possible. However, they’re not as common because they’re very inefficient (somewhere around 20%!) and waste a huge amount of energy.

They also don’t deliver as much power for the money as other types. Those are a few reasons they’re not used very often and aren’t very popular.

Class A/B

Class A/B amplifiers like this one were, until relatively recently, the only way to get big power with great sound quality in your vehicle with a good Watts per dollar ratio. Class D amplifiers are now eclipsing them in value and power per size.

Class A/B amplifiers are a compromise between class B amplifiers (in which the transistors that drive the output signal) aren’t switched on quite as long as in class A amps. However, to retain good sound quality they work in some similar ways as class A – just without wasting quite as much technology.

They’re close to about 50-65% efficient and do generate some heat even while doing nothing.

For decades they’ve been the most popular type of car audio amplifier in use. This basic design is used in the most low-cost amplifiers and even very high-end car amps. However, the better brands have much better design components and circuitry to keeps the sound quality very high and noise and distortion very low.

A/B amps come in a variety of low to high-power options and are often bridgeable to deliver more power.

Class D amps

Internal view of a Pioneer class D 5 channel car amplifier. Even though it might look the same as a class A/B amp at first glance, there are some notable differences. Class D amplifiers use different technology to deliver amazing power while greatly reducing power waste which is lost as heat.

Class D amplifiers are the newest technology and offer a new approach to audio amplification, with very high efficiency and fantastic new installation options.

As they’re around somewhere around 85% efficient they produce an extremely small amount of heat and the size of even a very high power amp can be 1/2 to 2/3 that of a conventional class A/B amp!

These amps work by switching power transistors in the circuitry on and off incredibly fast rather than them remaining on long like older technologies. The end result is electrical current flows and power use is reduced.

Class D amps convert the input signal into a squarewave which drives the power electronics. Once this signal is amplified, it is then smoothed and filtered, converting it back to a boosted version of the input signal. The output then drives your speakers at the speaker terminals.

They make installations easier!

Many powerful class D amps can fit under seats, in storage containers, and in other vehicle interior locations that were impossible for other amps in the past.

If you’re wanting the best bang for your buck, you’re hard-pressed to beat them! However, it’s critical to shop for the best quality as lesser brands often have poor noise levels and mediocre sound quality.

Class D amplifiers are the newest and most efficient car amp technology today. A great sounding and powerful amplifier that can drive a whole car audio system is small enough to fit inconvenient places like under your car seat. Very cool!

Although they’re very small and highly efficient, the main drawback is that they have a higher noise floor (lower signal-to-noise ratio) than A/B amplifiers.

The technology has been refined more and more until today and is now capable of producing excellent sound with very low distortion.

However, I’d advise staying away from lower-end brands because they’re still noisier and the sound quality isn’t up to par with well-engineered products by bigger brand names. Of course, it depends on your sound needs and what you’re willing to pay.

The good news is that D class amps are also a great value these days and are very affordable.

Car amplifier quality factors

The best car amplifier for you will have well-designed quality and great engineering. I bring this up because although you can get an excellent amplifier for your money (see below) some brands aren’t original designs, and they simply rebadge – that is, slightly change and rename – the same amplifier internal board and parts.

You’ll end up getting an “ok” amp in most cases but definitely not the best.

To avoid getting a lesser amp for your money, stick to midrange or higher-end brands like Alpine, Pioneer, MTX, Rockford Fosgate, and a few other major players in the market. Definitely see my recommendations here today as I’ll ensure you get a great one.

You don’t need to go broke when shopping but it definitely pays to choose carefully.

Understanding power ratings

You’ll see some amplifiers – in some cases even very cheap ones – sold with claims like “1200 Watts power.” This is completely misleading and is not what an amp in a small size is physically capable of producing.

Unfortunately, it’s one of the ways people new to car audio get ripped off and greatly disappointed. I always hate seeing that happen.

Don’t get mislead when shopping! Some cheaper brands use misleading numbers that are IMPOSSIBLE for them to deliver. Always check the “root-mean-square “(RMS) or “continuous” ratings. Those are an electrical engineering term to describe the actual useable power being delivered.

The best brands are “CEA-2006 compliant” which means the specs listed are proven and you can be sure they’re reliable and realistic.

When shopping for an amplifier, rely on the Consumer Electronics Association (CEA) power standard ratings to know you’re getting accurate specs and not being lied to. Reputable manufacturers list their specs using this ratings standard created in recent years because of the ongoing issue with exaggerated amplifier power numbers.

Realistic expectations and power you need

For a good quality amp that the average person can afford you can expect power ratings like 50W, 75W, or 100W RMS per channel into 4 ohms, for example.

The best car amplifier for most people will cost about a little under $200 for average power ratings or closer to $300 if you wanted a more powerful (like 100W/channel). Expect to spend more for even higher sound quality and extra features.

For most people wanting to upgrade a factory system or drive new speakers, at least 50W RMS per channel is good and can provide great volume, low distortion, and enjoyable sound.

This includes being able to drive your speakers with good bass, although you’ll probably want to block distortion-causing low-end bass by using a built-in high pass crossover option. With that, you can get more volume with less distortion – and more enjoyment!

For larger cone size subwoofers, plan to have at least 150W or so as a good rule of thumb for enough power to drive them well. Subwoofers are power-hungry so for good bass sound you need to plan ahead – don’t try to use a weak amp for heavy bass. If you want bass volume that vibrates your neighbor’s windows and rattles your car, get an amp 2 x to 3 x as much power (250W-500W).

If you plan on using subwoofers, expect to have about 150W minimum available, either from a single channel or from a pair of channels bridged together. For larger subwoofers like 10″ and 12″ which can really thump, I’d recommend 300W as a good rule of thumb.

You may be surprised how great and loud a well-tuned system with a 50W per channel amplifier can sound! I personally prefer 75W/channel or higher 4 or 5 amps as they’re flexible and have extra power on tap.

2 channel vs 4 channel amplifiers

If you only need 2 channels of power you’ll find plenty to choose from. However, try to think about future expansion!

Try to plan ahead just in case you want to expand or upgrade your sound system later. A 4 channel amplifier may be a better choice as it can always be used as a 2-channel amp but the reverse is not true.

The most common car amplifier installations

The majority of people who buy a car amplifier have one of a common number of needs in mind:

Connecting to a factory or aftermarket stereo to upgrade a system with front and rear speakers
Connecting to a factory or aftermarket stereo in order to add a subwoofer
Powering both front speakers AND a subwoofer for a complete sound system upgrade

Here’s a diagram showing these basic and popular systems.

(Click to enlarge image)

I personally prefer 4 channel amplifiers unless I need higher power for a 2-channel speaker setup, or for customers who don’t need rear speakers or the extra system flexibility. 2 channel amplifiers do tend to have higher power rating options available, but that’s not always the case.

Additionally, since most 4 channel amps sold today can be bridged for more power it’s usually not hard to find 4 channel or 5 channel amps with the power you need vs using a 2 channel model.

Factory system integration

If you’re using a factory stereo you can still get great sound but you’ll want to look for an amplifier with speaker-level inputs.

You can tap off of existing speakers in the trunk or from the rear of the stereo as needed to get a signal source. Small gauge speaker wire works fine for this. You’ll save the cost of a line level converter when installing an amp with speaker-level inputs.

In fact, some models now have an auto-on feature that senses when the speaker inputs have a signal and turns the amp on automatically. This avoids having to connect a remote-on wire to the amp.

More difficult systems like factory premium (factory amplified) systems often require more labor and hunting down additional wiring info. Generally speaking, however, it still can be done as long as you’re able to find a pair of full range speakers or speaker wiring you can tap off of to run to the amplifier’s inputs.

Choosing the best car amplifier

In my professional opinion the best car amplifier should be a good compromise of the following:

Cost
Power
Sound quality/specifications
Installation ease (based on your needs)
Features
Quality and the level of engineering design
Reliability
Proven buyer satisfaction

★ 5 of the best car amplifiers for your money ★

Product	Details
★ Best value! ★Alpine MRV-F300	Great sound for less money! An excellent value 50W x 4, 75W x 4, 150W x 2 RMS Evolution to class D design	Check on Amazon
JL Audio XD400/4v2	High-end sound and performance in a small package. Fantastic! 75W x 4, 100W x 4, 200W x 2 RMS Low-noise, crystal-clear sound quality NexD high-fidelity class D design. Only 8-9/16 x 2-1/16 x 7-1/8" In size!	Check on Amazon
Rockford Prime R1200-1D Mono	Up to an amazing 1200W RMS of slammin' bass power! Smart protection circuitry, Punch bass EQ, subsonic filter, and RCA outs Includes Punch bass remote	Check on Amazon
Rockford Fosgate P400X4	Class A/B sound quality that's affordable + modern compact design Built-in amp setup gain features. Thermal heat management system Bass EQ feature, remote bass option, compact size	Check on Amazon
AffordablePlanet Audio AC1200.4	Great budget 4 ch amp under $100 113W x 4, 225W x 2 RMS High level inputs, illuminated logo. Includes bass remote	Check on Amazon

1. Alpine MRV-F300 – Affordable, great sound, wonderful quality, and ease of installation in a compact size.

The MRV-F300 is Alpine’s most recent take on a class D amp that has been welcomed to rave reviews and it a fantastic way to drive your whole system from an amp small enough to fit below a seat! Unlike competitors, the company takes additional steps to reduce noise inherent in class D designs and provides 50W x 4 into 4 ohms and bridgeable power of 150W x 2 into 4 ohms.

Of course, it has crossovers (adjustable) for both subwoofer or full-range speaker use as well as a nice bass boost on channels 3/4.

The whole amp measures only 7 7/8″ W x 6.5″ D x 2 3/16″ H (200 x 165 x 55 mm) and provides speaker-level inputs for working with factory systems. I’ve also provided a full review here.

It features the usual over-temp and short-circuit protection Alpine has always provided and is an excellent buy at under $175. It’s also a great sounding little amp.

You can head over to Amazon to see the many great reviews and why so many owners love it.

2. JL Audio RB XD400/4 – 75W x 4 underrated power channels of some of the best audio you can buy…and it fits under a seat!

Still an industry leader, JL Audio has approached compact audio amplifier design by improving class D technology. They’ve introduced NexD circuitry which uses a much faster switching speed than the lesser competition to improve power delivery as well as noise levels.

The amp is rated at – and will actually outperform – the listed specs of 75W x 4 into 4 ohms.

It’s a fantastic and vibrant sounding amplifier that’s still very small at only 8.52 in. x 7.09 in. x 2.05 in. (217 mm x 180 mm x 52 mm) but can accept 4 gauge wire. Low and high pass crossovers are adjustable to 500hz for additional sound system control and a 2/4 channel input switch can use a 2-channel signal to run all 4.

An additional feature is a pair of RCA outputs with selectable output signal (mono summed or stereo) so you can daisy-chain more amps if you like easily. Wire terminals are very high quality (audiophile grade) and it’s one of the best rated amplifiers among buyers, too!

Another cool feature is the ability to plug in a remote bass knob (sold separately) to control the bass while drive when using subwoofers.

If you’re looking for one of the best amplifiers available today, this is it. It’s available at major online retailers but I've seen it for much less over at Amazon.

3. Rockford Fosgate Punch R1200-1D – A small subwoofer amp an AMAZING power output of up to 1200W!

The Punch R1200-1D is a beast in a tiny package. Measuring only 11-1/8″W x 2″H x 7-3/8″D, this little powerhouse can provide the following incredible power ratings: (CEA-2006 compliant power ratings)

400W RMS x 1 @ 4 ohms
800W RMS x 1 @ 2 ohms
1,200W RMS x 1 @ 1 ohm

It even includes a remote bass control in the package to allow you to adjust the bass level while cruising down the road.

As Rockford Fosgate is one of the best amp companies designing products in America today, it also includes a unique verification sheet with each and every amp that leaves the factory. This shows it meets rated specs and you know you’re getting what you paid for.

It’s a mono (subwoofer) amplifier so for subwoofer-only system expansion it’s a fantastic choice if you want real power that SLAMS, high SPL music, and the ability to safely run multiple subwoofers without overheating and shutdown.

A built-in low-pass crossover is adjustable from 50-250hz and a Punch EQ bass boost is another feature to help with getting the best sound from your system.

The amp can’t support speaker-level inputs but does feature RCA pass-through jacks for connecting additional amplifiers.

The Punch R1200-1D includes an awesome bass remote with connection cable that’s really to install. I really like and I’m sure you will, too! It makes cranking the bass up very convenient when driving.

This little amp is an amazing amount of clean, reliable sound in a compact package and normally sells below $300. Reviews are excellent and it’s a great choice if you want high-end power you can afford!

Definitely head over to Amazon to check out the current price.

4. Rockford Fosgate Punch P600X4 (and P400X4) – low-noise class AB sound quality, great power, and set up features no one else offers.

If your budget allows you to spend a little under $300 or so (based on the best price I’ve found when comparing), the P600X4 is one of the best on the market today. Rockford Fosgate has once again designed another fantastic sound-quality oriented class A/B design featuring their patented Trans-ANA circuitry to deliver lower noise and some of the best sound quality available in this price range.

They’ve used surface mount technology (SMT) to make the amplifier as compact as possible, measuring only 13-3/8″W x 2-7/16″H x 8-13/16″D in size.

The amp is CEA-2006 compliant and is underrated, delivering some excellent power:

75W x 4 into 4 ohms
150W x 4 into 2 ohms
300W x 2 bridged, 4 ohm stable

Plenty enough to power a fantastic sounding, high-volume system for nearly everyone!

The high and low pass crossovers are adjustable to 250Hz, while the Punch EQ2 is unique from other brands in that it’s adjustable for both bass and treble with 0-18 dB level possible at 45Hz and 12.5KHz. You can also add a Punch EQ remote control knob (sold separately) to adjust the sound while driving.

It doesn’t support speaker level inputs, but a 2/4 way input switch is provided for the RCA inputs.

One of the most unique features is the installation help provided by the instructions and the built-in C.L.E.A.N. gain setup system feature. When used with the included test tone CD, actually allows the amp to show the correct signal levels when setting the gain!

This will allow you to get the lowest noise and optimize for your amp for the best performance. You can also download test MP3 files as well to help you set it up.

Its sibling the P400X4 has the same features with 50W x 4 power and is less expensive.

It’s an awesome amp and definitely I recommend it to anyone who can afford it. It’s worth your time to head over and read more - the reviews are great!

5. Planet Audio Anarchy AC1200.4 – 4 channels of good sounding budget power

Let’s face it, some of us simply don’t have a lot of money to spend on a car amp. That’s ok – it’s understandable. Believe me, I’ve been there too!

If you still want good sound with adequate power and a way to get started with an entry-level system, the AC1200.4 is a great choice. For around $100 (or less) you can get an amp a good track record of happy buyers, built-in crossovers, and enough power to run your system and enjoy music on the cheap!

It can also connect to factory speaker-level wiring.

The Planet Audio is also sold as Boss and other brands with minor cosmetic differences, and overall all versions of it have pretty good reviews as well.

It’s not CEA-2006 compliant, so the power ratings haven’t been verified like more expensive brands:

4 ohms: 113 watts x 4 chan
2 ohms: 225 watts x 4 chan
Bridged, 4 ohms: 450 watts x 2 channels

I definitely recommend you step up to the Alpine MRV-F300 but if you can’t afford to do so, it’s a good way to get started enjoying great music.

Check out the great buyer reviews and current low price over here now.

Summary

Following my guide, try to buy the best amplifier you can according to the level of power you need and based on your goal: maximum sound quality, loud bass, or just an affordable but great sounding system.

To summarize, I recommend:

Buy an amp with 50W or more per channel; for a higher-end system I recommend 75W+ per channel.
Consider getting a 4 channel amplifier because of the additional flexibility they offer.
A mono or bridgeable amp can drive a subwoofer. Choose a minimum of 150W. If you’re heavy/loud bass fan look into 300W-500W RMS or more.
Brand name class D amps have the best sound quality while still fitting into small installation spaces.
Class D amps are now very good in terms of sound quality. However, if your goal is the lowest noise level possible you should still consider an A/B amp if the size isn’t an issue.

Don’t forget the wire! Check out this great amp wiring kit buyer’s guide with some fantastic choices you can afford.

Be sure to let me know in the comments below or via my contact page if I can help.

How To Hook Up A 4 Channel Amp To Front And Rear Speakers

September 16, 2020May 2, 2019

How to hook up 4 channel amp to front and rear speakers

Adding a 4 channel amp is a great idea. I’ve enjoyed powerful, crystal-clear sound in my vehicles for years using my own 4 channel amps.

But how do you hook them up?

In this guide I’ll show you how to hook up a 4 channel amp to front and rear speakers. After installing hundreds of amps in vehicles just like yours I’ll share with you the fundamental tips you need for great results.

And hey – don’t worry…in most cases you can do it yourself and get professional results on a budget!

Contents

Infographic – How to hook up a 4 channel amp (tips and general guide)

Basics first

If you’re reading this there’s a good chance you’re not familiar with installing an amp, connecting wiring, and other details related to hooking up a 4 channel amp in a vehicle.

Not everyone has installed car stereo equipment before so I’m going to be as thorough as possible and avoid making any assumptions about how much you know.

What is a 4 channel amp?

Today’s 4 channel amps offer newer technology, better sound, and more compact size than in the old days. An excellent example is the Alpine MRV-F300 50W x 4 model. It uses Class D technology to run extremely cool and yet it’s small enough to fit under a car or truck seat. Very nice!

What a 4 channel car amplifier is may seem obvious at first but there’s a bit more to know Additionally, there are some interesting (and good) ways they differ from 2-channel amps.

In fact, there are actually a few benefits you’ll get using one 4 channel amp instead of 2 stereo ones to power your front and rear speakers.

A 4 channel amplifier is a stereo amplifier with 2 more channels built in to boost (amplify) weak input signals to a higher voltage signal. This drives speaker voice coils to move the speaker cone and produce sound.

4 channel amplifiers add more channels into a more compact and efficient design than separate amplifiers would have.

Additionally, they offer more flexibility, as most can be configured for “bridged” operation which can give more power when you don’t need all 4 channels.

What is “bridging” an amp?

Bridged mode capability is a special design feature in which a “push-pull” set up is created: one channel (normally used for the left speaker) produces a signal that’s the opposite of the second channel (normally used for the right speaker).

This causes the speaker to receive a voltage audio waveform that is the difference between the two channels – resulting in more available power to speakers.

Essentially, bridged mode is a flexible way to get more power if you’re not driving 4 speakers. It means 2 channels are sharing the workload of one speaker between them and therefore and drive it with more power.

2 channel vs 4 channel amp diagram

A 4 channel car amp is basically an expanded version of a 2-channel amp. However, because they’re built together and not 2 separate 2-channel amps, they’re more compact. This saves installation space and makes it easier too. Additionally, most can be bridged to use 2 channels (or 3, depending on your needs) so you’re not restricted to using them with only 4 speakers.

The benefits of using an amp to drive speakers

Whether you have a factory stereo or a great aftermarket (non-factory) one, adding an amplifier is one of the best decisions you can make.

In-dash stereos are very limited in how much power they can produce. They can’t drive speakers with the same clarity and low distortion as a good amplifier can.

The maximum volume you’ll be able to get from your speakers will be pretty low, too.

There’s simply no way around it – most in-dash stereos are limited to about 15W-18W RMS of power for each speaker channel. That’s because they’re running directly from the +12V supply. Amplifiers are unique in that they take the +12V electrical supply and boost it to a higher voltage.

When a signal is boosted and sent out to your car’s speakers the voltage is much higher and the speaker can receive much more power.

That’s why tiny amplifiers are rarely worth bothering with – if there’s no special power supply inside, it’s simply not capable of producing much power.

Getting great sound

Powering speakers from an amp makes a big difference, and I’ve enjoyed excellent sound for years this way.

When an amplifier drives your vehicle’s speakers it’s often not even pushed to its limits. The sound produced at the speaker has lower distortion, doesn’t “bottom out” when heavy bass is played, and you can get a lot more volume, too!

Additionally, using an amplifier with built-in high-pass crossovers means you can block out lower-end bass that causes your speakers to distort and attempt to play music tones they’re not suited for.

The result is cleaner sound, less distortion, and great volume – you can crank your music even higher!

Just imagine driving down the road with the windows open and finally being able to blast the music you love. I’m confident you’ll love it as much as I do.

Things to know before you start

It only takes a few minutes to make a list of the parts, wire, tools, and other bits and pieces you’ll need. Planning ahead can mean the difference between getting your system going without major problems or having a frustrating time – or complete failure! I always get organized and get my items together before I start a job.

Planning ahead is very important. You don’t want to run out of wire or discover you don’t have the rights parts, for example. That will mean you can’t finish your project.

It’s even worse when you have to drive around town searching for items or you’re not able to do anything after the stores close. Believe me, I’ve been there, and it’s terrible!

Notes about wire, tools, and a few other things

When it comes to installations, always plan to have more, rather than not enough, wire. This goes for speaker wire as well as RCA cables.

The amplifier kits I recommend have the right length for your amp installation, but speaker wire & RCA cables are another matter in this case.

What length and size speaker wire do I need?

There’s no need to spend an excessive amount of money on speaker wire. 18 gauge is enough for many installations, but 16 gauge is a great choice too if the price is right. A great example is this AmazonBasics 100 foot roll. I recommend a 100 foot roll for many installations with a 4 channel amp (see why below).

Here’s an estimate of the worst-case scenario for the length of speaker wire required. I’ll use the example of installing an amp using speaker-level inputs, with the following typical installation:

Amp is located in the trunk
Speaker level signal connections near the radio (center console)

Let’s use roughly a 15′ length of distance from the radio to the amp. That’s a good estimate in my experience.

So we have:

Wire from the radio to amp (signal wire): 4 channels x 15′ = 60 feet
Wire from the amp to speaker wiring near radio: 4 channels x 15′ = 60 feet

Total estimated wire required: 120 feet.

That means you need 2 100 ft rolls of wire. Or at the least, 1 100 ft roll and 1 50 ft roll. If you’re planning to use a line-level adapter, expect to pick up a 100′ roll.

If your installation is using RCA jacks, expect a 100 ft roll also (4 channels x 15′ length estimate for the speaker wire from the amp).

What about RCA cables?

If you’re installing a 4 channel amplifier and using RCA cable connections, you’ll need to buy a 2nd pair along with your amp wiring kit, as most only include a 2-channel cable.

For most installations, I recommend 18′ length cables. That’s usually long enough for most vehicles and you should usually have enough length to hide the cables inside the interior and under the rear seat, etc.

There’s no reason to spend an excessive amount of money. Just pick up some good quality, well-made cables. Even a pair like these value-priced ones will be fine in most cases.

Tools you’ll need.

Crimp tools are great for installing your amp and speaker wiring with professional results. If you’re doing your own installation, you can get by with an inexpensive tool like this Pros'Kit crimp tool. Crimp connectors are sold separately in many automotive parts stores or general stores and are very affordable.

I recommend a few tools. If you shop carefully, you can avoid getting ripped off on tool prices. When connecting speaker wiring to factory wiring, it’s easier to use crimp connectors than solder.

Never simply twist the wire together and wrap it in electrical tape. Always use a reliable connection.

During warm weather, electrical tape adhesive can fail and the tape can come off of the wire. This exposes it to possible short circuits and potential damage to your radio or amp.

If you have access to a cordless drill, that’s fantastic! They’re great for drilling holes in the vehicle’s metal for mounting your amplifier or connecting the ground wire to bare metal.

I also recommend the following:

Wire cutters (some crimp tools have this built-in)
Roll of quality electrical tape
Wire ties (“zip ties”), 6″ length, bag of 100
A digital test meter for voltage measurement

A test meter is often incredibly helpful when installing an amplifier. However, you don’t need to spend much money! A basic but good budget model like this one at Amazon will work great.

I recommend getting an affordable but good digital test meter to find a switched +12V wire for getting a remote-on signal to the amp.

They’re also extremely helpful when troubleshooting power problems when something isn’t working.

Get your installation shopping list together

Here’s a general but pretty accurate list of what you’ll need for connecting a 4 channel amp to front and rear speakers.

Installation types 1 or 2: Factory radio or no RCA connections

4 channel amplifier with speaker level inputs or amp and line-level adapter
120 feet or more speaker wire, 18 gauge or larger
Amp wiring kit
Crimp tool and butt (wire crimp) connectors (25 or more at least)
Cutting pliers
Electrical tape
Wire ties, 6″, bag of 100
Test meter

Installation type 3: RCA connections

4 channel amplifier with speaker level inputs or amp and line-level adapter
100 feet roll speaker wire, 18 gauge or larger
Amp wiring kit
Additional RCA cables, 18′ minimum
Crimp tool and butt (wire crimp) connectors (25 or more at least)
Cutting pliers
Electrical tape
Wire ties, 6″, bag of 100
Test meter

Be sure to plan well and estimate the amount of speaker wire you’ll need. For the amp installation itself, I strongly recommend using a pre-made amp wiring kit like you’ll find here in my amp kit buyer’s guide.

You’ll also need to get a 2nd pair of RCA cables. I recommend 18 ft length or more. Don’t spend too much money, but do get decent quality ones.

How to get a signal to your amp

Image of an aftermarket (non-factory) stereo showing the RCA jacks and speaker output wiring. Either one can be used for getting a signal to an amp, but RCA jacks offer a better option. They’re normally lower distortion and allow using plug-in RCA cables. If those aren’t available, either an amp with speaker-level inputs or a line level (speaker level) adapter can be used.

In order to install a 4 channel amp and drive all 4 speakers, in many cases, the biggest obstacle is getting a signal to the amp. Once that’s done, the rest is usually a standard amp installation.

There are 3 basic ways to get a signal to your 4 channel amplifier:

Connect speaker outputs to your amp’s speaker level inputs
Connect a line-level adapter to the radio then use RCA cables to the amp
Connect your radio to the amp using RCA cables directly

NOTE: I won’t be covering factory sound systems that are “premium” and have a factory amplifier. Those such as Bose, JBL, and Mark Levinson, often found in luxury vehicles or special-edition models, are much more complex and harder to deal with.

In that case, my advice is to speak with a good installation shop first and do your research.

If you feel that factory amplified systems should be here as well, send me a message or comment and let me know

In a few cases, adapters are available to connect an amp to a factory amplified system’s audio wiring, but it’s often difficult or there are obstacles you won’t find until you get started.

One of the reasons why is that factory amplified systems often have non-standard wiring connections for the audio path and are prone to bad noise problems if you connect an amplifier without the proper adapter or wiring.

Which type of connection do I need?

If you have a radio with RCA jacks, skip on down to the next section.

However, if you have a stereo with no RCA jacks (which is always the case for factory-installed stereos) you’ll have to buy one of the following:

A “line level” converter
An amplifier with speaker-level (“high level”) inputs

1. Line level converters

Line-level converters like this PAC LP7-4 4-channel model are designed to take speaker-outputs from a stereo with no RCA jacks and adapt them to RCA jacks. Using this, you can run RCA cables to your amplifier.

Line level converters are designed to allow connecting to an amplifier’s RCA inputs by converting speaker outputs from a stereo to a low-level signal an amp can use.

It’s very important to buy a quality, well-designed line-level adapter to avoid noise, poor sound quality, and other problems. Don’t get the cheapest – instead, get a name brand model you can rely on (like the one above).

2. Speaker level inputs

Amplifiers with high-level (speaker-level) inputs like this one allow connecting to speaker wiring for a signal source. This avoids having to buy a separate adapter.

Speaker level inputs are common on many 4 channel amplifiers. These amps contain electronics that scale down speaker wiring signals to a lower signal safe for the amplifier’s input circuitry.

They’re simple to connect: normally it’s just a matter of connecting both positive (+) and negative (-) wiring for each speaker channel on a small wiring harness included. This then plugs into the speaker level input connector.

A typical speaker-level input harness for a 4 channel amp. The wires are color-coded to make installation easier. White = left front, gray = right front, green = left rear, and purple = right rear.

While it can save money (you won’t need a line-level adapter in this case) I often recommend that people consider buying a line-level converter anyway.

This allows an easier upgrade for your stereo later, which is very common for people to do. Using the line-level converter now will allow you to run RCA cables to your 4 channel amp to be used later if you buy a better stereo (which will include RCA jacks, almost always).

3. RCA jack (line-level) connections

RCA jacks offer a clean, lower-noise connection than speaker-level adapters do, but honestly, it’s not noticeable to the average person. RCA cables (line-level connections) are the preferred way to connect a signal to your amp if you have that option.

RCA jacks on the rear of a Pioneer head unit. This is the ideal way to connect your amplifier’s signal inputs, if available. For a 4 channel amplifier, you’ll need 2 stereo RCA cables to do so. White represents the left channel white red represents the right. These are standard colors for audio outputs for both car and home stereo.

If your stereo has RCA jacks, then congratulations. Things just got a bit easier – and potentially better sounding, too!

You’ll need 2 stereo RCA male-to-male cables (4 audio channels total) to run from the radio to your 4 channel amp. That’s 4 signal channels: left & right front and left & right rear.

4 channel amp signal connection diagram

Here’s a helpful diagram showing the most common connections you’ll need to make one of the 3 most common cases I mentioned earlier:

Connecting to your amp’s speaker level inputs
Using a line-level converter
Connecting your amp to the radio’s RCA jacks

You can also click here to view the .pdf document for print or download.

Connecting and running signal wiring

Speaker-level connections

As mentioned above and as shown in the diagrams, if you’re using speaker-level outputs to get a signal from the radio, you’ll need to connect wire. Ideally, you’ll do so near close to the radio, then run the wire together as a bundle.

You can bundle speaker wire together with wire ties to keep it neat and make the installation easier.

Estimate the length of speaker wire you need to reach the amp (or line level converter) for each audio channel. To do so, run a length of wire from the radio to where the amp will be installed, then allow a little extra and enough length to run around curves and interior parts.

Cut 7 more lengths of wire, for a total of 8:

4 channels (4 pairs of wire) going to the amp’s speaker level inputs
4 channels from the amp to the radio’s factory speaker wiring

I recommend connecting to speaker-level outputs using crimp connectors and a crimp tool for a reliable, solid connection. Blue connectors are normally the right size for 18-16 gauge wire.

Factory stereo color codes

If you have a factory stereo, you’ll need to find the wiring colors for the speaker wiring.

A great resource for that is The12Volt.com, where you’ll find wiring diagrams for your vehicle and color codes listed.

Making connections

After removing the radio you’ll find connectors like this for the factory stereo wiring harness. You’ll need to separate the speaker wires, cut them, and attach wiring to run to the amp.

Remove the radio and disconnect the factory wiring plugs or aftermarket radio’s wiring harness.

Cut the speaker wires, leaving enough length to move the wire and to have enough length to connect to the wire freely.

Strip a small part on both the stereo’s speaker wire and your amp speaker wiring. If using a line-level adapter, connect to the stereo’s speaker output side. Then connect the 4 pairs of wire to the speaker wiring in the harness.

Insert the stripped wire (about 1/4″ of bare wire) into the connectors and crimp them carefully using a crimp tool if you have one. Alternately, you can twist together wire, solder it, and carefully wrap it with electrical tape or use heat shrink tubing for insulation.

If using speaker level inputs on your amp, also connect 4 pairs of wire to the output of the stereo.

To make a neater, more professional installation, bundle the speaker wiring similar to this using wire (“zip”) ties. I recommend using 6″ ties which often are sold in packs of 100.

Once all wiring is connected, bundle it up using wire ties or, optionally, a little bit of electrical tape wrapped around. In both cases spacing out wire ties or tape about every 1″ or 1.5″ along the length of the wire works well.

Connecting RCA cables

Connecting RCA cables to an aftermarket (non-original) stereo for running to an amplifier.

If you’re using a line-level converter or have a stereo with RCA jacks, connect all 4 cables plugs to the front and rear outputs.

RCA cables are sometimes marked with left and right symbols (“L” and “R”). In some cases, white, clear, or some lighter color can be used to represent the left channel.

Connect the cables consistently so you’ll be able to recognize which one is which. If the front and rear RCA cables are the same, you might want to mark front and rear using some masking tape and a marker or pen.

Connect the remote-on amp wire

Don’t forget the remote wire! Amp wiring kits include a small wire that’s used to connect the amp so that it switches on and off with the accessory position of the ignition switch.

Locate a +12V wire that has power when the ignition is switched to “ACC” or similar but turns off with the key. You may also have good luck finding an existing wire color from vehicle wiring diagrams I mentioned earlier or from a Google search.

I recommend checking the wiring even if you have already located it online, just to be sure.

Before re-installing the radio connect this wire and run it alongside the speaker wiring.

How to connect a 2 ch. car stereo to a 4 channel amp

You can connect a head unit car stereo with only 2 channels (left and right) to a 4 channel amp easily. Ordinarily, all you need is 2 RCA Y adapter cables. The head unit’s left channel RCA jack should be connected to the left front and left rear amp inputs. Likewise for the right channel. If using speaker level inputs on the amp, use the connections shown above. NOTE: Use only ONE of the two connections above! Never connect both types at the same time! Speaker-level outputs will damage RCA connections.

If your head unit (car stereo) only has 2 RCA jacks or two pairs of speaker outputs, that’s not a problem.

As shown in the above diagram, you can connect 2 channels to a 4 channel amp using either the speaker level inputs wired in parallel or by using simple RCA adapter cables.

All you need is a decent pair (a total of 2) female to male RCA “Y” adapters like these low-cost ones from Amazon.

The sound quality will be exactly the same. Today’s amps are designed in such a way that there’s no harm in using a Y adapter to connect the amp. The amplifier will receive exactly the same signal, with the same quality, in the front channels as well as the rear.

The only drawback is there won’t be a front to rear fader control like with head units with 4 channels of outputs.

After connecting the stereo to the amp, you’ll need to adjust the rear gain to set the volume level for the rear speakers as needed for the proper volume depending on the stereo’s signal strength.

Installing the amp

An amp wiring kit like this one will make installing your 4 channel amp much easier. A good-quality one like this Belva 8-gauge complete kit includes not just wiring but much more. You’ll also need to pick up a 2nd pair of RCA cables (if using them) and enough speaker wire.

Your amplifier needs a good solid metal connection to ground and you’ll need to run the positive battery wire to the engine compartment. Your amp wiring kit will also include a fuse holder that should be installed near the battery as well (most kits include instructions, by the way).

You’ll also need to connect the amp’s speaker outputs to the wire you ran from the radio.

As it also applies to 4 channels amps, for the amplifier installation you can follow my guides here:

Here’s a basic diagram as well to help:

Setting up your amp

Once installed, you should set up your amp’s gain levels and crossovers for the best sound. In this image, you can see the adjustable crossovers for both front and rear channels. Turn on the high-pass crossovers and adjust to a setting close to 50-60Hz, to allow good bass for music but block low-end bass that distorts.

Once installed, you’ll need to set up your amp’s gain levels and crossovers, if available. Most sold today have that. (See my recommendations at the end for some great models)

Gain control is the amount of signal amplification the amplifier performs. Ideally, with a good input signal, it can be kept low to reduce any hiss or noise that can appear when it’s turned up high.

Here’s a great rule of thumb for how to adjust the gain for this type of system:

Turn down gain controls on the amp
Turn the stereo’s volume to 2/3 of maximum
Slowly raise the gain controls until the volume is enough

When finished you should have enough volume available from the stereo but noise should be minimal. You’ll still need to tweak it a bit if the volume is too high or too low.

Setting the crossover

As I mentioned at the beginning of this guide, using high-pass crossovers will allow more volume with less distortion and will help protect the speakers from heavy bass.

For both front and rear channels turn on the high-pass feature and, if an adjustable dial is available, set it near 50 to 60Hz. Some models don’t offer an adjustable frequency for the cutoff but are likely preset to a good level.

Test and tweak

Once installed, test and tweak your amplifier as needed. A great way to mount your 4 channel amp is by using a board mounted to the car, covered with speaker box carpet or other material.

Play some music you’re very familiar with and adjust things like bass, treble, and the fader as needed. Using music you’re very familiar with (of high quality) means you’ll be able to notice any problems with the sound fairly easily.

If you don’t already have one, you might consider later upgrading to a head unit with built-in equalizer (EQ) functions to help tailor the sound.

Summary and recommended products

Hopefully you’ve found this post useful. Hooking up a 4 channel amp to your front and rear speakers takes some work and time, but it’s a great way to get sound you’ll love.

Considering buying an amplifier? You can find some great 4 channel amps (including the Alpine MRV-F300 pictured here) in my 4 channel amp buyer’s guide.

You’ll also need a good amp wiring kit – I’ve got a good amp kit buyer’s guide here.

If you find anything missing or have suggestions, just leave a comment below or send me a message!

Marine Amp Vs Car Amp Differences – Can You Use A Marine Amp In Your Car Or Motorcyle?

September 17, 2020January 28, 2019

Marine amp vs car amp differences featured image

Are you wondering what makes a marine (boat) amp different from a car amp? Maybe you’re considering installing a marine amp in your car, truck, or motorcycle and want to learn more.

Relax – I’ve got you covered. I’ll explain in great detail marine amp vs car amp differences and why they just might be an excellent choice for you.

I’ve even opened up a marine amp to show you what’s inside. There’s some great news you’ll like also so read on!

Contents

Infographic – Marine vs car amp facts

Marine amps vs car amps: What are the differences?

Already familiar with car amps? You’re in for some good news! As I’ll show you later, marine amps offer some cool features and installation possibilities that you might not be aware of.

Marine Vs Car Amp Differences

Although they vary from model to model and brand to brand, in nearly all cases marine amps are extremely similar to car amps with a few differences:

Marine amps are cosmetically different: white colors and a marine/boat-oriented design
Special features that car amps don’t normally have: Direct Bluetooth connection, public announcement (PA) loudspeaker function, or others
Moisture & corrosion-resistant conformal (protective) coating on the circuit board and electronic components
Additional sealing of the amp to prevent moisture/water from entering (depends on the model & design)

Basically, marine amps are car amplifiers with some slight changes or more features. They’re otherwise nearly identical in most cases.

The most important difference is their resistance to moisture and corrosion which I’ll cover in more detail below.

Note: While marine amps may be sold as “waterproof” it’s more realistic to say they’re water-resistant.

That’s because although they’re resistant to water and moisture they shouldn’t be submerged underwater. Components like potentiometers (variable resistors, like for the gain & crossover controls) could still have water get inside which will ruin them.

Marine amplifier details and what to expect

Shown: Examples of marine amps – both popular sellers in marine audio categories. Left: A typical mini-amp, the Pyle PLMRA400 4 channel. Right: The high-power Rockville Phenom RXM-F3 with PA feature & microphone input. (Both have a conformal coating to prevent moisture damage and corrosion)

Pictured above are 2 popular marine amplifiers that are great examples. In both cases the printed circuit boards (PCBs) have a protective conformal coating applied. This is a hard, clear substance that resembles a thin layer of epoxy.

Marine amps are often sold as a slightly different version of their car amp counterparts.

The example Rockville RXM-F3 amp pictured above is available as the RXA-F1 with a different color & body and no conformal coating on the PCB.

Both are typical high-power, bridgeable amps with 4 x 65W RMS power output, suitable for marine loudspeakers or a subwoofer system.

Just like car amps, marine amps can be fully bridgeable and offer the same power output ratings or wiring options.

Marine amp conformal coating

An example of a marine amp’s circuit board with a protective conformal coating. The coating is a hard, clear, epoxy-like coating that acts as a protective seal over the printed circuit board (PCB) and components. It protects the electronic parts, contacts, solder points, and more against corrosive elements in marine use.

The issue is that unlike car, trucks, and other street vehicles, boats and marine vehicles are subject to much more difficult environments.

Things such as these are hard on electronics:

Heavy humidity
Salt spray
Changing outdoor temperature extremes

They cause problems like corrosion, oxidation, and potentially can damage electronic parts inside an amplifier. While it’s possible to use a car amp in a boat it’s really not a great idea because of this.

Marine amps are unique in that they offer this extra layer of protection in the form of a hard, clear, epoxy-like coating from the factory. This helps prevent corrosion and damage both to the amp’s parts but also electronic conductors and solder points.

Rockville marine amp guts illustrated

Internal view of the Rockville RXM-F3 4 channel marine amp. It’s basically the same in design as the car amp version.

Marine amps have the same (or almost the same) internal design as their car amp counterparts.

In fact, if you open up two versions of the same amplifier they’re extremely likely to look almost exactly the same inside.

How a marine amp works: diagram and details

As shown above, a typical high-power marine amp has the following major sections just like a car amp:

Power connection terminals & speaker output terminals
Fuse holders for protection
+12V step-up switching power supply
Input stages for noise protection, crossover functions, gain, bass boost, and more
Output amplification stages with high-power transistors

Input stages

Crossover controls on a typical marine amp. Input connectors (speaker-level or RCA jacks) direct the audio signal to the input stages. Crossover mode switches enable or disable full pass, low-pass, or high-pass functions. The gain (amplification) of the input signal is accessible here as well.

Input stages work to block the common problem of “ground loop noise” and allow you to filter out bass or higher frequency sounds (as you like) for the type of system you have.

Circuitry that provides extremely useful functions like speaker-level inputs, RCA jack inputs, crossovers, and bass boost are part of this section of components, too.

Power supply

A step-up switched mode power supply (SMPS), identical to that used in a car amp, creates higher voltages from the +12V supply of the battery. This boosts the +12V voltage to create a higher-power supply that is sent to speaker outputs where high power output can be used.

Without this, just like a marine radio or car stereo, you’re limited to the amount of power that’s available using only the +12V supply. That’s about 12W-18 watts or so which is pretty small.

That’s far too little for driving speakers with good volume when you’re enjoying a day on the lake!

Output stages & output transistors

Before loud music can be produced from your speakers the musical signal input has to be amplified. That’s the job of the amplification and output stages of an amp.

The signal inputs (from the RCA jacks or speaker-level inputs) are used to create a specially balanced pair of signals that multiplied thanks to the higher voltages from the power supply.

The high voltage connections attach to a set (usually one or more pairs) of high-current, high-power transistors which then drive the speaker output terminal.

Some special features marine amps offer

Marine amps often have some special features not offered with by car amps. Shown above are 2: A direct Bluetooth receiver function with control unit and a public announcement (PA) microphone feature.

What’s interesting about boat amps is some of the neat features they offer. Many are simply not available for car amps.

Direct Bluetooth for music streaming

Because a boat (or another outdoor vehicle) may not have a good stereo source available, some offer a direct Bluetooth connection for music streaming from your smartphone.

In this case, there’s no need for a marine radio source (head unit) as you can adjust the volume and control media direct using buttons on the controller.

PA feature

For loudspeaker public announcement (PA) functionality, some include a microphone that connects to the provided input jack. In this case, the amp will allow microphone audio to override the music and drive the speakers with high-volume speech.

It’s a feature sometimes used in boating near docks or anywhere on the water where it’s hard to yell to others long-distance.

Auxiliary inputs

Auxiliary inputs aren’t an option for car amps. However, you can do this with an inexpensive RCA to headphone adapter cable which will let you use any MP3 player or smartphone for the signal input.

That’s a great way to get a simple system without having to spend money on and install a stereo as well.

Phone charging USB port

A few models offer a USB +5V charging port which allows keeping your phone’s battery fully charged while in use. It’s a great feature when using a smartphone as your sound source.

Can I install a marine amp in my car or motorcycle?

A marine amp installed for in-vehicle use & testing. Don’t hesitate to use a boat (marine) amp yourself if you’ve got one!

Yes, you can install a marine amp in your car, truck, or motorcycle!

As a matter of fact, they actually offer some great installation options you might not have otherwise!

Here’s a list of some great options possible and problems they solve:

Marine mini-amps are great for reliable power and great sound in motorcycles
A marine amp is suitable for outdoor vehicles and is far more affordable than specialty amps from the vehicle manufacturer
You can build a sound system without a stereo! Marine amps with the Bluetooth receiver & controller option make this possible

Marine amps offer some excellent solutions for some unique installations like classic cars. Rather than spend a ton of money for custom fabrication or metalwork you can use an amp for direct, easy-to-install sound that works great.

They’re really aren’t any “cons” to worry about, aside from the cosmetic color and style. Additionally, when shopping that means it’s possible to have even more options and you can possibly find a great deal.

How are marine amps installed?

Marine amps have the same power and audio connections as car amps. However, as boats and yachts have unique wiring systems the audio signal source and remote-on wire sources may be different.

Additionally, some boats have 2 or more batteries so wiring may need to be done a bit differently.

Unlike cars and trucks, most boats have fiberglass bodies that don’t conduct electricity. There are a few differences to bear in mind:

The ground (-) amp wire must be run to the battery used for the audio power supply (same length as the power cable)
The remote-on lead wire has several possible sources: the radio remote wire, ignition switch, or sometimes an “accessory’ switch output provided at the control panel

One great feature is that if you’re using speaker-level inputs from a marine stereo some amps offer an auto-sensing feature to switch the amp on or off.

It’s a great way to avoid the need for a remote-on wire.

Although a standard car amp wiring kit is fine, I recommend a water-resistant fuse holder and extra length of ground wire as needed.

Summary

Let’s recap the most important points:

Marine amplifiers differ in a few basic ways from car amps: water/corrosion protective design, colors & style, and features offered
Marine amps are otherwise extremely similar to car amps and in fact often have a twin version sold for cars
They can be installed in cars, trucks, motorcycles, and much more. In fact they offer more installation options in many cases

Additional reading

Don’t forget the speakers! Tweeters help you get great sound you can enjoy in your boat or vehicle. Here’s a list of some of the best tweeters for the money.

The Only Alpine KTP-445U Review You’ll Need: A Tiny But Amazing 4 Channel Mini Amp

September 17, 2020December 26, 2018

Sometimes getting good sound can be really tough – most especially if you have limited space. And it’s a shame, too, because often that means you’ll have to do without.

My, how things have changed!

This little power pack of sound is a modern-day solution to a decades old problem – getting great sound in a tight space. In my Alpine KTP-445U review I’ll provide a detailed an honest review of this fantastic like amp.

Contents

Alpine KTP-445U basics

In case you haven’t noticed yet, I’m a big fan of this little guy – and very happy with what Alpine has come up with! I don’t normally expect much from miniaturized amplifiers, but in this case I can honestly say I’m impressed.

First off, we need to set the stage by understanding what this little amplifier is and isn’t. It is not an end-all solution for the best audio quality money can buy. Let’s be realistic – you cannot get “perfect sound” in an incredibly tiny package for less than $150.

When it comes to sound, there are always compromises that must be made. It’s important to have reasonable expectations. Any good engineer will tell you the same.

What to bear in mind…

Also, it’s important to remember that as I’ll be explaining below, this is a class D type of amplifier. Class D amps have several pros and cons to be aware of (which I cover in detail). It’s important to remember this when you compare it to other amplifiers you may be thinking about buying.

I’ll be reviewing it based on my extensive knowledge of the technology and the amp both as an engineer and an installer. Also, I’ll be very fair – and very detailed – when I make comparisons to bigger and more expensive amplifiers.

Behind the technology: understanding the KTP-445U amplifier design

In only the last several years class D audio amplifiers have become one of the hottest audio technologies in the audio world. This modern technology has improved greatly since the first class D amplifiers hit the market years ago. I’ve found that despite this many brands still leave a LOT to be desired. Unlike the KTP-445U I have been very disappointed by some I’ve tried.

What is a class D car amp?

Simply put, audio amplifiers are all based off on one or more basic “classes”, or categories that classify the type of design they use. Despite what you might see thanks to advertising, a car amplifier class always fits into one of 3.

These range from Class A (fantastic clarity and ultra-low noise specs, but expensive and a power hog) to Class A/B and now class D. For the most part, any other kind you might run across is just a variation of one of those. (For a “class T” amp is still a class D – that’s just marketing).

Class D amps were once only used for subs but now are mainstream

Until recent years, Class A/B amplifiers were the most common because they’re cost-effective, relatively simple in design, and don’t waste as much power as Class A designs do. Also A/B amps provide low distortion and high power levels for a good watt-per-dollar value.

Despite their good points, conventional (A/B) amplifiers waste a lot of electrical power which is turned into heat rather than power to drive speakers. Today’s amps are still somewhat bulky and heavy due to the large metal body needed to dissipate the heat created.

A class D car amp is a newer type of amplifier technology used to produce audio power more efficiently.

How do class D amps work?

A Class D amplifier works by “modulating” (chopping up) the incoming audio signal and switching the transistors used to amplify it on and off incredibly quickly. This results in a fantastically efficient design without huge amounts of power being turned into heat like designs from the old days!

Class D amplifiers are based on a switching circuit design approach. This means the design modulates – or transforms – the incoming audio signal by chopping it up into a series of on-and-off waveforms as the input signal is received.

This is used to switch power-conducting transistors on and off thousands or hundreds of thousands of times per second. Older audio amplifiers (like class A or class A/B) conduct electricity nearly all the time they’re on.

While A/B type amplifiers are about 50-65% efficient, Class D amplifiers can achieve an incredible 85-90% efficiency!

Because of this the amount of power being consumed by a Class D amp is greatly reduced – resulting in no need for a huge, heavy amplifier body or lots of heat being produced. This was a huge step forward in technology.

Fun fact: Some bare-bones miniature class D amps are smaller than a pack of cigarettes!

Additionally, electronic component sizes have evolved to make these amps smaller and smaller. The decades-old problem of “How can I fit an amplifier into a tiny space in my vehicle?” is now just a bad memory.

No longer do you just have to settle for a weak 15W per channel stereo head unit. You’re now able to get many times the sound in a package that’s far smaller than anything imagined possible only 10 years ago.

Alpine vs the competitors

Something you might not be aware of is that there’s a lot of junk out there. Many of today’s car amp brands are no longer selling unique designs of their own. Sadly, many amplifiers on the market today, including compact Class D designs, are rebadged models that share the same internal components and mediocre design and only have minor cosmetic differences on the outside.

Over the years, lower-end brands were bought out by larger companies and exist only for marketing purposes, not for quality.

I’ve even bought one of these competing amps for test purposes (perhaps one day I’ll do a write-up) and was very disappointed with the design & sound quality. Noise levels were unacceptable and upon examining it I realized quickly it was another low-end version of an “amp on a chip” design.

In the audio engineering world, this means shortcuts were taken at the expense of sound quality and performance.

Alpine has relied on its great engineering resources and the KTP-445U is different from the competition because it’s an original and fresh design. I was not disappointed to find it has the trademark Alpine quality and innovation that became my personal favorite over the years.

Also, Alpine doesn’t use misleading power ratings and specifications, unlike other brands. The power ratings and sound quality specifications I’ll go into below are realistic and honest.

This is important to me not just as an installer and an engineer, but because I need to be confident in anything I review and recommend. I know how it feels to spend your hard-earned money on products that disappoint.

KTP-445U features and specifications

Size

One of the biggest selling points is its size. The amp measures an amazingly compact 7 7/16″ x 1.5″ x 2.5″ (189 x 38.2 x 64.5 mm) in size. That’s smaller than pretty much any comparable amplifier available anywhere in the world today! I’m not kidding – I was expecting it to be much bigger. Basically all other high-quality Class D amplifiers below $200 today are at least 4 x the size of the Alpine.

Hard to believe how small it is. An amp with comparable power only a handful of years ago would have been 5 x times bigger. This one is small enough to hold in your hand!

Built-in high-pass crossovers

Originally I had expected the amp to be a “plain Jane” amp with NO features whatsoever, but it turned out I was wrong.

The amp actually, to my surprise, includes optional high-pass filters with selectable frequencies for the high-pass feature ( 60Hz, 80Hz, or 120Hz) to allow you to cut off speaker-distorting subwoofer bass if you like. Of course, you can always switch if off and run your speakers in “full range” mode if you like, but I normally prefer to block the lower bass frequencies.

My custom-installed 6.5″ speakers can’t handle the lower bass frequencies (they don’t do well below 50 Hz or so, so 60Hz is pretty close) so that’s very important to me.

High and low level inputs

Of course, I didn’t expect the Alpine to disappoint, but again they’ve done a great job in the design. The amp can work with both aftermarket head units via the or RCA inputs OR speaker-level inputs from a factory stereo! In other words, you can use the KTP-445U to get a more powerful and better sound even if you have a factory-installed stereo in your vehicle.

The included color-coded wiring harness makes it easy and it’s a feature I’m sure a lot of buyers just like you will appreciate.

Quick tip: When adding an aftermarket amplifier to a factory system and connecting to speaker-level outputs, be sure to plan for getting some small-gauge speaker wire. Plan ahead for enough length to go from the speaker wiring connections to the amp (and back again, if powering factory speakers).

One thing I’ve learned in my years of car stereo installation experience is that the ability to connect to factory-installed stereos is a huge plus. The Alpine can be connected directly to factory speaker wiring in order to “tap off” and get a good audio signal to feed into the amp.

While not as good as being fed from an aftermarket head unit via the RCA inputs, it’s still a great option and in my experience, when done correctly, still sounds clean and there’s very little distortion or breaking up at higher volumes.

You can also disconnect the factory speakers once the KTP-445U is connected to avoid any distortion issues if that’s a concern for you.
The included signal input harness allows connecting both RCA (low-level) inputs or speaker-level inputs to the amplifier easily. Inputs are color-coded and explained clearly in the owner’s manual. A similar harness is used to connect to the output (to connect to speakers you’d like to use)

There are switches for audio controls on the bottom of the amp if you need to choose speaker level inputs or change crossover functions. As an added bonus, even if you’re using 4 speakers and only have a 2-channel input, the amp can provide a signal to all 4 outputs. You won’t have to buy a pair of RCA Y-adapters.

In order to bridge the amp, you’ll also need to set the 2/4 ch. input switch to 2 channel as well.

Selectable option switches on the bottom of the amp allow you to adjust the crossover functions or split a stereo input into 4 channels. Also, this is where you must select the audio source before powering up the amp.

Front and rear gain controls

Separate front and rear gain controls allow adjusting the amplification level depending upon the input signal strength you have. Speaker-level inputs, for example, might require turning it down, while RCA-level inputs may require boosting it a bit. It’s highly dependent upon what kind of stereo you have. In either case, it’s easy to adjust. The KTP-444U can accept up to 4V RCA inputs which are considered a “higher end” signal strength for aftermarket units.

Not too much I have to say here – the front and rear controls are easy to use and easy to adjust. Also, the gain controls “feel” good because good quality components (potentiometers, which are just adjustable resistors) are used on the circuit board. This means that when you adjust the gain levels it won’t change over time and will have a good “feel” when you turn them.

Power

The amp can deliver up to 45 watts per channel into both 4 or 2-Ohm speakers, which is surprising because most miniature amps in my experience cannot handle 2 Ohm speakers. This means you could add extra speakers in parallel (to a degree) if desired.

It’s important to understand that 45 watts isn’t enough for extreme sound levels or to drive large woofers if that’s your goal. This amp isn’t designed for that.

I’d estimated with a good set of efficient speakers, however, you can get close to around 100dB of clear sound before it begins to give out due to its limits. For most people with normal listening habits, it’s plenty of power and you need not worry.

For reference, it may be helpful to know that most in-dash car stereos can provide only around 15W-18W RMS or so per channel of usable power.

Sound quality

For me, sound quality is extremely important.

It seems like every little bit of irritating distortion or poor musical reproduction I’ve heard really grates my nerves.

I’m happy to report the KPT-445U has great good sound quality and is very impressive for a tiny amp! If you recall what I mentioned earlier, this is a Class D amplifier. The benefits of Class D amplifiers are a fantastic size, great efficiency, and a lower weight, but one of the drawbacks is reduced sound quality.

I can say with certainty (and don’t just trust me on this – check the multitudes of other happy reviews) that the sound quality is very good. Remember when I mentioned earlier about how I bought another brand of car amplifier and was disappointed?

It was because the noise levels (the noise I heard when no music was playing) was far too high compared to the many amplifiers I’ve installed and listened to over the years. Not so with Alpine – they’ve done a great job in minimizing noise.

I can say I was pleasantly surprised. I came into my review of the KTP-445U expecting an “ok” experience but was honestly very impressed with what Alpine has done.

Here’s an excerpt from the company themselves:

In order to ensure that Alpine sound quality is heard at your ears, we’ve created a platform that offers an unbelievably low noise floor, taking extra care to ensure a clean signal path, with no extraneous interference. The end result: The Power Pack boasts 1 Watt Signal-to-Noise Ratio of 82dB or better.Alpine Electronics

In my opinion, this says a lot. Why? Because it takes additional engineering time and manpower – in addition to planning – to make the effort to make better sound quality a design goal rather than a forgotten number on a spec sheet somewhere.

I’d much rather pay a bit more for something I know is designed right from the beginning and I know sounds great rather than just made to be “ok” and barely passable.

Quick tip: If you have to increase the gain level greatly it also increases your chance of hearing the base noise level in any amplifier, including this one. For best results, the amp should have a good, strong signal so that the gain can be turned down, resulting in the cleanest output possible.

And by the way, for you spec nerds like me, the specs on this little amp are great. According to the company, the Power Pack distortion actually decreases at higher frequencies, resulting in a clean and clear signal where your ear is most sensitive to distortion (less than 0.03% THD+N @ 1W, 1% THD+N at rated power).

Here are some of the most basic specifications you need to know:

Note: the KTP-445U mini amp – despite its tiny size and simple design can drive 2 ohm speakers up to 45 watts each. I was honestly impressed and didn’t expect that.

Installation

Great for installation under seats and just about any small space you can think of.

The great thing about the size is that you can fit it in incredibly small spaces which were unheard of years ago. A great example is some of today’s vehicles in which there’s extremely tight space inside the dashboard, perhaps beside or behind the current stereo.

It’s a great solution to the most difficult installation problems which years ago would have required either a ton more money to be spent by customers or unfortunately cause some people to just “give up’ as there weren’t any other options.

It’s also a great fit for boats as well but you’d need to ensure it is protected against corrosion and exposure to the air and saltwater since it’s not marine rated. You can mount the tiny powerhouse by using the included zip cable ties to attach it to the nearest available wiring or mount it permanently using the included brackets and self-tapping screws.

Don’t forget that because of its light weight you could also use double-sided adhesive tape or Velcro if desired for convenience.

Note: Because it is so efficient and draws less electrical current than traditional amps, you won’t need to get a heavy-gauge wire installation kit and run extra wire. It’s possible to connect it to a nearby 12V supply from your car stereo, for example.

Accessories included with the KTP-445U

Mounting brackets (2)
Self-tapping screws (4)
Cable ties (2)
Required wiring harnesses

I would definitely suggest getting a few inexpensive items to make sure you’re better prepared for installation, such as:

A roll of speaker wire
14 or 16 gauge power and negative wire for installations placed further way
Wire crimp connectors (“butt connectors”) and a crimp tool
A small bag of 6″ or 8″ zip wire tie

Bridging the amp

Need more power? Amazingly – and to my surprise – it’s not a problem with this amp.

Just switch the 2/4 channel input switch to the 2 ch. input mode. Then connect the output speaker wiring in bridged mode and you’re done!

You’ll have 90W RMS per channel of high-quality sound at your disposal. Honestly, I didn’t expect that for an amp so small, but once again the engineering quality made all the difference.

Just one more reason I’m impressed with it.

KTP-445U vs KTP-445A

The KTP-445A looks very similar to the KTP-445U. However, it’s designed specifically for Alpine head units 2005 and later, not for RCA or high-level inputs from others.

When shopping it’s important to be aware of the KTP-445A model as it can cause a bit of confusion and comes up in search results.

The KTP-445A is a model of the KTP-445U (where “U” stands for universal; “A” stands for Alpine head units) designed only to work with Alpine model car stereos. The wiring harnesses included don’t allow using RCA connectors and the standard speaker-level inputs.

Aside from that, both share the same basic design and performance.

There are a few drawbacks to know…

I would have liked to have an optional low-pass crossover feature in addition to the high pass design. Perhaps it was a cost-cutting or design compromise decision that had them remove it. I’m not sure.

I have somewhat mixed feelings regarding the location of the switches used to control sound options. They’re located on the bottom, whereas ideally, they’d be accessible from the side or top. But ultimately that’s a minor complaint.

Review score & summary

All in all, in my opinion, the KTP-445U is a wonderful little 4-channel amplifier with great sound quality. It’s truly a dream come true if you want great sound but have especially limited space.

It’s not for those who need extreme power and volume levels. You can’t drive subwoofers or very high-volume speaker systems with this amp, but what it does it does well!

Head over to check out the current price and see the fantastic buyer reviews at Amazon.

Overall

8.8/10

Quality - 9.5/10
9.5/10
Sound quality - 8.7/10
8.7/10
Installation ease - 9.5/10
9.5/10
Features - 7.5/10
7.5/10

A well-designed and great sounding miniature car amplifier. One of the best compact amps I've seen.

Alpine has done it again with their approach to getting the most power and sound out of a tiny package. It’s a great upgrade for weak aftermarket or factory stereos. Thanks to its design it’s a great general-purpose 4-channel amp that can fit a wide variety of installation and audio system needs. You’re paying a few extra dollars for better sound and better design – and that’s exactly what you’ll get. You won’t be disappointed.

Pros

Amazingly small size!
Great sound, low distortion, and low noise design
Can handle 2 ohm speakers (4 channel mode)
4 channel outputs
Bridgeable to 90W RMS x 2 channels
Selectable 2/4 channel input switch (no Y adapters required)
Speaker level inputs
Installation accessories included
Great power: 45W/channel
Built-in optional high-pass crossovers
Simple installation / no large wire required

Cons

No low-pass crossovers
Option switches are located on the bottom as opposed to top or sides
Could use more zip ties in package

Check price at Amazon

Alpine MRV-F300 Full Review And Details: A Great Sounding 4 Channel Amp You Can Afford

September 17, 2020September 23, 2018

Alpine MRV-F300 amp on top of its package

I’ve been a huge fan of Alpine products and have been for years. I love my 4 channel amps and I’ve been enjoying fantastic sound for many years now.

Having the flexibility that a 4 channel amp gives is great when it comes time to upgrade your system later.

When it comes down to it, you don’t need a super-expensive amplifier to enjoy great sound quality. However, you do need to pick one that’s a well-rounded great choice.

I’ll tell you all you might want to know about the MRV-F300 before buying. Read on to learn more.

Contents

Alpine MRV-F300 review – First impressions

It’s a great looking amp, very compact, and housed in a well-designed dark brushed metal chassis. It feels solid in the hand, but it’s still relatively lightweight compared to conventional older amps of the same power rating.

I have owned other amps in the past with the same power rating and they easily weighed 3 times as much as the MRV-F300 does! It measures just under 5 lbs (around 10 kgs).

Build quality is great, and I notice there aren’t huge gaps or misaligned parts like on cheaper amps of the same Class D technology. I’ve tested other type D amps before, and easily noticed they weren’t put together well or felt a bit flimsy and just didn’t feel solid. That’s not the case here.

The amp looks great and the connectors are high-quality. You can make more reliable connection unlike lesser amps with standard screw terminals. Fit and finish are excellent, with no big gaps or sloppy assembly. The blue light on top glows when it is turned on (but not TOO bright, it’s not annoying). My opinion so far? NICE!

Connectors are very high quality and use hex-keyed screws to securely hold wiring connections. Connectors are clearly labeled, and take the guesswork out of bridging the amp if you choose to do so for more power.

The power connectors are circular inside and 8 gauge power wire will fit and is recommended for installation.

I really like what Alpine has done with the protective end caps it comes with – unlike amps in the past, they’re easy to get on and off.

They snap on and off! If you choose to mount it under a seat in your car or truck they’re great for protecting the wiring from shorts if you happen to have tools or coins lying around in your interior like I do at times.

Also, it just plain looks nice with them on!

By the way – upon opening the box you’ll find an Alpine Verification Certificate detailing the operation and performance of the amp you bought! Very nice.

MRV-F300 amplifier design and performance details

A huge advantage – compact size

The MRV-F300 has a cool glowing light on the top when powered to indicate it’s on. I love the compact size and honestly, I’m impressed with what they’ve fit into such a small package (Shown with end caps installed)

There’s a huge range of Class D car amps on the market today and most are pretty compact. The problem is that a well-designed car amp with decent power and GOOD quality sound requires a bigger circuit board and more parts – and that means bigger size.

Alpine, for several decades, has been several steps ahead of the lesser brands. They use surface-mount component technology (SMT) to reduce the size required in order to make a smaller and better-sounding amplifier.

Measuring only 7 7/8″ W x 6.5″ D x 2 3/16″ H (200 x 165 x 55 mm) it’s crazy small and can fit in creative places that older amps could never even come close to fitting in!

That’s a huge advantage! You could even fit one amp under each seat in some cases for a great way to have a multi-amp system that thieves won’t see.

Class D amp technology

Class D amplifiers are one of the most recent developments in the audio world. Unlike conventional Class A/B designs (which most car audio amps still use to this day) that are around 50% efficient, a Class D amplifier uses ultra-fast switching technology to bring efficiency to near 90%!

This means since you are no longer wasting huge amounts of power (which turn into heat, by the way) the amp can be reduced greatly in size and doesn’t need a huge power supply internally.

However, as I mentioned at the beginning of my review, there’s something you need to know: Class D amps have higher “noise floors”, another name for the baseline noise or “hiss” level you hear when the gain is turned up.

Also, these types of amplifiers must be well-designed to ensure the technology use doesn’t modify your music signal (distortion) when amplified.

That’s what they’ve done, as Alpine uses their own engineering rather than repackage and relabel a lower-end audio amp like some competitors do.

The end result is the ability to provide up to:

50W RMS per channel into a 4 ohm speaker x 4
75W RMS per channel into a 2 ohm speaker x 4
150 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode)

Performance and sound quality

Sound quality is just great as you’d expect from Alpine: music is full and clear, highs are bright and crisp, and bass is solid and easily drives speakers without giving out. It’s an excellent sounding amplifier and a winner! In the past I had my doubts about Class D car amps (after having a few bad experiences) but the MRV-F300 has changed my mind. It’s that good.

Bass hits hard and has a great impact, just as you’ve come to enjoy from conventionally larger amplifiers.

If you’re planning to drive subwoofers with moderate power and volume (up to 150W each) you won’t be disappointed. If you need slamming bass, however, I’d consider the sibling MRV-M500, a mono amp with much more power available in the same size.

I have excellent hearing and based on my audio design & listening experience, I can definitely recommend this little powerhouse.

The MRV-F300 features full range, low pass, or high pass crossover settings including 50-400Hz adjustable cutoff. A bass EQ (boost) feature is built-in too.

Audio controls

The crossover functions are easy to use. Controls and switches have a good, solid “feel” to them. One thing I’ve always noticed about Alpine Electronics is their products use good components that don’t feel sloppy when making adjustments. They also don’t change due to vibration over time after I’ve spent time & effort setting them up.

This amp is no different.

Note: the bass EQ boost is works only for the 3/4 channel pair when turned on. I’ve taken off points in my review score at the bottom as this feature in my opinion should be on 1/2 also.

One thing you need to know is that because it’s a Class D amp, by nature the noise level can be heard more when the gain is turned up higher. I definitely recommend adjusting the gain to a lower level that will still give adequate volume when the stereo is turned up high.

Alpine has done a great job in designing the amp, but it’s one of the trade-offs of this type of amp. Still though, it sounds wonderful and noise levels are basically imperceptible in most cases.

Additional features and installation

The great news is that it’s still easy to install – just like any other car amp as screw mounting is used to mount on tabs on each end of the amp (one pair of tabs on the control end and one pair on the power & speaker connection side.

It also works with speaker level inputs so it’s great for factory stereos too!

The amp fits great under seats and can still leave room for speaker crossovers! Here’s an example of a custom install using the amp when space is limited.

Actually if needed, because of its light weight, in more difficult installations you could even use industrial strength Velcro or some type of reliable double-sided tape to mount it if necessary. The amp won’t heat up and cause the adhesive to lose strength, unlike amps in the past.

As I mentioned earlier it looks more professional to use it with the end caps snapped on, but I’ll leave that up to you to decide.

Quick tip: Because the amplifier’s mounting tabs face inward, it may be a bit hard to install under a seat. Be prepared to use a short screwdriver or even remove the seat to make your job easier when installing.

Accessories included

You’ll get the following inside the box:

7.5″ Speaker-level input harness
2 snap-on terminal covers
Four 3/4″ Self-tapping hex-head screws
Owner’s manual (English/ French/ Spanish)
Alpine Verification Certificate

…so you’ll need to remember to pick up whatever else you need before you start your installation, along with an amp wiring kit. I recommend picking up a good quality but great-priced 8 gauge wire kit like this one I found at Amazon.

It’s a lot less hassle to be prepared, and you sure don’t want to end up paying too much or having to run out for supplies while in the middle of your install work!

Specifications

For your convenience I’m including the specifications directly from the owner’s manual as well as details I’ve found myself.

Alpine MRV-F300 Specifications

75W RMS x 4 (2Ω, 14.4V, ≤1% THD+N)
50W RMS x 4 (4Ω, 14.4V, ≤1% THD+N)
150W x 2 @ 4Ω
S/N ratio: >81dB @ 1W, >98dB @ rated power
Damping factor: >90
Front/rear adj. crossovers: Hi/low-pass, 50-500Hz, 12dB/oct.
3/4 channel bass EQ feature (50Hz, +12dB)
High-level speaker inputs
Blue accent power-on light
Same power in a 40% smaller chassis
Evolution to Class D digital platform
Snap-on terminal covers for easy installation
Fuse: 40A
1 year warranty
Compact size fits under seats
Dimensions: 8-1/4″W x 2-3/16″H x 7-15/16″D
Weight: 3.75 lbs (1.7kg)

You may have noticed that the signal-to-ratio ratio specified at 1W is lower than typical amplifiers. As I mentioned earlier, that’s an inherent design trait of Class D amps, but in practice with good speakers and the amp being sent a good signal level, it’s not really an issue.

I’m still pleased with the sound quality and wouldn’t recommend it if I didn’t feel you would be too.

Also note that the EQ boos is +12dB, in case you weren’t aware. That’s a very noticeable amount of bass increase.

Review score, pros & cons, and my final thoughts

I love this amp. For the money (it sells for a very reasonable price, usually somewhere close to $150 dollars or so) it’s a great buy.

As both an installer and a music lover I’d recommend it to nearly everyone except those who want extremely high signal-to-noise specs.

The MRV-F300 doesn’t disappoint as it’s a great performer – and definitely a great value, too!

Head over now to find out more and see why its one of the highest rated compact amps at Amazon.

Overall

8.7/10

Overall quality - 9/10
9/10
Sound quality & performance - 8.7/10
8.7/10
Installation ease - 9.2/10
9.2/10
Features - 8/10
8/10

A fantastic, great sounding 4 channel amp you'll be proud to own and can fit into small spaces

Is it small? It sure is! However, thanks to the superior Alpine design quality both music reproduction and power output are impressive for such a compact size. It’s a great performer musically and I love it. While many similarly priced class D amps by nature have a higher noise level than conventional Class A/B amps, Alpine has done a great job in minimizing noise.

Music is crisp, loud, and most of all enjoyable. This is an excellent amplifier for both aftermarket or factory stereos – with its small size it can fit safely away under seats or in storage areas. Factory systems gain the additional benefit of an auto-on sensing feature when the speaker level inputs are used. Not only that, but the included snap-on end caps round off a great-looking appearance nicely…and it’s priced close to the same as lower-quality competition models. Don’t pass this one up!

Pros

Excellent sound for a Class D amp
High efficiency – runs cool
8 gauge wire terminals
Flexible crossovers built in
Bass boost switch
Small size fits in many small areas
Great looking finish & nice power-on light
End caps provided for clean install
Bridgeable for 150W RMS each channel pair
Speaker level inputs

Cons

Bass EQ boost only on channels 3/4
Normal Class D lower signal-to-noise ratio (improves as power output goes up)
Closed power terminals mean its difficult to fit 4 gauge wire
Mounting tabs face inward rather than outward – no option to change them
No remote knob available unlike the sibling MRV-M500
No 2/4 channel input switch

Check current price at Amazon

5 Of The Best Amps For Highs And Mids – Get The Best For Your Dollar

September 17, 2020September 23, 2018

Best amps for mids and highs featured image

Want a system with amazingly clear and impressive sound? Let’s be honest: driving highs and mids from a head unit is almost impossible!

That’s where an amp comes in – you’ll get great power, awesome volume, and fantastic sound clarity. However, you’ll have to pick a good amp that won’t let you down.

To help you get the best for your money I’ve put together a list of 5 of the best amps for mids and highs. Each has a short review and the specs you’ll need to know.

There’s also a helpful buyer’s guide included below. Read on to learn more!

Contents

2 channel vs 4 channel amps

As you might have already guessed, 4-channel amps are a bit different than others. There are a few differences to know about when shopping and just to have a better understanding.

The main difference is that 4 channel amps contain a 2nd pair of amplification stages to boost the input signal and drive speakers.

Just like standard 2-channel amps, they contain a special section that steps up a vehicle’s 12V supply to deliver a higher one (often around positive and negative 28 volts or so)

That’s necessary to provide sufficient power that can drive your component speakers or highs and mids at a better volume with low distortion. For example, car stereos can only use about 12V to drive speakers, resulting a lower power that distorts easily.

According to Ohms law more power requires a higher voltage and that’s exactly what powerful car amps are designed to use.

4 channel amps are also a bit more compact in size as the additional 2 channels take up a bit less space than 2 separate 2-channel amps used separately.

Different features

In order to work in more applications, some 4 channel amps feature a 2/4 channel input switch. This means that if you have a source unit with only 2 RCA jack outputs you can still get 4 channels of sound to use from the amp.

Additionally, most 4 channel amps sold today are bridgeable, meaning that each pair of channels can be used to drive a single speaker for more power than each individual channel can provide. Because of this, they offer more flexibility for custom car audio systems than a single 2-channel amplifier can.

Some also feature different options like a bass boost for the rear channels (normally #3 & 4). The specific features you’ll find vary from brand to brand and model to model.

2 channel vs 4 channel car amplifier diagram

A diagram I’ve provided illustrating the differences between 2 and 4 channel amplifiers. Both work exactly the same way: a +12V supply from the battery is boosted (“stepped up”) to create a higher positive and negative voltage supply. These voltages are then used to drive speaker outputs which are an amplified version of the input signals from your car stereo. Not that 4 channel amps are normally more compact than 2 separate 2-channel amps of the same type.

What to shop for in good quality car amps

For mids and highs, it’s ideal to focus a few basic factors when shopping:

Sufficient power (in RMS watts)
Sound quality and the signal-to-noise (SNR) specs
Crossover controls

Basically, you’ll want an amp with good sound quality that can give a decent amount of power. For most applications, I recommend 50W RMS per channel minimum.

You’ll also want the ability to block distortion-causing bass by using high-pass crossovers on your tweeters or midrange speakers.

Signal to noise ratio

A signal-to-noise (SNR) measurement describes the ratio of the level of noise (undesired) to the desired musical signal. It’s measured in decibels (dB) and helps you to decide between a better product and a lower-performance product. Ideally the amount of noise compared to the signal level will be very small, represented as a larger number. For example, a SNR of 90dB and above is a good rule of thumb to look for. The noise I’m describing often appears a slight “hiss” when no music is playing and the amp’s gain is high.

Better amplifiers have a higher signal-to-noise (SNR) ratio. The SNR specification, measured in decibels (dB), is a standard amplifier measurement used to compare noise levels against others. It’s a ratio used to mathematically compare the level of noise that an amplifier’s electronics create vs the audio signal’s level.

As a general rule of thumb, the higher the SNR, the better. Amplifiers with great sound quality tend to have an SNR of 90dB and higher with some reaching above 100dB. That’s often found on more expensive and better-designed amplifiers.

It’s important to note, however, that unfortunately sometimes the specs are confusing. For example, at times some manufacturers exaggerate their amplifier specs or use the SNR value full power output, which is normally much higher.

Traditionally the most consistent measurement is by listing the SNR with no signal output and with 1 watt of power being driven.

Internal audio noise in an amplifier as viewed on a test instrument, enlarged. All amplifiers generate some internal noise…however the best models keep it at a minimum and are designed to produce good sound quality where noise is less noticeable.

When using tweeters (highs) and midrange or component speakers (mids), it’s often easier to hear the slight “hiss” an amp produces if the noise level isn’t very good.

Generally speaking, a well-designed amp will have this greatly reduced and this won’t be an issue. However, to keep noise from an amp down, it’s ideal to drive it with a good, strong signal from a head unit.

This way the amps gain level can be kept lower and noise output will won’t be noticeable.

Using crossovers with mids and highs

A good amp like the Alpine MRV-F300 will provide plenty of crossover options to not only protect your mids and highs but get the most out of them. By using high-pass crossovers, you can block the lower-end bass that they can’t handle and that causes distortion. The result is greatly clarity and much more volume!

Built-in crossovers in an amplifier are extremely helpful for getting excellent sound when using tweeters and midrange car speakers. The good news is that most, if not all, include them these days.

However, some are better than others in their flexibility and how they can benefit you.

How do crossovers work in a car amp?

Small speakers like midrange drivers or tweeters (for example, separately used or in a 2-way component system) aren’t designed to deliver heavy bass the way subwoofers can.

With only a low volume and a small amount of power, it may not be an issue. However, as soon as they’re driven to higher volume and with more power you’ll begin to hear distortion and the sound will “break up” quickly.

Crossovers work by using electronic filter sections to cut off, or filter out, the sound frequencies you want to prevent from reaching speakers.

For example, setting your amp’s high-pass option to 60Hz for driving mids will deliver a clean, nearly distortion-free sound at high volume.

Your options may vary

For mids and highs, always buy a model with crossovers built in. If you’re planning to drive woofers or subwoofers, be sure the model you’re considering has low-pass crossovers as well.

While some amps feature a fixed cutoff frequency of say 50Hz or so, some models offer adjustable controls which is even better. Adjustable crossovers allow you to better customize your system to your needs.

Additionally, products with a bass boost (or “EQ”) feature can help boost lacking bass in some cases.

Good amp design quality

A great amp like the JL Audio XD400/4v2 is designed with sound quality and performance in mind rather than cost-cutting for more profit. Better amps use higher-quality (and more up to date) components unlike cheaper models. Unsurprisingly, their sound quality is better, they last longer, and the enjoyment you’ll get is better, too.

When it comes to car amps, there’s a lot of difference between lower quality and higher quality models.

One big reason is that higher-quality amps pay attention to the design details that lesser amps don’t. In other words, they’re better engineered.

Higher quality amps often have these characteristics:

Better (and thicker) printed circuit boards (PCBs)
Surface-mount technology (SMT) components for shorter and smaller paths
Higher quality components
Better designs with sound quality in mind
Low-noise parts and proprietary circuits to improve sound quality

The good news is that it doesn’t have to cost much more money these days to get these kinds of features – many quality amps are very reasonably priced if you shop carefully.

The main difference you’ll discover is that bigger name brands such as JL Audio, Alpine, MTX, Rockford Fosgate, and many more have better experience and resources that they apply to their products.

If you pick just any old car amp there’s no telling what you’ll get! Unfortunately many are made primarily for profit and not for great sound and enjoyment.

RMS power ratings

To be sure you’re getting power from an amp as advertised, you can look for amps using power ratings that follow the Consumer Electronics Association (CEA) – 2006 compliance standards.

The CEA amp power ratings were established to help resolve the problem of so many confusing and misleading car audio specifications that are misleading to buyers.

Essentially buying an amp that features the logo ensures that the manufacturer’s power (and other sound) specifications are accurate and have been proven.

Choosing the right amp power for good sound

For adequate volume and in order to drive you speakers with enough power for dynamic, “punchy” sound, you’ll need enough power.

One reason is that when an amplifier is driven to its limits it is driven to clipping, meaning that the audio waveform the speaker sees is starting to get cut off.

In other words, the amp can’t drive the signal any higher and it begins to distort badly. It’s both a cause of terrible-sounding distortion and potentially damaging to car speakers as well.

To avoid this, pick an amplifier with enough power. For many cases I recommend at least 50W RMS per channel of power. Optionally, 75W RMS gives even more headroom and is still affordable.

The most important rule to follow is to have an amplifier with adequate power. That way it can produce music at the volume you want without beginning to distort.

What is a class D car amp?

More and more, you’ll find car amplifiers that are built on class D technology.

“Class D” car amplifiers work using a new design which relies on switching technology. They’re much more efficient than traditional car amps – sometimes up to nearly 90% efficient! Older designs were around 50-65% and wasted a significant amount of power as heat. What does this mean? Class D amps are much smaller and run cooler than older designs.

Class D amplifiers use a design based on a switching power supply and signal path. They chop-up the output signal by rapidly switch transistors on and off then restore the original (now amplified) signal back to a smooth sound wave, which then drives the speaker.

By doing so, they greatly reduce the amount of time the transistors are switched on and consuming electric current. This results in a large amount of power that isn’t wasted as opposed to conventional designs.

Originally used only for small home stereo amplifiers, the technology has matured and is now available in some of the best car amps sold today.

More advanced designs even have improved upon the concept and offer better sound quality and dynamic power output than average models offer.

Class AB vs class D amplifiers

Class A/B amps have been the mainstay for decades in the car audio world. The technology is fairly simple, cost-effective, and also can offer very good sound quality. The downside is that they create a lot of heat as they waste power and are larger and heavier than class D amps.

Class AB car amplifiers (often shown as “A/B”, since it’s a combination of 2 types) differ a lot from modern class D types. Unlike newer technology, they’re based on a design principle from as far back as the 1960s or earlier (based on some of the first transistor home stereo amps).

While they’re often found in lower-cost amps and can have good sound quality, they also have some disadvantages:

Low efficiency: often only 65% efficient
Generate a lot of heat due to wasted power
Require a larger and heavier body (heatsink)

As they’re not as efficient as class D designs, they can’t be designed as small and they can be a bit harder to install due to requiring more space.

However, if efficiency and size aren’t a big concern to you, they’re still often a good choice. Because of their tried-and-true design, they can produce very good sound at a good price and there are many choices to choose from.

Standard class A/B amps are often sold as budget models with different manufacturer names.

Class D amplifier sound quality

Class D amps do have a disadvantage, unfortunately. They’re more prone to have lower signal-to-noise (SNR) levels and poorly designed models will have more hiss than better ones.

The higher noise is a by-product of how switching amps work, and it’s a trade-off that comes with the benefit of better efficiency and smaller size, sadly.

There’s no way around it. However, choosing a good model (like the ones I’ve recommended here) will make sure you’re getting one designed to keep noise to a minimum.

Cheaper brands don’t care much about the sound quality like better brands do – and they don’t have the same audio engineering ability that the better choices offer.

I’ve tested both good and bad class D amps and I can tell you that there’s a significant amount of difference when choosing a better class D amp. They sound better, have lower noise, and have better power to offer.

In other words, they’re just all-around better!

★ 5 of the best amps for mids and highs ★

Our top picks

Product	Details
★ Our #1 Pick ★Alpine MRV-F300 4 Ch	Great sound for less money! An excellent value 50W x 4, 75W x 4, 150W x 2 RMS of clear, musical sound Evolution to class D design	Check on Amazon
Superb Sound!JL Audio XD400/4v2	High-end sound and performance in a small package. Fantastic! 75W x 4, 100W x 4, 200W x 2 RMS Low-noise, crystal-clear sound quality NexD high-fidelity class D design. Only 8-9/16 x 2-1/16 x 7-1/8" In size!	Check on Amazon
Rockford Fosgate Punch P400X4	Class A/B sound quality that's affordable + modern compact design Built-in amp setup gain features. Thermal heat management system Bass EQ feature, remote bass option, compact size	Check on Amazon
MTX Audio Thunder 75.4	MTX Audio performance and classic sound in a smaller package 75W x 4, 100W x 4, 200W x 2 RMS. Compact 12-5/8 x 2-1/4 x 6-5/16" size Designed with sound signal quality and reliability in mind	Check on Amazon
Ultra compactAlpine KTP-445U 4 Ch	Tiny size! Only 7-7/16 x 1-1/2 x 2-1/2” 45W x 4, 90W x 2 RMS power. High-pass crossover option Auto-sensing turn on for speaker level inputs	Check on Amazon

Amp reviews and details

1. Alpine MRV-F300 – Great sound, quality, and compact design. Excellent value!

I’m an Alpine fan and always have been. To this day the company still produces some of the best mobile audio electronics available today.

The fantastic compact but powerful MRV-F300 is a great example of an amplifier done right.

One of the most compact 4-channel amps of it kind today, the MRV-F300 puts the lower-end amps to shame. There’s a sleek-looking dark brushed metallic finish on the chassis. The blue backlit power-on light on type adds a nice contrast to the design when your system is powered on.

For a more professional-quality design, end caps are included that cover the connections and help hide wiring when installed. It’s a great touch that helps turn an affordable system into a pro-looking effect.

For about $150 or less you’ll get some great features:

50W RMS x 4 @ 4 ohms power
75W RMS x 4 @ 2 ohms
150W RMS x 2 @ 2 ohms bridged

You’ll get not only great power in size that’s small enough to fit under most vehicle seats but excellent crossover options, too. Speaker level inputs are no problem as it’s a built-in feature. You’ll also get adjustable full, low, or high-pass crossover controls. A Bass EQ feature boosts bass output on channels 3/4.

Measuring only 7 7/8″ W x 6.5″ D x 2 3/16″ H (200 x 165 x 55 mm) in size it opens up a whole new range of installation possibilities.

Alpine has once again used their advanced engineering resources to design a super-efficient class D amp that’s amazingly affordable. It’s also one of the best sounding of its kind.

You’ll get great system flexibility, too, especially for using mids and highs in your system:

50-400Hz high/low pass adjustable cutoff frequency
12dB/octave multi-stage crossover design
Front and rear crossovers are independent
Bass EQ boost feature for Ch. 3/4.

I was very impressed with this little amp for its price! As a matter of fact, I wrote a detailed review of the MRV-F300 found here.

It’s a great, affordable, and well-designed amp that’s an excellent compromise between power, size, sound quality, and price.

You simply won’t match the quality from competitors at this price range (around $150).

PROS:

Very compact – fits under seats!
Class D power efficiency
Good power (50W RMS x 4, 75W RMS x 4)
Bridgeable (150W RMS x 2 @ 4 Ohms)
Great sound quality & reduced noise
Alpine quality design
One of the most affordable/great value
Includes end caps for stealth install
Blue power-on accent light
High-level speaker inputs
Adjustable high/low-pass crossovers
Bass boost on ch. 3/4
Excellent buyer ratings
Nice satin brushed metal finish
CEA-2006 Compliant
Auto turn-on for speaker-level inputs

CONS:

Bass boost is only for ch. 3/4
Bass boost could be greater (12dB vs 18dB of others)
No remote level control option
No RCA pass through jacks
Bass boost frequency not adjustable
No auto-sensing turn on for RCA inputs (only speaker level)

I’ve awarded this one the Editor’s Choice for these many great reasons. It’s simply one of the best choices around today!

Don’t pass it up. Head over to see the happy buyer reviews and find out more at Amazon.

2. JL Audio RB XD400/4v2 – Music the way it’s supposed to be heard + modern amp tech & features. Fantastic!

JL Audio has been for years, and still is, a true leader in the car audio industry. The RB XD400/4v2 is another result of their pursuit of the best car amplification technology possible.

JL Audio has taken the modern class D switching design and upgraded it with their own higher-performance version called NextD.

You’ll get performance both in terms of power and sound quality that’s far above average. NextD uses a faster switching speed than lower-performing competitors do result in power that’s always available.

The audio design and higher-quality circuit board layouts also ensure lower noise and better signal quality, too.

The XD400/4 is simply without comparison when it comes to sound quality and performance. The crossover controls are on top (included cosmetic cover not shown) for easier control access. You’ll need the included hex wrench to connect power and speaker wiring as it uses different connectors for those than most.

You’ll get plenty of power to drive your mids and highs, too:

75W RMS x 4 @ 4 Ohms
100W RMS x 4 @ 2 Ohms
Bridged: 200W RMS x 2 @ 4 Ohms

These are under-rated numbers, too! The XD400/4 can actually exceed rated power output by a bit.

It’s a small amp too, measuring only a tiny 8.52 in. x 7.09 in. x 2.05 in. (217 mm x 180 mm x 52 mm). It’s one of the few ultra-compact amps that can accept a 4 gauge power wire.

You’ll get great signal and crossover features too, making it easy to drive the perfect system giving your mids and highs powerful, distortion-free sound:

Low/high-pass 12dB/octave cutoff frequencies: 50-500Hz adjustable
Pass-through RCA jacks for 2nd amp connection
2/4 ch. input adapter switch

PROS:

Very compact – fits under seats!
Class D power efficiency
2/4 ch. input switch
Great power (75W RMS x 4, 100W RMS x 4)
Bridgeable (200W RMS x 2 @ 4 Ohms)
Fantastic sound quality
Advanced class D (NextD) technology
Top-of-class quality and power
Includes control cover to nice install
Green power-on accent light
High-level speaker inputs
Adjustable high/low-pass crossovers
Optional remote level (HD-RLC)
Excellent buyer ratings
Brushed aluminum and black powder coating finish
CEA-2006 Compliant
3 remote-on methods (auto-sensing)
2 RCA pass-through jacks
4 gauge wire capable

CONS:

Optional remote sold separately
No bass boost feature
Speaker-level inputs require RCA splicing
Expensive

If you’re wanting one of the most powerful, smallest, and best-sounding amps available today, look no further.

It’s sold many places but I've found some of the best pricing over at Amazon.

3. Rockford Fosgate Punch P400X4 – Great sound in a small package – plus cool set-up features built in.

Looking for a compromise between price, size, and features? The Rockford Fosgate Punch P400X4 is one of the best and most refined versions of classic A/B audio technology available today.

Unlike other class A/B 4 channel amps, Rockford Fosgate has used their proprietary Trans-ANA circuitry design to not only reduce noise but to take sound quality a step further.

It’s a well-designed amp that I’m impressed with – the build and engineering quality really shows. Unlike competitors, Rockford’s design takes up less space and is designed to be able to handle stressful power situations with ease.

The Punch PX400/4 features a microprocessor-based heat management system that allows it to safely keep the amp running instead of shutting off like lesser amps.

That means during really hot days or high-power maximum listening levels you’ll be ok – the music won’t stop. Instead the system will monitor and maintain a lower power output to keep the heat at a safe level.

One thing I really like is how the company was able to fit so much technology into a package only 11-1/8″ x 2-7/16″ x 8-13/16″ in size.

A great choice for mids and highs, the P400X4 is an excellent choice for your money. It’s a CEA-2006 compliant rated amp so you know the specs are honest and it’ll deliver as promised. The signal-to-noise ratio (SNR) at the rated power output is a fantastic 105dB! It’s unique in that not only do you get flexible crossover features but additional set-up features to help you set the gain and input level settings during installation.

You’ll get plenty of power to run clear, loud, and enjoying quality music from component speaker mids and highs:

50W RMS x 4 @ 4 ohms
100W RMS x 4 @ 2 ohms
200W RMS x 2 @ 4 ohms

You’ll get some great crossover features, too:

Fully adjustable high/low-pass frequency levels: 50-250Hz
Optional adjustable Punch EQ w/ up to 18dB boost @ 50Hz or 12.5KHz
2/4 channel input source switch
Input level control allows speaker-level inputs

There’s also an optional Punch EQ remote control for easy dashboard bass level adjustments while driving.

Unfortunately, I did find one issue with the amp, and that is that it doesn’t offer speaker-level inputs so you’ll need an RCA line level adapter for that. However, a good one that will work with the amp is only around $15-20 or so.

Special built-in installation features

What helps make the P400X4 so different is the C.L.E.A.N. gain setup system built into it. With it, setup is easier and you’ll be sure you get the most from your amp and head unit!

Working with the including test tone CD (or test track MP3s can be used), the amp monitors and indicates input signal levels so you can adjust the gain for maximum output and minimal noise.

That’s a really cool advantage to have as it takes the guesswork and frustration out of trying to set up your system. It also means you won’t need to buy additional test equipment or accessories, too.

PROS:

Compact size – fits under some seats
C.L.E.A.N. setup features & test CD
Punch remote option
Input clipping indicators
Class A/B sound quality
2/4 channel input switch
Good power (50W RMS x 4, 100W RMS x 4)
Bridgeable (200W RMS x 2 @ 4 Ohms)
Great sound quality & reduced noise
Rockford Fosgate quality
Blue power-on accent light
Accepts higher-voltage signal (12V max)
Adjustable high/low-pass crossovers
Punch EQ boost adjustable (+18dB max)
Excellent buyer ratings
Nice black brushed metal finish
Muted turn-on

CONS:

No speaker-level inputs
Punch level control not included
No auto-on remote feature
No RCA pass through jacks
Less efficient than class D models
A bit larger in size than class D

As a great-sounding, well-made, and wonderful little amp you’ll love I highly recommend it!

Don’t waste any more time searching or shopping. Go find out today why it's one of the best-rated amps for highs and mids at Amazon.

4. MTX Audio Thunder 75.4 – Great power, sound, and affordability in a compact size.

Wanting excellent sound but need more power? I totally understand! In my own system, I use two 4-channel amps with 75W RMS per channel for crisp and detailed sound that won’t bottom out.

The MTX Audio Thunder 75.4 4-channel amp has exactly what you need for the same great sound.

The Thunder 75.4 gives you legendary MTX Audio design quality, great power and sound, and reliability, too. It’s also an under-rated amp and can slightly exceed the rated power specs.

And yet’s it’s still affordable, too, at around $200.

You’ll get plenty of power to drive component speaker mids or highs:

75W RMS x 4 @ 4 ohms
100W RMS x 4 @ 2 ohms
200W RMS x 2 @ 4 ohms

Using tiny surface mount technology (SMT) components, MTX designs their amplifiers not for bottom-dollar pricing like the competition does but instead for the best performance, signal quality, and value for your dollar.

In addition to a compact size that’s easy to install, you’ll also get a lower noise floor and excellent resistance to vibration. DC offset, thermal, and short-circuit protection are built in as well to keep your investment protected in case a problem comes up.

Based on classic and proven class A/B audio technology, MTX has taken the traditional design a bit further by using higher-quality audio path components as well as reducing signal path lengths to keep noise minimized.

Having used and installed MTX many times in my installation career I can tell you that they’re some of the best and definitely worth the money!

One of the smallest amps in is power class, the Thunder 75.4 measures a compact 12-5/8 x 2-1/4 x 6-5/16″ in size. Don’t let the small size fool you – it’s a hard-hitting little powerhouse! I like how the RCA inputs and crossover controls are placed on one end and the power & speaker connections are on the other. Well put-together, it’s a great choice for nearly anyone.

You’ll get some great crossover features as well – perfect for a custom system running separate mids and highs or even a 2-way front stage with a rear subwoofer.

Crossover specs include:

Front low/high-pass: 12dB/octave, 0-200Hz adjustable
Rear low/high-pass: 12dB/octave, 0-750Hz adjustable
Rear channels: Full-range, low-pass, or high-pass

The power connection block allows using 4 gauge wire, which is something I haven’t found on a lot of amps this size.

Sadly, to my disappointment, there’s no speaker-level input support. However, line-level adapters are relatively inexpensive, so that’s more of an inconvenience and definitely not a show-stopper.

PROS:

Compact size – fits under many seats
Class A/B sound quality
Great power (75W RMS x 4, 100W RMS x 4)
Bridgeable (175W RMS x 2 @ 4 Ohms)
Adjustable crossovers (hi/low 0-200Hz, 0-750Hz)
Great sound quality
Reduced noise design
MTX design quality & reliability
Adjustable high/low-pass crossovers
Great buyer feedback
5V capable RCA inputs
CEA-2006 Compliant
Includes MTX test certificate
Soft turn-on

CONS:

No speaker-level inputs
No remote level option
No auto-on remote feature
No RCA pass through jacks
Less efficient than class D models
No bass boost feature

Unless you have the most extreme demands, you’ll love this one. It’s a great sounding amp with fantastic power and it’s small enough to fit in many vehicle installations.

Check it out! Find out why it's a favorite among smart amp shoppers over at Amazon.

5. Alpine KTP-445U Ultra-compact – Great power powering mids and highs from a tiny size!

If you’ve got a vehicle that’s a tough installation challenge you simply want to avoid having the muss and fuss of a custom install, here’s the best choice. The KTP-445U universal ultra-compact amp is hands-down the best choice for your money.

It’s a fantastic installation option for both aftermarket or factory stereo head units for everything from car and trucks to boats or motorcycles.

Perfect for driving mids and highs with clean, high-efficiency power, it’s truly a stand-out marvel of modern Alpine design technology.

As seen in my detailed review of the KTP-445U here, it’s an example of some of the best engineering and sound quality you’ll get in a super-small package.

Measuring a tiny 7 7/16 x 1.5 x 2.5″ (189 x 38.2 x 64.5 mm), I’m almost in shock at how something so small can deliver so much. Despite the incredible size advantage you’ll get plenty of power.

The KTP-445U can deliver:

45W RMS x 4 @ 4 or 2 Ohms
90W RMS x 2 @ 2 Ohms

Despite that, it runs perfectly cool and draws nearly 1/2 as much electrical current as traditional amps. The modern class D design (with Alpine’s own proprietary touches) is one of the most efficient and best-sounding in its size and price class.

It’s so efficient that for many installations you can connect it directly to existing radio power wiring instead of installing a separate amp power wire!

Unlike other class D mini-amps you can drive 2 Ohm speakers as well.

One of the smallest car amps in the world today, the KTP-445U is in a league of its own. At only 7 7/16 x 1.5 x 2.5″ (189 x 38.2 x 64.5 mm) in size, it delivers impressive sound and power that you won’t get from most competitors. It’s so small it’s about the size of a laptop power converter, yet delivers enough power & flexibility to drive mids and highs for a whole system!

One feature I really like is that it’s “universal” and designed to be easy to install. Both RCA and speaker-level inputs are provided, making it a great match for factory systems too.

Don’t have front and rear RCA outputs on your head unit? No problem. Use the 2/4 channel input switch to take advantage of the built-in adapter and get 2 more channels immediately.

Alpine uses proprietary design and electronics technology to minimize noise levels and maximize sound quality that delivers a crisp, lively sound that’s good to the ear.

Despite being so small, I think it’s a great-sounding amplifier you’ll love and I really appreciate how much easier it makes installation.

At near $150 or so, it’s not the absolute cheapest out there, but for the sound quality, installation ease, flexibility, and enjoyment it’s great and definitely worth the money!

PROS:

Ultra-compact – fits in dash or nearly anywhere!
Excellent for factory system upgrade
High-efficiency class D design
2/4 channel input switch
Good power (45W RMS x 4 @ 4 or 2 Ohms)
Bridgeable (90W RMS x 2 @ 4 Ohms)
High-pass 60/80/120Hz crossovers
Great sound quality & reduced noise
Easy to install
Great wiring and signal harnesses (universal)
Accepts higher-voltage signal (12V max)
Excellent buyer ratings
Nice brushed metal finish
Handy mounting tabs
Includes basic mounting accessories
CEA-2006 Compliant
Auto turn-on for speaker level inputs

CONS:

No low-pass crossovers
Not suitable for driving woofers
No remote volume option
No auto-on remote feature
Auto turn-on won’t work for RCA inputs
High-pass crossover not adjustable – fixed to 4 pos.

I highly recommend this one if you want an amp that can fit nearly anywhere.

Have a look to see why no other ultra-compact amp at Amazon can compare.

Additional parts & reading

Need a great amp kit you can afford? Check out my recommended good amp kits here.

Thinking about installing an amp to an existing factory system? You can find out how to hook up a 4 channel amp to front and rear speakers here.

What Does A Car Amplifier Do? A Detailed Guide For You

September 16, 2020June 9, 2018

What does a car amplifier do featured image

Curious about car amplifiers? Do you have a car audio problem to solve or are you thinking about upgrading your vehicle’s sound system?

If you’ve wondered “What does a car amplifier do?” you’ve come to the right place.

In this post, I’ll cover everything you need to know including how they work and the different kinds.

Contents

Infographic – Car amplifier facts

What does a car amplifier do?

A simplified diagram showing the basic sections of a car amplifier and how it works. There’s a lot more to it, but the basics are pretty simple. A small, very low-level signal is input from a stereo and amplified to a much bigger – but identical – electrical waveform. This way it can offer lots of power and drive speakers with good volume. The +12V supply is “stepped up” (increased) to drive higher voltage to the output transistor stages.

A car amplifier boosts a very small electrical audio signal to a much higher voltage capable of driving loudspeakers.

Most car stereos can’t offer a high power output that can drive speakers with high volume and clarity. A great example is adding a subwoofer to your car. It takes a lot of power to get “slamming” bass!

How does a car amplifier work?

Car amps use a special type of internal power supply to supply their internal amplifier circuitry with a higher power. These sections then take a conditioned audio signal (provided by a stereo), boost it, and deliver it to the speaker terminals.

All amps have a few basic sections that are critical for driving speakers from only a +12V source. There are also some other sections that are essential and a few that are optional.

Nearly all typical car amplifiers today have the following subsections in their design:

A DC-DC (direct current) high-power switching power supply
Noise prevention (“ground loop”) circuitry
Speaker crossover circuitry
Bridging circuitry
Speaker-level input stages

Note that #5 (speaker-level input feature) is a product-specific option and may or may not be included. However, the others are found in nearly all car amplifiers with good power sold today. I’ll explain more about speaker-level inputs as we go.

As you can see in the diagram I’ve provided, some electronic components are attached to the metal body of the amplifier. That’s because as power is delivered to speakers some is wasted as heat. To help cool the high-power transistors, they’re attached to the heavy metal body of the amplifier.

Car amp power supplies explained

The illustrated main parts of a car’s switch-mode power supply (SMPS). Shown here is the nice little 4 channel Crunch PD2000.4 budget amp I bought from Amazon and opened up for you. The transformer is driven by high-power transistors extremely fast (many thousands of times per second). The SMPS chip controls when the transistor turns on and off rapidly according to power demands. The transformer uses magnetic fields to output a higher voltage supply on the other side of the +12V supply.

Although they’re powered from the vehicle’s battery connection, it’s impossible for a car stereo or amplifier to drive speakers directly with high power from only 12 volts. The reason is the mathematical properties of electrical power and the speaker impedance (resistance) for speakers.

Ohm’s law is a fundamental rule used to figure out things like power delivered to a load (here, a speaker) based on a certain voltage. A higher voltage can produce a higher power, just as you might have guessed by now. The same holds true for speakers in your car just as much as it does for a light bulb in your home.

A car amp’s switch-mode power supply (SMPS) is what makes everything else possible – it’s the most important part of the amp. It’s a critical section and necessary to get high power from only a 12V supply.

DC-DC switching supplies like those in a car amp are called step-up, as they are able to take a lower voltage and multiply it several times to a higher voltage.

A switching integrated circuit (IC) chip drives high-current transistors on and off thousands of times per second. They alternate cycles that enable and disable the +12V supply to the transformer. In doing so, the transformer, based on the number of turn of copper wire on it, produces higher voltages on its output.

A car amp’s switching power supply turns the high-current transformer on and off rapidly thousands of times per second. Two sides of the input side (+12V input connection) are turned on and off in alternating cycles. The waveforms look like these you see here.

Interestingly enough, it produces both positive and negative voltages! That’s to allow a full range of polarity when an audio signal is boosted and reproduced on the output.

Car amplifiers can draw a lot of electrical current. Many can easily draw up to 50A (amperes) but that’s usually only when near maximum power. During normal, low-volume use, they draw only a few amps.

Amplifiers are normally connected by a fuse directly to the vehicle’s battery for the positive wire. The ground (negative) wire is normally connected to a clean metal connection on the body. This is because a vehicle’s original wire usually cannot handle the amount of current an amp demands under heavy use.

How car amps turn on and off

In order to avoid having the amplifier stay on when you’re not using it, a “remote on” wire is used. Normally this connects to a dedicated wire on your stereo. Alternatively, it can be connected to an ignition wire that turns off when the accessory position of the ignition switch is turned off.

The remote wire, when at 0V, turns off power to the SMPS chip. This causes it to stop running. The amp then doesn’t draw any power from your battery.

You can use a very small wire like 18 or 20 gauge, as the remote wire input of almost all amplifiers draws only a tiny amount of current – often less than 25 milliAmperes (.025A).

Input stages, amplifier sections, and output stages

Shown here are two more of the major functional sections in a car amp: the amplifier & output section and the input stages. The input stage board consists of many smaller circuits to do things like providing crossover functions, making bridging for more power possible, providing gain control, and blocking ground loop noise. The amp stages take the audio signal from the input stage board, use the power supply’s output, and boost it to create a powerful output.

Input stages

The input stages (often grouped together, in this case on a separate printed circuit board as shown above) have a number of jobs to carry out.

These are:

Allow the amp to connect to stereos with no RCA jacks (speaker-level inputs)
Prevent terrible “ground loop” noise from being amplified
Provide high-pass and low-pass crossover functions
Allow adjusting the gain, or amplification level, of the amp

The input stages are made up of a type of extremely versatile electronic component called an op amp (operational amplifier). Op amps are basically little amplifier circuits built into a small chip that is used for a wide range of designs.

Noise prevention

Ground loop noise, which you may know as “alternator whine”, is a very frustrating and troublesome problem in the car stereo world. It’s an electrical noise that appears as a terrible whine which increases and decreases with the engine speed of your vehicle.

This type of noise is due to electrical currents that flow within a vehicle’s body and the connections of the audio components. When there’s a difference of electrical potential in 2 or more points in the system, a small voltage difference can exist.

Modern car amplifiers include circuitry to virtually eliminate this in typical installations.

Crossovers

Diagram showing how (passive) speaker crossovers like those in 2-way speaker systems work. Crossovers are a wonderful feature that can prevent potential damage to speakers. They also help prevent distortion and allow driving the speakers at higher volumes with clear sound. They’re a type of filter as they block unwanted sound from reach the speakers you’re using. Electronic crossovers in amps perform the same function but without large components like inductors and capacitors.

Crossovers are a great feature provided by today’s car amps. Most sold today include electronic crossover circuitry in the front-end (input) stages of the amp.

Electronic crossovers offer a low-cost, space-efficient way to send only bass or only upper-range sound to a speaker as desired. For example, when driving subwoofers, using the low-pass crossover in an amp will block everything except bass. Similarly, you can block low-end bass from smaller speakers by using the high-pass feature.

This offers a way to drive speakers with much more clarity and volume that you could otherwise.

Amplifier gain

As the name implies, amplifiers work by amplifying an input signal from a stereo. Because there’s no standard maximum signal voltage used by different stereos, a gain adjustment is necessary.

An amplifier’s gain adjustment allows better matching the speaker output level to the input signal level. It’s also a way to reduce noise as some car stereos have good, strong output signals. In that case, an amp’s gain level can be reduced and the amp’s noise (background hiss) level will be very low.

Gain is an incredibly important feature and the basis of all amplifiers in the electronic world.

Any kind of amp, from car amps to home stereos and even home DJ equipment have a gain that boosts the signal. However, they need to be set correctly.

Amplifier sections and output stages

Simplified illustration of the amplification stages and output that most car amps use. A car amp has large output transistors capable of handling large amounts of current. These are supplied by the switching power supply and drive the speaker. They’re controlled by some smaller components needed to split the audio signal into positive and negative halves.

Car amplifiers (as seen in the earlier image I provided) have a section dedicated to driving speakers. These sections contain small components like miniature transistors that divide the audio signal into two halves.

These signals are then used to drive larger, more powerful transistors from the higher-voltage power supply’s output to the speaker.

In doing so, the musical signal is amplified and the speaker is now capable of receiving a much more powerful signal. The speaker is driven by an identical but much larger waveform from the input signal received from a car stereo.

What are channels on an amp?

Channels are independent audio paths that are used to create a sound output from an amplifier. In stereo recordings, these are left and right audio sources that differ and provide left vs. right audio sound.

Left and right audio channels are separate outputs from a car stereo or other source.

They’re used to give fuller, more realistic sound when listening. Additionally, some stereos provide front and rear outputs pairs, although these are simply the same signals provided to drive an extra pair of speakers in the rear.

In most car amps of today, amplifier channels can be “bridged.” This means that 2 channels can work together to drive one or more speakers and therefore offer more power than one channel alone.

Typical car amp connections and controls

Shown: most car amplifiers have very similar connections and controls, with power connections and speaker outputs on one end. Audio inputs and gain controls are usually on the other end. This Crunch PD2000.4 4 channel amp is a good example of a typical amplifier. It includes speaker-level inputs (labeled as “Hi Input”, top image, white connectors).

Most car amplifiers, whether expensive or budget-priced, are very similar in how they’re set up. Generally, speaking power connections are wired on one end (bottom image) and RCA connectors and other controls are on the other (top image).

In the top image, you can see adjustable crossover dials and the switches to enable them. The point at which certain music ranges are blocked, called the cutoff frequency, are used is adjustable in this case by the user.

In other models, it’s a fixed setting operated with a switch.

Power connections

Power and speaker connection terminals on a Pioneer GM-D9605 car amplifier.

Power connections are typically made using larger-gauge copper wire and connectors, often included in an amp wiring kit. RCA cables are used to connect the amplifier to the audio signal outputs of the head unit from which music is played.

Note that to bridge 2 channels on the amp and deliver more power as a single channel, they’re connected in a particular way. The bottom image above shows the polarity and wiring connections required. They’re marked as “Bridged” as you can see.

In bridged mode, one channel provides the positive speaker connection and the other provides the negative.

Speaker level inputs

A speaker level input harness for a car amplifier. The speaker outputs from a factory or other stereo are connected to the wiring then plug into a connector on the amp. The high-level signals are converted to low-level signals similar to RCA inputs.

For factory-installed stereos, RCA jacks typically aren’t available. In that case speaker-level (also called “high level”) inputs, if available, can be used. These take the higher voltage speaker level signal directly from speaker wiring and reduce it to a smaller level the amplifier can use.

The other option is to use a speaker-level adapter to do the same thing.

How car amps are installed

A typical installation for a car amplifier. Large-gauge power wires are connected to the power terminals and fastened using screws. Speaker wiring is connected similarly. After installation, the sound system is tested and the amp’s gain control and crossovers are adjusted as needed.

In order to work properly, car amplifiers must be installed with sufficient size and type of wire. The most important reason for this is because a vehicle’s original wiring cannot handle the high-current demands of an amplifier.

For example, some car amps could draw as much as 50 amps at high-volume or when driving subwoofers very hard. Factory wiring isn’t rated for these kinds of demands and a loss of voltage (and consequently, power) to the amplifier would occur. Therefore we route a large enough power cable to the battery and make sure a good, clean electrical connection is made.

A sufficiently rated fuse, held in a fuse holder, protects the positive power cable. If a problem like a short circuit occurs the fuse would blow and protect against causing a fire.

There are several wiring connections used on all car amplifiers:

A fused large-gauge power wire to the battery (+12V)
Negative connection to the “ground”: negative battery terminal or car’s metal body
Remote-on wire to switch the amp on and off with the stereo or ignition switch
Audio input signals: RCA cables or speaker-level inputs
Speaker wiring connections

Fortunately, this wiring is often easily found pre-packaged and ready for use by buying an amplifier wiring kit.

Here’s a diagram I’ve created to help better explain visually how a car amp is typically installed. Ii shows one of the most common uses of a car amplifier: adding a subwoofer for having great bass.

Car amplifier installation diagram

How are car amplifiers beneficial?

Today’s amplifiers can power a whole car stereo system with excellent sound and power. Some like this excellent Alpine MRV-F300 4 channel model are very compact and can be installed under a seat. A good amplifier provides several times the power an average car stereo can. Also, they’re much more clear and crisp sounding.

Car amplifiers have many benefits as well as being a necessity in some cases. Typical car stereos, even today, can only produce about 15 to 18 watts of power per channel at most.

At higher volumes and when attempting to drive speakers that need more power, the sound from a stereo becomes distorted and terrible. Driving speakers with higher volume is basically impossible with only a car stereo.

That’s where a car amplifier comes in.

Car amps offer much better sound, especially for bass-heavy music. There are also some special situations where they’re the only option for upgrading the sound in a vehicle:

Factory stereo systems with no woofer
Factory-installed amplifiers that have died or are weak
The desire for powerful, clear sound when enjoying higher-quality music
Vehicle owners who want heavy volume
Boat and other outdoor vehicle owners (outdoor vehicles need extra power for better sound)

Additional benefits

As I mentioned earlier, many offer features like built-in crossovers that can prevent distortion and allow you to play speakers at higher volumes with enhanced clarity. Factory systems normally can’t do this and the sound will “break up” early when turned up to higher volumes.

Installing an aftermarket amplifier resolves this problem and allows more control over your audio system. Additionally, a system can easily be expanded to add a subwoofer for missing bass by either adding a 2nd amplifier or using 2 channels of a 4 channel amp to drive it.

2 channel vs 4 channel amps – what are the differences?

Think of 4 channel amps as an extension of a 2 channel model. They add 2 channels of speaker power but are often more compact than two separate amps.

4 channel amplifiers are nearly identical to 2 channel models. However, they do have a few differences and in some situations are more beneficial.

4 channel amplifiers are different mainly in their design: they have an extra 2 channels for adding more speakers.

There are several benefits of using a 4 channel instead of a single 2 channel amp:

You can drive front and rear speakers
Driving front full-range speakers and using channels 3 and 4 for subwoofers
They’re usually more compact than 2 separate stereo amps

Most 4 channel amplifiers today also bridgeable, so they’re very flexible in how they can be used. That is to say you’re not limited to using them for only 2 or more speakers: you can use 4, 2, or even 3 channels depending upon using the bridging feature.

Summary

Hopefully you’ve learned what you needed to know about car amplifiers. Here are the fundamental things to remember:

Car amplifiers boost a small signal to a larger signal than can drive speakers
They’re used to solve many car audio problems and improve sound
Car stereos can’t provide high power output like an amplifier can

Interested in finding some great amps that you’ll love? I’ve got a helpful buyer’s guide and some of the best amplifiers you can find here.

Thinking about connecting an amp to front and rear speakers? Check out my guide on how to hook up an amp to front and rear speakers.

Got questions, suggestions, or comments? Let me know in the comments below or send a message.

The Best 4 Channel Amps For Sound Quality – Top Picks And Buyer’s Guide

September 17, 2020June 5, 2018

Best 4 channel amp for sound quality featured image

Finding a good-sounding amplifier can be tough. I’ve put together this guide and recommended models to help you find the best 4 channel amp for sound quality.

Sound quality depends on a number of factors – not just one thing. It’s important to choose a well-rounded amplifier designed with sound quality in mind

As class D amps are also more common, I’ve added some important information about those as well.

Contents

Infographic – Car amp sound quality facts

What is a 4 channel amplifier?

A 4 channel car amplifier, as you may have already guessed, is extremely similar to most 2-channel (stereo) car amplifiers. However, there are a few differences you should be aware of. Just like 2 channel (or single-channel “mono block” amps) they contain a power supply with steps up the +12V battery voltage to a higher one.

This is necessary to create more power for the speakers you use. This is because when only 12V is available, a speaker can’t be driven with much power. That’s largely related to Ohm’s law and the basics of electrical power.

While similar, 4 channel models are built slightly differently. They’re a bit more compact as they incorporate 4 (instead of 2) independent audio amplifier signal paths and amplifier sections.

Many 4 channel amps also feature a 2/4 channel input switch. This is useful if connecting to a head unit with only 2 channels available in order to drive 4 channels of power.

Most today also are “bridgeable” – that is, they can be connected to drive a single speaker load from 2 channels for more power. Some 4 channel amps are configured slightly different than others and have additional options like bass boost or crossovers that can only be used for 2 of the 4 channels.

These types of details vary from brand to brand and model to model. You need to be careful when shopping to ensure the amp you’re buying meets your needs.

2 channel vs 4 channel car amplifier diagram

Diagram showing the basic differences between a 2 and a 4 channel car amplifier. Both work the same way: the +12V supply is “stepped up” (increased) to a higher voltage with both positive and negative outputs. These supply the amplifier transistor stages which are fed with the signal from your stereo. This basically just amplifies the very small signal from your stereo to a higher voltage that can drive speakers with a lot of power. Note that 4 channel amps are usually more compact than other models (especially class D amps).

What to look for in amps with good sound quality

The best sounding car amplifiers have a number of important features you should be aware of before buying. It’s important to have at least some understanding of what the specifications actually mean, what kind of power rating you need, and what you can generally expect to pay.

There are several basic factors to check when choosing a great-sounding 4 channel amplifier:

Signal-to-noise (SNR) ratio
Built-in crossovers/crossover specifications
Design quality
Root Mean Square (RMS) power rating per channel

Signal to noise ratio

The signal-to-noise ratio (SNR), rated in decibels (dB) is a way comparing the amount of audio signal to the level of noise signal in a car amplifier. Ideally the amount of noise will be low compared to the audio signal level. A 4 channel amplifier with good sound quality will have a number around 90dB and above. The best, depending upon the rating used, will be 100dB and higher. Background noise exists in all amplifiers and appears as a slight “hiss” when you listen with no music playing. It’s also more noticeable with the amp’s gain turned up.

Good amplifiers have a higher signal-to-noise (SNR) ratio. The SNR, listed in decibels (dB) is a way of comparing how much audio signal the amp has vs the amount of electrical noise it has internally.

Generally speaking, the higher the number, the better. Amps with great sound quality tend to be listed as having an SNR of 90dB and above, in my experience. Some of the best list their specs at 100dB and above.

However, it’s important to know that the specs can be a bit misleading. For example, it’s unfortunately pretty common for many to exaggerate their specs or they don’t list all of the ratings at certain power output levels.

It’s common to see better brands list the SNR with no signal output and also at 1 watt power output, where it tends to be lower.

An enlarged image of the internal noise produced by a car amp (zoomed in for better viewing). Noise in an amplifier is to be expected – all amps have it! However, a good amp is designed to keep the noise low and the music signal high.

In a system with great tweeters and good sound reproduction, it’s easy to hear the amp’s noise if you turn up the gain very with no music playing. Generally speaking, an amp with good sound quality will have the least amount and will be more difficult to hear. Driving your amp with a strong, high-quality audio signal means you can turn down the amp gain and keep noise to a minimum, too.

Crossovers and sound options

A great-sounding amp like this Alpine MRV-F300 4 channel model will have good crossover features built in. While it’s important to pick an amp with the best sound you can afford if your speakers are driven to distortion and can’t handle some frequencies any amp can sound poor. Making use of the crossovers can have a huge impact on your system’s sound quality!

The speaker crossovers (normally called just “crossovers”) can be very important for a great-sounding system. What’s fantastic to know is that even budget models today have them built-in unlike many years ago.

The crossovers (like on the Alpine amp pictured above) give you the ability to get more volume with less distortion out of your speakers. You’ll also get better clarity and sound quality.

Basically, small speakers like coaxial door speakers and even some higher-priced component speakers simply cannot produce low-end bass well as a subwoofer can. Because of this, when playing some of your favorite music you’ll begin to hear distortion and the music will begin to break up when you start to crank the volume.

Always buy a 4 channel amplifier with high-pass crossovers built in when using the amp for full-range speaker sound. For bass, be sure to buy a model with low-pass crossovers as well.

Some models have fixed cutoff frequencies (the frequency at which sounds above or below are blocked), which is less flexible than adjustable models. However, generally speaking, fixed ones are set around 50 to 60Hz which is ok in my experience.

Some models also include a bass boost feature which can help if you don’t have good sound controls on your stereo.

Design quality

Great-sounding amps like this JL Audio XD400/4 have well thought out and designed circuit boards, better quality components, and a design goal of better sound. They place the quality of the music above cost and manufacturing shortcuts that you’ll find in low-end amps. The result is a difference you can hear.

There’s quite a big difference in sound between lower quality (and cheaper) amps and car amps with better design. One huge reason why is that there are a lot of small details that get ignored by lesser amps that are used by amps with better engineering and design.

For example, car amps with better sound have things like the following in common:

Better (and thicker) printed circuit boards (PCBs)
Surface-mount technology (SMT) components for shorter and smaller paths
Higher quality components
Better designs with sound quality in mind
Low-noise parts and proprietary circuits to improve sound quality

What’s especially interesting to know is that you don’t have to spend a ton of money for these things – even some amps just under $200 can provide excellent sound.

The big difference is that the respectable name brands like Alpine, JL Audio, MTX, Kicker, and others have the engineering resources and expertise to produce car amps that are designed to sound good. The problem with picking just any old car amp is that they’re designed for profit. Not for great sound quality!

How can you know which models are worth buying? A great start is to check my list below.

RMS power ratings

These days, high-quality amplifiers provide reliable, demonstrated, and documented specifications for their power ratings and sound quality.

The Consumer Electronics Association (CEA) – 2006 compliance standards were established because of the confusing and misleading advertising ratings used by many car stereo manufacturers. It was created to give you clearly defined specs and ratings you can rely on when choosing an amplifier.

When choosing an amp with good sound quality, it’s best to shop for models (where possible) that advertise CEA-2006 compliant specifications. Doing so means there are no advertising gimmicks and that power ratings aren’t misrepresented.

Choosing the right amp power for good sound

For good sound, you’ll need adequate power. The reason why is that when an amplifier begins to be driven beyond its maximum power output level, it is driven into clipping, or cuts off, the audio signal driving a speaker. This is both a cause of serious, terrible-sounding distortion and potentially damaging to speakers too.

Amplifiers with adequate power won’t reach this point as they’ll still have enough power remaining before they begin to produce distortion.

I recommend a 4 channel amplifier with at least 50W RMS per channel for most people. If you’re like me and like to occasionally really crank it up, 75W RMS per channel is even better. Feel free to buy an even bigger amplifier if you like.

The most important part is to have an amplifier with adequate power that can produce music at the volume you want without beginning to distort.

What is a class D car amp?

When shopping for car amplifiers, you’ll be seeing more and more models in this category. It’s helpful to know a bit more about them before spending money. You’ll also want to know a bit more about sound quality as well. Some are great and some are disappointing.

Class D car amplifiers work on a relatively new type of amplifier design technology. They’re very efficient – in some cases up to nearly 90%! This contrasts with older designs which are around 65% efficient or less. What that means to you is they take up less space, generate less heat, draw less power, and often require smaller power wire.

Class D car amplifiers are those designed with a different type of power supply and sound reproduction than conventional, older technology. They work off of a type of high-frequency switching supply to modulate – or “chop up” – the incoming audio signal into a continuous flow of electrical on-off pulses.

These are then reconstructed and smoothed to drive speakers.

Originally this was used only for home stereo amps with decent but not impressive performance. However, the technology has greatly improved and now they’re capable of producing the great sound you’ll enjoy. I’ve used class D amps at home for some time now, and I’ve been pretty happy with them.

Class AB vs class D

Class AB amps like this Diamond Audio model take up more room, are heavier, and use much more electrical current than class D car amps. The additional metal heatsink they’re built inside of also adds to the cost. Some modern amps can deliver the same power with about 1/2 the physical size!

Class AB car amplifiers (often shown as “A/B”, since it’s a combination of 2 kinds) are different from class D amps in how they operate. Unlike class D designs, their transistors are switched on nearly all the time, consuming more power. Much of this power is wasted and appears as heat.

Most are around only 65% efficient or less. That means if an amp is delivering 100W of power to your system, it’s actually drawing around 135W and more! (Some additional power is wasted by the power supply and other sections)

That’s one reason they’re heavier and need a large (and costly) metal body: they have to get rid of the additional heat. Even without any sound playing, you’ll notice a class AB amplifier gets warm after a period of time.

Class AB designs are a combination and compromise between the older class B designs (more efficient than class A, but slightly worse sound) and class A (best sound quality, but less efficient). Hence the name they’re given.

They do have one advantage: The design is cheaper and easier to produce with pretty good sound on a budget.

Class D amplifier sound quality

These types of amplifiers can have a harder time producing low-noise audio. One of the drawbacks to class D amps is that higher noise levels (appearing a low-level hiss and so on) are a by-product. Lower-quality amps will have an amount of noise most people can hear if they listen closely.

There’s no way around it. When it comes to class D car amps, you’ll have to buy a very well-designed amplifier to get good sound quality. Cheaper brands compromise on the amount of filtering and the kind of circuitry they use.

Name brand amplifiers like those I recommend below have custom designs and advanced ways of dealing with those drawbacks.

Additionally, many cheaper class D car amps use off-the-shelf chips. The result is poor sound quality and high noise levels. I’ve personally tested both good and bad brands, and there’s a big difference in the sound quality!

Today’s choices are very good and do a great job of powering an entire system with fantastic, clear sound production…all while fitting into small spaces.

★ 5 of the best 4 channel amps for good sound quality ★

Our top picks

Product	Details
★ Our #1 Pick! ★Alpine MRV-F300	Great low-noise sound quality for less money! An excellent value 50W x 4, 75W x 4, 150W x 2 RMS Evolution to class D design	Check on Amazon
High end soundJL Audio XD400/4v2	Excellent signal/noise ratio. Superb sound quality 75W x 4, 200W x 2 RMS Only 8-9/16 x 2-1/16 x 7-1/8" in size!	Check on Amazon
Rockford Fosgate Punch P400X4	Built-in gain setup features for optimal sound 50W x 4 / 100W x 4 / 200W x 2 Compact size + bass remote option	Check on Amazon
MTX Thunder 75.4	Only 12-5/8 x 2.25 x 6-5/16" in size. Advanced class A/B sound design 75W x 4, 200W x 2 RMS underated power	Check on Amazon
Ultra compactAlpine KTP-445U	Tiny size! Only 7-7/16 x 1-1/2 x 2-1/2” 45W x 4, 90W x 2 RMS power. High-pass option Auto-sensing turn on for speaker level inputs	Check on Amazon

Reviews and amp details

1. Alpine MRV-F300 – Great sound, powers a whole system, and affordable!

Alpine developed an affordable but great-sounding amplifier small enough to fit under a seat but still power your whole system.

One of the smallest 4 channel amps on the market, the MRV-F300 puts lesser amps that are twice as big in size to shame! It’s a great-looking amp with a sleek dark brushed metal finish and cool blue power-on indicator on top.

The included optional end caps snap and off for an even cleaner looking installation. For those of you looking to flush-mount your new amp in a custom install, it’s a perfect choice.

The MRV-F300 is rated at a clean-sounding 50W x 4 RMS @ 4 Ohms and 75W x 4 into 2 Ohm speakers. It’s one of the best next steps in the evolution of car amplifiers. It’s bridgeable to 150W x 2 into 4 ohms, by the way.

Oh, snap! So many features for the price that it’s nearly impossible to beat. Not only does it have speaker-level inputs (wiring harness included) but also adjustable high/low pass crossovers, bass EQ (boost), and removable end caps.

Measuring a tiny 7 7/8″ W x 6.5″ D x 2 3/16″ H (200 x 165 x 55 mm) it fits into installation spaces that are impossible with older amps.

Alpine has used their engineering expertise to create an amp that’s one of the few super-efficient class D amps in its price range with reduced noise for enhanced sound quality.

Don’t just take my word for it – check out the great buyer reviews!

As expected, you’ll enjoy great system flexibility with the built-in crossovers (50-400Hz adjustable high and low pass, 12dB/octave) and a bass boost feature for channels 3 and 4.

I was really impressed with this little amp for its price! So much so that I wrote a full review of the Alpine MRV-F300 here.

It’s a sweet little powerhouse with great sound quality for what you pay. At near $150 or so, you’re simply not going to match the quality when buying a lesser brand. (You’ll need to shop carefully to avoid paying more than you should)

Why did I rank this one #1? Because it’s one of the best sounding all-around values that fits in places not many can.

PROS:

Very compact – fits under seats!
Class D power efficiency
Good power (50W RMS x 4, 75W RMS x 4)
Bridgeable (150W RMS x 2 @ 4 Ohms)
Great sound quality & reduced noise
Alpine quality design
One of the most affordable/great value
Includes end caps for stealth install
Blue power-on accent light
High-level speaker inputs
Adjustable high/low-pass crossovers
Bass boost on ch. 3/4
Excellent buyer ratings
Nice satin brushed metal finish
CEA-2006 Compliant
Auto turn-on for speaker-level inputs

CONS:

Bass boost is only for ch. 3/4
Bass boost could be greater (12dB vs 18dB of others)
No remote level control option
No RCA pass through jacks
Bass boost frequency not adjustable
No auto-sensing turn on for RCA inputs (only speaker level)

The MRV-F300 checks all the boxes in terms of sound quality, size, power produced, features, and quality. It also features speaker-level inputs for adding it to a factory stereo.

It’s priced right for just about everyone. Definitely head over to check out the amazing reviews and happy buyers at Amazon.

2. JL Audio RB XD400/4v2 – 75W x 4 of some of the best sound for your money that can still fit under a seat

Always a car stereo industry leader, JL Audio has been known worldwide for excellent sound, hard-hitting power, and some of the best engineering you can buy.

Their approach to building a super-compact and ultra-efficient class D amp was to take the average approach to amp design and throw it away – and used their unique NexD circuitry which uses a much faster switching speed than low-end amps do.

The result is improved power delivery and much lower noise levels. As far as sound quality goes, it’s one of the best modern car amps that money can buy.

The XD400/4v2 is one of the best sounding and best-designed amps in its class. The crossover features are built facing the top (which features an optional cosmetic cover) for an easier way to reach them in many systems. Note that you’ll need the included hex wrench to tighten and loosen the higher-grade wiring terminals. It’s a great amp!

Specified at an under-rated 75W RMS x 4 into 4 Ohms (100W RMS x 4 into 2 Ohms) it’s capable of exceeding its rated power.

Measuring a mere 8.52 in. x 7.09 in. x 2.05 in. (217 mm x 180 mm x 52 mm) it’s one of the few in its size class that can accept 4 gauge wire.

Adjustable 50-500Hz low/high pass crossovers are provided for great system flexibility and to help you block distorting bass when driving full-range speakers. The 2/4 channel switch allows driving a whole front and rear system without the need for rear RCA inputs.

Additionally, a pair of RCA output jacks make it easy to connect it to a second amp for system expansion. Wire terminals are audiophile-quality and it’s one of the best-rated amplifiers sold today.

PROS:

Very compact – fits under seats!
Class D power efficiency
2/4 ch. input switch
Great power (75W RMS x 4, 100W RMS x 4)
Bridgeable (200W RMS x 2 @ 4 Ohms)
Fantastic sound quality
Advanced class D (NextD) technology
Top-of-class quality and power
Includes control cover to nice install
Green power-on accent light
High-level speaker inputs
Adjustable high/low-pass crossovers
Optional remote level (HD-RLC)
Excellent buyer ratings
Brushed aluminum and black powder coating finish
CEA-2006 Compliant
3 remote-on methods (auto-sensing)
2 RCA pass-through jacks
4 gauge wire capable

CONS:

Optional remote sold separately
No bass boost feature
Speaker-level inputs require RCA splicing
Expensive

If you’re looking for one of the best sounding and smallest amps today, this is it.

It’s available at many places online but you can get it for a better price (and free shipping) at Amazon.

3. Rockford Fosgate Punch P400X4 – Excellent sound, small size, and great set-up features included

Able to spend a bit more? The Rockford Fosgate P400X4 provides some of the best sound out there in a 4-channel amp. While it may seem just many competitor’s products, there’s more to offer, however.

Unlike other conventional A/B class amps, the company has used its own proprietary Trans-ANA circuitry design to not just reduce noise, but to take sound reproduction to the next level. It’s a well-designed amp with real engineering quality through and through.

Additionally, the amp has a special heat management design using state-of-the-art microprocessor circuitry to manage heat levels without having to shut the amp off.

Because of their car electronics expertise and resources, Rockford was able to fit all this into a package only 11-1/8″ x 2-7/16″ x 8-13/16″ in size. Other amps in its power and price range (near $200) can’t match the size, quality, or features.

The P400X4 is capable of excellent sound quality. It’s a CEA-2006 compliant rated amp, meaning the specs are proven and reliable. Signal-to-noise (SNR) performance is excellent, with up greater than 105dB at rated power! As you can see in the image, crossovers, sound EQ options, and the set-up features are accessible with the top cover removed. A nice blue power-on indicator rounds out a sleek, modern design.

Power ratings are great, too, featuring enough to run most systems:

50W RMS x 4 @ 4 ohms
100W RMS x 4 @ 2 ohms
200W RMS x 2 @ 4 ohms

High and low pass crossovers are provided and are fully adjustable from 50 to 250Hz. The Punch EQ is cool bass and treble feature that helps enhance your sound with an adjustable 0-18dB of boost at 45Hz bass or 12.5KHz for treble.

An optional Punch EQ remote control know (sold separately) allows easy dashboard control of the bass level while driving. One drawback of the amp is that is doesn’t offer speaker-level inputs, but it does include a 2/4 ch. input switch.

The unique feature I like about this amp is the C.L.E.A.N. gain setup system built into it. When used with the included test tone CD, the amp can show signal levels to aid in setting up the gain for optimal performance. It’s a great advantage as it makes setting up your amp for the lowest-noise and best sound levels much more easily.

It’s conservatively rated, too, meaning the amp will exceed its rated power output. For added confidence when buying, a certificate of performance is included with each amp, too!

PROS:

Compact size – fits under some seats
C.L.E.A.N. setup features & test CD
Punch level controller optional
Input clipping indicators
Class A/B sound quality
2/4 channel input switch
Good power (50W RMS x 4, 100W RMS x 4)
Bridgeable (200W RMS x 2 @ 4 Ohms)
Great sound quality & reduced noise
Rockford Fosgate quality
Includes control cover panel
Blue power-on accent light
Accepts higher-voltage signal (12V max)
Adjustable high/low-pass crossovers
Punch EQ boost adjustable (+18dB max)
Excellent buyer ratings
Nice black brushed metal finish
CEA-2006 Compliant
Muted turn-on

CONS:

No speaker-level inputs
Punch level control not included
No auto-on remote feature
No RCA pass through jacks
Less efficient than class D models
A bit larger in size than class D

It’s a fantastic amp and I highly recommend it.

Be sure to check out the amazing owner reviews and the lowest price over at Amazon.

4. MTX Audio Thunder 75.4 – More power with good sound and build quality in a small package

Planning a system that needs a bit more power? I totally get it – in my system I’m using 4 channel amps with 75W per channel. It’s great having that power on tap.

With the Thunder 75.4 you’ll get legendary MTX Audio build quality and under-rated power (yes, their amps often can go past rated power!) in a size that fits in less space. And it’s still affordable, too!

MTX has cleverly designed the amp to squeeze in lots of power:

75W RMS x 4 @ 4 ohms
100W RMS x 4 @ 2 ohms
200W RMS x 2 @ 4 ohms

The design uses tiny surface mount technology (SMT) components for shorter audio paths and for excellent resistance to vibration. Thermal, DC offset, and short-circuit protection ensure your amp will protect itself in case a problem occurs.

It’s based on classic and proven A/B amp design with MTX’s own patented audio design touches. Having installed both budget and higher-end MTX amps many times, I can tell you they’re definitely well worth the money.

The Thunder 75.4 is one of the smallest in its power class at only 12-5/8 x 2-1/4 x 6-5/16″ in size. It’s a great basic, hard-hitting, and compact amp. It’s well-made and a good use of your money if you’re looking for a good compromise between sound quality, power, and installation ease. I really like the user-friendly crossover features and how simple and uncluttered it is.

The high-pass crossover is adjustable up to a nice 750Hz, while the low-pass is adjustable to 200Hz max. 4 gauge wiring connections are available and are very well made – they’re some of the best I’ve seen.

Unfortunately, speaker-level inputs aren’t available on this model.

If you demand extreme sound quality, then it’s probably not for you. However, if you’re wanted very good sound quality in a smaller, easier-to-install package that won’t break the bank, it’s a good choice.

PROS:

Compact size – fits under many seats
Class A/B sound quality
Great power (75W RMS x 4, 100W RMS x 4)
Bridgeable (175W RMS x 2 @ 4 Ohms)
Adjustable crossovers (hi/low 0-200Hz, 0-750Hz)
Great sound quality
Reduced noise design
MTX design quality & reliability
Adjustable high/low-pass crossovers
Great buyer feedback
5V capable RCA inputs
CEA-2006 Compliant
Includes MTX test certificate
Soft turn-on

CONS:

No speaker-level inputs
No remote level option
No auto-on remote feature
No RCA pass through jacks
Less efficient than class D models
No bass boost feature

At around $200 or so, overall I’d say it’s a good value and is worth checking out.

Head over now and have a look at the many happy buyer reviews left at Amazon.

5. Alpine KTP-445U Mini Amplifier – A good-sounding amp with tiny size for difficult installations

I’ve decided to include the KTP-445U here as well. While it doesn’t have the same high-end specs like other amps I’ve recommended, it’s a great sounding amp for more difficult installations. Some installations like pickup trucks and motorcycles are especially tough.

That’s where Alpine’s expertise provides a solution not just for extremely limited amp space, but for anyone wanting an amp that’s easier to install and draws less power.

As I explained in my detailed review of the Alpine KTP-445U, it’s an example of advanced engineering and satisfying sound quality in one of the smallest sizes in the world. This is a highly efficient class D amp that runs cool and provides 45W RMS to 4 channels. Not only that, but it’s bridgeable to 90W RMS x 2 channels, too!

Despite that, it runs cool and draws minimal current. During installation you can even connect it directly to standard head unit wiring for the power supply, if using it for typical (average power) systems like driving 4 full-range speakers.

It handles 2 ohm speakers as well.

The KTP-445U is one of the smallest car amps in the world today. Despite measuring only a tiny 7 7/16 x 1.5 x 2.5″ (189 x 38.2 x 64.5 mm) in size, it’s capable of delivering great sound and good frequency response. It’s so small it’s about the size of a laptop power supply – yet delivers enough power to drive a full system in your vehicle!

What’s particularly great (in my opinion, based on my experience) is that it also provides both speaker level and RCA inputs. It’s a great match for both factory and aftermarket car stereos.

Don’t have 4 RCA jacks, only 2? That’s no problem, either. The 2/4 channel switch allows you to drive the additional rear speakers without a problem.

Alpine’s design is especially effective at reducing noise levels and to maximize sound quality while providing crisp sound and the kind of high-end treble response you’ll enjoy.

Of course, quality often doesn’t come cheap, but this little guy is affordable, priced near $150 or so depending on where you shop.

PROS:

Ultra-compact – fits in dash or nearly anywhere!
Excellent for factory system upgrade
High-efficiency class D design
2/4 channel input switch
Good power (45W RMS x 4 @ 4 or 2 Ohms)
Bridgeable (90W RMS x 2 @ 4 Ohms)
High-pass 60/80/120Hz crossovers
Great sound quality & reduced noise
Great Alpine build quality
Easy to install
Great wiring and signal harnesses (universal)
Accepts higher-voltage signal (12V max)
Great for motorcycles, outdoor vehicles, and boats
Excellent buyer ratings
Nice brushed metal finish
Handy mounting tabs
Includes basic mounting accessories
CEA-2006 Compliant
Auto turn-on for speaker level inputs

CONS:

No low-pass crossovers
Not suitable for driving woofers
No remote volume option
No auto-on remote feature
Auto turn-on won’t work for RCA inputs
High-pass crossover not adjustable – fixed to 4 pos.

Buyer reviews are great and based on my personal experience, you’re going to love it. It’s an installer’s dream come true, too!

I’ve found some of the best pricing anywhere here at Amazon.

The DIY Car Amp Rack Guide – How To Build Your Own Car Amp Rack In One Day

September 16, 2020April 28, 2018

Making your own DIY car amp rack may seem like something that’s out of reach. Or maybe you don’t know where to begin and you’re worried you’ll have to pay someone else a lot of money to make one.

Here’s an affordable way to build a do it yourself (DIY) car amp rack in one day.

I still use these same car amp rack plans in not just customer vehicles but my own, too! I love how simple but professional looking they are. It’s pretty cool getting compliments on how great and pro-level it looks.

Now you can build your own car amp rack that looks great and is affordable, too!

Contents

Infographic – Basic amp rack how-to guide

Getting your tools & supplies ready – what to know first

Tools you’ll need

You’ll need a number of tools to do the job well:

Phillips screwdriver
Cordless drill + Phillips bit (not essential but highly recommended) or standard electric drill
Pliers – I recommend square-jaw, locking, or other types but needle nose can work, too
Scissors for cutting material + utility razor (optional)
Staple gun (optional)
1/8″ drill bit suitable for metal
Basic tape measure or measuring tape
Something to take notes with
Permanent marker

As you can see you won’t need many tools. That’s part of the reason this approach works well. I’m hoping to help you carry out this with as little money and hassle as possible.

If you can, borrow any tools you don’t have from others to save money and time.

For many basic items you can get great deals at stores like Harbor Freight Tools, Wal-Mart, or even the Dollar Tree $1 store. If you shop carefully things like pliers can be found for around $2 a pair.

A staple gun can be bought when you go shopping for the materials you need, but it’s completely optional. They can drive strong staples into wood unlike a standard stapler and they’re great for stapling fabric securely. You can pick up a staple gun for close to $15 or so.

Will I need a power saw?

Fortunately, most likely you won’t need a saw. In the sections that follow you’ll need to shop for wood, but if your city has a Home Depot or Lowe’s hardware store, the great news is that they offer free wood cutting when you buy wood! And that’s also that much less work you have to do, too.

Parts to pick up before installation time

Metal mounting brackets (straps)

Car stereo metal mounting straps are fantastic for installation and will make building & installing an amp rack much easier. You can buy them finished in black, which I highly recommend, or with the standard metal finish. 9″ straps are fine in most cases, and you can buy a 5 pack or similar to save money. You’ll need at least 4 straps if using these.

One item I highly recommend is excellent metal mounting straps like these Metra BS9BK. They’re FANTASTIC for many types of car audio installations and are used very often by professional installers.

They’re strong enough for mounting an amp rack securely but are flexible enough to bend into odd shapes for more challenging installations.

I’ve used these for years to install almost anything in places you would think were impossible to put a sound system in!

It may or may not be possible to find some at your local stereo shop or electronics store that carries car stereo accessories, so you really need to check beforehand. Expect to pay $10 or less including shipping, although some can be found for around $7-8 for 2-4 straps.

Note: Another option is to use standard metal brackets like “mending plates” that are stocked at local hardware stores. I’ll explain more about the pros and cons of those later.

Speaker carpet vs. fabric

Black automotive-grade speaker carpet (left) is great looking and durable. There’s no backing on it so it can be stretched and cut easily. However, you may have to order it, and it may cost more than regular fabrics like black felt (right) that you can find locally.

To finish your amp rack you’ll also need a good-looking & durable material to cover it with.

Backless automotive carpet (often call speaker box carpet) tends to be very durable and offers a great look. Colors like charcoal, dark gray, or mixed black colors are often available.

Otherwise, I recommend buying a good black fabric like felt. You can expect to spend $10 or so in that case, as it’s usually sold in 1 or 1/2 yards (1 yard = 36″). You may also find a different soft black cloth on sale while you’re there.

Suitable fabric can be bought often for a discount price locally from arts & crafts stores like Joann, Michael’s, and sometimes Wal-Mart.

Measuring installation space

Get basic measurements for the best place you find for installing an amp rack in your vehicle. Think in terms of fitting a large rectangle there, even if you don’t think a flat amp rack can be mounted on some areas that are curved or stick out. Don’t stress if there’s not a perfectly flat area available – that’s actually very common! We’ll cover dealing with curved or unusual surfaces later.

Begin by using your tape measure to find out how much space you have in your trunk (or cargo area, depending on your vehicle) where you can install a rectangular board.

The measurements don’t have to be super-exact but a close estimate of how much space you have available horizontally and from top to bottom. For example, measure from several inches below the rear deck of your trunk to about 1″ to the base of the trunk near the interior carpet or trim.

That should give you a good estimate of what to work with. Be sure to save in your notes the measurements you took.

Don’t forget the weight

As an assembled amp rack will be heavy so you need to be sure to measure the available space as if the assembled rack is resting on its bottom in the vehicle. T

Check for good places to mount the amp rack brackets

While you’re measuring, look for good places where you can fasten your mounting brackets when the amp rack is installed in the car.

Look for a section of the car’s metal body where:

It’s safe to drill a hole without damaging anything underneath (always check!)
The metal is sufficiently thick & strong enough.

In most vehicles, the sheet metal in the rear is the same thickness throughout, so that’s usually not a problem.

Planning your amp rack setup

Planning your amp rack setup: place your amps on your floor and use your tape measure to estimate how much room your amps will need for clearance with wiring & cables installed. Also allow some spacing beside the amplifiers (the top and bottom of the amp rack).

Put your amplifiers on the floor and line them up as you’d like them to be placed on your amp rack. Place them next to each other with enough space so that there’s enough clearance to connect power wire, speaker wire, and RCA cables as needed.

If you’re tight on space you may need to consider using 90-degree bends for the wiring and right-angle adapters for the RCA connections.

When you’ve got the amplifiers lined up with enough space, measure a rectangle with enough clearance before and after the ends of the amps and a little extra clearance from the top to bottom.

Keep enough space!

Don’t make the amp rack spacing too small – you don’t want it right up against the sides of the amplifiers.

You’ll want to allow 2″ space or more at the sides of the amps if your installation measurements earlier will allow for it.

Write down the measurements in your notes as you did earlier.

Your shopping list and tips

You’ll be able to buy nearly everything you’ll need in only a few trips, but planning ahead as much as possible will save money and keep the problems to a minimum.

Give yourself enough time during the day for running around town and dealing with traffic to get what you need. Start shopping early in the day or the before if you’d like to build & install your amp rack the same day.

I hate being stressed out and running into problems right in the middle of a project or installation, so take my advice and try to get what you need the day before if you can.

Be organized and write down or print out what you need before you go. Don’t be sloppy and cost yourself extra time, gas, and stress.

Materials list

Hardware:

With your notes, head out to your local hardware store for the following:

Spray adhesive
Metal brackets (if not using metal car stereo straps)
#8 Phillips head machine screws, 4-pack or similar
#8 washers, small package
#8 machine screw nuts
3/8″ pan head Phillips screws
3/8″ length self-tapping screws
Wooden board

3M Super 77 is a great spray adhesive. There are lower-cost adhesives available but in my experience, I’ve had problems with the adhesive being weak and the fabric can come off by itself. Super 77 usually costs close to $10.

I recommend this one for car audio projects. It provides a strong adhesive and it’s reliable unlike cheaper brands that fail or aren’t very strong. You do have to be careful to not get it on you or nearby objects when using it, however. You can 3M Super 77 Multipurpose Permanent Spray Adhesive Glue, Paper, Cardboard, Fabric, Plastic,...

Choosing a wooden board

You’ll need a wooden board like this to build your amp rack. In the building materials section of your hardware store you’ll find wooden boards that are about 1/2″ or so thick and usually come in lengths of 4 ft. or longer. Pine is the cheapest but is more prone to warping and is weaker than others, but it’s suitable if you’re on a budget. It’s not suitable for installations exposed to a lot of humidity or moisture.

Using the measurements you wrote down from planning your amp rack, buy a wooden board that’s the same or close width to what you measured. To save costs buy one with length closes to your length measurements for what you need.

Quick tip: To save time and hassle, try buying your supplies at Home Depot or Lowe’s if you have one nearby. They offer free wood cutting to customers in the building supply section, so you’ll be able to tell them the length you need and they’ll do it for you.

More about metal brackets

Mending plates and other metal brackets are sold in pairs or 4 packs for smaller sizes and individually or in pairs for the larger sizes.

As I mentioned earlier, if you’re not able to use (or buy) car stereo metal installation straps you might be able to get but with hardware store brackets.

Right-angle brackets and “mending plate” (flat) brackets are also helpful for assembling and installing your amp rack.

Unlike metal car stereo straps, mending plates are nearly impossible to bend. They’re very strong but the drawback is that they’re fixed in length and not suitable for curved or more difficult installation needs.

You can usually find them sold in packs of 2, 4, or 8 for a few dollars.

Fasteners

Self-tapping screws (left) make mounting brackets fast and easy if you have a cordless drill as they simultaneous drill a hole then screw into metal quickly. Regular pan-head screws (right) will work well for mounting your amps to the amp rack. Use #8 machine screws (below) and nuts with washers to fasten your mounting brackets to the rack securely. They’re better suited for this than using only pan head screws.

Machine screws work with nuts and washers. They’re great for attaching brackets to your amp rack board, for example. They come in packs with standard sizes. I normally use #8 machine screws for many projects.

Fabric/covering material

If you’re going to get fabric locally instead of ordering it, arts & crafts stores are where I’ve often found discounted black material I could use for building amp racks.

Ideally, try to get a material with a dark color that’s durable and stretchy. I recommend a strong felt material or similar basic fabric.

Be sure to ask the cashier or attendant for suggestions about what you’re planning to build. Honestly, sometimes they’re helpful and other times they’re fairly clueless when it comes to good suggestions, but at least if something is on sale they’ll normally let you know.

If you’re planning to buy fabric instead of backless speaker box carpet, try checking the clearance tables while you’re shopping. I’ve often gotten fabrics at a MUCH lower price by doing this. There’s a good chance you’ll find a deal! Black fabric is very common and should be easy to find.

Remember that fabric is normally sold in units of 1 yard (36″ in length) or 1/2 yard (18″ length) in many craft stores.

You’ll need to do just a bit of math to figure out how much you need. Try not to get exactly the same length as your measurements.

I strongly recommend you have a bit extra if it’s your first time working on a project involving fabric and a spray adhesive. Typically I use about 2 yards of material and have a small amount left over when I’m done.

The height is nearly always much more than I need.

Making your amp rack – covering the board

After having your board cut to the length you need and planned for its time to put the finishing touch on it and assemble the amp rack.

Now that the board is a length that will fit into the installation space you have and that will allow enough space for your amp wiring & cables its time to cover it and make it look nice.

Find a good place to work where glue overspray won’t get on surrounding things indoors.

Place your board on the fabric and trim it to a good size, allowing several inches past the board of extra fabric on each side. I recommend allowing at least 6″ or so, which you’ll trim as needed.

Follow the rest of the steps in the diagram below.

Spray adhesive is very hard, if not impossible, to remove from your clothes and other materials so be very careful when using it. Use light, consistent spraying strokes. You don’t need to use a tremendous amount, but it does help to spray some on both the wood surface as well as the fabric you want to glue.

Using adhesive on both surfaces gives an even stronger bond. After spraying, waiting about 15-30 seconds and lightly touch the glue to see if it is tacky.

If so, tightly pull the fabric over and onto the wood area you sprayed. Then rub the fabric firmly with your palm for a few moments to make sure there’s good adhesion.

The fabric, no matter how well you tried to trim it, will likely overlap each other a lot. If you have a utility knife with a sharp blade that makes trimming a bit easier than using scissors.

Otherwise, slightly pull up edges where needed, cut with the scissors, and place it back into place.

You may need to reuse the adhesive spray on some parts. It’s a bit tough to do in small sections but by quickly and gently tapping the spray nozzle you should eventually get the hang of it.

Putting it all together

Now that you have the board covered it’s time to assemble it.

Drill a 1/8″ (or close) hole in each corner and mount a bracket/strap to each hole using a #8 machine screw + washer on the top (amp) side and on the backside use a washer and nut.

Tighten securely using pliers while keeping the machine screw from turning by holding a screwdriver.

Once all the mounting brackets are in place and facing the direction you need them to be, place the amps on the board and mount them using the measurements for spacing you wrote down earlier.

Be sure to leave enough length for the mounting brackets to reach the mounting points in your vehicle that you found during the first steps.

Excess bracket length can remain hidden behind the amp rack for less hassle when installing and for a neater appearance.

Installation – Mounting your rack

Ok, it’s time for the “fun” part! Carefully put your assembled amp rack in the vehicle and begin the “fitting” process.

If you’re mounting it vertically, put as much of the weight at bottom of the vehicle and begin seeing how your brackets will fit to try to get the brackets parallel to sheet metal for mounting.

If you’re using bendable metal straps as I recommended, bend those such that they will allow the amp rack to rest on the straps when in the car.

When that’s done, hold the amp rack in place and begin doing the same for the top. Keep using trial and error until you have a pretty good way for the amp rack to rest securely in the vehicle and to have enough attachment points for the mounting brackets.

Once that’s finished, begin trying to use your cordless drill to drive the self-tapping screws through the brackets and into the body.

I highly recommend using washers on the screws to fit well over the bracket’s hole and keep the fit very tight. This is especially important in a moving vehicle as they vibrate quite a bit and screws may loosen over time.

If you’re having difficulty doing this step while holding the amp rack in place, then use a permanent marker to mark the bracket holes where you’d like to use the screw, remove the amp rack, then drill the screw holes alone.

Then you can return to place the amplifier rack and more easily fasten the screws either with the cordless drill & bit or with a screwdriver.

Taking your amp rack to the next level…on the cheap!

Want something truly unique? You can use an LED light kit (often below $20) to add accent lighting to your cool amp rack. It’s pretty simple to do and will really get compliments from anyone who sees it.

A fantastic idea is adding accent lighting to your sweet-looking new car amp rack.

Using an awesome low-cost LED lighting kit like this one under $20 mounted above the amp rack in order to glow down on them will give an incredible look and really make it shine.

I’ve done this several times (including putting an acrylic clear window in front) and people gave me lots of compliments!

Neon and LED lighting systems are lightweight so you should be able to install them using only zip ties. Overall, it’s usually very easy and it can be done on a budget if you shop carefully.

Wiring is simple as many kits can be powered by +12V directly and wired to a relay to switch on and off with your car stereo using the remote-on wire.

DIY car amp rack plans cost estimate

Here’s a good estimate of what you can expect to pay for all materials (not counting tools) depending on where you shop. Don’t forget to check your amplifier packages for screws you can use, as some include a 4-piece set.

Item Est.	Cost
Wood	$10.00
Fasteners	6.50
Metal straps	9.50
Fabric	12.00
Spray glue	9.75
TOTAL:	$47.75

Additional info

Take my guide and give it a try! It feels awesome when you get it all together and see how great it looks. Your friends and other people you meet will give you compliments and that’s a fantastic feeling, believe me.

Thinking about adding LED lighting? Be sure to check out my detailed car interior LED light kit installation guide.

If you’re still deciding what to do about buying amps and you’re on a budget, have a look at my great budget amplifier guide here.

Kenwood KAC-M1824BT Review – A 4 Channel Bluetooth Marine / Motorcyle Amp That Makes Music Fun

September 17, 2020November 26, 2017

Kenwood KAC-M1824BT review featured image

Shopping for an amplifier for a boat or even a motorcycle is especially challenging.

What some people don’t know is that electronics installed in vehicles exposed to the elements and air moisture (especially boats and other marine vehicles) are subject to additional problems like corrosion.

In my Kenwood KAC-M1824BT review, I’ll go into great detail about how the marine amplifier measures up and if it’s right for you or not.

Is it just hype, or is it a great way to enjoy easier music while you enjoy the outdoors? Read on to find out more.

Contents

Kenwood KAC-M1824BT – First impressions

What really strikes me at first is the small size and the great-looking finish.

The amp measures a tiny 6-11/16″ W x 1-13/16 H x 3-7/8″ D. The first thing that strikes me (besides the amazingly small size) is the build quality and how good it looks.

The connectors (including the RCA jacks, too) are protected from moisture and salt or dirt by plastic covers you can remove as needed. It’s a great touch I like considering where the amp may end up installed.

The fit and finish are great: parts line up correctly, indicating great that Kenwood quality which the brand is known for.

Kenwood isn’t reselling another brand’s electronics with some small cosmetic changes and putting their logo on it as some cheaper brands are doing nowadays.

I’m glad. I wanted to be impressed by this little amp – and I was not disappointed.

I absolutely love how Kenwood is bringing new technology into play in a miniature package that can be installed nearly anywhere!

Build quality is great! The product is assembled professionally and compactly – no signs of the sloppy handiwork prominent in cheaper amps. The wiring harness connector (shown on the right) provides wiring outputs for the speakers, power, and remote on lead (if used, see notes below). To the left is the USB charging jack that allows you to charge your phone while you play music!

More about the amp and what it can offer you

Audio amplifiers haven’t changed much over the years. They’re powered by a +12V supply and connect to speaker level wiring or RCA cables on a head unit for an audio signal. Additionally, they’ve always been somewhat large and heavy.

At least that’s how it used to be – the Kenwood KAC-M1824BT is actually significantly different in a way that really gets me excited for all the installation possibilities and great ways it can be used.

Bluetooth is a fantastic way to play music, too.

The amplifier is neat and compact, with RCA jacks, the wired remote connector, and audio controls on one end. The other end features the wiring harness for speaker level inputs, power connections, and speaker outputs. End caps are included to protect the unused connectors from allowing debris or water inside.

Marine amplifiers are basically the same as car audio amps with a few additional changes to make them durable when exposed to harsher environments like those in a boat or outdoor vehicles.

A unique way to enjoy music – directly via Bluetooth!

Unlike other amplifiers, Kenwood has created a cool new design that makes installation and enjoying music much easier for you.

You’re no longer forced to install a head unit in addition to installing an amp when you need more powerful and clear sound. And you won’t have to deal with an old, low-quality (or broken!) stereo you’ve already got.

Not only that, if you’re reading this there’s a great chance you’re just like me – I’m constantly listening to streaming music or music files on my phone.

I love the amazing choices I can enjoy from Pandora, Spotify, and yes, even YouTube! The possibilities are fantastic because I’m only limited to what my smartphone can play – which is pretty much anything!

The amp basically allows you to enjoy music in 3 ways, depending on your installation and usage needs:

Connect to an aftermarket stereo using RCA cables
Connect to a factory or aftermarket stereo that doesn’t have RCA jacks by using speaker-level inputs
Connect to Bluetooth

Note that it’s not mandatory to connect to a stereo at all. That’s what I like so much about it – you can have a completely hidden sound system installed away from thieves who are just looking for an easy opportunity to steal a nice stereo.

By using only your smartphone as a music source it’s possible to use no stereo or completely remove the existing one!

Bluetooth connectivity

The KAC-M1824BT features a wired remote which acts as a remote control for your phone’s music app and for pairing. Pairing itself is easy as long as you follow the instructions outlined in the owner’s manual:

Press the SRC button on the controller to enter Bluetooth mode
Press and hold the “>||” button
Use your Bluetooth on your phone to connect to the amp

The wired controller is easy to install using the flush-mounted holder or double-sided tape (both are included). Using the remote, you can switch between songs in the blink of an eye! Even better, if you activate Bluetooth mode you can control tracks, volume, play/pause features, and so on without even touching your smartphone! Very nice!

When paired, the controller’s backlight illumination will light up in blue and you’re ready to go!

From there on out you won’t need to use the same pairing process anymore – just turn on Bluetooth on your smartphone it will connect automatically. Up to 3 devices can be paired/stored in the amp.

The remote works just like any remote control: for many music apps on your phone, you can control playback/pause, skip forward and backward, and even adjust the volume!

I love the feature as it’s extremely convenient. You can store your phone and won’t have to touch it – just use the wired remote!

Bluetooth sound quality

Audio quality over Bluetooth is great and it supports the A2DP and APT-X protocols for high-quality, higher-bitrate audio sound reproduction.

If you’re not already familiar with those, they’re more updated versions of protocols used in Bluetooth software to enhance how much of a music signal can be reproduced. Basically, they’re currently one of the best protocols available.

I personally use APT-X as my Sony Xperia phone supports it, and I love how great it sounds when used with a receiver that supports this feature.

I wasn’t expecting APT-X support, as it’s not that common – so this is a nice surprise for sound quality enthusiasts.

Bluetooth connectivity is reliable, by the way, and I don’t have any complaints about that itself – so nothing to worry about there.

Amplification technology used

The Kenwood KAC-M1824BT uses class D technology which is a modern super-high-speed switching approach used to increase efficiency. That’s what makes the amazingly small amp size possible.

Because of this (efficiency levels near 90%!) a class D audio amplifier uses far less electrical current and generates much less heat. Consequently, you can use smaller power wire during installation.

It’s important to understand that a poorly designed class D amp is noisy and suffers from lower sound quality. Kenwood’s design features a well-engineered approach and I’m very happy with what they’ve done.

Sound quality is very good and I definitely recommend it for all but the most demanding of listeners. But then again, if you’re installing the amp in a boat or motorcycle sound quality is something that is compromised already as listening to speakers in an open-air environment means having to deal with a lot of quality and volume loss anyway.

Overall sound quality

Kenwood’s specifications state a signal-to-noise ratio (SNR) of 90dB although the industry-certified CEA-2006 specs are rated at 74dBA. Although that may sound low, in practice the SNR ratio is measured at 1 watt/14.4V and actually greatly improves as more power is delivered.

So when you’re actually driving speakers with moderate or high volume the actual noise level will be very low – well within the 90dB SNR range.

Overall, during testing the amplifier sounds very good, I’m happy to report. Using my reference test tracks I could hear great dynamic transients and crisp, responsive sound.

I’m a big Spotify and Tidal music fan and normally listen using a higher fidelity music quality option. When used with the Kenwood amp I wasn’t disappointed and the sound I’ve become accustomed to came through loud and clear.

The amplifier is actually quite small and well-packaged. Quality is great throughout and doesn’t disappoint. I was pleased with nearly everything about it, aside from a few audio control features that I thought should have been provided (see below).

Installation and audio source functions

Switching audio sources

I like how simple it is to switch between the stereo inputs or your smart phone’s music – just push the SRC button and it switches between them.

The backlight changes to red when the RCA or speaker level inputs are in use and blue when Bluetooth is selected.

Installation

Installation is very straightforward like any standard car stereo amplifier. You’ll need to connect the +12V supply wire, remote on lead, ground wire, and RCA cables if using an aftermarket stereo.

When using speaker level inputs, there’s an added bonus: the amp features a nice auto-sensing option which means it will turn on automatically when a music signal is sensed and it won’t require you to use the remote-on wire.

The outward mounting tabs mean the amp is pretty easy to mount on a board or other suitable location (4 mounting screws are provided). Two 13.5″ wire ties also help with installation.

The wiring harness is actually fairly long, measuring about 59″ so unless you’ve got a longer reach to make that’s pretty helpful.

Included are 2 wire ties, the wiring harness, 4 mounting screws, and a mounting base for the controller. Double-sided adhesive for surface mounting of the remote controller holder is included too.

Since it’s so small in size you can mount it in far more locations than conventional amplifiers. This is a definite plus, and for that reason, I think it’s a great choice for many.

The average person who lacks installation experience can face some hard – and discouraging – obstacles when trying to install a larger amp in tight spaces.

Why fight a battle you don’t have to?

Sound controls (and what I don’t like)

Ok, this is the one area in which I have a few complaints. Although the amp sounds great and I love the Bluetooth controller’s simplicity, you’re limited to a front/rear fader in the form of a small dial on the front of the amp.

The fader control only applies to the Bluetooth source. It doesn’t apply to the RCA input signals & speaker-level inputs.

There are no high or low-pass filters available unlike many amps available today, and that’s a shame. By eliminating this option Kenwood has restricted it to more basic setups in which full-range speakers are used.

I also noticed the amp doesn’t feature any kind of bass boost or equalization options like others, unfortunately.

Because of this, if you’re driving tweeters on are using speakers which need a high-pass filter to block low-end and distorting bass they can’t handle, you’ll have to rely on traditional passive crossovers to do so.

However, if you’re the average person just trying to get good sound to full-range speakers it’s not an issue.

Marine / environmental qualifications

The amplifier is manufactured with a conformal-coated circuit board and is suitable for not just marine applications but in any environment that may introduce dirt, moisture, salt, or other potentially corrosive substances.

But don’t worry, it’s just as home in any car or truck, too!

Note: the amp is resistant to moisture but it’s not waterproof.

USB charger port feature

The amp cannot transfer audio with the cable, but you can charge your smartphone through it as you enjoy music. Just use the 1A 5V charging jack at the end of the amp.

It’s a convenient feature that works well, but you’ll have to purchase the USB extension cord yourself.

Power ratings

Kenwood’s power ratings are accurate and confirmed, as the company is CEA-2006 amplifier compliant.

Rated power delivered is:

45 watts RMS x 4 at 4 or 2 ohms
90 watts RMS x 2 bridged at 4 ohms (4-ohm stable in bridged mode)

This is sufficient for average coaxial (2-way) speakers that most boats or motorcycles can use. You could use it with component speakers as well if necessary, although if you need higher performance you might want a more powerful amplifier.

Review score & summary

This is a fantastic amp and a great way to build a small system that’s affordable gives you great-sounding audio in nearly any installation.

It’s a great choice and one of the best in its class for the money. Head over now to find out why it's a best seller over at Amazon.

Overall

8.6/10

Overall quality - 9/10
9/10
Sound quality & performance - 8.5/10
8.5/10
Installation ease - 9/10
9/10
Features - 7.9/10
7.9/10

A compact, well-performing amp with pleasing sound quality and Bluetooth music connectivity. A great basic amplifier for boats, motorcycles, cars, or trucks.

The Kenwood KAC-1824BT is a very compact amp that is well worth the money. At only 6-11/16 x 1-13/16 x 3-7/8″ in size installation in tight spaces a breeze. Sound and performance are great, with both 45W x 4 or 90W x 2 power options. Bluetooth pairing is simple and reliable. Construction and design are good with no quality issues. Unused connectors are protected by covers included in the box.

Because of the unique design, you’re able to use the amp with only your smartphone and no stereo if desired. The intuitive remote makes controlling music apps and volume really convenient. Unfortunately, there are no crossovers or bass boost features, so the amp is best suited for full-range speaker systems – you won’t be able to drive woofers with it. Overall, it sounds wonderful and is really worth the price – a great choice for boats, outdoor vehicles, or just about any application where you want a quality basic amplifier with Bluetooth connectivity.

Pros

Remote is easy to use and well-labeled
Speaker level inputs
Auto-sensing if speaker inputs are used requires no remote-on wire
Can control music apps via Bluetooth
A2DP, APT-X audio quality support
Great overall sound!
Very small size
Supports up to 3 paired devices for Bluetooth
Bridgeable to 2 channels (90W x 2)
Quality design
Good signal-to-noise ratio at typical volumes
Conformal coating on circuit board
Protective covers for unused connectors to block exposure
Clear instructions with diagrams
Reliable Bluetooth connectivity
No apps required to use
Built-in USB phone charger port
Wired remote is simple to use & install
Remote has nice backlighting and good “feel” to buttons
Conformal coated circuit board

Cons

Fader dial is only applicable to Bluetooth
No 2/4 way “Y” switch to run all 4 channels from 2 RCA inputs
No high or low pass crossovers
No bass boost available
Auto-sensing for turn-on only works for speaker level inputs
USB charger port requires extension cable (not included)

Check current price at Amazon