Rockville RXA-F1 4 Channel Amp Hands-On Review: A Budget Winner You Shouldn’t Pass Up!

Rockville RXA-F1 4 channel car amp review featured image

I’m a big fan of 4 channel amps for a lot of reasons. Seeing another budget amp maker like Rockville on the market really got me curious.

I couldn’t wait to get my hands on one, install it, and put it through the paces in everyday use. Fortunately, I can say I found some nice surprises I didn’t expect.

In my hands-on review of the Rockville RXA-F1 4 channel amp I’ll tell you what I found, how it sounds, and if it’s worth the money. I’ve even opened one up to show you what’s inside.

Contents

Basics first: Getting to know the Rockville RXA-F1

Rockville Phenom series amplifier examples

Several of the best-selling Rockville amplifiers from the Phenom model line shown with both true RMS power ratings (2 different measurements are used). Phenom series amps are highly affordable class A/B amps with a conventional design.

The RXA-F1 amplifier is one of a number of members in Rockville’s Phenom family of amps. It’s a best-selling line of amplifiers based on traditional class A/B technology design. What helps set the Rockville line of amps apart from other budget brands are the Consumer Electronics Association (CEA) 2006 industry standard power ratings.

That’s a great thing as way too many budget-priced amps still use misleading specs such as “peak” or “maximum” power. CEA-2006 ratings mean an amp is certified to deliver the rated power advertised.

They also list (as do some other manufacturers) another RMS power rating that’s measured differently. Not to worry though as I’ll explain more about that later.

In the Phenom family you’ll find several types of amplifiers:

  • 4 channel models
  • 2 channel models
  • 5 channel models
  • Mono (single) channel bass amps

The company also offers a budget-priced line called the DB series too. However, the Phenom series provides slightly better sound quality specs and features the DB series doesn’t (although the DB series are still a good choice as well).

The Phenom series models are only a few dollars more than DB models so they’re really hard to pass up. The main difference, however, lies in the features as the Phenom series offers more.

Most models are good sellers in today’s market and sell for around $90-$125 or so depending on the model & power level. They’re also good-looking, too!

More about the RXA-F1

Price-wise, the RXA-F1 is definitely in the affordable range: No products found. Not bad!

Image showing a side by side comparison of the Rockville RXM-F3 marine amp vs RXA-F1 car amp

The RXA-F1 car amp is also available in its twin version the RXM-F3 marine amp. Both have the same general design & power ratings, too. However, the RXM-F3 adds a protective coating to the circuit board and a microphone loudspeaker feature.

Its twin, the marine version RXM-F3 is almost identical aside from the different cosmetic package, conformal coating to protect the circuit board, and a microphone loudspeaker feature.

The RXA-F1 is also bridgeable. CEA-2006 power ratings are up to 95W RMS x 4 at 2 ohms, 65W x 4 @ 4 ohms, or 200W x 2 RMS (CEA-2006) power. However, the amp can deliver a fair amount more power than the CEA-2006 ratings.

I’ll explain more about that as we go.

Unboxing and first impressions

Image of unboxing the Rockville RXA-F1 amplifier with contents shown

I finally got my hands on it! My Rockville amp finally arrived and I got started unboxing right away. Inside the box was the amp’s production certificate, accessories, and manual. It’s well-packaged too, with snug foam inserts holding it in place. I really prefer the foam over styrofoam any day.

Upon opening the box I got a good impression. We’re off to a good start, so far!

Immediately after opening it up you’ll find the amp’s production certificate stamped with both the CEA-2006 power ratings and the serial number inside. It’s a nice touch.

Granted, it’s not as detailed as the production certificates provided with some much more expensive amps (like those by Rockford Fosgate, MTX, and so on) but that’s ok.

The certificate gives the impression that each amp has power measured individually during production but that’s not the case. Regardless, it’s not really an issue.

What we really care about is having the amp meet its rated power output as advertised. I’ll cover that a bit more in detail later.

Front view of the Rockville RXA-F1 car amplifier packaging

The RXA-F1 comes neatly packed in a good-looking box with secure packaging to keep it safe inside. However, despite being marketed with true power ratings (CEA-2006 & standard RMS specs) they still list the power on the box as “peak power.” Why? I don’t get it.

All in all, my RXA-F1 was well-packaged and everything looked good. Despite being a budget amp line I’m happy with what I found after opening it up. What I don’t care for is the use of the peak power ratings on the box like less reputable amps use.

I just don’t get that in this day and age. That’s more of a nuisance though and not a “real” issue.

What’s in the box?

Image showing the Rockville RXA-F1 package contents including accessories provided

As unboxing is straightforward let’s get right to the good stuff: What comes in the box?

You’ll find the following inside:

  • A nice owner’s manual
  • Warranty card (1 year warranty)
  • Speaker level input harness adapter
  • Four #8 1″ pan head mounting screws with rubber washers
  • The amplifier

The included screws are #8 pan head screws and should work well for nearly all installations. I used them myself during testing. They’re definitely the right length (no complaints here).

Installer tip: I recommend you drill pilot holes before driving the screws into the mounting surface when mounting it.

That’s because driving screws into some materials without pilot holes (using a 1/8″ bit) can cause them to split & crack badly. For soft woods like pine if making your own DIY car amp rack however that’s usually not a problem. For other materials like medium density fiberboard (MDF), particle board, or fiberglass it can be a big problem!

The included rubber washers are used between the screws and the amp’s mounting feet on the outside ends. That helps prevent marring of the plastic mounting feet and allows having a lot really secure mount too.

So far, so good. One thing I did notice, however, is that the hex wrenches you’ll need to tighten and loosen the wiring terminals aren’t included. The sizes you’ll need are 4mm (5/32″) and 2mm (5/64″).

Bondhus 12232 8 hex wrench setAs the amp doesn’t include the 2 hex wrenches you’ll need to use on the wiring terminals, you’ll need to pick up a decent cheap set like these I found at Amazon.

The great news is that you can use up to 4 gauge wire in the power terminals.

Build quality and checking fit & finish

Image showing close up aspects of the Rockville RXA-F1 4 channel amplifier from different angles

Close-ups of the RXA-F1 from different angles to show the build quality & fit and finish you can expect. Overall, it’s a well-built amp that looks better than I expected for such an affordable amp. It’s also very attractive despite using a fair amount of plastic on both ends. There’s a nice black brushed metal center inlay that I really like.

As I always do, I gave it a good “once over” to check the build quality, assembly, and find any noticeable flaws. Overall, it’s a good-looking amp and well made.

There’s a lovely black brushed metal centerpiece on the top of the amp with the Rockville logo and emblem. It’s a nice-looking touch and has a bit of class to it.

General design and finish quality

As car amplifiers go, it’s the same tried-and-true design: An aluminum heatsink chassis. However, the Phenom series of amps have a slightly unique design in that the sides are a dark gray instead of black like the top. There are also some false hex-head chrome screws in the centerpiece which add another nice touch.

Front and rear end sections are made of plastic and serve as the mounting feet, which is my only real gripe (metal mounting feet are much more durable and can take more force without warping or cracking.)

Overall, fit and finish are very good. It’s a good-looking amp and you might guess it’s more expensive than it really is if you didn’t know better. I like it!

The downside of being a budget amp is that to keep costs low older technology is used. This means unlike some of today’s more compact amps the trade off is the amp is bigger. Just something to be aware of before buying.

A note about budget amp quality

As I’ve own and have tested several Rockville amps, I have noticed a few minor quality control issues. In 1 or 2 amps I’ve had a dial or two (gain or other adjustment dials) were a bit misaligned with the end panel opening. However, that’s a fact of life sometimes for budget products.

Overall I’ve been pretty happy with the quality and with the RXA-F1 is no exception.

Front and rear panel details

Image showing close ups of the front and rear ends of Rockville RXA-F1 amplifier

Shown: Front and rear panels with controls and wiring connections for the amp. For a budget amp, it’s actually very good. Wiring terminals need hex wrenches to use them, but give a clean, solid, and reliable connection you’ll like. RCA input jacks and the crossover controls are easy to understand and well laid out.

Wiring terminal quality & installation notes

To be a budget-priced amp, you’d think you’d get the same inexpensive wiring terminals that so many other amp manufacturers use. That’s not the case here, and I’m really happy to see that!

Wiring terminals use a solid machined metal design where instead of using a simple vertical screw and square contact like others, you’ll get a solid 360-degree opening. Hex head screws tighten within each wiring terminal for a very secure and clean connection point.

In testing I found them to be reliable, great for avoiding stray wiring, and good-looking too. While the openings do face out at a very slight downward angle (only a few degrees), in practice they’re still easy to use.

Note! Don’t use a cordless screwdriver or drill to tighten the wiring terminal screws. You could potentially strip the screws or break your hex bit. I recommend doing it the “old-fashioned” way: by hand.

A standard sized 60 amp automotive fuse is replaceable and conveniently mounted between the terminal strips. Labels are clear and easy to understand, although the bridging labels aren’t provided for some reason.

Probably due to the limited amount of space. Bridging is easy – just check the owner’s manual to be sure you’re using the correct terminals (Left channel positive & right channel negative).

The control panel & audio jacks

Rockville RXA-F1 amplifier controls and inputs labeled diagram

The Rockville amp’s control & input panel is jam-packed with good stuff! Above is a labeled diagram to help you understand it better.

Honestly, in the case of this amp, it’s a bit surprising how much is packed into the control & input panel end. There’s quite a bit to explain here so I’ll start by covering the basics. I’ll leave the more advanced features to a separate section later in my review.

The control & audio input end of the amp provides the following inputs, outputs, and control features:

  • Speaker level input harness (provided) and RCA front & rear input jacks
  • RCA pass-through jacks for connecting to more amps
  • Front crossover switch: Ch. 3/4 Clone, full-pass, and high-pass options
  • Front crossover adjustments: High pass frequency
  • Rear crossover switch: High-pass, full pass, and low or bandpass options
  • Rear crossover adjustment: High, low, and bandpass high/low options
  • Status & protection indicator light
  • Front & rear gain level adjustment
  • Rear channel bass boost adjustment
  • Crossover frequency multiplier switch: 1x/10x positions
  • 2/4 channel input mode switch

Each end of the amplifier also has 2 plastic areas resembling a grill that act as vents for cooling. At the bottom and next to each vent area is a plastic mounting foot as well.

Crossover controls

While it might seem confusing at first, in all reality the controls are pretty straight forward. Fortunately the owner’s manual is really helpful at explaining everything.

You have the following flexible crossover modes:

  • Front channels: Use in full range, or high or low-pass mode (via the clone switch option)
  • Rear channels: Bandpass, high-pass, low-pass (with bass boost option), or full range

The 12dB/octave high-pass adjustable frequency range is 50-300Hz (1x mode) or 500Hz-3KHz (10x mode). The low pass range is very generous: You’ll get a range from 50Hz to 3KHz with 12dB/octave cutoff also.

A bass boost is available and offers up to +12dB of adjustable boost. However, it’s only available on the rear channels. Likewise, the bandpass filter mode is only offered on channels 3 & 4 as well.

You’re not restricted to only the specified adjustable cutoff frequencies, either: Push the crossover multiplier to get a range that’s 10x the listed numbers (I’ll cover that in more detail later).

Speaker level inputs – Another cool feature!

Image showing a Rockville car amp speaker level input harness

Rockville Phenom amps provide speaker level inputs in case you don’t have RCA jacks handy on your head unit. Factory radio? No problem! In fact, to my surprise, there’s an auto-on remote feature built in when using this.

I’ve got to hand it to Rockville: I didn’t expect an auto-on feature to be available. While it’s a feature I’ve seen in more expensive amps it’s a surprise to find in an amp under $100.

When using speaker level inputs, you won’t need to connect a remote on wire! There’s a cool feature built in where the amp will automatically switch on or off when it senses a high-level signal from your stereo.

While that’s excellent and can save you a lot of work, there’s a minor gripe I have: Front and rear speaker level inputs aren’t labeled in the owner’s manual for some reason.

The +/- speaker input wiring is labeled on the amp, so you’re good there. However, the owner’s manual doesn’t tell you the front/rear wiring colors, so you’ll have to sort through that at installation time.

The Rockville’s amp guts revealed! What’s inside?

Closeup internal view of the RXA-F1 Rockville 4 channel car amplifier guts and circuit board

Close up view of the RXA-F1’s internal components. 1) The front-end stage of the circuit board (inputs, crossovers, and controls), 2) the switching power supply, and 3) one of the output stages of an amp channel.

To help you get a better feeling for what you’ll be getting if you buy one, I opened my amp to show you all the gritty details.

While the Phenom series of car amps are able to offer good power and features that has to come with compromises, just like any other value-priced electronics. To keep costs low, Rockville uses a modern version of the proven class A/B amp design.

While you won’t get the ultra-compact size and efficiency of modern class D amps (which you’ll pay for more, by the way, in many cases) that’s a fairly small trade off you’ll have to live with when saving money.

Overall, after giving it a close look-over I can say it’s well done. While it’s a single-sided board (conductive traces are on the bottom of the PCB) there’s heavy use of solder on the traces for extra conductivity and current flow with less resistance.

It’s a well-designed board for this price range.

Design specs & notes

Internally, the amp uses a single-sided printed circuit board (PCB) and through-hole components with a bit of hand assembly. While higher end brands are super small these days and use specialized semiconductors and chips, Rockville’s design uses off-the-shelf components for the most part.

The fact that their design doesn’t use the latest, fanciest, or tiniest parts isn’t a problem at all. That’s because while the design has to be that way to cut costs, in fact, the result is still a well-done and great sounding amp.

Even today many audiophiles use through-hole components for high-end audio boards so it’s not an issue.

Standard bipolar output transistors are used. Undervoltage & high-temperature protection is built in as well.

The adjustable control potentiometers (used for gain, crossovers, and bass boost levels) are of good quality, too.

Note: The company also advertises that the Phenom amps use audiophile-quality capacitors and feature a “class G” design.

Basically this means while it’s a traditional class A/B amp, the power supply reduces output depending upon power needs to reduce waste and help improve overall efficiency.

Specifications

Rockville RXA-F1 Specifications
  • CEA Compliant Power Ratings:
    • 260 Watts (4 x 65 Watts) at 4 ohms and 1% THD+N
    • 380 Watts (4 x 95 Watts) at 2 ohms < 1% THD
    • 2 x 200 Watts bridged @ 4 Ohms < 1% THD
  • RMS Power Ratings:
    • 800 Watts (4 x 200 Watts RMS) @ 2 ohms
    • 800 Watts (2 x 400 Watts RMS) @ 4 ohm Bridged
    • 500 Watts (4 x 125 Watts RMS) @ 4 ohms
  • Peak Power: 1600 Watts (2 x 800 @ 2 ohms or 1 x 1600 @ 4 Ohms)
  • High-Speed MOSFET Power Supply with self-regulating efficiency output
  • Studio-Grade Bipolar Output Stage Transistors
  • Fully Adjustable 0-12dB bass equalizer
  • 2-Ohm Stable Stereo
  • 4-Ohm Mono Bridgeable
  • 3 Channel Mixed-Mono Capable (Tri-mode)
  • Mute and Delay Soft Start System
  • Full IC-Controlled Protection Circuitry
  • 2 CH/4 CH Input Mode Switch
  • RCA Preamp Line Output
  • Speaker-level input
  • Auto-on remote sensing for speaker inputs
  • ELNA Brand Audiophile Capacitors
  • Status Mode LED Indicator
  • Signal to noise ratio (SNR): > 100dB
  • Minimum THD:  < 0.05%
  • Frequency Response: 10Hz – 40KHz
  • Fully Adjustable 12dB / Octave Crossover with Differential Circuitry
  • CH3 & CH4 Low Pass 50Hz – 3KHz
  • CH3 & CH4 High Pass 15Hz – 1KHz
  • CH1 & CH2 High Pass 50Hz – 300Hz (x1), 500Hz – 3Khz (x10)
  • Sensitivity: 100dB @ 1w / 1m
  • Damping Factor: > 200 @ 100Hz
  • 60 Amp Maxi Fuse
  • Dimensions: (W x H x L) 8.5″ x 1.8″ x 13″

As you can see, there’s no shortage of good specifications for the amp. However, real-world testing is what really counts for what matters in my experience.

Understanding the RXA-F1’s power ratings

Diagram explaining CEA-2006 vs uncertified RMS car amplifier power ratings

It can definitely seem confusing when you first look at the amp’s power ratings. However, there’s a logical reason they provide 2 RMS power ratings. Continuous root mean square (RMS) power ratings existed long before the industry standard CEA-2006 method of rating an audio amplifier’s power came along.

They differ in a few ways, but both are useful when comparing similarly rated electronics:

  • CEA-2006 power ratings are measured when an amp’s power output reaches 1% distortion. This is a lower number than what an amp is capable of producing (with higher distortion) in nearly all cases.
  • The continuous RMS power (sometimes called “uncertified” power) is a measurement of the power an amp can put out continuously until the signal begins to clip.

Clipping is the point at which an amp can’t amplify the input signal anymore. It’s also a terrible form of distortion and can potentially damage speakers. That’s why we try to avoid it always.

The “uncertified” rating is how much “useable”, or how much power you can continuously expect to get, out of an amplifier for the rated speaker load.

The important thing to remember is this: When comparing car amps, compare similar power ratings. Otherwise, it’s not a fair comparison and can be very misleading!

Fortunately, the Rockville amps are industry certified to deliver at least the CEA-2006 power ratings advertised. In fact they’ll exceed those up to the uncertified (continuous) RMS ratings.

A quick note about the signal-to-noise ratio (SNR)

Signal to noise ratio car amp diagram

The signal-to-noise ratio (SNR) is measured in decibels (dB) and is a way of comparing the amount of “hiss” or base noise level an amp produces compared to the musical signal. A higher number is better, and typical car amplifiers are around 90dB and above.

Rockville lists the Phenom series (at least several of the prime models) as having an SNR ratio of greater than 100dB, which is very good. You’ll have to pay a lot more money to get even higher numbers, and it’s really not worth it unless you’re a true audiophile or want competition-level performance.

Note that they don’t specify how that’s measured. In some case  the SNR is measured at 1 watt, and/or at a higher power output where amps perform better. Those more specific rating specs are a bit rare among car amps, though.

However, in my test experience, the Rockville did well for the average user. With a good clean signal you’ll be enjoying no noticeable “hiss” at all.

My test setup and installation

Diagram showing Rockville RXA-F1 4 channel amplifier test setup

Shown: My test setup used to find out how the Rockville amp performed in the real world daily.

Alright, on to the good stuff! Once I got the amp I was able to install it, tune my system, and give it a real-world test.

Installing the RXA-F1

Collage image showing the RXA-F1 amplifier test installation and setup

Installing the RXA-F1 for daily testing and putting it through its paces. Yeah, I installed it at night! That’s how badly I wanted to try it out and start enjoying it, ha ha!

I used my test setup (piggy-backing off of my original everyday system) to power and supply a super-clean audio signal to the Rockville amp.

Overall, installation is pretty easy, although I did have to find my own hex wrenches for loosening & tightening the wiring terminals screws as I mentioned earlier. I also had to check the owner’s manual for bridged wiring instructions as bridged connections aren’t printed on the amp itself.

I did find that the speaker wiring terminals can be a bit tricky, as they’re a bit deep inside: You’ve got to be sure you’ve got the speaker wire inserted fully. Otherwise, after tightening the screws it’s possible to pull the wire out and you’ll have to start again.

No problems with the power & remote wire terminals, however. They’re easy to work with and everything went great. I fired it up and gave it a day of burn-in time before I evaluated the performance.

NoteIf you’re using a head unit with only 2 channels instead 4 (front/rear), you’ll be fine. The 2/4 channel switch allows you to drive all 4 amp channels from only 2 input channels without needing to buy a pair of RCA Y adapters. Just set it to the “2” position.

This works for both RCA inputs and the speaker level inputs as well.

How does it sound? Real music and test tracks

Car amp test tracks playing snapshot

Some reference car audio test tracks I used for testing the amp and verifying sound quality. Top: Autosound 2000 Test CD #102. Bottom: A high-fidelity album from Mapleshade Music featuring unprocessed, excellent sound quality used in some high-end car audio demos.

Using my reference test CDs (as well as music I enjoy and I’m familiar with very well) I ran the amp through a series of tests to check some important characteristics:

  • Sound quality & clarity
  • Stereo imaging
  • Bass sound quality
  • Power output with real music

I do this because it’s important to be consistent when testing different audio components including amps. For example, if I were to change the way I tested the amp (change it from the previous installation) I could easily add 1 change that unfairly gives the wrong impression.

To be consistent, I use very high-quality audio tracks and I’m familiar with high-fidelity test tracks as a known good frame of reference.

After quite a bit of listening time I formed my overall opinion: The RXA-F1 is a great-sounding budget amp with very good musical fidelity. Stereo imaging is spot-on and there’s no noticeable compromise in the sound vs. the next higher-priced competitors.

Example of Spotify music tracks playing screenshot

Listening to your favorite everyday jams on Spotify (or whatever music source you like) is enjoyable and fun with the Rockville. Music is crisp, clear, and can really jam hard when you crank the volume. Bass-heavy songs like Ne-Yo’s Miss Independent come through clearly and with plenty of power. In fact, I had a lot more power on tap when I needed it.

The music quality was great, with crisp, dynamic highs and punchy bass. While it’s a teeny-tiny bit less clear than my old-school reference amps, it’s still very good for the money. When I say it’s “good”, I really mean it sounds very good.

I even caught myself thinking about changing my old reference amps for more & more powerful Rockville amps. The watts per dollar value – and features and flexibility – are unusually good for the money. For a lot less than I paid for my old amps I could get 2 Phenom amps with more power and channels.

My overall impression from listening

I have to say, however, that unless you’re one of the pickiest audiophile listeners, you’ll really enjoy it. It’s a very clear, musical amp that has a ton of power just waiting to perform.

While bridging the rear 2 channels to drive my 10″ test subwoofer worked well, in all reality it could use a bit more power if I wanted serious slammin’ bass. However, it’s not designed to drive a subwoofer with slamming bass – it’s a good compromise between price and power that can run the average system.

With 200W RMS available to my 4 ohm JL Audio sub, I got some very nice bass with a very pretty good amount of power and volume. (Note: If you need even more bass, I’d recommend picking up a good budget mono amp.)

In everyday use it did well and I had lots of power just waiting.

I have to say, however, that unless you’re one of the pickiest audiophile listeners, you’ll really enjoy it.  It’s a very clear, musical amp that has a ton of power just waiting to perform.

The crossovers worked well and are easy to set. Nothing special to mention there (aside from the bonus features built in, which I’ll talk about below) which is a good thing.

It did what it’s supposed to do: It simply works right and gets the job done as you expect.

Owner’s manual quality

Image of the front cover of the Rockville Phenom car amp front cover

Honestly, the owner’s manual is surprisingly good. I’ve seen quite a few over the years and most are pretty weak when it comes to instructions, set up, and getting the most out of the amp.

This one’s better. While it covers several models in the amp family (which is fine, and typical for most amp manufacturers) the instructions apply equally to the main amps in the product family.

Where there are differences it’s made clear to avoid confusion.

Image of the Rockville Phenom car amp owner's manual content example

It’s easy to read and you’ll get clear instructions on how to wire up pretty much all speaker systems you could think of. There’s also the tri-mode option, in which 2 channels are used both in stereo and with a 3rd speaker connected in bridged mode at the same time.

In that case they even provide passive crossover component values (capacitors and inductors) to help you too.

As I mentioned earlier, however, when using the speaker level input feature the harness adapter coloring isn’t listed in the manual for some reason, which is odd. I’m not sure why that is, but it’s a pretty small complaint.

Regardless, you’ll be able to connect speaker level inputs using the (+) and (-) symbols which are shown both in the manual and are printed on the amp itself.

Special features that set it apart

Image of Rockville car amp manual clone function instructions

As shown in the owner’s manual, the RXA-F1 has a very cool featured called the “Clone” setting on the front channel pair crossover switch. This duplicates the rear channel settings perfectly for the front channels, taking away any need to try to fiddle with them to match.

Ah yes, here’s where things get interesting – and even better – yet again!

The RXA-F1 has some really neat features I’ve almost never seen in an amp like it, if at all on other amps with few exceptions.

Clone feature: Set the front crossover switch to “clone” and you’ll duplicate perfectly the gain, crossover, and other settings you’ve used on the rear channels. Only the rear RCA inputs (3/4) will be active in this case.

This is great for bridged mode where you’re only using 2 channels for more power or when you’re running a fancier system and need specific crossover settings with only 2 channels.

1x/10x crossover multiplier: I really like this one! In “1x” mode (default setting) the 50Hz-300Hz range is available for a high-pass filter. When set to “10x” the 10 times multiplier is active, allowing a range of 500Hz-3KHz from the same control.

That’s a great addition and adds a lot of extra system flexibility.

Bandpass filter: This one’s really unique as well, and excellent for 3-way or even some bi-amped 2-way systems.

The rear channels offer not only a high pass filter (15Hz-1KHz), a low-pass filter (50Hz-3KHz), but also both can work together to provide a bandpass filter. Both the low and high pass adjustments will work the same in that case but will work in unison.

Note: You won’t be able to use the amp to drive a 4 subwoofers in 4 channel mode as there’s no low-pass crossover for the front speakers.

In practice that’s not a problem, as that’s not something anyone would normally do anyway. You’ll be able to use the amp in bridged mode for one or both pairs when using subs instead.

Review score & summary

Honestly, the RXA-F1 is one of the best values – and best sounding – budget amps I’ve seen in a long time. I’m impressed as it seems like you get a lot more for your money than you should.

Mine was under $100 but it feels like I should have paid even more. It’s got everything that makes a good car amp: Great sound, plenty of power, good looks, and the right features. The unique features and true power ratings really help set it apart from competitors in its price range.

It’s definite “Yes!” in my book. While it can’t match the small size or efficiency of today’s class D amps, it proves that you can get a well-rounded amp that’s powerful and sounds great using proven class A/B technology.

Image showing RXA-F1 amplifier with Editor's Choice badge

Update: I found out you can get the amp and RWK4 4 gauge wiring kit combo for only a few dollars more here. That’s a really sweet deal while it lasts.

Overall
9/10
9/10
  • Overall quality - 8.8/10
    8.8/10
  • Sound quality - 8.8/10
    8.8/10
  • Power & performance - 8.8/10
    8.8/10
  • Installation ease - 9/10
    9/10
  • Features - 9.5/10
    9.5/10

If you're in the market for an affordable 4 channel amp, look no further

Surprisingly good for the price (under $100), the Rockville RXA-F1 is one of the most well-rounded budget amps I’ve had the pleasure to own and test. While there’s the occasional production hiccup, the overall quality is very good – in fact you’ll feel like you should have spent more.

The sound quality rivals that of more expensive class A/B competitors and you’ll get features no one in this price class offers. In real-world testing it really delivers and meets power expectations with clear, fun sound. While there a few tiny quibbles, it’s simply a great value that’s too good to pass up. Industry-standard power ratings are a nice change of pace vs the misleading ratings of competitors. If you need an affordable 4 channel amp this is a winner!

Pros

  • Great sound quality for price
  • High watts/dollar value
  • Very flexible crossovers
  • Bridgeable design
  • Clone feature makes 2 channel mode easy
  • Crossover multiplier switch
  • CEA-2006/continuous true power ratings
  • Nice finish & build quality
  • High quality speaker terminals
  • Thermal and short circuit protection
  • Good, clear owner’s manual
  • Bass boost EQ (adjustable)
  • Bandpass crossover option
  • Tri-mode capable
  • “Class G” power supply for more efficiency
  • Available in marine version RXM-F3

Cons

  • No speaker terminal wrenches included
  • No speaker input harness color diagram
  • Plastic mounting feet (vs metal)
  • Occasional minor quality control issues
  • No low-pass filter on front channels
  • Bass boost limited to +12dB max vs +18 of others
  • No bridging label near terminals

How To Hook Up A 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)

Hook up amp 4 channel amp front rear speakers infographic diagram

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?

Holding Alpine MRV-F300 amp in my hand

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

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

Clip art image of a face thinking - Things to know content image

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?

wire of 16 ga speaker wire

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?

KNU Conceptz KCA-K4 4 gauge amp wiring kit RCA cables imageIf 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.

Image showing example crimp tool and crimp connectorsCrimp 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

Etekcity MSR-R500 digital test meter example

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

Image of a paper checklist being prepared with a marker

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

  1. 4 channel amplifier with speaker level inputs or amp and line-level adapter
  2. 120 feet or more speaker wire, 18 gauge or larger
  3. Amp wiring kit
  4. Crimp tool and butt (wire crimp) connectors (25 or more at least)
  5. Cutting pliers
  6. Electrical tape
  7. Wire ties, 6″, bag of 100
  8. Test meter

Installation type 3: RCA connections

  1. 4 channel amplifier with speaker level inputs or amp and line-level adapter
  2. 100 feet roll speaker wire, 18 gauge or larger
  3. Amp wiring kit
  4. Additional RCA cables, 18′ minimum
  5. Crimp tool and butt (wire crimp) connectors (25 or more at least)
  6. Cutting pliers
  7. Electrical tape
  8. Wire ties, 6″, bag of 100
  9. 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

Example of the rear of a car stereo installation closeup

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:

  1. Connect speaker outputs to your amp’s speaker level inputs
  2. Connect a line-level adapter to the radio then use RCA cables to the amp
  3. 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

PAC LP7-4 4 channel line level converter

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

Car amplifier speaker level input example
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.

4 channel amp speaker level harness example

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:

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

4 channel amp signal connection diagram
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

Image of car stereo wires crimped

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

Image of factory stereo wiring harness

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.

Wire bundle with zip ties example

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

Example of connecting RCA cables to rear of a car stereo

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

Diagram showing a 2 channel car stereo connected 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.

RCA y adapter cable image

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

Product image of Belva BAK82 amp wiring kitAn 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:

How to install a 4 channel amp diagram

Setting up your amp

Alpine MRV-F300 4 channel amp end viewOnce 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:

  1. Turn down gain controls on the amp
  2. Turn the stereo’s volume to 2/3 of maximum
  3. 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!

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

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

2 channel vs 4 channel amplifier image

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

2 channel vs 4 channel amp 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

Signal to noise ratio car amp diagram

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.

Example image of car amp internal noise level

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

Alpine MRV-F300 4 channel amp end view

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

RB-XD400/4 amp internal viewA 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

CEA logo

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

Internal image of a 4 ch. amp

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

Image Product Details
sample-table__image★ 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
sample-table__imageSuperb 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
sample-table__imageRockford 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
sample-table__imageMTX 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
sample-table__imageUltra 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!

Alpine MRV-F300 amplifier Editor's Choice imageI’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

Alpine MRV-F300 4 channel amp end viewYou’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!

RB-XD400/4 amp side viewJL 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.

RB-XD400/4 amp top view

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.

Punch P400X4 top view

 

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.

Punch P400X4 controls view

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.

MTX Thunder 75.4 side view

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!

MTX Thunder 75.4 end 1One 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!

Image of Alpine KPA-445U with accessoriesIf 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.

Image of Alpine KPA-445U mini amplifier controls

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

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 infographic

What does a car amplifier do?

Illustration of how a car amplifier works

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.

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:

  1. A DC-DC (direct current) high-power switching power supply
  2. Noise prevention (“ground loop”) circuitry
  3. Speaker crossover circuitry
  4. Bridging circuitry
  5. 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

Illustrated car amp switching power supply section

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.

Car amp SMPS waveforms example image
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

Illustrated image of car amplifier audio 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

2 way speaker system and crossover diagram

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

Car amplifier output stage illustration

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

Crunch PD2000.4 car amplifier ends image

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

Pioneer GM-D9605 wiring terminals close up image

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

Pioneer GM series car amplifier high level input harness image

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

image of car amplifier having wire connected
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:

  1. A fused large-gauge power wire to the battery (+12V)
  2. Negative connection to the “ground”: negative battery terminal or car’s metal body
  3. Remote-on wire to switch the amp on and off with the stereo or ignition switch
  4. Audio input signals: RCA cables or speaker-level inputs
  5. 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

Notated diagram showing typical car amplifier installation

How are car amplifiers beneficial?

Alpine MRV-F300 amplifier installation example

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?

2 channel vs 4 channel amp diagram

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

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

Car amplifier sound quality facts infographic

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

2 channel vs 4 channel amp 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

Signal to noise ratio car amp diagramThe 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.

Example image of car amp internal noise level

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

Alpine MRV-F300 4 channel amp end view

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

RB-XD400/4 amp internal viewGreat-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

CEA logo

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

Internal image of a 4 ch. amp

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

Image Product Details
sample-table__image★ 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
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sample-table__imageHigh 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!
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sample-table__imageRockford 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
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sample-table__imageMTX 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
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sample-table__imageUltra 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
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Reviews and amp details

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

Alpine MRV-F300 amplifier Editor's Choice imageAlpine 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 on 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.

Alpine MRV-F300 4 channel amp end viewOh, 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

RB-XD400/4 amp side viewAlways 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.

RB-XD400/4 amp top view

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

Punch P400X4 top view

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.

Punch P400X4 controls view

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

MTX Thunder 75.4 side view

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.

MTX Thunder 75.4 end 1The 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

Image of Alpine KPA-445U with accessoriesI’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.

Image of Alpine KPA-445U mini amplifier controls

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.

Suggested reading

Don’t forget your amp kit! Check out my helpful guide for good amp kits here.

Need some more information on how to install it? Here’s a great guide on how to hook up a 4 channel amp to front and rear speakers.

The Best 4 Channel Car Amplifiers – Buyer’s Guide and 5 Excellent Choices

Image of 4 channel amps custom installed

I love 4 channel amplifiers! As an installer and a car audio fanatic I’ve installed, tested, and tried many over the years. In my opinion, 4 channel amps are some of the most flexible and the best value. However, finding the best 4 channel car amplifier can be tough!

In order to help you find the best for your money I wrote a helpful buyers guide. I’ve also provided 5 excellent models with reviews to help you get an amp you’ll enjoy.

Contents

What is a 4 channel amp?

4 channel amps, as you may have already guessed, are extremely similar to 2 and 5 channel models. They do share a few differences, however. They too use a single power supply to provide a higher output voltage, stepped-up from 12V, to drive the speakers with more power than is possible with only 12V like factory systems.

Following this, they contain 4 independent audio amplifier sections which these days are normally designed in such a way that each channel pair can be bridged for additional power if desired. Some have features such as a bass boost control that may be used only for 2 of the 4. This varies from brand to brand and model to model, so it’s important to be sure before buying.

Internal image of a 4 ch. amp

A 4 channel amplifier is basically the same as a 2 channel amplifier with 2 additional audio channels in a more compact design. It’s important to note that some, however, do have special features (such as a bass boost option) available only on 2 of the 4. This 4 channel class A/B amp (show here) has quite a few transistors on the left-hand side to drive the outputs. That’s one reason it’s longer than a 2-channel amp alone.

System flexibility and advantages

4 channel amps are very flexible and offer a number of advantages over other models. You can configure (and easily reconfigure) many different types of sound systems in your car.

For example:

  • A 4 speaker system (front/rear)
  • Front full-range (2 ch.) + bridged subwoofer
  • High pass/low pass component speaker setup, with tweeters on channels 1-2 and woofers on 3-4
  • Front speakers with a high-pass crossover and front woofers on low-pass channels

When adding a 2nd amp, the possibilities are even more extensive! Remember that it’s ok if you don’t use all channels present in an amp – there’s no harm in having a speaker output disconnected.

What to look for in a car amp

There are a number of basic features that although are very common in modern amplifiers you should always verify they’re present before purchasing, rather than assume.

I recommend an amplifier with built-in high and low-pass crossovers. The best ones are adjustable although that’s not a big deal in everyday use. But it does make it easier to tailor the sound to your liking and it’s especially true when using the high-pass feature to block lower end bass from speakers that can’t handle it in order to prevent distortion and get more clean high volume sound.

Ideally you’ll also have an amplifier with good terminals that are easy to connect power and speaker wire too but stay nice and tight after installation.

Class A/B vs class D amplifiers

Technology has improved a lot in the last several years when it comes to car amplifiers. Although the traditional designs that have been around for decades, class A/B amps, still remain.

Whereas as traditional A/B amplifiers are based on a design in which driving transistors largely remain on during use (even when no audio is present) and are only near 65% efficient, class D amplifiers are nearly 90% efficient and can be designed to fit into much smaller chassis.

A class D amp works by switching the transistors that create an audio waveform incredibly fast, saving energy and bringing heat levels down to an incredibly low level.

Class D amplifier sound quality

Class D amps do have one drawback: because of how they operate, the noise floor is somewhat higher than that of A/B amps, which you can hear as a slight hiss if you listen closely and especially if the gain is turned up high.

It’s critical to buy a well-designed brand name amp to get the best sound and lowest noise as lower-end amps aren’t as well designed. 

Today’s brand name 4 channel class D amps have reduced noise levels and generally overall better sound than others, and proven by the many happy customers who’ve said the same.

The good news is that a well-designed amplifier of this type can have great sound quality. Highs are crisp and bass is tight and punchy, just like older designs. Again, it’s really important to shop carefully to get the best sound.

Class A amps are low-noise designs somewhat similar to A/B, but even less efficient and generally not as common. They’re often much more expensive, too.

Image of Alpine KPA-445U mini amplifier controls

Class D amps use relatively recent design to produce efficient power and can be incredibly compact as they don’t waste large amounts of energy as heat like older amplifiers. This excellent Alpine KTP-445U 45W x 4 mini-amp. for example, measures only 7 7/16 x 1.5 x 2.5″ (189 x 38.2 x 64.5 mm) in size!

Why choosing a class D may be the best choice

Because they’re so small, this type of amplifiers opens new possibilities for installation and can fit in areas previously completely unavailable! That’s a fantastic advantage as you can do things like the following:

  • Place an amplifier under a seat (or 2 for a multi-amp system)
  • Install them in storage containers in your vehicle’s interior
  • For trucks, they can be placed under the normally limited space under the rear folding seat
  • Hide them from thieves looking in your vehicle to avoid theft

Because they’re so efficient you can actually get away with smaller size power wire. Remember that while they have great power output, very similar to traditional amps, they use almost 1/2 of the power draw of older amps!

That means they draw a lot less amperage and can you won’t need as large a power wire. As the price of copper wire has risen over the years, that’s a big advantage!

However is having the lowest noise level possible is a concern for you, then perhaps A/B is the best choice. I’ll list some models below that are great choices.

How much power do I need?

As an installer, I generally recommend a minimum of 50W RMS per channel into 4 ohms. If you’ll be driving subwoofers and are likely to want very heavy, high-powered bass you should select a model with much higher bridged power instead.

For most people a 50W RMS x 4 amplifier is fine, as it provides sufficient volume and bridging the amp generally provides around 150W into 4 ohms, which is sufficient to drive a subwoofer well for great bass sound.

For great sound with additional high-volume ability, I would choose a 75W per channel or higher model.

★ 5 of the best 4 channel car amplifiers for your money ★

Our top picks

Image Product Details
sample-table__image★ 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
sample-table__imageHigh 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
sample-table__imageRockford 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
sample-table__imageMTX 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
sample-table__imageUltra 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

Product reviews and details

1. Alpine FRV-F300 – Great sound in a small package – one of the best values available today!

Image of MRV-F300 amplifier end

This is one of the most compact and best sounding 4 channel car amps today. It features end caps that snap on and off for a cleaner-looking installation, great sound, 50W x 4 (4 ohm) / 75W x 4 (2 ohm) power, and is the next evolution in car class D technology. It measures only 7 7/8″ W x 6.5″ D x 2 3/16″ H (200 x 165 x 55 mm) and is so small it easily fits under seats too. It’s bridgeable to 150W into 4 ohms.

Alpine has done additional engineering work to reduce noise in the model, and it shows…or should I say it can be heard! Few class D amps can say the same.

Alpine MRV-F300 4 channel amp end view

Full crossovers as expected and a bass boost is available on channels 3/4 as well. Speaker level inputs are provided, too, in case you have a factory system you’re looking to upgrade. I’m so impressed with it that I did a full review you can read here. This is a fantastic and great sounding powerhouse you shouldn’t miss! It sells for close to $150, depending on the retailer.

It’s a very cool amp that’s affordable and one of the best all-around buys. Don’t waste any more time if you’re looking for a fantastic-sounding way to power system – head over to check out the amazing reviews at Amazon now.

2. Rockford Fosgate Punch P400X4 – Powerful, all-out fantastic sound and bonus setup features

Punch P400X4 top view

If your budget allows you to spend a little more, the P400X4 is one of the best on the market today. Rockford Fosgate has used class A/B design with their own Trans-ANA circuitry to deliver lower noise and some of the best sound quality available in this price range (around $200).

The company’s legendary expertise in car audio design makes it possible to get all of this in an 11-1/8 x 2-7/16 x 8-13/16″ size. That’s because the company uses the latest and best electronic components available –not the cheapest like competitors!

Punch P400X4 controls view

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.

A Punch EQ remote control knob (sold separately) can be added for adjusting the sound while driving. It doesn’t support speaker level inputs, but a 2/4 way input switch is provided for the RCA inputs.

What I really love – and what definitely sets it aside from others, is the C.L.E.A.N. gain setup system feature which, when used with the included test tone CD, actually allows the amp to indicate signal levels to aid in setting up the amp gain. It allows you to the lowest-noise and best optimization for your amp.

The amp is conservatively rated (will actually exceed its rated specs) at 50W x 4 into 4 ohms (100W x 4 into 2 ohms) and 200W x 2 when bridged to 4 ohms. A certificate of performance verification is included, too!

It seems like so many online retailers are charging way too much for it, so take my advice and check out the lower price I've found at Amazon.

3. MTX Audio Thunder 75.4 – 75W x 4 of clean, reliable MTX quality power in a smaller package

MTX Thunder 75.4 side view

If you’re wanting the absolute lowest noise in your music but still want something affordable, the Thunder 75.4 can give you that – and more power in a smaller package than other similar amps!

MTX has managed to fit 75W x 4 (@ 4 ohm) channels of crisp, powerful musical reproduction into a package that’s only 12-5/8″W x 2-1/4″H x 6-5/16″D in size thanks to using surface mount technology (SMT). It can also deliver 100W x 4 @ 2 ohms and 200W x 2 bridged to 4 ohms.

MTX Thunder 75.4 end 1The high-pass crossover is adjustable and reaches as high as 750Hz while the low pass is adjustable to 200Hz. 4 gauge-capable power connection terminals and well-made, secure speaker wire terminals round out a great design you’ll love. However it doesn’t provide speaker level inputs.

It’s a fantastic and powerful compromise between cost, size, and power, selling for less than $200.

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

4. Alpine KTP-445U Mini Amplifier – One of the smallest and best sounding mini amps available today. Truly a great amp that fits nearly anywhere.Image of Alpine KPA-445U mini amplifier controls

As I wrote about in my extensive review, the KTP-445U is a marvel of Alpine’s expertise in compact audio based on class D technology. As not all of us have room for a standard sized amplifier (even the compact ones listed here) it solves the problem of having very limited installation space while still providing up to 45W of clean sounding power into 4 channels! And it even handles 2 ohm speaker loads.

The amp measures an astounding 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! It can be installed using the included brackets or even using zip ties if you’re working with a more difficult installation challenge like putting it inside a dashboard opening.

Image of Alpine KPA-445U with accessories

Even better is that it features built-in high and low-pass crossovers which are enabled by switches on the bottom. You can also use all 4 channels with only a 2-channel input source thanks to the built-in “Y” adapter function. Both RCA and speaker-level inputs are provided.

Alpine has taken great care with a fresh design of their own in order to minimize noise and keep the sound quality level high with crips high-end response you’ll love. It sells for somewhere around $145.

Head over to check out the amazing reviews from others and the best price at Amazon.

5. Planet Audio Anarchy AC1200.4 – 4 channels of good budget power and sound that works

PLanet Audio AC1200.4 amp top

Have less than $100 to spend? You’re in luck, as you can still get a good buy and plenty of good, powerful musical sound that’s easy to use and looks good too. It can also be used with factory speaker level systems. Thanks to the AB traditional design you can spend less and still get better sound quality than some of the low-end competing products out there today.

Power is 113W RMS x 4 into 4 ohms (225W x 4 into 2 ohms) and bridged 450W x 2 into 4 ohms. It features high/low pass 12dB crossovers and an adjustable 0-18dB bass boost on channels 3/4. It also has thermal and speaker short protection circuitry.

lanet Audio AC1600.4 amp end view

The Planet Audio amp shares the same basic design as the parent Boss company brand, just so you know. It’s not on the level of the models I’ve listed above, but offers decent quality and isn’t short on having enough power to let you enjoy a great system in your vehicle.

It’s a good deal and budget priced. You can check out the current price and the many happy reviews before buying.