How To Connect A Car Amp To A Home Stereo (With Diagrams)

Using a car amp…at home? It’s not such a crazy idea after all! While it’s true that it’s not super easy, it’s really not all that hard and you can do it.

In this article, I’ll explain how to connect a car amp to a home stereo with clear diagrams anyone can understand. I’ll also show you all the little things you need to know before you try so you avoid disappointment & headaches.

First things first: Can a car amplifier be used at home?

Can a car amp be used at home man thinking

The good news is that YES, one way or another, you can definitely connect a car amp to a home stereo.

However, since car amps use a different power source the single biggest challenge is getting enough power to them. They also use a remote-on wire to turn the amp on & off so it doesn’t draw power and kill your battery when installed in a car.

Fortunately, these (and other) problems are fairly easy to deal with. Here’s a list of what you’ll run into when using a car amp at home:

  • Signal inputs: Not all home stereos have RCA line-level jacks, so this may require a workaround to connect to your amp’s audio inputs. Some amps make this pretty easy, however. (This isn’t much of a problem as you’ll see from my diagrams below)
  • Power source: Unlike home stereos that are powered from alternating current (AC), car amps work from a +12V direct current (DC) supply. You’ll need a +12V AC-DC power supply with enough current to run the amp. Not just any AC/DC 12V adapter will do as you’ll see later.
  • Turning the amp on/off: This is actually really easy! You can simply disconnect your DC power supply and let the amp shut off or use a simple switch to turn the amp on and off. I’ll show you how to wire the car amp so it can turn on.

The bad news is that unless you have the parts you need already, you’ll probably have to spend a little bit of money to get it working well.  The good news is that most of what you need can be found and bought new or used but you may need to order some online.

Sadly, retail stores are usually poorly stocked when it comes to power supplies that you can use for a car amp indoors. You’ll have much better luck online at places like Amazon or electronic parts suppliers.

How to use car amp with a home stereo + diagram

How to connect a car amp to a home stereo diagram

The way you’ll connect your car amp depends on both your home stereo and your car amp’s features as I mentioned earlier. You’ll end up with one of 3 situations:

  1. Home stereo with no RCA output jacks + car amp with speaker level inputs: It’s actually fairly common for home stereos and home theater receivers to have no full-range RCA jacks you can connect to the amp. In this case, if you’ve got a car amp with speaker level inputs these can be connected to either an unused pair of speaker terminals or alongside speaker terminals in use. The amp’s speaker level inputs will scale down the speaker inputs to a low signal it can use.
  2. Home stereo with no RCA output jacks + car amp with RCA jack inputs only: In this case, you’ll have no choice but to use a line level converter commonly used for car audio. Just like in #1 above, these are connected just like speakers to unused speaker terminals or alongside an existing speaker set. This will drop the signal down to a very low level that’s used by the amp’s RCA inputs. Note: I strongly recommend getting a decent quality model converter with adjustable outputs for best results.
  3. Home stereo with full range RCA output jacks + car amp: This is the easiest way by far, but not all home stereos have full-range RCA output jacks. Some only have subwoofer RCA output jacks which are bass-only outputs. Full-range RCA output jacks can be connected directly to the car amp’s RCA inputs.

How to connect the remote-on wire on a car amp

How to connect remote wire on car amp used in home diagram

In all cases, you’ll also need to wire the amp with power and a remote-on wire so it can turn on. You can do this one of several ways:

  • Jumper the remote on terminal:  When wiring the power and ground 12V connections, you can use a small jumper wire from the +12V terminal to the remote terminal so it’s on any time the amp has power.
  • Just a jumper wire + switch: Basically the same, but you can also duplicate how a car stereo’s remote on wire works by using a simple inline switch on the remote wire to turn it on/off yourself.

If you’re using a switch you can leave the AC/DC power supply plugged in if you like. When the amp’s remote wire loses its +12V signal, the amp will switch off internally and draw zero power.

Example of line level converter with remote wire output Axxess AX-ADCT2

QUICK TIP: To make things even easier, you can use a line level converter with a built-in remote wire output feature which will automatically turn the amp on or off with the speaker input signal.

Note that these do need a power and ground connection.

What is a line level/RCA converter and how do they work?

Image showing examples of line level RCA converters

Shown here are two examples of line level/RCA speaker level converters that work well for home receiver/amp to subwoofer use.

Line level converters (also called RCA speaker level adapters) are small electronic devices that connect to speaker outputs from an amp or receiver and scale down the higher-voltage signal to a low level (“line level”). The outputs are RCA jacks which can then be connected to an amplifier or subwoofer with RCA jacks.

They’re extremely handy in the car stereo world because they make it possible to connect a stereo without RCA outputs to any amplifier or powered subwoofer. We can also use them for home stereos, too.

How much do line level converters cost?

While you can get the el-cheapo ones for under $10, I don’t recommend those. Expect to spend around $15-25 or so for a good one. No need to spend too much these days as there are lots of good values out there.

What voltage & size DC power supply do I need for a car amp?

Example of how to estimate car amp current used

You can get a rough estimate of the maximum amount of electrical current you’ll need for a car amp using its maximum RMS power as shown here. However, if you’re not using an amp to its full capability you can get buy with a smaller (and less expensive) power supply.

What voltage does a car amp need?

Car amplifiers, when installed in a vehicle, work off of a voltage range as the engine runs. Although we say cars & trucks use a 12V supply, in reality, a car amp is designed to work from somewhere around 11V to 14.4V or so as the alternator in your vehicle raises or lowers it’s output while charging the battery.

Therefore you can use a power supply with a DC output similar to this, but I recommend 12V to 13.8V. Most power supplies you can buy are one of these.

What size power supply do I need?

Car amp DC power supply examples

You’ll need a power supply with a decent amperage (A) rating. Regular wall adapters won’t work as they’re very weak (0.5 to 1 amps or so). You can find 5A supplies for under $15 depending on where you shop. Desktop computer “ATX” power supplies are affordable and available in power ranges up to 500W or more. They’re easy to find but need a certain wiring connection in order to turn on.

In order to figure out how big of a DC power supply you need, you might want to calculate roughly the amount of current your amp will draw at full power. Once we know that, we can take into account wasted power that all amps use up and come up with a fairly accurate number.

Just so you know, class D car amplifiers are more efficient and therefore waste less power (and draw less current) than standard class A/B amps.

If you’re not sure what class your amp is, if it’s a class D amp it’s usually stated on the box or the amp itself. Class A/B amps often don’t state it anywhere. (Many new amps are class D so I wanted to take that into account)

Estimating amp current

You can estimate amp current based on the maximum RMS power of the amp. Don’t use “peak” or “maximum” watts as these don’t reflect the actual continuous power a car amp puts out.

As class D car amps are around 85% efficient and A/B amps are around 65% or so efficient we can use that to estimate the total current an amp would need.

Class D amp example:

Estimating the current used by a 50W RMS x 4 amp, all 4 channels used:

  1. 4 x 50W = 200W total. (200W/12V) = 16.7A.
  2. Take into account power waste: 16.7A/.85 = 19.6A
Class A/B amp example:

Estimating the current used by a 150W RMS x 2 amp, both channels used:

  1. 2 x 150W = 300W total. (300W/12V) = 25A.
  2. Take into account power waste: 25A/.65 = 38.4A

As you can see, to run a car amp at full power you’ll need a pretty big power supply! However, the good news is that it’s only if you really want to drive the amp at full capacity. For lower-power, casual listening, we can get by with a smaller (and thankfully, cheaper) power supply.

Realistic power ratings you’ll need

For just listening to music with decent volume, I recommend at least a 2.5A supply for small amps (under 50W/channel). For 4 channels or higher power ones, I’d get a 5 amp or bigger. If you’d like to have more power, consider getting 15A or above.

You can find a 5A supply for under $15-$20 if you shop carefully. 10A and 15A supplies are fairly popular so they’re usually really affordable, too. However, when it comes to much bigger supplies that will let you drive a subwoofer with heavy bass, for example, those can be expensive: $100 and above.

Connecting 2 RCA stereo outputs to a 4 channel amp

Diagram showing a 2 channel car stereo connected to a 4 channel ampWhat if you’ve got a 4 channel amp? No problem! You’ll still use the same methods shown earlier but you’ll need to jumper either the speaker level inputs or the RCA inputs using “Y” connections to get a signal to the rear channels too.

Most car amps with front & rear speaker level inputs can be wired to 2 speaker input pairs as shown in the diagram here. When using RCA connections, you can pick up a pair of inexpensive female-to-male Y adapters to split the signal from 2 into 4 connections. (Don’t spend too much on Y adapters as you can use a decent pair of cheap ones just fine)

QUICK TIP: Some car amps have a 2/4 channel input switch built in for this purpose. In that case, setting it to the “2ch” position will supply a signal to all 4 channels. For some amps this only applies to the RCA inputs so be sure to check your owner’s manual.

Can I use 8 ohm speakers with a car amp?

4 ohm vs 8 ohm speaker power comparison graph

This graph shows what happens when you use an 8 ohm speaker in the place of a 4 ohm one. The 8 ohm speaker will work – however, it comes with a price. Since the 8 ohm speaker isn’t matched to the 4 ohm car amp, it can only receive up to 1/2 the power output and has a lower maximum volume than a 4 ohm speaker would.

Using 8 ohm home speakers in place of 4 ohm ones with your car amp won’t hurt anything. There’s a catch, however. They’ll only develop 1/2 the power of a 4 ohm speaker meaning lower maximum volume is possible.

For example, if you were to use some home stereo 8 ohm speakers instead of 4 ohm speakers, you’d notice the volume would be a bit lower than when using 4 ohm ones. That’s because a speaker needs more and more power output to increase the volume more and more; also 8 ohm speakers allow only 1/2 the same amount of electrical current to flow vs 4 ohms.

Car amplifiers & car head units don’t have a high voltage supply like home stereos and home amplifiers do. That means they’re designed to use lower impedance (lower resistance) speakers to develop the same amount of power by letting more current flow.

As long as you’re aware of this it’s ok, because they’ll still sound and play fine – you just can’t get the same power and as much volume when you crank it up vs using 4 ohm speakers.

I have a hum (ground loop noise) from the amp. What can I do?

Example of an RCA ground loop isolator

Example of a ground loop isolator you can use to break the ground conductor connection in RCA cables to eliminate ground loop noise.

Unfortunately, noise is a problem with car amps despite them being designed to prevent it. It’s also true that home stereos and amps are known to sometimes create “ground loops” between different electronic components via the RCA cables.

Ground loop noise happens when there’s a slightly different potential (electrical voltage point) between the grounds of an amp, stereo, and other components. Despite everything you try, sometimes it’s nearly impossible to eliminate.

In that case, you can use a ground loop isolator to connect inline in the RCA cables. This usually does the trick. Note that you shouldn’t try to get the cheapest you find because they can negatively affect sound quality.

You can find a good one for $10-$25 or above depending on the brand and features. The good news is that they’re super easy to use: just connect them to the RCA cables and you’re done!

Marty

About the author

Marty is an experienced electrical, electronics, and embedded firmware design engineer passionate about audio and DIY. He worked professionally as an MECP-certified mobile installer for years before moving into the engineering field. Read more »

Your comments are welcome.
  1. Hi Mike,

    I have a covered pavilion with open sides in my back yard and have installed an outdoor TV. I want a better sound solution for the TV but due to the elements i do not like the 110v house current options – I would like to install a 12v marine head unit, amp and speakers that i will power from a deep cycle marine battery connected to a charger. To get the audio from the TV is it really as simple as running RCA or optical line from the TV to the stereo head unit aux inputs? Thanks

    Reply
    • Hi Pete. Yes, it generally really is that simple, as long as the TV doesn’t give you any headaches about the audio output & you have access to a stereo line level or optical output.

      In some TVs, the outputs are disabled by default and you have to switch them on to get them working. Do be aware that it’s not unusual for the TV’s audio output jacks to have a constant volume (doesn’t change with the remote’s volume adjustment) but it depends on the model.

      It sounds like it should be pretty straightforward in your case.

      Reply
  2. Hi Marty,

    I purchased a car subwoofer JBL GT-12BP 12″ and now I’m waiting for my amp to arrived JBL club A600 600W High Performance Monoblock Car Audio Amplifier. I want to connect these two with my AV Receiver AVR-S750H from Denon. Could you please help me and suggest a good 110v to 12v converter. Thank you !

    Reply
    • Hi, it depends on just how much power you’re planning on driving the subwoofer with. Either less than is possible with the amp or up to the full 350W. Realisitically, if you’re using it indoors, you’ll never get close to the fully amp power. It also depends on what your budget is.

      A good quality power supply with a 30A (or higher) rating should work fine. Here’s an example of one that would be a good one to consider. Best regards.

      Note: Sorry for the delay in responding, I caught something and and have been extremely sick for about a week now. :(

      Reply
  3. I picked up a single Ikon CM6800 speaker the other day and for the fun of it, I’d like to attach an Alexa smart speaker to it to make it the biggest smart speaker possible. The 2 12” subs are powered in it (supposedly 500W) but the other 6 mid and high speakers need amplification so I’d like to turn a car amp into a mono block amp to power those 6. I’m just going to screw all parts to the back of the massive speaker.
    So it’ll be AUX out of the smart speaker, 3.5mm Jack to RCA into the car amp and then a single pair of bridged wires out to the speaker inputs. It’s 8ohm so I’ll be using the biggest car amp I can find, 4-500 watts

    Reply
      • Yes. Sorry got distracted and didn’t finish what I started. The smart speaker only has 3.5mm audio out Jack, is there a way to improve audio quality from it to an amp?

        Reply
        • Hi Chris. In principle you could connect the line out to an equalizer to better adjust the sound before the amp. I wouldn’t use anything less than 13 bands if you do.

          Best regards.

          Reply
  4. Really helpful article! We are using a 40×4 amp but have it set to channels so 40×2/12 = 6.6 amps. But we happen to have a hefty power supply from some old computer speakers that is 12v by 1.5 amps. What’s the risk of using this power supply since it is underpowered? It works but I want to be sure we won’t create an overheating problem or something.

    Reply
    • Hi Jonathan. The power supply you have may work for low volume/power from the amp. There’s always a chance that the amp’s power supply may monetarily pull a lot of current at start-up and cause an issue.

      But I’ve used small power supplies for bench testing car radios & amps without issues. I would give it a try and let it play for a little while and see if the supply becomes very hot or anything similar.

      Reply
  5. Ok so trying to figure out what exactly I might need as far as power supply amps needed, I have a RZR1-2500D Amplifier 1ch. RMS Power 2Ω-650W x 1 RMS Power 4Ω-450W x 1. Now this is my dilemma I have 1×15″ DVC Subwoofer that I’ve dropped down to 1Ω-0.5Ω. I’d like to get your professional opinion as to how much my power supply should be (amps wise) without a lot of waste.

    Reply
    • Hello there, Anthony. Well that amplifier isn’t rated for below 2 Ohms – did you mean you will wire the subwoofer for 2Ω? The power supply you need will depend on the power you want to get from the amp.

      Getting a lot of power from a car amp indoors requires an AC-DC supply with a very high current rating. However, often we don’t need the same power level indoors as we would in a vehicle (because vehicles are wasteful for acoustical power, and need more power to make up for it).

      You can use my calculator here to help, as it will allow you to change the vales and see what you get: https://soundcertified.com/car-amplifier-dc-power-supply-amp-calculator/

      Long story short, you may be ok with a 25A-30A AC-DC supply for low to moderate listening levels. Since the amp is a class D, it won’t waste as much power as an older class A/B would.

      Best regards!

      Reply
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