How To Wire A Computer Power Supply To A Car Amp

There’s more than one way to power a car amp in your home. Even so, computer power supplies are easy to find and make a great option – if you know how.

In my detailed guide, I’ll show you how to wire a computer power supply to a car amp. I’ve also put together some great diagrams, tips, and more to help you enjoy your music with less hassle and fewer headaches.

Can a computer power supply run a car amp? What to know

Can a computer power supply run a car amp man thinking question

Yes, it’s possible to use a PC computer power supply for powering a car amp. 

There are a few things you’ll need to know though. For example, unless you’ve got a higher-power model supply you won’t be able to drive speakers with the same power you could when installed in a car.

Do you need to hook up the remote wire on your car amp?

Yes, a car amp won’t work without a +12V signal on the remote wire terminal. The amp’s internal power supply is controlled by this wire and acts as a shutoff control. Likewise, you’ll want to either turn the power supply on & off as I’ll show you or use the remote wire as a shut off in order to keep the amp from drawing power when not in use.

Computer power supplies also have a particular control wire you’ll need to connect in order to switch the supply on as I’ll show you.

Computer power supply current (amps) & power limits

Computer power supply 12V current rating examples

Examples of the current output (amps) for a typical 200W supply and a higher-power 700W supply. The current output will limit how much power you can get from a car amp.

Computer power supplies are available in a wide range of power output options, with 1500-200 watts being very common but others as large as 700W or more can be found (although they cost a bit more). This is important to know because the current limit of a power supply will limit how much power your car amp can produce.

That means you need to be aware that for higher-power amps you can’t expect to drive speakers with the full power output it’s rated at. The good news that unlike in cars, speakers used in your home use less power for the same volume because vehicle interiors are poor for sound and require more power for good results.

How to power a car amp with a computer power supply (diagram and details)

How to wire a computer power supply to a car amp diagram

Using an ATX (desktop computer) power supply for a car amp isn’t hard – in fact, you only need a few steps:

  • Power connections: Cut the +12V wires (yellow) and the same number of ground (black) wires. Strip the insulation to leave about 3/8″ to 1/2″ bare wire. Twist them together tightly or use a crimp connector (ring terminal, spade terminal, etc) and connect to the amp’s power & ground terminals, being sure not to leave any stray wire strands sticking out to cause a short-circuit.
  • Supply on control: PC supplies don’t turn on even if the on/off switch on the case is used. A PC motherboard uses a control signal to the “supply on” wire pin. To do the same, you’ll need to find, cut, and jumper this control signal wire to a ground wire either directly or with an on/off switch if you like [See diagram]
  • Amp remote wire: There are several great ways to do this and I’ll cover them below.

Once you’ve connected the +12V and ground wiring then ground the “supply on” wire the supply should start up and your car amplifier should power on. There are some cases where you could have a problem, however.

NOTE: If you’re using a high amount of current be sure to use all or nearly all of the yellow +12V wires to connect to the amp. Just like with a car amp installation, you need enough wire conductors to supply higher current without losing voltage from insufficient wiring.

A note about some amps

Larger, very high power car amplifiers can sometimes draw a short current “spike” when they’re first connected to a power source after being disconnected. That’s because they contain large capacitors that, when first connected to power, momentarily draw a huge number of amps.

When this happens it’s possible it could trip the self-protect mode in your power supply. If that happens you can try starting the supply and then wait before turning on the remote wire. You can also leave the supply running when the remote wire is disconnected so the amp’s capacitors don’t discharge when the amp is turned off.

It’s possible you may need a more robust power supply if it happens but it’s not a problem most people should run across.

Remote wire options & examples

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

The car amp “remote” terminal uses a low-current +12V input to start its power supply & related circuits. You’ve got a few different options you can use:

  1. Jumper wire:  When connecting the power and ground 12V connections, you can use a small jumper wire from the +12V battery terminal to the remote it so it’s on any time the amp has power. 18AWG or smaller wire is fine (you don’t need a large gauge wire).
  2. Jumper wire + switch: The same as #1 but to control it yourself you can add a simple inline switch on the remote wire. This is helpful if your power supply doesn’t have an on/off switch or you’d rather leave it running.
  3. Home stereo use – RCA converter with remote lead: If you’re connecting the amp to speaker outputs on your home stereo you can use a line level converter with a remote wire output. This will turn the amp on and off automatically with the stereo’s output.

If you’re using a toggle switch on the remote wire you can leave the AC/DC power supply plugged in. When the amp’s remote wire is off (disconnected) the amp will shut off and it won’t drain power.

Using a line level converter with remote wire output

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

An example line-level converter with remote wire output. You’ll need to connect these to 12V power and ground for the internal electronics to work. When the speaker level inputs detect a signal the remote wire output will produce +12V and turn on your amplifier. When the speaker signal is lost it will switch it off automatically.

Connecting a laptop, tablet, or smartphone to the amp for audio

Diagram for how to connect audio signal to a car amp used in your home

What’s great is how many options you have for getting an audio signal to your amp’s inputs. In fact, nearly any analog (non-digital) jack can be used from almost any device. Smartphones, tablets, and laptops can be used either by their headphone jack or via Bluetooth.

Just be aware that not all headphone or audio out jacks are created the same –  some work well and have good sound & volume while others can have low volume and “meh” sound quality. However, the good news that generally speaking they’ll work well and I’ve used this approach several times with no complaints.

Connecting your smartphone or tablet via Bluetooth

You also use an affordably-priced Bluetooth receiver for around $25 from places like Amazon. They offer a direct line output jack or RCA jacks to go into a home receiver and a car amp just as easily.

Be sure to get a decent brand as the generic/no-name brand models tend to have sound quality problems and can produce odd noises between music tracks playing on your phone, for example.

What if I have a laptop with no headphone jack?

Example of a USB to headphone audio adapter

You can use a cheap USB to stereo 3.5mm adapter to get a headphone sized jack to connect an audio signal to your amp. They’re really affordable (under $10 in some cases!) and are a good option if your laptop’s headphone jack is broken or none is available.

If you’re like many people and want to enjoy music, movies, or more from your laptop there’s a problem if you don’t have a line-out or headphone jack – or if it’s just not working. A great option is to use a USB audio adapter as it’ll provide a 3.5mm jack you can connect to your amp’s RCA inputs.

I’ve found some for under $10 available with both the older USB-A and the new USB-C connection as well.

How to connect a car amp to a home stereo

How to connect a car amp to a home stereo diagram

You can also connect your car amp to your home stereo if you like. There are 3 ways to do it:

  1. Home stereo with no RCA output jacks + car amp with speaker level inputs: It’s fairly common for home stereo amps and receivers not to have RCA jacks available to connect to. If your amp has built-in speaker level inputs these can be connected to either an unused pair of speaker terminals or alongside speaker terminals in use.
  2. Home stereo with no RCA output jacks + car amp with no speaker inputs: You’ll have no choice but to use a line level converter in this case. These are car stereo adapters that you connect to speaker wiring or speaker terminals. This will drop the signal down to a level compatible with the amp’s RCA inputs.
  3. Home stereo with full range RCA output jacks + car amp: This is the easiest way 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.

speaker to line level converter examples image

Line level connectors will let you connect a car amp with no speaker inputs to any home stereo. You can connect these to unused speaker terminals on the receiver or amp as well as in parallel with home speakers already in use.

NOTE: It’s important to buy a quality, well-designed line-level adapter to avoid noise, poor sound quality, and other problems. Don’t get the absolute cheapest – instead, get a name brand model you can rely on (like the examples you see above). Fortunately you can get a nice one like these for around $15-$20 or less these days.

Dealing with ground loop hum (noise)

Example of an RCA ground loop isolator

You can use a ground loop isolator to break the ground conductor in RCA cables but still carry the audio signal. Since the ground connection can carry the noisy signal that gets amplified this often eliminates ground loop noise.

One thing you might not count on running into is noise. Ground loop noise, which appears as a very annoying 60Hz “hum”, is somewhat common for home stereo equipment. Unfortunately, despite car amps being designed to eliminate it, it can still happen.

One thing you can do is to try using a small gauge wire and connect it between the grounds or metal casing of the car amp, the RCA cables, and the power supply. If the noise disappears you can connect the wire to those points as a solution.

Alternatively, a ground loop isolator can often get rid of it. Connected inline with the RCA cables, they work by physically disconnecting the RCA cable’s ground connection while still sending the audio signal. They’re not expensive, but it’s a good idea to shop carefully as the “el-cheapo” units don’t always carry the entire audio range well and can cause a loss of sound quality you can notice.

Your comments are welcome.
  1. Hi Marty.
    Love the great work you have put into your site!

    I have a spare 750W fully modular (meaning cables plug into the power supply and are not hard wired to it) ATX power supply that shows it has 62AMPS on the +12V side.
    I am trying to get as much of those 62AMPS out of this as possible as I want to power two amplifiers; these are spare as well just sitting in my garage. One 200 and the other 400watts RMS (class A/B). All the supplied cables with the ATX power supply are black but thanks to your colour diagram I’ve worked out which is which.
    But it looks like I still only really have just the two +12V power cables that I can use from this supply as well?
    How many of the earth cables should I connect to the two amps?

    Reply
    • Hi John & thanks for the note – I’m glad you like my site & that it has been helpful. If I understand your question correctly you’re wanting to know how many of the negative lead wires from the supply you’ll actually need to go to the amps.

      It depends on the size of the wires coming out of the supply, but they are typically about 18AWG each. So you’ll need roughly enough to handle the current you’ll be drawing. Technically speaking (especially since you’re dealing with short distances), you could use two wire to each amp. However, it it were me I’d use 3 to 4 or even more ground wires bundled from the supply to each amp. Like wise for the +12V side, assuming you have that many available from the amp.

      However, if you’re only going to use them with low/moderate power, 2 wires each for pos. & neg. to each amp should be fine. Hopefully that helps.

      Reply
  2. Much appreciated for the reply Marty.
    I have the two amps and a head unit. Maybe I send one GND wire to the head unit and the rest to the 2 amps?
    There’s only two +12V outputs on the ATX, I assume one +12V for each amp? And for power for the head unit, I assume I can use on of the lower voltage power outputs, or will the head unit need part of the +12V power?
    What’s wrong if I just grouped all the power output wires together and just split three ways, one to each appliance..
    Cheers, John

    Reply
    • Hi, yes in that case that would work. If you only have two +12V outputs then you don’t really have any choice. That’s odd as most ATX supplies have several.

      The head unit will need +12V for sure, as most quit working when they get somewhere close to ~10-11V. If you want to group them and then run a connection to each you can do that as well.

      Reply
  3. Hi Marty,

    I followed your instructions and am now powering my 1200watt amp with a pc power supply. I think it’s going to work, I have power, but now I can’t figure out what I need to connect the subwoofer out jack (back of the home stereo) to the RCA jacks on the amp. Thanks in advance!

    Matt

    Reply
    • Thanks you for getting back to me Marty. I tried the standard “Y” adapter and it didn’t work which is why I was thrown off. So I tried hooking up my phone directly via rca cables and am not getting any sound or interference. I’m willing to bet the computer power supply isn’t enough to power the amp. The power supply only has 2 +12v wires. Not sure what I’ll do next. Running out of scraps to try to swiss army my beloved 1,200 watt mono block BOSS amp and MTX 5500 12” sub and self made custom box. Maybe I’ll suck it up and buy an actual ac/dc converter…

      Reply
      • Hi Matt, just to clarify, have you verified that the power supply is switching on? Because you should have sound. Does the amplifier’s power indicator light up?

        I would (preferably) use a test meter to check you have close to +12V as expected at the amp from the battery power terminal to the ground terminal and then the remote-on terminal as well.

        It only takes a very minimal amount just to power up the amp and play a bit of music – which is one reason you can use those supplies for a bench test setup as well. Hopefully you’ll find the issue. Should you not, at least the switching +12V supplies are affordable these days. :)

        Reply
  4. Hi Marty, quick question. I have an eclipse 1200w amp with 2 alpine type R 12 subs 500 RMS. I also have a 1 Farad stinger capacitor. Lastly, I happen to have a corsair 750w atx power supply. I know you mentioned the shorter wire lengths allow for reduced wire Guage but was running 4 Guage when in vehicle. Do you think, at maybe 50% gain, I can get away with the 750w corsair? Will the stinger capacitor help at all? Does this all really work without a 12v battery in line? Seems surprising to me the atx supply can handle the Quick power draws but hey, I learn something new every day! Amazing article by the way!

    Reply
    • Hi Nick. I don’t know the specific model number of the Corsair ATX supply you have, but the one I found was rated for 62A @ 12V output. That would be just under 50% output capacity for the Eclipse amp at 2 ohms.

      The capacitor (once charged) yes can help with preventing tripping the self-protect circuitry on a power supply. Some supplies are pretty bad about falsely sensing a “short circuit” condition under heavy load while better ones don’t do so as easily. A capacitor can help offset this.

      Really it depends on how hard you drive your subwoofers. During deep bass when the bass “hits’ very hard it can draw a lot and potential reach the limit of a power supply, so you won’t really know until you drive it to that point. However, for average listening it’s probably going to be fine. Having a higher quality ATX supply is definitely a good move because the cheap ones are pretty bad about failing way before their rated power output. :(

      I’m glad you liked my article, and thanks! :)

      Reply
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