How To Connect & Power A Car Amp In Your Home + Diagrams

It might seem puzzling at first, but it’s actually not that hard to connect and power a car amp in your home.

In this detailed guide I’ll show you how along with detailed diagrams anyone can understand.

Here’s what you’ll learn:

  • Car amp power supplies: what voltage & current ratings you need
  • How to wire a computer power supply to an amp
  • How to connect a car amp to a home stereo, smartphone or tablet, or Bluetooth
  • Additional tips to make it easier & offer more options

First facts: Can I use a car amplifier in my house?

Can I use a car amplifier in my house man thinking image

Yes, it’s possible to use a car amplifier in your house. You can also connect a car amp to any home stereo, your smartphone, and more as an audio source.

There is a catch, though. Because car amps use a different power source than home stereos the biggest problem is getting them the power they need. Not only that, but they use a remote-on wire to turn the amp on & off to avoid draining a car battery – meaning that needs to be dealt with too.

Here’s a list of what we’ll need to cover:

  • Signal inputs: Not all home stereos have RCA line-level jacks, so if you’d like to connect an amp to your home stereo it may require a workaround I’ll show you. You can also connect a car amp to nearly any smartphone or external Bluetooth receiver.
  • Power source: Unlike home stereos powered by an alternating current (AC) electrical outlet, 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 – I’ll cover this below.
  • Turning the amp on/off (remote wire): Home stereos or other audio devices don’t have a remote wire output to switch your amp on and off. However, there are some easy ways to deal with this, too.

You also need to know that:

  • Unless you have all the parts already, you may need to spend a little bit of money to get what you need & get it working. The good news is that most of it is affordable and you can even make use of some power supplies like a computer DC supply you may left over.
  • Retail stores are pretty bad about not having the parts you may need, so you might want to plan ahead and order parts online. You can find many affordably priced parts on Amazon, eBay, and from electronic part suppliers.

Choosing a power supply for car amp use

Example of how to estimate car amp current used

You can estimate how much electrical current (amperage, “amps”) your amp will draw based on its maximum power given in watts RMS. However, the truth is that’s only if you need a lot of power. For casual listening, you can get by with a lot less.

Basically, there are 2 ways to go about choosing a power supply for a car amp:

  1. Getting a “good enough” power supply if you’re not driving the amp hard (fine for casual listening)
  2. Estimating the amp’s current draw based on its power rating (useful for when you want serious amp power)

Of these, #1 makes it a lot simpler. You may be able to use a DC supply you’ve already got handy or a leftover computer power supply (sometimes called an ATX power supply).

What voltage does a car amp need?

Car amps normally work off of a range of voltages, not just 12 volts, although that’s used as a general reference. In fact, as a vehicle’s engine runs the alternator charges the battery and the voltage can range from near 12V to about 14.4V. 

For home use, choose a power supply with a DC output from 12V to 13.8V, with 12V being perfectly fine to use. When shopping most of the higher-current supplies you’ll see are 12V anyhow.

At around 11V or so car amps and other car stereo equipment may shut off so it’s important to have enough voltage available.

What size power supply do I need?

Car amp DC power supply examples

Powering a car amp in your home requires a power supply with a decent amp rating. Standard wall adapters won’t work as they’re very weak (0.5 to 1A, usually). You can find bigger power supplies like a 5 amp model for under $15 if you shop smart. Desktop computer ATX power supplies are cheap, easy to find, and range in power ratings up to 500W or even more.

Quick tip: Computer power supplies can offer 15 amps or even more current output making them a great solution. They’re available in a variety of power ratings such as 150W to 500W or more.  A good ATX power supply will have enough power output for the average person if you’re not trying to get a ton of power from an amp.

Option #1: Getting a “good enough” power supply for casual listening

When not driving an amp & speakers hard, I recommend at least a 2.5A supply for small amps (under 50W/channel). For 4 channels, I’d get a 5A or bigger. If you’d like to have more power, consider getting 15A or above.

If you shop around, you can find a 5A supply for under $15-$20 if you shop around some. 10A and 15A supplies are fairly popular so they’re usually under $30-$35 dollars or so. When it comes to much bigger supplies that will let you drive a subwoofer with heavy bass things tend to get expensive.

Very high current power supplies are around $100 and above for 30 amps or more – that’s especially true for traditional transformer-based power supplies. Those require a very large, high-amperage transformer which drives up the cost.

However, one of the best options is to use a desktop computer power supply (“ATX” power supply) as they’re easy to find and have pretty good power output.

Option #2: Estimating amp current needed for higher power use

If you’re planning to use a car amp to drive speakers hard, you’ll need a lot of amperage, which you can estimate pretty closely. We also need to consider wasted power to come up with a final number. (All amps waste some power as heat and draw some additional current for that reason)

  • 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, it’s probably class A/B. Class D amps normally say so on the amp itself, the box, or sales info. Class A/B types have been so popular for years that it’s a pretty safe assumption.

You can estimate amp current based on the maximum RMS power of the amp. Don’t use “peak” or “maximum” watt power ratings as these are misleading. We need to use the continuous power (RMS) the amp really delivers.

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:

Estimate amps used by a 50W RMS x 4 channel amp:

  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:

Estimate current used by a 150W RMS x 2 channel amp:

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

As you see, to run a car amp at full power, you’ll need a pretty big power supply! However, most people don’t, so it’s usually a lot less hassle (and less money) to use one of the other supplies I showed examples of.

DIAGRAM – How to wire a computer power supply to a car amp

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 usually. It’s a matter of a few steps:

  • Power connections: Cut multiple ground wires (black) and multiple +12V wires (yellow) and strip them for 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.
  • Supply on control: PC supplies don’t automatically come on even if the side switch is on. Normally a motherboard uses a control signal to the “supply on” wire pin. As shown in the diagram above, you’ll need to jumper the wire by cutting it, stripping it, and either connecting to a ground wire permanently or you can use a toggle switch.
  • Amp remote on wire: As there are several good options for this, I’ll cover this in more detail below. 

Once you’ve connected the supply-on wire to a ground wire the power supply should start and your car amp should work. Note that in some cases, it is possible to have a problem.

Huge, high-power car amplifiers can sometimes have a short current “spike” they draw when first connected to power. In some cases, this can trip the self-protect mode in power supplies. If that happens you can try starting the supply first and then give the remote wire power after a moment.

It’s possible you may need a more robust power supply if that happens as well. This shouldn’t be an issue most of the time, though.

Note: When using a computer power supply, it’s important to use mutiple power and ground wires – not simply 1 each. Since we normally use higher current amounts, bundling wiring is necessary to help share the amperage load.

(ATX power supply wiring is typically about 18AWG which is good for a few amps but not larger amounts.)

Remote wire options for turning the car amp on

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

A car amp’s remote-on input uses a low-current +12V signal that starts its internal power circuitry. There are several good ways to do this:

  1. 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. 18AWG or smaller wire is fine.
  2. Jumper wire + switch: Basically the same, but you can also use a simple inline switch on the remote wire to turn it on/off yourself.
  3. Home stereo use – RCA converter with remote lead: If you’re connecting an amp to speaker outputs you can use a line level converter with a built-in remote wire output. They’ll automatically turn the amp on or off with an input signal present.

If you use 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 won’t drain power.

RCA adapters with remote wire output

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

Example of a line-level converter with a remote wire output feature. When the speaker level inputs have a signal, it creates a +12V remote wire signal. When no signal is detected, the remote wire will go to zero volts and turn the amplifier off. Unlike a regular converter, these need +12V and ground connections to work.

How to connect a home stereo, smartphone, or other audio sources to an amp

What’s great is your many options 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. I’ll cover some of the main ones here:

  • Smartphones, tablets, and laptops can be used either by their headphone jack or via Bluetooth (see below)
  • Any home stereo receiver or amp can be used – even vintage ones!

How to connect a smartphone or other device to a car amp (diagram & options)

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

Be aware that headphone jacks can be a good or bad audio source depending on your particular device. Even though they’re usually not quite as good as RCA outputs/AUX output jacks, I’ve had pretty good experiences doing using this with brand name smartphones or tablets.

In fact, I use this method to test a car amp at home.

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 for this reason.

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.

How to connect a car amp to a home stereo (diagram & options)

How to connect a car amp to a home stereo diagram

How you connect your car amp depends on your home stereo and your car amp’s features. 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 audio-out jacks. In this case, if your car amp has speaker level inputs built-in these can be connected to an unused pair of speaker terminals or alongside speaker terminals in use. The amp’s speaker level inputs will scale down the speaker signal to a much lower signal the amp needs.
  2. Home stereo with no RCA output jacks + car amp with RCA jacks only: In this case, you’ll have no choice but to use a line level converter used for car audio. Just like in #1 above, these are connected just like speakers to speaker terminals alone or alongside connected speakers.
  3. Home stereo with full range RCA output jacks + car amp: This is the easiest way by far. Unfortunately, not that many 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, but subwoofer RCA jacks won’t work for full-range music since they only pass bass.

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. Both take a higher voltage speaker level signal and drop it down to a low voltage suitable for the amp’s input section.

Line level converters (also called RCA speaker level adapters) are small adapters that reduce the higher-voltage signals from speaker outputs to a much lower voltage (“line level”) used by a car amp’s RCA jack inputs. They can be connected directly to a ratio, amp, or speaker and provide RCA jack connections.

They’re really useful because they make it possible to connect an amplifier to a signal source that you otherwise can’t.

What to do if you have ground loop noise (humming)

Example of an RCA ground loop isolator

A ground loop isolator you can use to “break” (isolate, disconnect) an amp’s RCA ground connections from that of an audio source to eliminate the electrical path that causes ground loop noise.

Sadly, noise can be a BIG headache when it comes to car amps despite them being designed to prevent it. The same is true that home stereos, too: anything that carries a signal and has a ground connection can create a “ground loop” that gets picked up by the amp and then turned into a very annoying noise you easily hear.

What causes ground loop noise?

Ground loop noise happens when there’s a slightly different potential (a slight difference in voltage) between the ground connections in an amp, stereo, and other components. Despite everything you try, sometimes it’s nearly impossible to eliminate.

In that case, you can try a simple RCA cable ground loop isolator which often solves it. Note that you shouldn’t try to get the cheapest you find because they can negatively affect sound quality.

Depending on the brand and features, you can find a good one for $10-$25 or above.

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. Ok so for a power supply could I use a power supply that went to a modem router it’s 12-14 Volts and I think 75-100 amps? And if so I do I connect so I can just plug in and flip the switch?….if not what about a ballast for the big thousand watt grow lights? They run on 110 or 220 switchable butt I only have laptops and no place around here sells computer parts

    • If it’s a standard AC-DC power supply then yes that would work for powering car stereo items like an amplifier>

      > f not what about a ballast for the big thousand watt grow lights? They run on 110 or 220 switchable

      If it’s 110V or 220V AC you’ll need an AC power source, not DC.

    • No way your routers running 100amps. You are looking at a relativly expensive psu to push that kind of amperage, Roughly 1600w on pc psu’s is often around 100amps.

      Do grow light ballasts output 12v? Don’t they vary the output to start the lights etc? I dont know much about them to be honest but unless they are outputting 12v they are not useful.

  2. Hi, I have a Corsair HX1200 that I use for my PC. It being a modular power supply, do you think I could unhook the mother board cable and get power from the pins on the power supply?

    *I dont want to cut any wires with it being my main power supply, so any solutions that could be similar to this that go without cutting or modding to much would work too. Thanks :)

    • Hello Demetrie. In principle, yes that could possibly work. It will depend on how many amps you’ll need to get from it along with how much power your PC needs as well.

      You can buy inline male to female ATX wiring harnesses that will allow you to get access to the wiring without having to cut the original. You could then either tap off of those in the harness and to go wiring terminals/blocks or something similar for access.

      You definitely should check to see if any power consumption specs are available for the motherboard then subtract that from the power supply’s rated output.

      : If you’re planning to power a car amp or etc and subwoofers, the car amp may cause the ATX supply’s output to sag when the bass “hits.” This could cause an issue if the motherboard is running, so that’s just a heads up in case.

      I would recommend using a separate supply you find for a deal instead of using the same one, if possible. Best regards.

      • Very cool. I’ll have to look into buying another wire then. I probably wont be using the amp and the PC at the same time, but even then at idle it doesn’t pull much power. Buying another supply isn’t really a great option, especially considering its a 1200W RMS amp and 1250W RMS subwoofer. Thanks for the help Marty!

  3. I recently was at tha junk yard for random parts and came across a infiniti with the factory bose system with the 5’1/4 middle subwoofers it has two in a box that fits in the spare tire, anyway I left wit it my infiniti has a system already so I want to put it in my den use my phone to play music for fun really ,I build all kinds of diy stuff, point of this I know most all about it but tha factory amplifier does not have rca Jack’s what do I connect my phone to if it’s all wires I’m stuck help a guy out ,if I don’t have to buy no extra stuff be better few ideas if u can

    • Hi there. It depends on the year model the Infiniti.

      • Late model factory systems may not be able to work outside of the vehicle because they will no longer have an in-car network connection (LAN or CAN network bus, for example).
      • You’ll need to look for a Bose integration adapter as it’s likely not compatible with a standard RCA signal connection.
      • You’ll also need to find the wiring schematic for the vehicle, then find the pinouts to get it working with an AC-DC power supply.

      This is probably not going to be an easy project unfortunately because chasing down factory connector wiring pinouts can be tough. I’m not saying it’s impossible, but unless you’re comfortable with electrical wiring, electronics, etc. it may be a bit ambitious in this case.

      Honestly, you’d be better off either getting a simple Bluetooth mini radio/amp or mini amp to do the same thing. Or a standard car stereo with Bluetooth and/or AUX input jack then use a power supply.

      Best regards & good luck!

  4. Yea I’m ambitious for sure ,always taking things apart for mosfet to nichrome wire, relays ect…
    So this just a personal mission trying to learn all I can .anyway I’ve seen on YouTube people are doing it but there’s never no info or gud views to see .can I run to the speaker input with aux or run out rca from them then hook to my phone to play audio like that? Is there any way to piggy back off any wiring if not I’ll try to see if I can go from the circuit board and see if I can add something that way ,any info will be great or some kind of link on the subject

    • Hi Anthony it depends on the particular factory system. Some work with line level signals, some others don’t (or at least not directly without some adaptation), so I can’t say for sure. It always depends on the particular kind. If you look up the year model etc. you can see if any integration adapter was needed for that particular model/system in many cases.

      You could try going from the PCB, sure, but I usually get the vehicle schematics and try to see what I’m dealing with then go from there. This is a kind of outlier subject so I don’t have a link I am aware of to be able to provide, sorry. You could try owner’s forums for that particular make/model and see if there’s any info.

      Sometimes people post info on working with a factory system and what they’ve found out. Best regards!

  5. Quick question having a setup like the one’s mentioned above; is it safe to add a car audio capacitor between the dc supply and the amplifier?

    • Hi, yes you can add one if you like. Just be aware that charging a capacitor acts momentarily like a short (cause a current spike) so it’s possible it could trip the self-protect mode on some power supplies.

    • Hi Keith. Yes, actually it can definitely be done. However, since that appears to be an AC-AC step-down transformer, you’ll need to rectify the output and add capacitors to create a steady DC voltage output. Essentially how it’s done for a lot of home amplifiers & receivers with an internal AC-DC supply.

      However, it’s not that complicated if you’re handy builing things and there’s a ton of information on the web that can help. The parts are widely available also.

  6. very useful info that is easy to understand, much appreciated!

    I have a question, I will be running a low profile powered sub that you usually use for under the seat car installs and I will be connecting it to home theater sound bar through its sub out connector (LFE). Now the impendence on the website for the sub is 2.6 ohms. Will there be a problem running it? It is technically connected to a car amp that is built in on the sub but im not sure i can rewire to 8ohms. I know most home theater receivers are for speakers that are 4-16 ohms but since it is going to a car amp even if is at 2.6 ohms, I am hoping thats not a problem though I’m not sure. the amp in question is a Planet Audio P8AWK 8″ 800W Amplified Subwoofer System with Enclosure.

    • Hi Roberto. I see that you’re wanting to use a self-contained powered subwoofer, which is not problem. Since it already has an amp built-in and the subwoofer’s already matched to it, all you have to worry about is getting a line-level signal to it (the LFE out jack) and a +12V power source.

      When you connect the LFE (subwoofer) output jack to the powered sub, it will only “see” the very high impedance input jack on it. The subwoofer won’t be directly connected to it.

      It’s a different situation if were were talking about connecting a car sub, without an amp, to a home receiver or home stereo amp, etc. In this case it’s no problem.

      Sounds like a good use of one of those compact car subs, in fact! Those could fit in a lot of places inside a home. :)

      Best regards.

  7. I ‘m having some difficulty understanding the amp calculation examples. In the a/b example, where does the 2 amp come from?

    I’m looking to power an mrp-m650 amp (400 W @ 4ohms) to a 12” alpine R type with duel 4 ohm voice coils.

    • Hi, the “x2” is intended to mean 2 channels, as is commonly included in specs for car amplifiers. But I’ll edit that to make it more clear going forward. My apology if it wasn’t clear.

      For the MRP-M650, you can use its fuse amperage rating as a guide (60A total). Or you can use the calculation examples in my article to find a reasonable compromise using a decent AC-DC supply to get a moderate amount of power.

      Also, here’s a calculator I added to help as well:

      Best regards.

    • Hi, you could use one but will still need to rectify it to DC. But I believe there are kits or pre-built PCBs with all you’ll need already assembled out there & available. They’re popular for home stereo projects etc.

  8. I have a dual 400 watt amp and a sub that goes with it. I have a sound bar that the amp can hook up to. I’m just not sure what to do about getting them amp to power the sub. What would be your suggestion?

    • If you have enough channels you can just connect the subwoofer to the amplifier. Unless I’m not clear on what you’re asking.

      Most amplifiers have a low-pass crossover feature so that will take care of getting good bass sound from your passive (non-powered) subwoofer. Best regards.

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