Wiring a Car Audio Amplifier and Headunit Up Indoors Using PC Power Supply





Introduction: Wiring a Car Audio Amplifier and Headunit Up Indoors Using PC Power Supply

Proud to be the first on instructables regarding HU's
I'm going to show you how to wire up a car amplifier and headunit in your house without the need for a battery and charger.
This instructable will allow you to wire in the following configurations:
Amp and headunit steps 2-7
Only the amp steps 2-5
Only the headunit steps 3, 4-7

You want a powerful PSU for this, the amps are important, the bigger the better really, from a reputable brand preferably.

IMPORTANT!! Don't be an idiot, turn your power supply unit off and disconnect it from the mains when you're working with the cables. ALSO I'm not responsible for any damages incurred. Although I'm sure most of you know that already...

I've only seen one other instructable on doing this, but they didn't cover the headunit part of the build. The person was Br14n and a link is in one of the steps.

A video :D

Please let me know what you think.

Step 1: Forethought (update 17.3.15)

OK an update to the instructable and a few things of note. (17.3.15)

Firstly I don't run this system anymore, haven't done for years, somewhat regret getting rid of the stuff but there we go.

Some new power supplies have a silent operation mode until x amount of current of being drawn, so when testing that your PSU turns on it would be great if you had a PC fan or anything to connect to it that will always turn on when there is power to it.

Another power supply note, if this is going to be permanent then I highly suggest you follow one of the numerous test bench power supply mods on this site. This will allow a simpler design, less cluttered appearance and easier hook up.

Another power supply note, screw it they're all power supply notes. I've read somewhere that someone was having trouble getting their PSU to turn on, they had a sense wire which required 3.3v as well as the shorted PSU_on wire to ground. If you have issues, check your manufactures website. Gather your details. Google is your friend. Personally I've never come across this but that's not to say it doesn't exist.

Step 2: You Will Need..

You will need...

A PSU (power supply unit) from a PC or XBOX (original).
Wire cutters.
A car stereo amplifier.
A headunit

Basic tools.

Step 3: Preparing Your PSU

OK I'm assuming you have removed or are able to get access to all cables from your PSU.

Oh by the way, the PSU can, if you want, remain in the computer or XBOX, if you do this then you don't need to do this step but your PC or XBOX must be switched on when using the amp. (Not recommended).

I decided to not cut up my PSU cables as i may need the computer it came from at some point, you will need to find the pins shown in the pic, they are on the connector that was originally on your motherboard, the cables should be green and black, any black ground connector will do the trick. you will need to bridge these, either by doing what I've done (looping wire from one to the other) or cut them and splice them together.

Now a quick check, turn on your PSU and if the fan spins you're all set for the next step.

Step 4: Wiring Your Amp

So you have your amp ready? Good.

This is a good reference, it was made by BR14n https://www.instructables.com/id/How_to_use_an_old_Xbox_PSU_to_power_a_car_amplifie/

As i chose not to cut cables I've merely inserted a length of cable into the end of the molex connector, you may wish to cut the cables (cutting makes for a more secure system). I suggest using every (except one, you need it later) 12V rail there is (that's the yellow wires) to ease the load.

However you choose to do it you need at least one 12V rail running to your battery+ on your amp, this is providing power. As the picture shows you need to connect your ground on your amp to the black ground cable from the connector.

Once you have your two cables connected you're ready for your next step.

Step 5: Power Up the Amp

Here's where whether you're using a headunit or not comes into play, I advise everyone to do this step as a test or as a completing step.

Get a small loop of wire and strip the ends, put one end in your remote on the amp and the other in the batt on your amp.

This will mean that when you turn your PSU on the amp's indicating light should turn. If this doesn't happen then something's gone wrong. Now for those who only have a amp to wire up then you're done, all you need to do is connect your speakers and your RCAs and give her a test run.

Those of you who want to use a headunit can do either of the following:
1) Leave your set up as is so that you can have any source input to your amp without the need for the headunit to be on. I personally use my laptop as a source a lot so this works best for me.
2) Remove the loop from the batt to the remote and instead link from the remote on your amp to the remote cable from your headunit, this means your amp will only be on if your headunit is.

Step 6: Wiring and Powering Up the Headunit

This step its pretty simple. You need one 12Vrail and one GND from the PSU and (if they aren't marked up) a wiring diagram or similar for your headunit to identify the wires. This info is ready available online, what isn't right?

Take the 12V rail from your PSU and run it to the 12V on your headunit, this will also need to run to your ACC (accessory), the pic shows how I did this.
And the last thing is to connect the GND.

That's it, you're done. All you need to do now is connect RCAs from your unit to the amp, add some speakers and switch her on.

There is one more optional step. and is required for those just using a headunit.

Step 7: Using Your Headunit With the Amp

The colours of the cables for each channel from the HU.

You may be thinking "wait, don't cars have speakers that don't run through an amp?", yes you're right, and that's what this step is for.

If you want additional speakers or you dont have an amp, maybe you killed it during a previous step, you can use the stereos standard outputs, on my headunit they are in pairs and are coloured purple, white, grey and green. All you need to do is splice these cables or extend the cables to your speakers.

Here are the colours and the channels. Remember this is MY unit so yours could be different, refer to that wiring diagram I made you find earlier. Or if you can't find one then you could always connect a single speaker and use the balance and fade options on the unit to work it out for yourself.
FR - grey
FL - white
RR - purple
RL - green

Step 8: My System Specs and Final Thoughts

Just for anyone who might be interested, here are my system specs.

I'm running a 500WATT 4-channel Kenwood amplifier with (at the moment) one 800watt 12" Alpine subwoofer and 2 400watt Kenwood 6x9's.

I also have a couple of 700 watt Kenwood subs too, not being used at the moment, in need of boxes.

This setup certainly has a kick to it, great for parties . Anyway if you've got this far i assume everything went well and you are now enjoying the clear sounds from your new sound system.

Please, comment and let me now how you got on, I want to hear about your successes and even your failures, it could hold vital information that may have been overlooked. If you've been lucky enough to get it working then post pics, links and whatever else to show your handy work off.

Thanks for reading, and happy listening.

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hi. i have 1000wx4ch car amplifier. my plan to connect this to my portable guitar amp.

my question, if i want to use the PSU, what will be enough to power up the AMP?

what will be the calculation to find suitable PSU? P = V*I ?

thank in advance.

hey mate, could my 420w pc psu run a 500w amp cranked up? thanks

Basic math should answer that for you. Also a 420w PSU doesn't supply 420w, it loses some of the 420w it takes in conversion. You want a 650+ unbranded or 600w bronze+

when I connect the power (yellow) and ground (black) to the amp, the protection light flashes on the amp and the psu fan quits spinning. What am I doing wrong?

sorry about the wait. just for a sanity check. you do have them round the right way correct? also make sure the PSU is powerful enough to power the amp. make sure there aren't any shorts either. also, connect before switching on. low volume to start with, and build up. other than that, I'm not sure. I wish you the best of luck.

My head unit design with 2 5.25in speakers and 2 2in speakers , also with 2 5x7in (not in picture)


looks way cleaner than mine did. good job bud.

How do I match my psu to amplifier/sub ?

I already have a head unit hooked up and a few speakers running off of that (have had it for a while) and I just made the decision to try a subwoofer in my room with this set up. I have a 185 watt output power supply unit , a 1000 watt car amplifier , and a 250watt rms Phoenix gold 10" subwoofer.
I understand how to wire it , that's no problem for me . But will this 185 watt psu be able to power the amp and sub?

it should run, but there won't be a chance in hell youll be able to max it. so long as you keep under the maximum load of the PSU it should be OK. you be pulling maximum draw unless you have it cranked up after all.

Hello all! I'm looking for a bit of help. I plan on using a Bluetooth/aux/usb only head unit and cannot get a definitive amperage draw our running amps. I have access to multiple power supplies and I'm trying to spend as little money as possible for the sport of it. I have a 12 volt 3.7 amp power supply I'd like to use to power the head unit, a ps3 slim I was thinking of using for a 800 watt Kenwood amplifier kac-9104d. Is the first power supply enough, or should I use the ps3 power supply for the head unit and a old pc supply I have? I was thinking of using a digital bas reconstruction processor and possibly an equalizer. I'd like to be able to charge a phone from the usb, or add extra ports in for charging, or a wall out let or both hahaha. I have a lot of old much laying around and I figure I might as well use it. Any help is good help and I'll share the project. 8)