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

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

About: im a fiddler, but i screw up a lot hence why as i write this i have one 'ible. but dont fear! i will find something of use that hasnt been done before. when i have the time that is.

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
http://www.youtube.com/watch?v=xI3s7F36E4c

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.

3 People Made This Project!

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91 Comments

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

1 reply

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?

1 reply

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)

image.jpg
1 reply

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?

1 reply

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)

4 replies

Sorry I was hasty and forgot to add that I don't need all 800 watts, I do have a smaller amp and a much larger. This will be outdoor for my patio and does not need to be obsurd! Hahaha. I also have an old turntable/8 track/ radio chest that I may build this into. What would be the best way to get audio from the three?

I'd say some sort of switch. Maybe a three position toggle one, really not sure how to word it (three pole? three throw? I don't know).

A lot of info there but the long and short of it is this, head units don't draw a lot of current. The speakers themselves are pretty irrelevant as it's the amp that's taking the power. You may even be able to run the equaliser off of it too.

A bit more info:
jl audio (tr570cxi) 2-way 5"x7" speakers (pair)fit 6"x8" 1/2" textile dome tweeter4-ohm impedance10-50 watts RMS

Jl audio (tr600cxi) 2-way 6-1/2" speakers 1/2" dome tweeter4-ohm impedance10-50 watts RMS power rangefrequency response: 59-22,000 warranty: 1 year

Like I said this is laying around, I will be looking for a sub 8-10"

Tried it My Friend, to Power a Sub on My 5.1-AMP, and You get Horrible Interference/Buzzing from PSU...

Would You know how to Stop this? (by the way tried using a Blocker,off a Head Unit, to No Effect.!)

5 replies

sounds like the Kenwood amp is amplifying a dirty signal. have you tried running the sub from a different source? to eliminate the amp/sub combo? that's what if try, or just turn it up haha win win in my books that solution

Hey BadBrad...

Thanks for chucking in, as a matter of fact, I actually sorted it last night with, a much Lower Powered, 300w (Mercury) PSU, don't know how good they are but it sounds sweet now...

No-Interference/Buzzing-(Only Me.!!) & No Tripping out just when it starts to get Good.! Oh sorry I had tried one of those Multi-Volt Uni-Power Adapters, 500ma Regulated, it was clear, but just Nooo Power, to Run-it-well. So the Amp jus kept on Clicking out, for a second, then again and again... You get the Picture...

But Anyhoo Sweeeet Now...

Than You again...

Dan

P.S. I am No-Master at all, so can I please ask, with it being a 300w PSU, does that relate to Wattage in Sound i.e 300w Amp..?

Forgive Me if You can't breath from Laughing so hard, but My mind kind of works that (Logical) way...

Nice-1

A good rule of thumb is that a digital system is about 85-90% efficient. for example, if you have a digital sub amp and it says 300 watts, it will put 300 watts into the speakers but that 300 is just 85-90% of what it draws from it's power source, so when we math that out it should need about 333-353 watts. Of course with some amps that 300 watts is rms and you get peaks that are higher, though in personal experience testing out both laptop chargers and desktop psu's you can often exceed the ratings by about an extra 20-50% without much risk, but I wouldn't recommend it, since I was just experimenting with a couple designs since that was all I had to power my amps. Either way, as long as it sounds good and you can be sure nothing is overheating when your blasting your music you should be just fine.

A good rule of thumb is that a digital system is about 85-90% efficient. for example, if you have a digital sub amp and it says 300 watts, it will put 300 watts into the speakers but that 300 is just 85-90% of what it draws from it's power source, so when we math that out it should need about 333-353 watts. Of course with some amps that 300 watts is rms and you get peaks that are higher, though in personal experience testing out both laptop chargers and desktop psu's you can often exceed the ratings by about an extra 20-50% without much risk, but I wouldn't recommend it, since I was just experimenting with a couple designs since that was all I had to power my amps. Either way, as long as it sounds good and you can be sure nothing is overheating when your blasting your music you should be just fine.

that is a question I unfortunately don't have a straight answer to, I do however believe that are not related. as the 300 watts is the output, not input. on both devices. the amperage is important. if your amp draws up to 20amps worth of current the PSU needs to be able to supply that if you want to max the audio amp out, if your supply doesn't cut out at the volumes you're playing it at then the supply must be enough. although it could be running out of spec, not ideal on a brand I've never heard of. on a corsair or antec etc I'd say you'll be fine. but like you, I am no master, and probably have it completely wrong.

but I'm glad you got it sorted, I'd love so to it!