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Running Car Amp with Computer PSU

H

homestarmy

Diamond Member
I know it is possible, but what do I need to know about doing this?

I know obviously that I would need a remote lead to turn it on, no problem because I can run that directly from the PSU, no? And I can calculate what can work via the badge on the PSU, correct?

As in 18A on he 12v would let me run a 300w amp, correct?

I am mainly wanting to test a stack of amps that I have sitting around.

Any articles on this?
 
But what else do I need to know? What happens if you connect an amp that requires more power than the PSU can give? And if there are two rails, can I use them both somehow? How would it be wired?

Also, which pins do I short on the 20-pin connection to trip it to turn on?
 
I've overloaded computer PSU's with electric motors -- they just turn off. They seem to have a sort of circuit breaker. If you've ever shorted one out you've seen the same thing. They don't work again for a while, seems like they need about a minute unplugged before operating again. Can you tell I'm an amature?

Short green with any black to turn on the PSU.

To combine the rails I'd just splice them together, but I'm a know nothing. I think that if you do this you can possibly run too much current through either regulator (there's two if it's two railed PS), and burn things out. It's easy though.. better than all the hoops to combine regulators.

BTW, no need to bump your thread so often.
 
Aaah, you want to use it to bench test them. I was confused at first thinking you wanted to use the PSU to run the amp in the car, and I was 😕
I'm kinda curious too.
 
Sorry about bumping so much, I didn't realize they were so close.

Yeah, I want to use them to bench test. Can anyone speak further about using both rails to power the amp? I'm thinking about using an X-Connect PSU so I can just destroy one cable for this purpose that I wouldn't be using anyway. That and since it has already died (need to send it in for replacement), I don't trust it being in a computer.

I was also thinking, maybe I can use the Xeon six pin power cable. I'll never use that. That should have a 12v lead in it, right?
 
Oh well, the dual rails thing doesn't matter that much since I will probably just be using this Ultra one that I already have. It has 34A on the 12v, so hopefully I should be able to run a 400w amp. That should cover most of what I would need.

I could probably run a higher powered amp than rated if it was turned down very low, is that correct? I don't need to blast, just test.
 
Can't be done. The 12V section of most computer power supplies won't supply more than a ferw amps if you're lucky. Its the 5V section that has all the current capability.

Secondly, a switching power supply (used in a computer supply) is inherently more noisy than a linear supply. Switching supplies are typically not used in amplifier applications, except class D amplifiers. One caviat is that car applications have inherent noise due to spark, and other interference sources...
 
I'm sorry, but I don't believe this. It cannot be done at all, or it cannot be done to run a high power amplifier?

And 12v will not supply only but a few amps? This is the part I do not believe. I understand they overrate power supplies, but you're telling me that the power supply states it will put out 34A, but it will only put out what... 3-5A?

I understand the noise, but will that cause it to not run completely? Sure, there may be sound quality issues, but I want to test if they will run at all.
 
Originally posted by: yellowfiero
Can't be done. The 12V section of most computer power supplies won't supply more than a ferw amps if you're lucky. Its the 5V section that has all the current capability.

Secondly, a switching power supply (used in a computer supply) is inherently more noisy than a linear supply. Switching supplies are typically not used in amplifier applications, except class D amplifiers. One caviat is that car applications have inherent noise due to spark, and other interference sources...
Click to expand...

A single 6800Ultra graphics card will use 4.5A from the 12v rail.
Add in a second and you have 9v.
What you are saying is a load of bullshit.
http://www.xbitlabs.com/misc/picture/?s.../ati-vs-nv-power/6800u_table-b.gif&1=1

^^ Ignore quoted poster
 
So how many Amps do you think I can realistically expect from the 500w Ultra X-Connect? It is labeled at 34A on the 12v. Could I run a 400w or 300w amp with the gain lowered?
 
If all you're wanting to do is test if they turn it on, it will work fine for sure. Just hook up the PS and connect green with black (I think? double check that before you do it) and hook up the amp - yellow = 12v, red = 5v. Doesn't matter which black you use.


I'm not sure what you'll need to do if you're wanting to really "test" them with hooking up a speaker and playing a bunch of heavy bass or whatever. Just try it with a cheap power supply and see what happens.
 
Hahaha, to all the people that said it can't be done, my roommate has just what you are speaking of.

He has 4 daisy chained +12V leads from 4 PSUs feeding the amp that drives his sub. He has one more PSU powering his headunit.

He gutted the daisy-chained PSUs and desoldered all extra leads. From there, he used a plastic electronics enclosure to create an all-in-one unit with a push/pull fan configuration.

The bass really thumps on his 12W7.
 
PSUs are something around 480W and 16A 12V IIRC.

The next time I'll see him (and his home car audio system) will be in 2 months when we go back to school. So ... not sure if he has pictures anywhere accessible.
 
Why not just get a AC to DC converter, and just do it like that?

They're not that expensive days.

Better than frying all your amps.

 
Originally posted by: lokiju
Why not just get a AC to DC converter, and just do it like that?

They're not that expensive days.

Better than frying all your amps.
Click to expand...

Agreed 110%. 😉

If you want lots of cheap 12V power check out converters for RV's. They're SMPS like a PC and specifically designed for powering 12V loads and charging large batteries.

Text

You could get a 60A converter and a pair of 125 A/h "deep cycle" batteries and have enough power to drive the largest amps through the roof if you wanted. 🙂

 
See, the difference is Free After Rebate vs hundreds of dollars. I am testing amps that may not work in the first place...

Any cheaper converters out there?

BTW, I just remembered... I do have a car battery charger in my garage... could that be worked into the equation? It is something like this.

So I could just connect that to the battery, wire the amps to the battery as well and be set? But then I'd have to get a spare battery... what would be best for me to look into getting battery-wise?
 
Free After Rebate PSUs FTW.

AC to DC converters are still expensive in comparison, and no, they will not fry your amp if you wire it correctly.
 
Right. How complicated can it be? Run a 12v lead to the 12v input. Then run another 12v lead into the remote connection to turn the amp on. What else is there? And then short the leads on the PSU to turn it on.

On a side note, could you run a 3v or anything else to the remote to turn it on? It is just a switch that needs to see SOME voltage to turn it on, correct? Should the voltage matter?
 
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