PC Power supply

[catfaneng]

Does anyone have much experience with pc power supplies? Is there any reason that using a 12V power supply from a desktop will not work to power a car stereo that is pushing two 130 watt max speakers? Will the power supply produce enough continuous current?

 

[geekEE]

PC power supplies typically will output a lot of power on their 3.3V and 5v outputs, but the 12v outputs is a lot less as there are not that many things that use 12v in a PC. It's not even close to what you're going to need to output 260W.

By the way, can your stereo actually put out 130W/channel, or is that what the speakers are rated at? It wasn't clear from your description.

 

[felixc]

In order to properly drive power from the 12V rail, there must also be a good power drive on the 3.3 and 5 volt rails, as they are all winded from the same transformer and the main feedback control comes from either the 3.3 or the 5 volts. The most recent ATX2 supplies have extra power at the 12V rail because the latest graphics cards are using the 12V to power on-board switchers for their chips. But you still need to feed them a good load on the 5 and 3.3V rails.

 

[killabyter]

it should work, but should be aware about some issues: switched power supplies like a pc one, will produce much noise in the audio band, because of the current switching.

pc supplies are not intended to withstand for extreme current requirements like a bass sound, so would oscilate or shut down, even damage if subs are connected. be careful.

regards

killa

 

[itsmoked]

A PC supply may not put out anything unless a certain input signal is in place.

I don't think I've ever seen one that DIDN't state what its outputs were limited to on the label.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[sreid]

260 watts at 12 Volts equals 21 Amps, much more than any PC power supply will supply (more like one Amp at 12 V).

 

[catfaneng]

The speakers are rated at 130 watts max which means they are probably 40 watts rms. I connected to my car stereo and they sounded pretty good. I have heard of people using pc power supplies for this but they have to do some rigging with the 3.3 v and 5 v rails. If this wont work does anyone have any other suggestions? I thought about purchasing a regulated supply but didnt want to spend the money.

 

[IRstuff]

You could get something like this:

http://www.tigerdirect.com/applications/searchtools/item-details.asp?EdpNo=544429

TTFN

FAQ731-376

 

[BobbyNewmark]

Give it a try! It might work badly, but probably won't fry the stereo. Pick one that doesn't need a minimum load on the 3.3 and 5 volt outputs, and stay away from the cheapest models. Do not attach one of those giant car stereo capacitors: it might make the power supply oscillate, and it's pointless because the power supply doesn't droop like a car battery does.

What's with all the bad information? Good modern PC power supplies are strong. Last year I put one in a laboratory instrument driving a 12 V, 0.5 ohm heater controlled by an audio-frequency PWM. It didn't break a sweat, and saved loads of money over a "proper" supply. As an example, the Enermax EG851AX-VH(W) can put out 28 amps on its puniest 12 volt rail. Depending on its internal construction, you might be able to parallel the 12 volt outputs to get 38 amps total.

"switched power supplies like a pc one, will produce much noise in the audio band, because of the current switching."

The modern ones switch way above the audio band. If noise turns out to be a problem, a choke and capacitor should take care of it.

"PC power supplies typically will output a lot of power on their 3.3V and 5v outputs, but the 12v outputs is a lot less as there are not that many things that use 12v in a PC."

On modern supplies the 12 V rail is by far the stoutest. It's just not practical to run a pair of 130 W processors on 3.3 V: the needed wires are too thick. The processors, video, and motors all run on 12 V, and often the memory and chipset do too.

"pc supplies are not intended to withstand for extreme current requirements like a bass sound,"

They most certainly are. Consider a game that has 50% utilization with a 100 Hz frame rate, running on a pair of 100 W CPUs and a pair of 50 W video cards. The PS would easily see a 100 Hz, 250 W square wave load on its 12 V rail.

"60 watts at 12 Volts equals 21 Amps, much more than any PC power supply will supply (more like one Amp at 12 V)."

If you have money to burn and reliability isn't a worry, there are units that go up to 72 A.

 

[itsmoked]

sreid; Um.. ah.. My PC's power supply puts out:

20A @ 5V
24A @ 3.3V
0.8A @ -12V
and
42A @ 12V

http://www.antec.com/specs/NeoHE550_spe.html

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[sreid]

Wow, shows what can happen when you answer a question you really don't know the answer to. Years ago, the 12 V supply was whimpy but clearly it is not today!

 

[geekEE]

I too hang my head in shame for answering with my knowledge of PC power supplies from a few years ago. I guess that's why it's always good to get a second opinion (and a third and a fourth...)

 

[itsmoked]

LOL

I bet your older supplies had NO 3.3V either. I was resurprized when I looked mine up.

My video card spec states that it "needs a minimum of 28A @ 12V"

This is why a functional "Suspend" is absolutely vital, as leaving a PC with a high-end video card running all day will put the "hurt" on you.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com