Car Audio Power

BrightSideSC

Member
Oct 1, 2012
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0
0
I have heard of people using PC Hardware (PSU) to power their car audio systems, and I was wondering HOW? What Wattage would they use? What Brands? How would the wiring work? Etc...
 

Golgatha

Lifer
Jul 18, 2003
12,250
656
126
You could do it, just don't have any idea why you would want to. Car audio runs on 12V, but you'd need a hella big PSU to run anything decently high wattage. Also, the loss from DC to AC to DC rather than just going straight DC to DC is pretty much wasteful and pointless.
 

Soundmanred

Lifer
Oct 26, 2006
10,780
6
81
Most PSUs, even large ones, would only be able to run small system, possibly a head unit and a few speakers running of the internal amplifier. Subwoofers and external amplifiers are out of the question (at any appreciable volume at least). They simply can't provide the amperage necessary.
 

HeXen

Diamond Member
Dec 13, 2009
7,828
37
91
AFAIK, it's a cheap way to bench test or run an extra audio stuff, like a head unit or very small amplifier in your garage or home instead of buying a shelf stereo or something. I never heard of anyone wanting to use high powered amps in their home or anything for this but back in the day, the ghetto kids would use a high amp battery charger and car battery hooked up in their house to some car subs and amp to power a Rockford Fosgate Punch 100 or something. But most normal people just use it to test their audio gear.

Here's a how to
http://www.instructables.com/id/Turn-Computer-Power-Suppy-into-Car-Audio/
 

Conroe

Senior member
Mar 12, 2006
324
32
91
I've been running an car amp off a older xbox 360 brick I found cheap at a thrift store. You have to ground one wire to get it to turn on if I recall correctly (much like a computer PSU.) It's rated 14 amps and that is more than my 2x40w amp can use. That powers my jobsite blaster. I use a game cube brick and a cheap Chinese 2x15 tripath board for my computer speakers. I have a laptop power supply and a 2x50 tripath board too.
 
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Raduque

Lifer
Aug 22, 2004
13,140
138
106
I used an older FSP PSU - 450w and I think 2x20a +12v rails - to power a cheap car amp and subwoofer for my computer audio system. I lopped off all the +12v wires from the molex connectors and twisted them together for the positive and same for the negative with the black wires.

MAJOR fire hazard, so I don't recommend it, but it actually worked pretty good. The amp was a low-power amp only putting out maybe 50w RMS, but it was good enough for feel-able bass from a single 10.

I then used the same PSU with one molex wire bundle soldered onto a barrel plug to run my RC heli's lipo charger. I don't use it to run the amp anymore.
 

mindless1

Diamond Member
Aug 11, 2001
8,390
1,568
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Yes you can easily and safely run a car audio system off an ATX PSU, just not an additional secondary amp unless it's a very low powered one.

Use a PSU with an honest wattage rating so you know where you stand with available 12V current, and preferably one with a single 12V rail. Cut the connectors off the leads on at least enough leads that you end up with some margin, ideally (rated 12V current / 6A per lead) = # of 12V leads needed. Now do the same for the negative leads.

Twist and solder all negative leads together and the same for positive, and solder to the corresponding points on the radio wiring harness. If you don't have the harness you'll have to take the radio apart and solder leads to it, or source the harness which should be dirt cheap from a junk yard if it's an OEM factory equipment stereo.

On some PSU you might have an overvoltage shutdown situation if you don't put a bit of a load on the 5V rail. A power resistor is one easy option for that load, something like a 25W chassis mount 2 ohm resistor that you put heatsink grease on and bolt to an old heatsink, something like the following: http://www.digikey.com/product-detail/en/KAL25FB2R00/KAL25FB2R00-ND/1646179 then just strip and solder one 5V and one ground lead to the resistor.

You might also want to wire up a SPST power switch to the green PS-On PSU lead and a black ground lead or if the PSU has its own power switch on the rear you can just solder those two wires together and of course you should cover all solder joints with heatshrink tubing to insulate them, and mount the heatsink with the resistor to something that can withstand the heat as it will be getting hot enough you can't comfortably hold it unless it is a fairly big heatsink... something roughly 1" H x 2"W x 2"D or larger should suffice, something like a heatsink from any regular power level desktop CPU made in the last dozen years.
 

mindless1

Diamond Member
Aug 11, 2001
8,390
1,568
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MAJOR fire hazard, so I don't recommend it, but it actually worked pretty good.

How so? It's a relatively low voltage and ATX PSU have short circuit / overload protection.

There's nothing inherently dangerous about powering an amp that needs less current than the PSU 12V rail is rated for, if only you use enough leads to be capable of handling the load, insulate them so there can be no short circuits, and mount a power resistor on a heatsink where it won't be in contact with anything with a low melting and combustion temperature. Most people would probably mount it on the PSU lid so a little airflow from the PSU fan helps to keep it cooler.