Powering car amp with computer PSU's - Problems.

[corkscrew]

Hi guys! I'm trying to run a car amp off of computer PSU's for my home theater.

ANYwho, I have a 500watt and 300watt computer PSU's connected to a car amp. All 12V (Yellow) lines (-minus the ones in the mobo connector), and all grounds are connected (minus mobo connector ones).

Both PSU's are hardwired to power on when plugged in. With everything except the remote wire connected they power up fine. The moment the 12V + is connected to turn on the amp, both PSU's shut down. They start up after a power disconnect and maybe 10 seconds. The power LED on the amp lights up briefly.

The amp is an old MTX 2150.

I have a MR16 bulb running off of the 5+ line, but it seems to make no difference.

I also tried (through bleary eyes last night) to trigger the remote wire with a 12v SLA battery. Same behavior as simply running a jumper from the 12V+ to the remote line.

 

[mdd0127]

Try a pre-charge resistor. Hook up an inline 1k resistor precharge circuit from the power supply output to the amp's 12v in, power on the remote, then, after a few seconds, bypass the pre-charge resistor, connecting the main power. It my be that the initial current inrush to charge the caps in the amp is tripping the psu's. Does the amp power up and operate normally off of a battery?

 

[mdd0127]

Another alternative would be picking up an old Kenwood 100 watt receiver and a pair of Cerwin Vega towers from the thrift store for $50, plugging it in, and enjoying your home theater without having to worry about a fire breaking out in your entertainment center or something. I've seen computer PSU's do some crazy stuff that would make even LFP proud!

I have a big pile of old car stereo amps that I'm always trying to concoct uses for. For some reason, they're all still sitting in that pile. :wink:

 

[corkscrew]

Try a pre-charge resistor. Hook up an inline 1k resistor precharge circuit from the power supply output to the amp's 12v in, power on the remote, then, after a few seconds, bypass the pre-charge resistor, connecting the main power. It my be that the initial current inrush to charge the caps in the amp is tripping the psu's. Does the amp power up and operate normally off of a battery?

I'll have to check the amp against a car battery this weekend. Otherwise I'll try the precharge idea.

I already have a deck and some quality speakers - I'm trying to setup the car subwoofers for the surround sound, as we already have those, vs buying a powered sub or AC Amp.

 

[vanilla ice]

Get a buffer 12v sla then hook up your psu to that. I used to run a completely car audio system in my bedroom with a battery and 12v supply.

But like the others say its easier to just get a home reciever. People give away perfectly good receivers because of the new 13.7 or whatever surround that they had to have just came out. Those old 2 channel guys make great sub amps.

 

[corkscrew]

Get a buffer 12v sla then hook up your psu to that. I used to run a completely car audio system in my bedroom with a battery and 12v supply.

But like the others say its easier to just get a home reciever. People give away perfectly good receivers because of the new 13.7 or whatever surround that they had to have just came out. Those old 2 channel guys make great sub amps.

I have a home receiver. It just has a pre-amp output for the sub though, the built in amp is just for the surround sound speakers.

I'll try the PSU --> Battery --> Amp idea tonight.

 

[amberwolf]

Couple of decades ago, I used to run a 4-channel (with one blown channel) Blaupunkt unit about the size of a PC CDROM drive as a portable and home stereo, powered off an unknown-wattage big server PSU, using an SLA from an old UPS as a buffer. Worked great; my favorite part of the thing was it's "auto EQ setup", it put out a burst of white noise, and with it's built-in little mic it tested the room's characteristics, including delay on each of the speakers (I only used two), and setup itself for the "ideal" flat EQ settings for that room. I wish I knew where that thing wound up. (it wasn't loud, but it was NICE)


Anyway, it had the same problem yours does, of shutting off the PSU from inrush current/overload, when I just hooked it up to it directly; I never thought of the precharge back then, but it would probably have worked, too. But the SLA across the 12V worked fine, until the battery started to age too much after a couple of years, and started shutting down the PSU itself.

 

[corkscrew]

I like the sounds of that auto setup device Amberwolf!

I used a 3.5A/h SLA to precharge, and then powering the PSU on, I connected it too the amp, and then removed the battery. It runs, but is a pain to start up every time.

I haven't gotten it set up in a permanant state, as I'm going to only use one sub. (Have a double box with two DVC Fosgate 800W 12" and only a 150x2 MTX amp! It's my roomies setup so it's the first I've really looked at it. )