Not quite modding, but would you be able to power a car amiplifier thats 800watts max and 400watts rms with around a 200 - 500watt computer powersupply? I want to get two 12" car audio subs running in my house, and I want to know whether its worth putting any money in.

I know I can power A 100W total (50W/channel) with a small 200W PSU, with 12V @ 12.3.

So Im going to say yes..

BUT!!! IMPORTANT!!! YOU MUST USE a LOW ohmage HIGH POWER resistor on the 5V Rail. (Say around 1Ohm 50W, Mount it on a heatsink from a dead PSU. That should be enough to load the 5V rail down enough to get you a good enough voltage on the 12V rail. The better you load the 5V rail the better your 12V rail will be.

Quote: Originally Posted by AlkalineOmen Not quite modding, but would you be able to power a car amiplifier thats 800watts max and 400watts rms with around a 200 - 500watt computer powersupply? I want to get two 12" car audio subs running in my house, and I want to know whether its worth putting any money in.

Oh sure, that's easy. I've powered a Legacy 1000W 2-ch amp on a 180W PSU to drive a RockfordFosgate 15" HX2 for my home theatre. Damn Man!! That thing would shake crap out of cubbords upstairs!

To be perfectly honest, I didn't even load the 5V rail and everything worked fine. But I could see how loading down the 5V rail will give you better 12V voltages.

Go for it! Rock On Dude!!!

Jobi

Hmm, well I have a big background in car audio. A Legacy 1000 watt amp is really prolly only 300 rms or less. So IF your gonna try it I'd definitely recommend using like a 400w psu. Good luck and let us know.

Quote: Originally Posted by Dead_Man Hmm, well I have a big background in car audio. A Legacy 1000 watt amp is really prolly only 300 rms or less. So IF your gonna try it I'd definitely recommend using like a 400w psu. Good luck and let us know.

Very true, I do really wish I had a matched amp for my Fosgate, but the legacy I have powering it now seems to handle it pretty good. The amp won't push more than 400W RMS, which is pretty $h!tty considering its a 1000W amp. But I got the Legacy Amp and the 15" Fosgate HX2 on eBay for $280 bucks, and the sub alone is worth around $700 last time I checked.

But yeah, if you're gonna wantto push more than 300-400W out of a car amp, you'll probably need quite a hefty PSU to dish out the current. Maybe you could try rigging in some capacitors... I don't know. Dead Man likely knows more than I do and thinks I'm talking BS by now. So listen to him

if you really want to get up to that wattage id buy a class D plate amplifier designed for hometheather subs. its much more effiecient than going from 120 to 12 volts then back to more than 90 inside a car type amplifier.
then again its probably more expensive.
lets note that 800 watts on 14 (fourteen, most car amps will run on up to 16 volts to goose alittle more out) you have more than 57 amps. at 400 you have 28 amps. as noted above a cheap amp usually puts out much less power than advertised but still 20 amps is far more than a typical ATX power supply will get you. of course you wont be getting that loud inside your home (unless you party) but if you want to i would suggest building your own simple ~13 volt power supply with a large transformer. this supplies way more current than a little computer switching supply. you can get a board that already has the rectifier and caps or you can make your own. you need a bridge rectifier rated for your load, a few large caps (more than 1000uf) some smaller ceramic caps for filtering (around 0.01 uf) and maybe a large choke. you can find various designs online. having clean power i would argue is not hugely important because of the inverter that is already inside the car power amplifier. you can also buy a prebuilt unregulated power supply like this at different electronics stores (usually a ham shack or even radio shack)
a tip for you is to put the subwoofer box in a corner and kind of have the room corner act as a horn. i know less than 100 watts through a 12 inch in the corner is plenty loud already.

If I hook up a less rated powersupply, will it just not get as loud? I've got an old 225watt server psu laying around that I think im going to use, but I still want it to have that nice punch. And im gonna go talk to my electricity teacher to see if he can snag me any nice resistors from the school

Quote: Originally Posted by AlkalineOmen If I hook up a less rated powersupply, will it just not get as loud? I've got an old 225watt server psu laying around that I think im going to use, but I still want it to have that nice punch. And im gonna go talk to my electricity teacher to see if he can snag me any nice resistors from the school

I think your best bet for that would be to hit your local pawn shop.I picked up a nice 800watt amp for just over 100 bucks.It's a Kenwood but it pounds.
As for the legacy.I'd rip it apart and use it to mod your tower.Thats what they do best.(LOOK NICE).

Quote: Originally Posted by steve fisher As for the legacy.I'd rip it apart and use it to mod your tower.Thats what they do best.(LOOK NICE).

Hey! I agreed with you, but it's the only amp I've got!

Quote: Originally Posted by AlkalineOmen If I hook up a less rated powersupply, will it just not get as loud? I've got an old 225watt server psu laying around that I think im going to use, but I still want it to have that nice punch. And im gonna go talk to my electricity teacher to see if he can snag me any nice resistors from the school

The signal coming out will just be clipped. Meaning instead of looking all perfect, the peaks will be clipped, so yes power will be reduced.

You guys keep forgetting how powersupplies work. Just because it is a 500 watt PSU doesnt mean that it is good fo a 400 or even 300 watt amp. You must remember that the rails on the PSU are divided up. So the 12v rail might only have like 280 watts and the other 220 watts are used by the other rails. You should always get the right tool for the right job so you dont hafta do it over. Just sell the amp and get a HT amp.

Or make a power supply yourself. I know where to get cheap parts to make a 12v 14Amp Powersupply. It will be linear or brute force though..

Aside from sounding crappy, clipping can damage a speaker.

Quote: Originally Posted by Cpt.Planet You guys keep forgetting how powersupplies work. Just because it is a 500 watt PSU doesnt mean that it is good fo a 400 or even 300 watt amp. You must remember that the rails on the PSU are divided up. So the 12v rail might only have like 280 watts and the other 220 watts are used by the other rails. You should always get the right tool for the right job so you dont hafta do it over. Just sell the amp and get a HT amp.

As long as you get the reccomended Amps, and Voltage(on the 12v rail, a PSU should work fine. The other rails don't matter, the amp only uses the 12v.

Or just get a nice 12v powersupply from an electonics shop.

not to sure about how it would do for a car amp but i have used old power supplies to power up motors ccl ect.12volt 5volt ect you name it works great for me i play around with wiring and all alot and this lil 200 watt does fine for what i do and i do push it some times. so i think it would have no problem with a car amp but no promises