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Old 12-17-2003, 12:17 PM   #1 (permalink)
I'm a family man - I run a family business.
Redjake's Avatar
Location: Wilson, NC
Car Amplifier/PC PSU

I want to make a subwoofer for my home theater. I have a car amplifier for a car sound system, two subwoofers (without boxes), and an old Sparkle PSU laying around. Is there a way I could run the 12V line from the PSU into the amplifier and it actually power it? The amplifier would only be doing 125 RMS for each sub, 200 Max. That's a combined total of 400 watts. The PSU is 350, but I seriously doubt I will be maxing out these subs anytime soon. Besides, I read that the RMS is normal usage or something. I would need a way to actually turn the PSU on, because it won't turn on without the case switch, right? And the case switch runs to the motherboard?

I was wondering if I could just flip the power switch on the back of the PSU on, but I looked, and this model doesn't have a switch

I could buy a dual subwoofer enclosure box, and mount the amplifier on it, and put the PSU inside the box somewhere, right? I'm pretty sure car amplifiers use a 12 volt line, so this is where my idea started. I've checked other forums but I need a lot of opinions on this before I start anything

Then I could run the AV cables from the amp into a mono/subwoofer wire and run that straight into my receiver.

Just an idea...Anyone had any experience with rigging this sort of stuff up?
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Old 12-17-2003, 09:04 PM   #2 (permalink)
turning it on...

I can't help you with most of your questions, but I should be able to answer one. To turn on the power supply without a mother board, you simply have take the ATX connector(the big one) and insert a paper clip into the green wire socket, and any of the black wire sockets. Obviously you can solder wires into them and hook a switch up.
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Old 12-18-2003, 08:55 PM   #3 (permalink)
shakran's Avatar
I was gonna do the same thing you're attempting. Just never got around to it. In my research I did find that you'll need to shield the IDE cable or you'll suffer major data loss.
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Old 12-18-2003, 09:55 PM   #4 (permalink)
!?!No hay pantalones!?!
saltfish's Avatar
Location: Indian-no-place
First off..

A 12V power supply from a computer PS is the wrong voltage..

I know, you're lauging, but...

At 12v, you car battery would be nearly dead. Many, if not all cars have a full charge/charging voltage of between 13.8V-14.4V DC.

Next, 125W RMS for each sub would be equal to 250W RMS total. So, think about the efficiency of the amp. 250W RMS out would be somewhere around 500W in.

So, at 13.8V and 500W is like 36.25A; unless you have a comp PS that could give you around 40A @ 12V; though you would lose efficiency by attempting to run the amp at 12V.

Second, you would really have to consider what kind of box/enclosure that you would want to put these speakers in, there is a lot of noise associated with moving/bare woofers. Look into a bandpass box for home use.

Try looking for a 40A 13.8V supply, either new or refirb if you're interested in doing this.

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Old 12-19-2003, 09:59 AM   #5 (permalink)
I'm a family man - I run a family business.
Redjake's Avatar
Location: Wilson, NC
why would 250W RMS out be somewhere around 500W in?

And yeah, I am going to get a bandpass box like my old one.

I know that cars actually run above 12V, but that doesn't necessarily mean that an amplifier has to have above 12V does it?
Off the record, on the q.t., and very hush-hush.
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Old 12-22-2003, 09:09 AM   #6 (permalink)
!?!No hay pantalones!?!
saltfish's Avatar
Location: Indian-no-place
First off, from my experience, amplifiers waste a LOT of power. A good way to test this is to run the amplifier, then, put your hand on it. All of that HEAT that you feel is wasted power, power that never made it to the speakers.

Now, car amplifiers are designed to run at voltages higher than 12V. You will have less output power at a lower voltage. If you have the paperwork that came with they amp, they may have given the output ratings at 12V.


How much capacitance does this PSU have? If you do decide to do this I would add at least a .5F capacitor.

Next question, on the side of the PSU does it give you a Current Rating for the +12VDC line? A common fallicy with PSU's is that 450W PSU, well, the +12VDC could only supply 5A which would be 60Watts.. The 3.3V@75A or the like, will make up the majority of the allowable power.

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Old 01-15-2004, 08:21 PM   #7 (permalink)
steveincolumbus's Avatar
Location: BFE, Kentucky
short and sweetm NO it will not work, you need a bigger PSU, like one made for running automotive stuff, go to Radioshack or a real electronics store and they can help you...

what you are saying is sorta like can my pickup pull a semi trailer?, it has a hitch on it.......... wrong time and not enough power............
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Old 08-26-2004, 08:32 PM   #8 (permalink)
This is quite possible..

Hello, came across this thread and thought I would put in my two cents. First of all, I have been running my computer sound system off of a RockfordFosgate 400.4 punch power amp for 6 months now.

The particular PSU I'm using is a Hipro 160w unit. I desoldered the entire 12V rail from the board, and soldered monster cable directly to it (including ground). I'm currently utilizing roughly 48% of the amps total power(180w RMS).

I've had no issues what-so-ever from this setup, and let me add how sweet this thing sounds

Don't be afraid to experiment a little bit, you never know what you will come up with.

Good luck!

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Old 08-28-2004, 11:36 AM   #9 (permalink)
merkerguitars's Avatar
Location: Wisconsin...
Do it the easy way I did....get an old bass guitar amp and hook that up to the sub box and wire it with the home stereo....works great!
Donate now! Ask me How!

Please use the search function it is your friend.

Look at my mustang please feel free to comment!

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amplifier or pc, car, psu

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