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Old 19th June 2005, 10:21 PM   #1
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Default start with a computer power converter

I am a newb that likes to collect junk and i found the perfectt thing for an amp. It is the power converter from a computer. now that i have it i have no clue how to build an amp but am willing to try.

PLZ help me
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Old 19th June 2005, 10:40 PM   #2
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my goal is to get 400 watt rms 800 peak
I also have polk audio speakers the kind that mount on the monitor and a generic surrond sound dydtem from walmart
neither work but i can salvage many a part from them
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Old 19th June 2005, 10:45 PM   #3
Netlist is offline Netlist  Belgium
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Hi Dave and welcome.

There must be possibilities to build a small amp with a computer power supply but what you are aiming for is a little over-enthusiastic. Do you have a schematic in mind or at hand from something you would like to build?

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Old 19th June 2005, 11:17 PM   #4
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I think a more modest plan is called for.
Most computer power supplies can't put out enough juice to accomplish something as ambitious as 400W. Furthermore, they generally top out at 12VDC positive and the negative 12VDC (if any) is generally pretty limited current-wise. The 5V is pretty useless unless you want to run a few relays or something like that.
If you were fortunate enough to have a reasonable amount of current available on the -12V supply, you could build a Mini-A or something along those lines. However, the difference between your goal and reality will become obvious when I drop in the datum that the Mini-A is a 10W amplifier...and that's assuming +-15V rails, not +-12V. With 12V rails you'd be looking at something on the order of 6.5W.
I stubbed my toe on a computer power supply today and turned it over to look at the ratings. I believe it was 7A at +12V, but only .39A at -12V. And that was a fair-sized power supply.
Your best bet would be to consider finding a car amplifier that draws some amount of current that your power supply can reasonably be expected to supply.
You'll run into a few problems:
--Car stuff generally just doesn't sound that good. Loud? Yes. Quality? No.
--Stay well within the current ratings of your computer power supply. If you get too close to the specified output, you may blow the power supply.
--Computer power supplies--just by the nature of the way the way they work--tend to provide power that isn't exactly suited for hi-fi use. It's heavily laden with switching transients. They're designed with efficiency in mind, not fidelity.
You can probably pick up a car amplifier cheap in a pawn shop or perhaps off of e-bay. That would give you a comparatively cheap way to experiment with your power supply.

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Old 20th June 2005, 06:30 AM   #5
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i really dont have any ideas yet but i would like to find something that would fit maybe in two or three converter cases but still use the fans and power supply
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Old 20th June 2005, 12:35 PM   #6
eLarson is offline eLarson  United States
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How about the addition of a switching DC-DC converter to take the high-current 5V line up to a more reasonable voltage?
Would a woodchuck bother to chuck MDF?
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Old 20th June 2005, 01:32 PM   #7
moe29 is offline moe29  United States
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A computer power supply is the perfect thing for... a computer.

As a "newb", why are you saddling yourself with a power supply
that has not been designed for audio purposes?

You should be looking for a project that is basic, sounds good,
and maximizes the chances of finishing it with a working amp!

Since you've ended up on the Pass side of things here in diyAudio,
i'd reccomend at least reading the original ZEN article.


good luck!
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