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Old 2nd August 2003, 12:59 AM   #1
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Post PSU from a PC

The idea to build my own computer speaker/amp setup was spawned today at bestbuy when a person… (sad to say I don’t even know his name , but he is called swirv on here… thanks to him telling me about this site)… anyways he started telling me about how he was the chief engineer at DEW Recording Studios and then went into details about his on building. He asked me about my skills etc... I basically told him I was pretty good with electronics… etc… He presented me with the challenge to build my own amp/speaker setup. So here I am now getting started and I have considered adapting a computer PSU. Please give me some pros and cons… Computer PSUs have 12v and 5v. I know you have to have some sort of a load(resistor) on the 5v side for the 12v to power. Well… now hopefully I will have some replies…
~Conrad
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Old 3rd August 2003, 02:21 AM   #2
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if you search this forum you will find lots of info about using PC PSU's. I however feel its easier and better to build the psu from scratch. A chipamp is going to be influanced heavily by the design of the PSU.

Chris
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Old 3rd August 2003, 01:48 PM   #3
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I searched and really couldn't find much, but I guess I will just build my own anyway. Thanks...

~Conrad
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Old 3rd August 2003, 08:22 PM   #4
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the thing about PC power supplies is that they are rife with switching noise -- and, unless you use a DC-DC converter, the voltages aren't high enough to run a chip-amp.

for a few bucks you can get a nice torroidal transformer and you're good to go.
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Old 3rd August 2003, 11:15 PM   #5
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you can replace the rectifiers for the -12volts with one of simmilar rating as the +12 volts so that you can have 24volts out of a pc psu, you can even play around with pin1 inout of the tl494 pwm regualtor chip so that you can get up to 28volts or so without too much circuit modifications, then another psu and you can have a +/-28volts supply...fyi i am into pc psu repairs and modding...
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Old 4th August 2003, 12:21 AM   #6
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Desktop SMPS supplies are typically optimized for high-power 5V output and relatively low 12V power.

I would instead recommend that you consider notebook power supplies (external) because they typically provide one output at significantly higher voltage. I have seen 18-20V (I believe Dell have fairly high voltages, possibly even higher than 20V, most others are about 18V as I recall).

Newer devices have about 65 or more watts. If one assumes 20V power supplies:

If you build a balanced amplifier, you only need one such unit. A balanced amp into 8 ohm speakers should yield 50W per channel, 4 times that into 4 ohm speakers but then the power supply will be holding you back of course. You will typically not be able to get up to these levels.

Also, if you find that outputs are truly isolated, you can use two units as a split supply, doubling available power to load, and still providing 50W per channel in a traditional stereo amplifier (both channels into 8 ohms.

Petter
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Old 4th August 2003, 12:35 AM   #7
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alright, thanks.... Looks like I am just going to build one. I have spare desktop PSUs but on notebook... thanks agiain

~Conrad
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Old 6th August 2003, 12:45 AM   #8
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Quote:
Desktop SMPS supplies are typically optimized for high-power 5V output and relatively low 12V power.
true, but the 5volt and 12volts come from the same transformer, so that if you are not taking current from the 5volt rail, then the power can be used by the 12volt rail instead, this is doable....
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Old 6th August 2003, 02:12 AM   #9
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How are transformers in the computer PSUs? usable?
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Old 6th August 2003, 11:50 AM   #10
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i've pulled enough computer power supplies apart to know that it's unlikely you'll find a transformer/toroidal inside worth using for an amp

basically they typically have a bunch of different size transformers inside, so even tho a psu is rated at 300w for example, it WILL NOT deliver all that on one voltage line.
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