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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
computer power supply for synth?
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olledahlberg



Joined: Nov 28, 2012
Posts: 23
Location: sweden

PostPosted: Wed Jan 02, 2013 7:05 am    Post subject: computer power supply for synth? Reply with quote  Mark this post and the followings unread

Noob question: Would itbe possible to just harvest the power supply from any used computer and use it for our synth builds? I just took out 2 from old computers that was in the garbage and they have +12 v (18 amps) , ground, -12 v (0.8 amps) and a some other voltages? If it works, anyone can find old junk computers anywhere and use the power supplies instead of just waisting them...
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amongstmyselves



Joined: Sep 01, 2012
Posts: 15
Location: Australia
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PostPosted: Wed Jan 02, 2013 2:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

howdy olledahlberg,

I would say that the quality of the pure dc coming out of a computer PSU would not be clean enough for audio and would need extra smoothing. But I'm no expert in this area. If the dc is not clean enough you will get hum.

hope this helps. But of course you could just try it anyway and see what happens.

Steve R.
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elmegil



Joined: Mar 20, 2012
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PostPosted: Wed Jan 02, 2013 3:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

PC Supplies are switching power supplies, and synths generally are recommended to work with linear ones. A switching supply is a lot noisier, as amongstmyselves points out.

On the other hand, I ordered a supply when I was starting out that I thought was linear but in fact was another switching supply, and I've used it as my bench supply ever since and had no problems with it that I have noticed. I believe it was built to a higher standard than your typical PC supply, but who knows.

I certainly don't think there's any reason the PC supplies wouldn't work, so I'd say go for it, with your ears open for potential troubles.
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Wed Jan 02, 2013 4:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

I was thinking the same things as elmegil allready mentioned, but there is one more thing.

computer PSU's usually have a build in netfilter. These filters only work when it's connected to an earthed socket.
But that can cause ground loops resulting in a lot of hum. If you don't earth them it can put half the mains voltage
on your GND. But that probably depends on the filter that's used (if there is one)

I found this out the hard way when I build an amplifier years ago and used one of those filters I had laying around.
As a result the power transistors fried whenever a cable touched the case, untill I found out what was causing it. Rolling Eyes

_________________
"My perf, it's full of holes!"
http://phobos.000space.com/ http://www.acidtrash.com/ Stickney Synthyards
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olledahlberg



Joined: Nov 28, 2012
Posts: 23
Location: sweden

PostPosted: Thu Jan 03, 2013 1:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Ok, I see. Ill probably just make a bench power supply from one ofthem and go for my orginal ideas with wall wart or transformer.
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analog_backlash



Joined: Sep 04, 2012
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PostPosted: Thu Jan 03, 2013 3:23 am    Post subject: Reply with quote  Mark this post and the followings unread

This may be a little bit off the subject, but I have one of those plug in multi-voltage switch mode PSUs and I've found that on old (and cheap) Casio keyboard doesn't work properly on it. It produces a superimposed buzzing noise over the keyboard output, which obviously is not what I want to hear! I don't know if the same problem could occur when using an old computer PSU.

Gary
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otcx



Joined: Jan 14, 2006
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PostPosted: Mon Feb 11, 2013 4:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Some years ago i try PC psu, but it did not work properly. So i purhased Doepher psu.
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