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hacking pc psu for well regulated 5v output

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Full Member level 3
Dec 25, 2002
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hacking old psu

Hi All,
When i'm listening music from my pc, i hear low frequency (50hz) noises. My amplifer's psu is well regulated but soundcard's output is very bad. Can i put a capacitor between 0v and 5v at pc psu? Unfortunetely, it's switch mode, i don't know anything about switch mode power supplies. I have 40v 15000uF capacitor, Should i put it?

sound card between 0v and 5v

Is you PC (!!!) and amplifer propertly "grounded" ?

noise in switcj¿hin power supplies

i agree with dainis, the switching power supply noise is at frecuencies upper than 20 khz ussually so the noise should come from somewhere else, (the ground is a good guess)

Don't put those capacitors into your switching power supply. The noise you hear is most likely the result of a ground loop. Try to disconnect other imputs from your amplifier (i.e. tuner with antenna cable).

If your tuner (which is probably also connected to your amplifier) is connected to the local cable company use a special filter which minimises ground loops.

This helped for me.

But as others told you try to disconnect everything that is not needed first. If the low freuency noises disappear reconnect one item after the other until to noise reappers.

Now you have found the source of your problem ...

hope this makes sense for you

Be careful, this capacitor is too big!
You can disturb power-up voltage sequence and destroy
you comp! And it is not the solution!!
Check, first of all, that your cable between soundcard and
amplifier properly shielded to PC ground, check that PC
and amplifier have the same signal ground, common grounding
via 220/110 outlet is not enough, may be you'll need even
disconnect outlet ground from amplifier and stay with
signal ground only, that amplifier get from sound card.

When i record sounds from microphone input, the noise occurs, too (i didn't connect microphone!). So i think the problem's reason is interrelated with psu. Thanks jourval, i won't try to connect the capacitor. The noise source is not ground loop circuit, i tried to connect the grounds and noise increased.


Are you sure it is a parasitic noise comes from powering? It may occur when you use very low quality sound cards.Also a device wihch shares sources with sound card makes a noise like yours.Check it with another card, if possible.


for soe old soundcards, sometimes low freq. noise disappear
if disconnect cable between CD-drive and soundcard.
In this case you can't direct play audio disks, but you still
can do it via winamp or any other "software" player.

I bought Sound Blaster Live 5.1 for 40$ and the problem doesn't occur! My old sound card is Zoltrix Nighingale.

Yes it is most comprehensive solution!

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