when i turn on and off a load (20W / 12V) quickly via a L293, the PSU has a nasty noise/ripple voltage...
Unfortunately that same PSU powers my sound card, too...
That causes an unrequested humming...
What can i do against that noise?
qucs says, i need 1F in parallel plus 1H in series in order to get plain 12V DC again...
Is there a more intelligent way?
Maybe some kind of a DC-DC-converter? :
For power saving reasons I would prefer to use the same PSU (efficiency: >89%) for all my devices (certainly with individual fuses)...
I wouldn't like to use an additional USB sound card for the same reason, because i am afraid that my main board would continue to power it, although it is disabled in the BIOS...
I think you should use a separate PSU for your audio card, since noise is everything... and your setup doesn't help, plus it would clear the benefit of using an external sound card.
Could be also a ground loop issue, it happens easily on cars setup. Just attach your iPod to the line-in and charger at the same time...
However I know almost nothing about capacitors...
I think the idea of using separate power supplies is a good one! The hum is likely due to excessive current draw causing the smoothing capacitor(s) in the PSU to discharge too quickly.
when i turn on and off a load (20W / 12V) quickly via a L293, the PSU has a nasty noise/ripple voltage...
It sounds like you are using the power supply beyond its specified range of operation.
Check the dynamic loading specifications.
What can i do against that noise?
qucs says, i need 1F in parallel plus 1H in series in order to get plain 12V DC again...
Is there a more intelligent way?
Maybe some kind of a DC-DC-converter? Roll Eyes
A DC-DC converter should help provided it is specified for the type
of step changes to the output required by your application.
