OT: S/N-Ratio measurment - help

[Rene Schmitz]

Hi Tim!

Don't forget the dirt that comes from the powersupply. 
Digital and analog GNDs must meet at the edge connector, not at the mains
GND terminal, some manufacturers don't even include on card regulators, etc. 
(Look for a computer with star-grounding and linear PSU ;->) 
Best thing to do would be to power the card from an extra linear PSU, or
via a DC/DC convertor. And I wish they would float the in/outs, I get
groundloops everytime I plug something into a soundcard.

Bye
 René


At 14:57 07.02.00 -0800, you wrote:
>I am not at all surprised to hear it. Think about the setup: here you have an
>A/D converter with the bottom bit at around 25 uV. Then you put into a PC
case,
>one that is metal and sealed up to keep those nasty emissions from exiting
the
>case. So you have this sound card sticking up in the noise breeze like a
>high-tech sail. And oh by the way, no shielding what so ever on the card,
except
>for whatever carefull layout they may have done. Noisy? Of course it is.
>
>Fortunately, steps can be taken. Extensive shielding if the card should help
>quite a bit. For example, a cheap shield can be made by sandwiching aluminum
>foil between two layers of shelf paper. Carefully wrap the shield around the
>card, and then ground the shield real well. Make sure nothing gets shorted by
>the shield. 
>
>I can't guarantee this will help, but its definitely worth a try.
>
>
>Tim Ressel--EMC Compliance Engineer
>Hewlett-Packard
>Verifone Division
>916-630-2541  
>tim_r1 at verifone.com                     
>


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