My evil modular plans

[brad sanders]

Tony Clark <clark at andrews.edu> was saying...

>   Well grounding is a given....

Actually, Tony, it's NOT a "given!" This is one of the reasons sound
cards have, in general, a bad rep. It takes some pretty careful layout
even in a piece of "hifi" equipment (like a CD player). In a PC the
problems are even worse. Crystal Semi has an excellent appnote on this
in their databook.

This is also why you might find many sound cards that are virtually
identical; the chipmaker suggests a "reference" design, and it
behooves the board makers to stick close to this even if they're
adding more "features" (circuitry).

Even outside the box, grounding is much more important with a PC. For
example, I was having a VERY hard time making decent connects with my
19.2 modem. I cheked the outlet, and found it was ungrounded on the
third pin. By rewiring it I improved modem connect rates. I also have
tube amps, and my PC is connected to my stereo. Because they plug into
outlets on opposite sides of the room (different circuits) it
sometimes helps (if my amps are on) to unplug the minijack that
connects the PC and the stereo. (Yes, I have really lousy phone
service...)

The point is, grounds aren't a "given."

>  The more important aspect of doing this 
>particular chore would be to have a clean power source....

Neither is more important. A clean power source does one NO good if
there's several uA of noise current flowing through a ground trace in
the wrong area. There's little one can do about this in a board that's
already built, but it's crucial if one is designing a new card.