Bypass cap's

[Steve Varner]

Well, it seems you guys all read the same bypass cap book  ;-)
I'm mainly using analog synth modules and have a regulated power supply
with a bipolar +15/-15 and a +5V power output. I'm using a design that is
the same as the Electronotes PCC and Thomas Henry's power supply. I run 4
wires (18 awg) up through the synth and tap in using those blue tap-in
connectors. The 4 lines (+15 / -15 / +5 / Gnd) that were tapped out then
run to a hard-drive-type power connector and clip into to a connector
mounted on the board.
Sooo... Mark got me a bit worried when he said:

Mark Amundson wrote:

> 3. Use 10uf to 100uf tantalum or electrolytic caps for local supply sag
> issues. Do not use these caps if you have regulated supplies and good
> beefy wiring as they may cause more power supply hum than their curative
> effects.

Exactly how do these "larger" caps on the power supply inputs to the module
cause power supply hum?

It seems that a lot of other people on this list are using this size cap on
the power lines and smaller ones into each IC. I was under the impression
that the caps on the ICs were usually only necessary for digital circuits
and for op-amps that handle low-level signals.

SV