AW: multiple power supplies in a modular

[Haible Juergen]

	>   Actually it is rather important what size cap you use as
what you are 
	>making is an RC filter.  You want the cutoff to be something
that's going 
	>to cut out most of the crap.  Utilizing a 100uF with 100 ohms
gives a nice 
	>cutoff of 15 Hz, filtering out that 60Hz stuff even.  :)  But I
don't 
	>like utilizing 100 ohms due to the drop in power supplied to
the chips.  
	>I tend to use 22 ohms instead.  This gives a cutoff of ~70Hz or
so which 
	>is adequate enough to kill all high frequency garble.

I never made serious experiments on this, but reportedly it's not that
important
to filter out everything down to a couple of hertz if you are using
*opamp*
circuits.
Opamps tend to have excellent power supply rejection at low frequencies,
but poor rejection as frequency increases. So maybe even combinations
of 22 Ohm / 10uF (or something similar) make sense.

(Discrete circuits are different, of course, because normally you use
resistors and not current sources there.)

JH.