multiple power supplies in a modular

[Ingo Debus]

Paul Perry wrote:
> .....well I am not an expert (where has BJ the expert from the
> land of Volvos gone?) but I notice that separate digital and analog
> EARTHS seem to be the important thing....(joined at one point only)
> so the current pulses at switching do not result in local analog "earth"
> points going high or low momentarily.....

And of course separate supply connections. Any decoupling capacitor is a
AC connection between supply and ground.

> and anyone who thinks they know how to decouple can put an old 555
> timer on the board with a low level preamp and listen.....acid test!

Another acid test: try to prevent a TL7705 from false triggering in a
noisy environment. This is where I once finally succeeded with an
inductor in the TL7705's power supply line. There was a big relay on the
same PCB.

Ingo