Re: [AH] Doepfer Opinions (PSU CROSSTALK)

From tonyallgood
Sent Sat, Feb 9th 2008, 10:07

No matter how good any module filters out power supply noise and/or 
whether it regulates the voltage coming into it, all modules need a good 
reference ground or 0V. I believe that many crosstalk issues that are 
power supply related are coming from contaminated grounds and not from 
the actual voltage supplies. In this respect the modular manufacturer is 
at the whim of the power distribution system that the owner has chosen.

The best option is a star distribution system of grounding with no 0V 
ground return paths via the cabling. This is usually impractical in a 
large modular system that mixes formats and manufacturers.

Alternatively, a belt and braces approach of true mesh earthing via the 
case and power supply may also work well if given a little thought from 
the outset.

Remember too that earth loops can sometimes cancel out and a badly wired 
system can actually behave itself very well, until you change module 
orders or add a new one into the mix.

I fixed up a small format modular system last year which had power 
supply coupling problems. In the end a decent star based distribution 
system for the noisy and sensitive modules, lots of additional 
decoupling, a nice thick solid ground and careful module placement 
solved the problem entirely.

Its a minefield to be sure. And we haven't started discussing radiated 
crosstalk and capacitive coupling.