Doepfer

Hi david

> only a few modules work correctly, a few not at all and a few with a very bad ground hum.
Did you measure both voltages with one of the "bad" modules plugged in?

Did you check the modules separately one after the other, or did you 
plug in all at the same time? If the latterm then try them separately.

I do not know the non-Doepfer modules you mentioned, but maybe they rely 
on a connection frontplate -> electrical-ground (0Volts).

Florian