Doepfer

Hi

 > I am having serious humming problem in my modular system .


Did you monitor the Doepfer rig standalone (without any connection to 
the outside world but the powerconnectors - no MIDI!!!) and insert a 
headphone in a VCA out - it will be not extremely loud, but will be 
enough for checking. Is the hum also there without any connection to the 
outside?


If no: There is only one serious method for tracing a hum. Disconnect 
everything in your studio, and reconnect one cable after the other and 
check after each cable, whether the hum is added. And if i say 
"everything" I mean everything. All power cables, all audio, speaker, 
lan, midi, usb whatever cable. You start with no cable connected at all. 
Then you start from the beginning:

Poweramp to poweroutlet and speakers to Amp -> switch on -> check
Mixer to power and to Poweramp -> check -> switch Mixer on -> check
Reverb to power -> check -> switch Reverb on -> check
Efx-Send to reverb in -> check
reverb left out to fx return left -> check
reverb right out to fx return right -> check
and so on...

In my studio this took a whole day, but it was worth the effort.


BTW: To my experience today to most likely source for humming are USB 
midi or audio interfaces which are supplied by USB instead of a separate 
own powersupply.

Florian