Doepfer

Hello

to both Nathan and Jon: is this a mechanical sound or does it come from 
the speakers?

If it comes from the speakers, disconnect the audio out from the A100 
system, and connect a headphone with a mini jack connector to the output 
of the last module in the audio chain (example: VCA or mixer) and turn 
it up. Do you still hear the noise?

If yes, then the problem is in the A100

If no, then the problem is in the combination of the A100 with the rest 
of your system


To Jon:
Do you use an computer with and USB Audio interface?
If yes: Is the interface USB-powered?
If yes: use an interface with an separate power supply.

USB-power on Audiointerfaces in a studio like environment introduces HF 
from the digital signals of the computer in the audio ground. Those are 
useful only for standalone usage.


Florian