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