Hi!
I have issue with digital noise. I record (multitrack) my music to USB drive/stick. I format drive before every session, as A&H recommends.
I’ve always heard a bit this digital noise during recording session (which come in my opinion from USB stick, at least I hear it at the same time when USB light flashes), but I haven’t heard it later on my recordings. But now I started to record also from ST3 (front panel stereo input) and recordings from ST3 channel there is also digital noise is recorded 
Is it general problem? Is there anything I can do?
Since ST3 is used for USB drive playback, there must be some sort of internal electrical noise isolation problem. Workaround: don’t use ST3 while recording.
Aha, so ST3 is basically useless input?
Wonder if A&H support knows this?
No, not useless; but less useful than we would like it to be.
We record to a video camera via a matrix output and to a cd recorder from the secondary LR output.
There is some noise on the camera, but none reported on the CD. We think the noise may be due to the camera circuits.
I would not call ST3 a useless input. In the pre amp menu you can select ST3
to be the 1/8 inch stereo front panel input or the USB stick stereo playback.
I use it as the USB playback.