tfabris carpal tunnel
Registered: 20/12/1999
Posts: 31630
Loc: Seattle, WA
Since connecting the Empeg with the AC adapter eliminated the whine. I would assume that you are getting the noise at the empeg unit and wouldn't mess around with your amps any further.
Not true. Ground loops can be tricky things to debug. Even with what he stated, it still could be a grounding issue with either the amps or the empeg. These things are all interconnected.