May not be your solution, but something I found interesting in a similar circumstance. We have a three way light (dim, medium, regular/bright) in the same room as my system, different outlet/different circuit. My wife put a standard light bulb in this lamp (vs. a 3-way light bulb). Whenever the lamp was turned on to anything less than full/regular/bright, I got a buzz through my amp.
Once we put one of those small flouresent lights into a overhead light that had a dimmer connected, whenever it was set to dim (even very slightly) it results in audible issues.
Not sure if either may be an issue in your case, but thought I would share this experience FWIW.
Once we put one of those small flouresent lights into a overhead light that had a dimmer connected, whenever it was set to dim (even very slightly) it results in audible issues.
Not sure if either may be an issue in your case, but thought I would share this experience FWIW.