One thing for everyone to consider...Only after taking the appropriate safety precautions, open your house electrical service box and check all of the grounds. In other words, tighten all of the grounds that may not be sufficiently grounded. I did this years ago after discovering that when I touched the clothes dryer, it hummed. Sure enough, a couple circuit grounds were not well secured. Tightening those connections brought about an immediate cure of that problem.
I don't know if this will help with the issue at hand, but it is a good thing to check. Floating grounds does not a good audio system make!
I don't know if this will help with the issue at hand, but it is a good thing to check. Floating grounds does not a good audio system make!