Yeah..I think MOST voodo power supplies are isolated. So that’s probably not it. WHICH power supply is it, do you know?
Though, regardless, if I were you, I would try this:
Leaving everything in place…just TRY attaching the stock power supply to your h9…then get a long extension cord and plug it in in a different room. On a different circuit.
If this solves your problem, it’s grounding. If not, it’s not!
Side questions…do you have the buzz when you are using patches in both pre AND post modes? Is it the same?
Also, does the input or output volume affect the buzz at all? When you go to tuner, does it mute the buzz?
I don’t have a plan..just looking for ideas.