If it is a DC bias then a isolation transformer may help. If the isolation transformer wants to hum because of to high voltage then it may have a higher voltage tap you can try. You could also move the isolation transformer to the breaker panel. I have a 5kVA unit that I intend on wiring tothe breaker panel and then put my dedicated outlet on it.
How to get rid of transformer hum?
I have a pair of Pass X600s and an ac line with about 5% clipping of the sine wave. This gives me a large amount of transformer rattle (mechanical hum). I have built a line filter with two diodes and a couple of caps that has gotten rid of 80% of the noise but I'm looking for a inexpensive fix. My power company will not fix the power coming in unless it is clipping by more than 7%. Any suggestions?
Tommy
Tommy