DC? that's new to me. How does that happen?
I'm sure Klaus is a man of his word and if there is a genuine issue it will be handled. But I will give the amp more time first.
The power going to the end of the house the systems is on is a separate run with only a few circuits (3 or 4) it was an addition years ago.
I'm going to look into the power conditioning /regulating ideas for now.
Thanks for all the ideas so far. I can only hope it (hum) does not return and this thread can be history.
Time to crank up some tunes