Jeff, I sold a Krell KRC-3 to a guy last year. It was in like new condition with original box,warranty etc. Worked perfectly in my system. Diconected it , packed it and shipped to the next state over which UPS delivered the very next day! He calls me and tells me that the unit has a wicked buzz. So I co through all the grounding issues to no avail. I told him to return it to me on his dime and sold it to the next person in line and they were thrilled with it. I would, and did take it back. I knew there was nothing wrong with it, but felt it was the correct thing to do. Hope this helps, and good luck.
Bill
Bill