Anyone had buzz/hum problems with Parasound C1?

Trying to help a friend troubleshoot a consistent problem he has with this in him system.

Thanks in advance
Let me rephrase: My friend owns a C1 and has experienced persistent low level hum/buzz that is C1 dependent in his system. It is not due to external power or ground loop issues; this has been fully analyzed. Just curious if anyone else has experienced similar symptoms and what the solution was.

Steve, have you or your friend contacted Parasound for technical support? Based on just one call, I found them to be helpful.

Sorry, no experience with a C1.
Thanks Pryso. He has sent the unit back to Parasound for repair. I'll let interested folks know how this turned out. Seemed reasonable to ask if others had similar issues. Perhaps this one is a one-of-a-kind situation.