Hum in ARC Ref 3 not on 0 but 1-103 light buzz

I have a Reference 3 that was dead quiet for a year using RCA and XLR interconnects. All the sudden one day I got a hum which only occurred when using the CDP.
I replaced the power tubes in the Reference 3 and the hum was gone. As an experiment suggested by my dealer I put the original power tubes back in the Reference 3, using the RCA interconnects the hum was back, switched to the XLR interconnect and the system was dead quiet again. The Reference 3 does that sometimes.

Although there are only 250 hours on your tubes (is that correct, are you the original owner?) if the power tubes are out of balance it will create annoying sounds. Give ARC a call and discuss this with them if you are able to eliminate the ground loop hum theory.
Personally, I think it’s the power tubes.

John,
Good question.
But then again, I expect that from you! :-)
Good job to all.

Glad to hear the good news :)