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

Sounds like a ground loop hum. Since it wasn't there when you first bought the Ref 3, I can only assume that you have recently made some electrical change in your home that is now inducing this hum. It could be anything from new audio equipment, to new cable or satellite tv, to a dimmer switch just installed. So you have to start troubleshooting, thinking of any recent changes may be helpful.

This link may be of some help. Good luck.

Cheers,
John

Mine is dead quiet - no different than a SS preamp in fact.

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.

Hello

thank you very much for your input. I've been away for business travel to the far east (interesting places!). I will try your suggestions and let you know what the results are!

Cheers,

broederen

Have you tried listening with the LED turned off? There is noise given off by the LED. Seems odd to me that a ground loop hum starts at 250 hours of tube life. Have you called Leonard at ARC? If the cheater plug makes it go away, then yes it is a ground loop hum BUT I would never recommend using a cheater plug for fear of electrocution or frying your Ref 3.
I would definitely check your tubes and I bet ARC would send you replacements with only 250 hours of use ( I love that tube timer on the Ref3)