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

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)

This was a rare nut to crack! '

I have tried all your suggestions (interference from powersupply, groundloops, other cable influences, cable-tv, noise pickup from surrounding, display ref 3 on/off, exchanged tubes, got the ref3 technically checked, ......) but that would only slightly change the situation. Many thanks for the help, it was very usefull.

At last we did a small experiment. We connected the outputs of the Ref3 to a rca line-in connection on the pre-amp of the Kronzilla (not on the amp, the pre-amp and amp were bridged by jumpers) and voila the hum was gone!

I'm not a technician but the hum was identified as a mismatch of gain in the system particulairy between pre-amp and amp.

Some specs of Ref3
gain : 5.6 db single ended output or 11.6 db balanced
rated output: 1 V RMS single ended into 200K ohm

Some specs of Kronzilla SXI amplifier
rated input: 0,75 V RMS into 47K Ohm at 50 Watt (single ended)

During commisioning of ampliers I have listened to the combination of Ref 3 with Kronzilla SX (without built in pre-amp) which was dead quiet. According to unofficial specification (an article in a Hifi-magazin) the input is 1 V RMS into 47K Ohm at 100 Watt (single ended)

So now we have found the issue, it will be interesting to see what the technical solution will be.

Will be continued.........

Cheers,

Broederen