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

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

Broederen, thanks for the update. Let me ask you a question, in your original post, you stated that the ARC Ref 3 "suddenly" started having these noise problems. Looking back, did these noise problems suddenly occur when you introduced the Kronzilla into the mix or started running the Kronzilla just as an amplifier?

I'm just trying to line up timeline's to figure out if you did in fact make an electrical change in your system that instigated this noise issue. It would seem strange that the Ref 3 was operating properly, then all of a sudden had problems. That's why I originally suggested that there was a electrical change made that initiated the noise.

Cheers,
John

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

Hello John,

Thanks for your reply,

I've contacted Marek Gencev from Kronzilla. He was very kind to reply me today (27 january)

The situation is getting to its climax. He made me aware of another change I overlooked. At the time I bought the Kronzilla I did not have a Cardas Golden Reference RCA interconnect. I used temporary a Cardas Golden reference XLR cable with Cardas adapters till I got my new Cardas GR RCA cable which I installed during the change in location.

At Marek's suggestion I put this cable back and the HUM looked gone...., but (in these types of situations there is always a but) the "pink noise" (still audible at 1 meter and independent from ARC pre-amp setting) , a part of the HUM was not gone. On this part Marek is still thinking because in another high-end set-up the ARC was dead quiet. But somehowe the Kronzilla SXI have still some "relationship" issues but improving..........

To be continued....

Cheers,

Broederen