Mon Amor hum

[Aural Robert]

I have had a small issue with one amp since I put it into service and am finally getting to post and hopefully a fix for it.

I have a small hum in my left Mon Amor amp. I've been listening to a lot of ambient music lately and I can hear it in the background where it doesn't belong.

When I power up the amp by itself, it's dead quiet. As soon as I power on the BeePre, the hum starts.

I tried changing the input selector switch to see if it was source related but no change. I tried plugging the power amp into the different output jacks but no change – every one (both L & R) causes the power amp to have a small hum. I tried moving tubes from R to L and no change. I tried different interconnects but no change.

Increasing the volume makes the music louder but the hum does not increase accordingly. With nothing playing, cranking the volume to 100% I can hear tube rush but the hum does not change.

The right channel is working fine, no hum or any problems at all. My Mainline is also plugged in to the BeePre and there is no hum to be be heard there in either.

So my deduction is that the amp itself has a problem. I looked under the hood and all the connections appear to be well soldered and connected in the right places. All the measurements are within spec although my DC dial on the amp shows 50 instead of 60 – this is identical to the right amp.

Seeking advice and suggestions. Thanks in advance.

Aural Robert
... Where's this Dinah-Moe comin' from ...

[Paul Birkeland]

Do you have the BeePre 1 or 2? 

Is this a 60Hz hum or a 120Hz buzz?

I suspect with something like this that you may have a little debris in an odd spot touching the chassis plate and some other connection in the amp.