Amp hum.

Sometimes transformers can hum. I'm not an expert but you can tighten the mounting screws and/or the plate screws if it has plate screws. 

This could be a number of things.

Swap the L/R inputs on the amp to see if the hum follows the cables or not.

Then have it seen professionally.  This could be bad diodes, caps or tubes.

Could be an electric phenomenon called "DC Offset" and certain MOSFET amp transformers are sensitive to it.

google it, thee are products that address it. I live in an old house and had that issue even tho I installed dedicated AC leans for my audio gear.

emotiva CMX-6 (or the 2) solved the problem for me.

n80 your amp is pretty old it wouldn't be a bad idea to have a tech give it a once over whether it's the source of your hum or not.

Thanks guys. Will look into getting it checked out but on the other hand probably not willing to shell out big money to have it done. The place that it came from is still in business so I can check with them.

It sounds like a bad tube. Swap one tube at a time from L to R and vice versa.  If the hum changes to the other speaker you have found your problem.  I have had this happen to me a couple of times.  This is a process of elimination with the tubes until you find the bad tube.  

What willgolf said, simple. Unplug and plug the valves back in, TOO. Same with your connections. Unplug and plug ALL the way back in.. Just 101 service.. Easy and quick. ZERO dollars, too. Move the valves left to right one at a time you’ll figure it out pretty quick.. You have a valve going under water 10 to 1. Their suppose to.

Regards

Thanks guys. That's all easy enough so I'll give it a shot.

Touching the amp or pre amp changes the volume of the hum.

That isn't a tube. That's some sort of ground problem; apparently its affected by heat.

Does it do it on all inputs to the preamp?

Since its in the right channel only, power cords and the like are off the hook. This seems like good advice:

Same with your connections. Unplug and plug ALL the way back in.

Update on right channel amp hum.

Was changing the hookups on my Sonos Connect into my Oppo (which I use for DAC and CD) and I noticed a little Oppo USB device which I think is a sort of Bluetooth or digital signal receiver that I had plugged in a while back to see if the Oppo would do AirPlay (it does not; too old apparently). So I unplugged it and threw it in a drawer. No hum since then.

I also changed the Sonos Connect from coaxial to optical into the Oppo at the same time so I can't say for sure which relieved the problem. Changing from coaxial to optical did seem to solve a lot of the glitching in the old Sonos Connect though.

Anyway, both problems seem to be solved. Baffled but happy.

Charles Mingus: Amp Hum

Sorry, couldn't resist/