A persistent hummmm...

I have a Zesto Bia 120 all tube, Class A amplifier. I am currently using it with a pair of Volti Razz speakers - pretty efficient horn speakers. My problem is a hum that is audible from the listening chair. Most music masks the sound, but in the quieter passages, there it is. It hums the same way when nothing else is connected to it - just amp to speakers, or when the preamp is hooked up. I have had an electrician out to the house to check the ground. It was good, but he put two more 8 ft. copper bars in the earth - no difference. I had sent it out to George Counnas, the designer/owner of Zesto. He checked it out (and upgraded it while it was there). He couldn't make it hum. 

I have tried using an extension cord to other power outlets in the house, and the hum was no different. I have changed speaker wire in case my regular wire (no shielding or conventional insulation) was acting like an antenna. I have used a iFi DC filter. Obviously, I have changed over the tubes (KT88's). I use a PS Audio Power Regenerator, and it hums less when the amp is plugged into that device than when it is plugged directly into the wall.


When I use a high powered Class D amp, I do not get hum. When I use an old Scott 299A all-tube integrated, I do. That makes me think something is making the transformers hum, and the Class D doesn't have them in the same way.  


I remember reading that Michael Fremer had a persistent hum with his gear, and finally changed out a lot of his house electrical set up. My two electricians can't see a problem, but clearly, there is one. Anyone have any suggestions for other things I could try?


I live in the Boston area of Massachusetts - does anyone know electricians or audio experts who specializes in these kinds of problems? 







Yes, from the speakers. Hum and buzz caused by coffee machine plugged in. Adjacent room, but IDK about circuit. Many years ago.

We have multiple dimmers in our house. Noise is reduced by not turning them on or running them in bright. They are not even on the same circuit. Something to think about. 

Seems like it's the Amp

I feel for you

A hum in my system turned out to be a bad preamp 

Latest hum from subs was solved by grounding to my amp chasis

WHICH PS Audio regenerator do you have?  The reason I ask is that ASR did a disassembly of the newer unit type and found that the mains is still directly connected to the outputs.  All the newer units do is run a filter/regenerator that  contributes a small fraction of the total, in parallel.  No real isolation.

I just recently purchased a new, to me, amp and had a persistent hum. I used my fluke to test the shield on all the interconnects, all good. The new amp was a 2 conductor wall plug, didn't matter if it was plugged in 180 degrees or not (which sometimes cures TT issues). Finally used a meter test lead to go between a cover screw on the new amp and my reference ground at my power conditioner. Instant cure. It was a failure of a ground point inside my preamp.I have ordered a 3 conductor IEC socket. ALL of my other equipment grounded through 3 conductor power cables, so never knew there was an issue...

That darned 60 cycle humm  :?