I can sympathize. A hum can get into your head until the whole musical experience is ruined. I too have a hot tube amp and my speakers boast of a 104 db efficiency rating. (Asking for trouble but I owned speakers before I discovered the amp) No matter what (and I mean, no matter what) the hum, though minimized, could still be heard from my chair between songs and even during songs if they ever took a breath. This forced me to stay on a certain type of music that maintained a clatter while I was trying to forget about the hum. Nearly ruined the whole experience forever UNTIL....I rearranged my room to be able to move 4 feet further away from my speakers. (Kilpsch Lascala II) Problem solved!! I can lean forward and put my head back in the "hum zone" but back 3-4 feet nearly zero hum. Why is this? I have many theories but no real 'scientific' answer. AND of course, very few can rearrange their listening room so as to gain both width and depth. I removed 10 bookshelves around and behind my listening areas to gain that extra space. This comes after a million other attempts. Yes. I had an electrician run two dedicated lines directly from outside power box to my listening area, Changed in and out tubes incessantly. Sent back to manufacturer to install grounding harness and new improved everything. And while everything helped a little, moving back has made it so weak I finally don't even think about it any more. A side benefit to all this isolation etc is that the quality of reproduction has also improved,
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?
Thanks,
David