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? 






Interesting. Leaving the speakers attached, with the inputs disconnected I’d put a multimeter on the outputs, set it to AC and see how many AC volts you are getting. It may be that your few millivolts of AC (humm) are "normal" but also too much for your high efficiency speakers.

 I know very little about this, but Vandersteen suggested I try touching a wire (any old hookup wire) to the various chassis of the system and to the 3rd ground wire of a wallplug (just take the stripped wire and shove it into the round (not spade) hole.....one component was the culprit...gone now.

@dtorc I can commiserate.I,m trying to solve this exact problem right now. My system (on profile) has been running dead silent for years, I had this problem when I first built the system but after struggling with it for I can’t remember how long ,it disappeared. System is running on a single 20 amp home run straight into a plastic box with an Audiquest receptacle. 200 amp service has two 8 foot ground rods one in front and one under the panel which are bonded together,I’ve completely broken down and rerouted all the interconnects and AC cables which are name brand, Ive changed all tubes since I had a complete set of extras ,I’ve moved components around and done all the same ruling out procedures discussed in this thread, no joy! It’s driving me crazy, its a buzz and a hum combined if that makes any sense,audible thru all drivers and tweeters. Anyone? Thanks in advance!

I had a weird buzz coming through my Forte / Quicksilver combo in my last home.  It was a plug in air freshener.   It was on a different circuit but still cause noise.  Took a long time to figure that out.  

I had a Zesto preamp and i can honestly say it is the quietest , blackest , free of noise component I've ever owned.   I am not surprised George said it checked out OK.   

In my new place I had a different kind of buzz / noise.   That was rooted out quickly.  It was an ethernet cable running alongside and touching a speaker wire behind the rack. 

Good luck.  


Have a new Hi Fi Rose streamer, hooked up last night. Sounds pretty good but for the first time-hum. Can't handle hum so here I go as well. 

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