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
Sorry - in the list of things I said that I tried, the cheater plug should have been first. No luck there.
I have changed the inout tubes a few times, and that doesn't seem to affect it. I don't know whether there are quieter versions out there ( I used JJ 12 Au7's).
I think the that the power, which comes from the PS Audio Power Regenerator is pretty clean, at least according to the scope built in to the unit. But something is off, clearly...
Thanks for thinking with me...
David |
Yes - I sent the amp out to the manufacturer/designer, and he said he didn't get any hum at all. Of course, i don't know what speakers he uses, and you are right - the efficiency of the speakers certainly exacerbates any hum problem the amp has. I think I may need an electrician who is mindful of audio needs. Most are not, I'm finding. |
@dtorc An electrician won't be able to help. He'll be out of his league trying to understand why the PS Audio regenerator is able to help. Since it helped only a bit, since you swapped tubes and also sent the unit back, its my surmise that Zesto didn't really test it out completely. You might suggest they use headphones instead of speakers; many headphones are 110 dB efficient so low level noise is easily heard. Is the buzz at the same level in both channels? If one channel has more buzz, it might not be the amp at all. So if the buzz is different between channels, try swapping the interconnect cables left for right at the amplifier inputs and see if the problem moves. If it does, the amp might be off the hook.
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Hi OP! I think the place to start it to understand if the hum is inherent to the amp, or perhaps a ground loop issue. Disconnect all inputs and listen. If you still hear a humm its an amp issue, and as I think you suspect, may only be noticeable because of your high efficiency speakers. OTOH, if the hum vanishes with no inputs, it's a ground loop or upstream problem. |
