2. amps-preamps
  3. 188545-177823

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

dtorc
oddiofyl's avatar
oddiofyl
3,464 posts
 

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.  

 

dentdog's avatar
dentdog
473 posts
 

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. 

yoyoyaya's avatar
yoyoyaya
613 posts
 

@OP. That kind of hum problem can be very difficult to diagnose. As you have found out by using two different valve amplifiers, tube amps are inherently more susceptible to low frequency hum - often at the frequency of the mains - 60Hz in the US. Tubes aside, I have known situations where certain amplifiers hum in certain installations and do not do it anywhere else, with no apparent reason. Though it would be a bit of a pain, you could move the amp and speakers to another room to check if there anything in the listening room that is inducing the hum. But before that, I would disconnect all electronic appliances in the house and see if the hum disappears. Then you can reconnect the one by one to see if you can identify a cause. It's a long shot because the PS Audio regenerator should deal with that, but in the circumstances, every option has to be explored.

carlsbad2's avatar
carlsbad2
1,380 posts
 

Has the amp ever been quiet or did it have this hum from the first time you used it?

I’ve had hum from tube amps associated with noisy tubes. Atmasphere already confirmed you swapped the input tubes whch are more likely to be the problem. I’ve had full boxes of tubes that were noisy so it is possible the replacement tubes are just as noisy.

Have you used any connection improvement products? These are dangerous as they can create a path to ground.

Jerry

db_db
1 posts
 

@dtorc 

I had a similar experience with a horn/tube combo. Do you have any dimmer switches nearby that can transmit RF? Also, a dedicated home run to the panel is recommended. Since you live in the “Boston” area, do you have an old house? Some electrical panel updates can cause ground loop issues with old BX wiring. 

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