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AUDIO FORUMS >> General Discussion and Support >> Yet another “why is my amp humming “ question
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Message started by JP on 12/11/22 at 23:51:56

Title: Yet another “why is my amp humming “ question
Post by JP on 12/11/22 at 23:51:56

Hello. I have a Tori jr mk2 and I have 96 db spatial audio x5 speakers. When I turn on the amp there is no hum. Then after 15-20 seconds it builds up into a crescendo and then returns to a baseline hum that I can faintly hear about 9 feet out without any music playing. It is not volume pot dependent. The right speaker may have a little louder hum than left. I changed rectifier tubes and input tubes without any difference. I do have a dc snubber which also didn’t help. It’s a 60hz noise
Thoughts ? Normal operation?

Title: Re: Yet another “why is my amp humming “ question
Post by Tony on 12/12/22 at 00:14:54

I can faintly hear about 9 feet out without any music playing

At 9 feet, that sounds pretty loud, and I wonder what others might think. I had a hum problem that I tracked down to an internal fuse that had blown, not the fuse where the power cable attaches to the amp. From the listening position now, I can hear no hum. With my ear next to the speaker, I can, but it is faint - not an issue.

Title: Re: Yet another “why is my amp humming “ question
Post by JP on 12/12/22 at 00:22:16

Thanks for reply. The rest of my system - vpi signature fatboy turntable, don sachs linestage, Zesto andros deluxe 2 phonostage , and the spatial audio x5s.
The hum has been there since day one ( about a year ago ). I briefly contacted decware last year but dropped it at the time. No resolution at the time but I wasn’t too aggressive in pursuing then

Title: Re: Yet another “why is my amp humming “ question
Post by Tooppy on 12/12/22 at 10:27:04

If I am not wrong I read in the manual of my UFO-2 how to solve some of these minor hum problem, one being to use the same power plug than the source. But it is from quick read memory, you should check it out.

Title: Re: Yet another “why is my amp humming “ question
Post by dank on 12/12/22 at 11:28:48

If it really is 60hz, that would kind of imply the tube heaters. As I believe everything else is full wave rectified which would make the hum 120 hz. First thing I would do is confirm 60 vs 120 hz.

Dan

Title: Re: Yet another “why is my amp humming “ question
Post by JP on 12/12/22 at 11:33:26

It’s a lower pitched hum rather than a buzz. Sounds similar to the hum if you are close to the transformer

Title: Re: Yet another “why is my amp humming “ question
Post by dank on 12/12/22 at 12:14:04

I believe there were some mods done a while back involving 100 ohm resistors to ground on the heater AC supply. This referenced the supply to ground rather than letting it float. Might be worth looking into that. The fact that it is a mod basically means that not all amps have a problem with it - if they all did the problem would have been identified and fixed before the amp was ever released. Possibly, only certain tubes have issues with it. I would make sure you have swapped out all tubes, for a trial at least, and not just the rectifier and input tubes as you stated.

Dan

Title: Re: Yet another “why is my amp humming “ question
Post by JP on 12/12/22 at 12:23:23

Should I start with oa3 , el 34 or all of the above? Swapping them all out can get a bit pricey. Also should I try a kt77 instead of el34 perhaps ?Thanks

Title: Re: Yet another “why is my amp humming “ question
Post by JOMAN on 12/12/22 at 14:50:45

Have you tried plugging the your amp into a different circuit? Recently I had the same issue as you describe with my UFO25 (I thought it was the UFO25). Very long story short... Turned out the the problem was with another component that was connected to the same filter. The filter does not have isolated individual receptacles and the hum was being fed through it to anything that was connected to the same supply.

Once I was able to isolate the offending component I was able to eliminate the hum, entirely! Corrected the issue and everything is back plugged into the filter with no hum at all.

I have ordered a Puritan PSM 156 to replace my filter. It has individually isolated receptacles. Replacing and upgrading my filter was the next thing to do anyway, this just accelerated the timing

Title: Re: Yet another “why is my amp humming “ question
Post by JP on 12/12/22 at 15:05:09

I have a deep core 1800 and a audioquest Niagara 1100. Don’t have another outlet close enough to try a different circuit

Title: Re: Yet another “why is my amp humming “ question
Post by dank on 12/12/22 at 16:38:20

Even if its pricey, I firmly believe you should have a full compliment of spare tubes for your amp. They don't have to be new, or even the same type, where compatible tubes are involved, but they should work. That way you will always be prepared to swap out tubes when a problem comes up.

Dan

Title: Re: Yet another “why is my amp humming “ question
Post by Steve Deckert on 12/12/22 at 16:49:28

Which channel hums louder? What tubes are in the amp now?

Steve

Title: Re: Yet another “why is my amp humming “ question
Post by Tony on 12/12/22 at 16:53:03

Hey Dan,

Over the past four weeks, I have meant to write about my exploration of the Genalex Gold Lion KT77 vs. the Cryotone EL34 in my amp. My bottom line is that it is a draw. I keep going back and forth between the two, and last night I gave the nod to the Genalex.

Still, when considering the price, Genalex was less expensive when purchased from various online sources. Theoretically, the longer life span should go to Cryotone.

Title: Re: Yet another “why is my amp humming “ question
Post by JP on 12/12/22 at 17:51:45

Thanks for replying Steve !Right now I have the decware branded rectifier and I recently ordered from you the 6n5p input tubes. The output tubes are the stock ones that you sent with the amp as are the 0a-3s. I have tried other input tubes and rectifiers without much difference. I’m splitting hairs but the right channel may be a little louder than the left.
When I initially power on there’s no hum. After about 15 -20 seconds it becomes prominent and then backs off in volume and remains in a “steady state “. The volume pots make no difference and it’s there without anything but the speakers hooked up to it.

Title: Re: Yet another “why is my amp humming “ question
Post by armstdav on 12/12/22 at 18:28:04

JP,

Have you explored whether the issue is actually with the Don Sachs? I own one and it's susceptible to hum with certain amps. Mine has a ground lift switch which usually takes care of it. If yours doesn't have the switch, you might try a 3 prong adapter on the power cord for the Don Sachs, or the power cords for your other equipment. Ground loops can be tough to track down.

Title: Re: Yet another “why is my amp humming “ question
Post by JP on 12/12/22 at 18:48:54

Doubt it’s the sachs. Disconnected the sachs from the Tori jr and hum still there

Title: Re: Yet another “why is my amp humming “ question
Post by JP on 12/12/22 at 20:24:08

Doubt it’s the sachs. Disconnected the sachs from the Tori jr and hum still there

Title: Re: Yet another “why is my amp humming “ question
Post by JP on 12/17/22 at 14:57:18

Hopefully I may have found the issue. I installed a quad of gold lion kt88 and just turned the amp on alone. Now I have to put my ear up to woofer to hear any hum ! Much quieter than the EH el34s that came with the amp
I will do some listening tests later but this is encouraging!

Title: Re: Yet another “why is my amp humming “ question
Post by Steve Deckert on 12/17/22 at 18:00:47

Push pull amplifiers are rather dependent on the tubes matching. If one tube in a push pull pair starts to drift causing the pair to no longer match, that channel will start to hum.

The TORII JRv2 has been designed with dual volume controls so that matched pairs can be used instead of matched quads. If you have two matched pairs instead of a matched quad it would be fairly easy to mix them up which could cause both channels to hum. In that case removing one output tube from each channel and reversing them would restore the matched pairs and the amp would no longer hum.

That may be what caused your hum issue. If not, it will surely be what causes someones hum issue down the road, so that is why I post : )

Steve

Title: Re: Yet another “why is my amp humming “ question
Post by JP on 12/17/22 at 18:57:35

Thanks Steve! I can’t remember because it’s been a year. Are the matched pairs marked ? If not maybe a good idea to do so to avoid this issue in the future