Does tubes have a very low buzz / hum?

bikingbuddha

Well-Known Member
I am in the tube world for past year and i am hooked. I bought couple of cheap tube amps off the internet and fell in love with tube sound. Recently i came across this little chinese made tube amplifier called sherwood DT-555. Don't bother searching for it, i tried everything and i couldn't find anything. So that's not the story :)

my question is "Does all tubes produce some kind of very low level noise hum / buzz which can be picked up in zero silence of headphones like HD650?"

I can hear it on my amplifier when it is in zero silence, no songs playing, everything zero. I can only hear this on HD650. All my other headphones doesn't work with this amplifier because they become noisy ( low impedance headphones have a problem with this amp)

I tried rolling the tubes from "Tungsol 2c51", Russian 6n3-p, 6n3-EV, GE 5670, Chinese stock tube 6N3. They all have the noise, and it is least at Tungsol 2C51.

I just want to know if this is normal on tubes....! it is no there when i plug the headphones directly to the notebook.

PS : this hum is very very very low.... nothing that could even barely disturb the music.
 
I have a Kenwood tube receiver from 1962 [KW-60] that was recently gone through and repaired by a tech. It works and sounds great but yeah, I noticed the one time I used headphones [Grado SR325is] some low level "swooshing" like sounds that would come and go when no music was playing. I mean, it's there but not at all intrusive and you cannot hear this through the speakers. Don't know if it's supposed to be like that but it's not an issue for me as is.
 
I think most old tube receivers didn't have headphone jacks for this reason, and for having to switch in and out load resistors. I have heard these noises on many "quiet "amps, and was surprised at what could be heard, just touching tubes revealed how monophonic some were.
When you plug in the headphone, does it disconnect the speakers?
 
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my question is "Does all tubes produce some kind of very low level noise hum / buzz which can be picked up in zero silence of headphones like HD650?"

I can hear it on my amplifier when it is in zero silence, no songs playing, everything zero. I can only hear this on HD650. All my other headphones doesn't work with this amplifier because they become noisy ( low impedance headphones have a problem with this amp)
All amplification devices have intrinsic noise levels. Tubes being bigger are probably more susceptible than SS devices to certain kinds of noise. Also the higher the gain in the circuit the more susceptible it will be to noise.
 
its probably more a case of the AC heaters having a small amount of leakage. That, and the high impedance circuits that are prone to noise pickup just collecting noise from everywhere. The magnetic field from the transformer is a source to be sure. In a custom built amp you can do a lot of things that will make it not hum but production designs all have some amount of compromise.
 
In a perfect world they will be silent, but in reality its not uncommon to have a little bit of noise in headphones. Its difficult to get tubes absolutely dead silent.

It has this very low noise in the background and i think it's tube. In my amplifier tubes take a little while to switch on and when it does i get that background hum.... it is very low though. i think it's alright for a little amp like what i have besides it is not a dedicated headphone amp. it is a speaker amp as well. i never seen it anywhere else on the internet or any other place, i call it the "Amp from another dimension". lol!. I took these pictures when i bought it. Now it is running on Tungsol 2C51 tube.

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I think most old tube receivers didn't have headphone jacks for this reason, and for having to switch in and out load resistors. I have heard these noises on many "quiet "amps, and was surprised at what could be heard, just touching tubes revealed how monophonic some were.
When you plug in the headphone, does it disconnect the speakers?

Yes they do disconnect the speakers automatically. This isn't very old. I checked it and it is made somewhere in 2008 and it is a hybrid amplifier. I call this little amp "the Amp from another dimension" because it has no information available anywhere else or in the internet, not even in their official website provided in the amp itself. i even contacted sherwood in china and different countries, none of them knew about it. Currently it is running on tungsol 2C51 tube and it has that very minor background noise. it is not intrusive at all but it is there and it comes when tubes come alive after switching on the amplifier. it takes a little while to power up the tubes.

small1.jpg small2.jpg IMG_20180910_132333.jpg IMG_20180903_154322.jpg
 
Most of the time on a Hybrid amp, the headphone and speakers are powered by solid state devices. Tubes have a tube rush (Thermal Noise) which is a slight hiss. If your tubes are noisy they could have more hiss than usual, this could be solved by trying different tubes and seeing which is the quietest. If you try several types of tubes and dont hear a difference, it could be from the solid state devices. If you listen to cheaper solid state guitar amplifiers they are very noisy and the hiss starts when you turn the amp on. I had a newer fender small practice amp and a fender vintage champ amp side by side and turned on, and I did not believe how noisy the solid state amp was. This amp could be using cheaper devices that you are hearing. You could see how noisy the amp is when hooked to speakers.
 
Most of the time on a Hybrid amp, the headphone and speakers are powered by solid state devices. Tubes have a tube rush (Thermal Noise) which is a slight hiss. If your tubes are noisy they could have more hiss than usual, this could be solved by trying different tubes and seeing which is the quietest. If you try several types of tubes and dont hear a difference, it could be from the solid state devices. If you listen to cheaper solid state guitar amplifiers they are very noisy and the hiss starts when you turn the amp on. I had a newer fender small practice amp and a fender vintage champ amp side by side and turned on, and I did not believe how noisy the solid state amp was. This amp could be using cheaper devices that you are hearing. You could see how noisy the amp is when hooked to speakers.

Thank you for the reply. I only have one Tung-Sol 2C51, i will switch it with a 5670 GE JAN and see how it goes. I have few couple of Chinese 6n3 and russian equivalents as well. I will try them all and see which is less noisier.
 
Here are the test results.

#1. GE JAN 5670 - Hum gets slightly worse than the tungsol. (Tried two tubes of the same type)
#2. 6N3P-E (Russian) - Hum is higher than tungsol but better than 5670 (Tried two tubes of same number)
#3. 6N3P-EV (Russian) - Hum is same as the "E" above. (Tried 5 Tubes)
#4. 6N3 (Chinese - Beijing) - Hum is better than all above but worse than Tungsol

Winner is "Tung-Sol 2C51" which has the lowest noise of all above so i keep it in the amp once again.

I don't know if this very low level hum is the nature of these tubes. It is so low. When i switch on and after a while tube comes alive and then gets the sound in headphones. (When there are no music playing) and when headphones get power after the tubes switch on i can hear some kind of background hum. Very low level and never interrupts music but it's there. Some kind of vibration in the silence.
 
Tubes and headphones can be a perfect match. Tube noise is usually easy to minimize in order to be unobtrusive. Unless, that power supply is a switching power supply, as was so popular with the hybrid headphone amps. If you set up the SMPS (switching mode power supply) near a turntable, phono or mic gain stage, then noise is almost guaranteed. Using unshielded interconnects is also a source for noise to enter, even though the hyrid hdphone amp has low gain.

So, is this hum or buzz ? Buzz indicates a possible poor connection or oxidized connection, or lack of proper shielding. Hum indicates a power supply deficiency, as in a power supply cap which is leaking AC when only DC should be measured...

I use hybrid headphone amps for "cans" as well as using them as line stage preamps. Their setup and positioning can be critical.

IIRC, the hybrid headphone amp birth rate blossomed after the Musical Fidelity X-Can appeared on the scene...
 
IMO, we know a lot more about grounding and eliminating hum today than in decades past. Unfortunately, I don't think all that knowledge has been applied by the makers of many tube amps, though some I'm sure do. FWIW, most solid state receivers I've tested also have some hum with headphones. Now, noise (hiss) is something different. All active devices have noise. Good designs minimize it, but headphones are very sensitive. 1 lousy millivolt of noise is easily heard with 'phones. There are dead silent headphone amps, but not many.
 
Tubes and headphones can be a perfect match. Tube noise is usually easy to minimize in order to be unobtrusive. Unless, that power supply is a switching power supply, as was so popular with the hybrid headphone amps. If you set up the SMPS (switching mode power supply) near a turntable, phono or mic gain stage, then noise is almost guaranteed. Using unshielded interconnects is also a source for noise to enter, even though the hyrid hdphone amp has low gain.

So, is this hum or buzz ? Buzz indicates a possible poor connection or oxidized connection, or lack of proper shielding. Hum indicates a power supply deficiency, as in a power supply cap which is leaking AC when only DC should be measured...

I use hybrid headphone amps for "cans" as well as using them as line stage preamps. Their setup and positioning can be critical.

IIRC, the hybrid headphone amp birth rate blossomed after the Musical Fidelity X-Can appeared on the scene...

More like a buzz sir!! very low level. I must say this buzzing is worst on all my other headphones. only on HD650 that it is barely audible.
 
For more information on your amp, look up the Qinpu Q-2.

I don't know how to thank you. Probably you are from another dimension as well . Please don't get offended, thank you so much sir. I was looking all over to figure out what it is. Now I can even trouble shoot this cute little amp.
 
Tubes and headphones can be a perfect match. Tube noise is usually easy to minimize in order to be unobtrusive. Unless, that power supply is a switching power supply, as was so popular with the hybrid headphone amps. If you set up the SMPS (switching mode power supply) near a turntable, phono or mic gain stage, then noise is almost guaranteed. Using unshielded interconnects is also a source for noise to enter, even though the hyrid hdphone amp has low gain.

So, is this hum or buzz ? Buzz indicates a possible poor connection or oxidized connection, or lack of proper shielding. Hum indicates a power supply deficiency, as in a power supply cap which is leaking AC when only DC should be measured...

I use hybrid headphone amps for "cans" as well as using them as line stage preamps. Their setup and positioning can be critical.

IIRC, the hybrid headphone amp birth rate blossomed after the Musical Fidelity X-Can appeared on the scene...

Alright here is an update sir...! Today I removed the amp and checked inside, nothing is wrong to the naked eye but I removed all the screws and derusted them.then cleaned up the headphone socket for any dust or rust. Used a tiny wee bit of wd40 inside the earphone socket. Now the buzzing had turned to a audible humm in low impedance headphones.

For hd650 things are much better.... The low level almost inaudible hum/buzz has almost vanished.
 
Here goes another update.

Today i had time again to check through everything. I connected my Onkyo D-V3A Speakers and listened very carefully. I was wrong... the buzz/Hum is also there. This low level Buzz/Hum like some kind of white noise which is in the background does not respond to the volume pot either.

If something is wrong inside the amplifier... what could it be....? it could be one of those small caps?. This one does't have a three pin power connector so i have to try grounding it on a different way and see if it is still there.
 
Another update and this is the final i think. I must correct few things i have realized.

The hum can be controlled by the volume pot. It goes up and down. I couldn't notice it earlier with the Sennheiser but i am trying it with IEM called KZ ATR. it's very noticeable with this one. Humm is there with a HISS. I will try to record this noise and post it for easier troubleshooting.
 
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