• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Isolation of tube equipment from speaker vibration?

Jump to Latest
M

MikyK

Member
Joined 2018
#1
Hello, today I was playing music threw EL84 SE amp. I was curious about the vibration from the music, I touched the tubes by hand and they were vibrating pretty badly.
Do you think that this can have effect on the sound?
What would be the best treatment?
Anyway, I wish you luck in year 2021 🙂
Thanks everyone for your opinion. Best regards, Michal
 
#2
Happy New Year to you.
Back many years ago when I started with valve equipment, we made a valve 'computer'.
It was just 128 ECC81 flip flops but did the job!
We had an issue with noise on the shop floor and fitted 'noiseless sockets', they were standard B9a sockets but mounted in a rubber surround.
I would have said it is cheaper to replace the noisy valves but then I wasn't in control of the build.
Some sites sell new old stock shock resistant B9a sockets. Have a look on those Russian sites.
 
#3
Valves lived happily for years inside radios and radiograms, sharing the same box as the speakers. No one worried about valve vibration, probably because it was swamped by all the cabinet resonances!

I'd worry less about your EL84s vibrating than the risk of burning your fingers! 😀

If you are still worried, you can always fit EL84 valve damper rings.

EuroDamper Tube Damper Rings for all 9 pin preamp tubes and EL84 power tubes.
 
#5

Attachments

  • valve base isolation grommet.jpg
    valve base isolation grommet.jpg
    8.6 KB · Views: 143
#7
My DD Servo amps sit on a metal platform integral to the structure of the Monitor 3 Acoustat speakers. I too noticed resonance when touching the amp. So when I put a 1" thick fiber scratch pad like the ones used for floor polishing machines, it virtually disappeared with a remarkable improvement in sq, not huge but noticeable.
 
#11
In my current project I use 6SN7’s with KT150’s. When the 6SN7’s are heating up, after a minute I can hear ‘em making little sounds, showing the internals of the tubes are expanding and settling to the new, much higher temperature. Yes, it’s clearly audible.

If you touch the tube (with your fingernail) it’s very audible too.

They are however not affected by playing music at normal levels.

Regards, Gerrit
 
#12
Galu said:
Valves lived happily for years inside radios and radiograms, sharing the same box as the speakers. No one worried about valve vibration, .....
Click to expand...
Valve manufacturers were very concerned about microphonics through the 1950's. Many valves were specifically constructed to mitigate microphonic levels, and were tested to remain below certain levels, which in general were related to a radio console with speaker in the same cabinet as the valve equipment chassis.

You have to put your mechanical hat on for vibration reduction design. One target is to reduce the vibration level passed to the valve equipment chassis, and the other target is any sensitive valves on the chassis. Vibration (acceleration) is attenuated when the vibrating frequency is above the natural resonance of the object of interest. For a chassis, the weight of the object (the chassis) is large, and so like a car shock absorber, the compliance and stiffness of the 'interface' to the chassis must suit. Similarly for a particular valve (which has a much lower mass) - its interface to the chassis must also have a suitable compliance.

Following on from that Mullard link in post #5 is a general article link in:
https://www.dalmura.com.au/static/Microphonics%20in%20valves.pdf
 
#14
Galu said:
Valves lived happily for years inside radios and radiograms, sharing the same box as the speakers. No one worried about valve vibration, probably because it was swamped by all the cabinet resonances!

I'd worry less about your EL84s vibrating than the risk of burning your fingers! 😀

If you are still worried, you can always fit EL84 valve damper rings.

EuroDamper Tube Damper Rings for all 9 pin preamp tubes and EL84 power tubes.
Click to expand...


I've never had any issues with vibration of tubes.... as long as they're quality tubes.
My 12AY7/6BQ5 console amp is situated right between two 12 inch woofers.


But the china closet nearby sometimes suffers from its glass panel doors rattling if I crank up the music.
 
Last edited:
#17
Galu said:
Valves lived happily for years inside radios and radiograms, sharing the same box as the speakers. No one worried about valve vibration, probably because it was swamped by all the cabinet resonances!
Click to expand...
Well, they actually DID 😱
I remember old datasheets stating "freedom from microphony/howling" or some equivalent term.
Lab measurement power output level was 50mW.
"Maybe" they also stated "15 cm away from the speaker" or some similar distance spec, fuzzy memories.
 
#18
Hello guys, thank you all very much for replies and for the materials, Im reading it right now. I will probably try all tips the materials and you mentioned to me.



I realised having separate power supply which sits on a shelf above the amp can be also useful, because this unit vibrates quite a lot, and dont translate to the amp section.


Thank you all for the help. Best regards, Michal
 
You must log in or register to reply here.
Top Bottom