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In Reply to: RE: Tube Preamp Vibration Control Suggestions? posted by pictureguy on June 11, 2017 at 13:18:14
So, as I understand what you are saying, since the microphonics are caused by an undesired motion of the filament, then a tube damper couldn't help for two reasons: (1) airborne vibration would not reach the filament through a vacuum and (2) mechanical vibration would be jiggling the filament because of the tubes coupling to the preamp socket and it's coupling to the PCB, etc., and a tube damper surely couldn't impact that.
Makes sense to me! Hmmm.
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> jiggling the filament because of the tubes coupling to the preamp socket and it's coupling to the PCB, etc., and a tube damper surely couldn't impact that.
Surely it could. Acoustic sounds couple to the glass and the board. Changing the properties of the glass (which is a good stiff resonator) would change the vibrations of the tube-holder-board-filament-electrode system.
I would take the empirical experience over decades of people damping microphonics and out of control feedback howl with tube dampers.
Tube dampers may YET work at Diminishing microphonic vibes.
This is pretty easy to test and also cheaper than dirt, unless you are going thru some pirate of a parts seller who marks up the essentially inexpensive O-Rings to the moon.
If I owned tube gear, I'd test this. Yes ME. I can get a grip on the science of this pretty easily.
Find out what Size you need and buy the lowest temp material which will work. O-Rings also have what is called 'durometer', which is a measure of 'bounciness'.
Rubber may melt too easily and May work only on the lowest temp tubes. Other compounds have better temp resistance. We used (red) Silicon in some applications while for other uses we used either Viton or Buna-N. (nitrile?) For EXTREME chemical resistance (plasmas / RF / agressive chemistry) we used Ethylene Propylene = EP for short. This stuff is Wacky Expensive.
I'm just thinking that Isolaton of the tube socket from the chassis MIGHT help. Or it could hurt, since vibration in the tube would not be directly coupled to a High Mass object....the Chassis.
I'd secure the tube socket with Nylon screws and nuts and something between. Maybe sheet Silicon Rubber? I'd have to look at a current tube socket / chassis to think about what else might be done.
Airborne vibration WOULD reach the filiment but would have to mechanically couple to something which was coupled to the tube and the internals which support the filiment. That's why I'm not too 'big' on o-ring tube dampers, but would certainly devise a measurable test.
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