"Sander deWaal"

Microphonics are your worst enemy in tube phono
stages.

True, and there are helpful tube dampening mechanisms
to reduce microphonics.

You mean those silicone rings?
They only help to avoid bringing the glass-enevelope in resonance.
Otherwise, for the innards of a tube, they do nothing.

Example of products:
3M Viscoelastic tube dampener ($3.50)

Ensemble Tubesox damper ($65 pr)
which is make of Kevlar and copper thread.
This works fine but doesn't fit some of the
unusually small based tubes like the 6922
Mullard.

Bluenote - Midas Hi-Fi ($80 pr.)

Right-Way Audio - Tophats ($120).

Audio Research, as I remember, has dampening
rings for sale, too.


Remember that tube characteristics are highly dependent
on the relative placing of the internal electrodes.
When they get moved relative to each other, parameters will
vary. That's something that a dampening ring *outside* the
glass container can't prevent.

The only "tweak" that is a bit helpful is to mount the
tube socket with rubber braces and spacers onto the
chassis.

Apparently 6922/6DJ8 are also subject to EMF/RF
distortion. In my microphone preamp they are fully
shielded (metal screw-down covers).


Even then, a really microphonic tube will manifest itself,
and has to be replaced.

It has not been mentioned but there are also tube
devices designed to reduce the temp of the glass
envelope.