Tube dampers
Janos
Here's a recent message from the Tube DIY asylum (with due references,
I hope they do not mind me quoting them - you can read the full post
at:
http://www.audioasylum.com/forums/tubediy/messages/93004.html
Posted by cheap-Jack (A) on January 03, 2006 at 11:37:58
In Reply to: Re: Drivers, Loads & Interstages posted by fatbottle
on January 3, 2006 at 06:38:09:
Recipe: (1) Teflon sealant tape used to seal up pipe union joints
by plumbers, available from Home Depots for only 62 cents for a 5-ft
roll.
(2) computer mouse rubber pad, with a thin fabric glued on its top
side. A buck a piece from any dollar marts. The fabric is crucial to
provide physical pulling strength of the rubber pad.
Simply wrap 5 to 10 rounds TIGHTLY on the upper part of the
tubebody, depending on the tube being a power driver (more heat) or
just a phonostage signal tube. The idea is to provide adequate heat
insulated foundation for the tubebody damper. I folded up the tape as I
wound it as it is a bit too wide for 9-pin tubes.
Next is to cut out a small square, say 1 1/2" side, from the
computer mouse pad. Then cut a round hole in the centre of the rubber
square, which will act as the tube damper. The size of the centre hole
got to be big enough to SQUEEZE the tube through but tight enough to
hold the rubber square in position on TOP of the Teflon sealant tape.
It is the tightness of the rubber square against the tubebody does the
damping tweak.
.... that's the asylum quote.
Leonard, you could try that to tame the microphonic 12ax7 in the PAS.
One word of caution: this trick will go against the tube life
expectancy. I'd say you could wrap a few rounds of copper tape around
the tube, and put the teflon tape on it to dissipate the heat from
under the teflon-blanketed area. I would not recommend doing it on
power tubes, as their life will be severely shortened. Those guys run
too hot, and need to dissipate at the hot surfaces.... however, before
applying this (or any tube damping tweak) always test (by touching the
operating tube) which parts of the tube are colder, and which are the
hottest. Ideally, the damping should go to the coldest place to allow
adequate heat dissipation. Avoid the hottest area.
Good luck!
Janos