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Damp Tube Microphonics

From kee–(at)–ustin.ibm.com Sun Nov 13 15:47:46 CST 1994
Newsgroups: rec.music.makers.guitar
From: kee–(at)–ustin.ibm.com ()
Subject: Re: tube covers, etc.
Originator: kee–(at)–een.austin.ibm.com
Sender: new–(at)–ustin.ibm.com (News id)
Date: Wed, 9 Nov 1994 14:20:39 GMT

In article <39mrck$a--(at)--ewsbf01.news.aol.com>, twang–(at)–ol.com (Twangr) writes:
> I’ve got a Marshall JCM 900 with a tube cover that refuses to come off one
> of the preamp tubes. Any magic tricks out there? Also, any thoughts on
> isolating microphonic preamp tubes?

For the tube cover, I’d dunk tube and all in a kerosene or light oil bath,
let it soak in, then work the cover off. After all is well, dunk them
– separately now 🙂 – in an acetone or other lighter solvent bath to get
the oil off. Obviously , be careful about the flammability of the stuff you

For the microphonic tube, get a Speidel Twist-O-Flex watch band or something
similar and make a loop of it just big enough to go snugly around the tube.
This works by lowering the resonant frequency by adding mass.

There exists a synthetic rubber-tarlike stuff that will withstand high
temps that can be gooped in a loop around the tube, both adding mass and
mechanical damping, but I forget the name of it. Try over in rec.audio.high-end,
maybe someone knows the name.