Mike Gilmour wrote:

"mike" wrote in message
.net...
Thank you to all for the info.
I know Audio Research uses them on all their products.
just curious
Thanks again
Mike M

Try it for yourself. Wind 20 turns of teflon tape directly around a tube
and listen. Bill Beard used to do that I believe on signal valves.
Personally I'd prefer to select less microphonic signal valves. The metal
vaned coolers however do IMO extend power valve life considerably and if you
ground the coolers on signal valves it acts a bit like shielding. You don't
see screening cans around much nowadays. The very slight hum on my amps
went when I grounded the signal valve coolers.

I'm waiting for the flak ......... ;-)

I don't see a need for tube dampers.
Pick non microphonic tubes, and all will be well.

Besides, some micro tubes would be still micro
with dampers, since the elements sway around if the mica discs are loose.

They used to place tubes in aircraft in tight fitting metal surrounds in an
effort to keep
them cool, with an air flow past the metal.
The planes flew so fast the air flow was hot, so they had to use refrigeration
to keep them cool.
That made the planes heavy, since gridges are that way,
and so some bright spark said let's use solid state.

The fridges are still parked in an old hangar in Arizona; I suggest
all cool dudes drop by and get a few of these US airforce units to keep the
tubes cool.

The only place I use those spring loaded metal jackets is on phono amps,
and they help reduce hum, although I don't have much, since I use a j-fet
in cascode with a 6EJ7 for the first stage of a phono amp.

Patrick Turner.



Mike G