Tubes with shields

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In Reply to: Re: GE JAN 6CG7's I have; identical except one type posted by grinagog on March 7, 2007 at 19:04:30:

grinagog,
Yes, the 6CG7's shield is always wired to- I forget, perhaps it's PIN 9(?), and the question is whether the corresponding socket is wired to take that pin to ground. Since the shielded ones are quieter in your amplifier than the unshielded, the shield demonstrates a discernible sonic affect when accomodated- wired properly.
-Very good to know, as this is a key feature in choosing between the various 6CG7 and 6FQ7s. And it means shielding between plates that catches "overruns" off the plates does make the tube quieter.
Other shield tubes: I'm curious now how many other tubes had similar isolation between the pieces, as I came across a couple of tubes with shields when buying some NOS for a McIntosh MR67 tuner. I'm looking at a black plate, halo getter RCA 6GH8A and there is definitely a shield between the pentode and triode sections. The shield is unplated or nickel in contrast to the plates. An Amperex 6GH8A (made by LRT, France) is interesting as the shield pierces the upper mica and two triangular ears project up and support the getter. This shield is shiny also and is a very clever, very strong looking construction. 6AV6s have this kind of gothic-looking architecture as well. I like the way it locks thwe whole tube structure together. It must be quite rigid.
Well, I'm learning something this evening- those shields do work for a living. I wonder why the trade off in noise was thought worth the cost savings when going to the 6FQ7- was the 6FQ7 by then a mainly a TV or tabel radio tube with wider tolerances for noise?
Cheers,
Bambi B

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Follow Ups Full Thread

Topic - has anyone heard distortionby the lack of the screen in a 6FQ7... - jarthel 14:38:41 03/07/07 (6)

Re: has anyone heard distortionby the lack of the screen in a 6FQ7... - tvr2500m 09:14:54 03/08/07 (0)

Re: has anyone heard distortionby the lack of the screen in a 6FQ7... - Alpha Al 20:09:45 03/07/07 (0)

The 6SN7, 6CG7, and 6FQ7... - Bambi B 18:23:07 03/07/07 (2)

Re: GE JAN 6CG7's I have; identical except one type - grinagog 19:04:30 03/07/07 (1)

Tubes with shields - Bambi B 20:54:24 03/07/07 (0)

Re: has anyone heard distortionby the lack of the screen in a 6FQ7... - Len_ 15:56:12 03/07/07 (0)

Follow Ups

Tubes with shields - Bambi B 20:54:24 03/07/07 (0)

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