RE: Close matching

Posted by Jim McShane (D) on January 23, 2012 at 07:14:51

In Reply to: Close matching posted by Victor Khomenko on January 17, 2012 at 07:23:55:

Hi Victor,

Let me quarrel just a bit with your statement.

While the degree to which a tube will change over time differs, they usually behave in similar fashion - that is to say a given tube/tube type will tend to drift the same direction as its mates. You can observe this during the "burn-in" fairly easily. That's what I find.

Also, while tubes can and do indeed drift apart (not in EVERY case, but in many cases), the odds of the tubes staying close enough together to function as matched tubes is increased by providing a tube set that starts at a common point. Regardless of the drift involved, tubes with 40 ma difference in cathode current when first installed (as can occur with randomly selected 6550s, KT-88s) will never be as close as tubes that started 3 ma apart.

So I do find merit with:

a. A run in to stabilize the tube, and

b. Matching tubes under real world voltage/current conditions, and

c. Matched power tubes in general

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Follow Ups Full Thread

Topic - Best alternative to ARC for tubes - ron w2 08:42:32 01/15/12 (21)

Does ARC need very tight gm matching? Why? - Frihed89 04:22:00 01/16/12 (15)

Close matching - Victor Khomenko 07:23:55 01/17/12 (10)

RE: Close matching - Jim McShane 07:14:51 01/23/12 (1)

RE: Close matching - ron w2 14:51:43 01/23/12 (0)

RE: Close matching - ron w2 13:13:56 01/17/12 (6)

I have a different analogy for you - Victor Khomenko 19:34:08 01/17/12 (5)

RE: I have a different analogy for you - ron w2 12:47:23 01/25/12 (2)

RE: I have a different analogy for you - casouza 19:55:39 01/25/12 (1)

RE: I have a different analogy for you - ron w2 04:19:33 01/26/12 (0)

RE: I have a different analogy for you - ron w2 15:40:15 01/22/12 (0)

RE: I have a different analogy for you - ron w2 08:20:32 01/18/12 (0)

RE: Close matching - Frihed89 11:32:36 01/17/12 (0)

Not all ARC amps can bias each output - E-Stat 11:14:05 01/16/12 (0)

RE: Does ARC need very tight gm matching? Why? - ron w2 05:10:54 01/16/12 (2)

RE: Does ARC need very tight gm matching? Why? - Jim McShane 08:15:40 01/16/12 (1)

RE: Does ARC need very tight gm matching? Why? - ron w2 09:26:33 01/16/12 (0)

RE: Best alternative to ARC for tubes - JSTRM 21:03:33 01/15/12 (0)

RE: Get Jim McShane on it, sells tubes, Also, member AA.................nt - Neff 18:13:37 01/15/12 (0)

RE: Best alternative to ARC for tubes - The Lost Bears 09:09:39 01/15/12 (2)

Bear, what tubes did Jim recommend? - Steve Graham 10:16:05 01/15/12 (1)

RE: Bear, what tubes did Jim recommend? - The Lost Bears 16:03:39 01/15/12 (0)

Follow Ups

RE: Close matching - Jim McShane 07:14:51 01/23/12 (1)

RE: Close matching - ron w2 14:51:43 01/23/12 (0)

RE: Close matching

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