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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: RE: Matched Tubes, What does it Actually Mean posted by Nunki on July 19, 2020 at 04:28:49:
Maybe that's what it means to you?
I spend a huge amount of time sorting out NOS stuff (yes the spread can be enormous).
To give you some idea, out of a box of 15 s/h 807s I got maybe 2/3 pairs.
Idem when I weeded my way through 25 NOS 5B254M (STC 807).
From the 25, 3 were DOA, making an internal arc/flash when started up.
Several were weak, several were uber-strong.
In the end I got 2 quads and a few pairs out of it, with the duds just going for decoration.
From my large boxes of 250+ NOS pentodes I get a spread of between 9m/a (well under spec) under true working conditions to 22m/a (well over spec).
As they degas, within a few minutes they stabilise, so you have to let them get warm.
In my dual QUAD pentode amp I match all 8 to within 6%.
It takes a lot of patience, because they do drift a little.
How do I do it?
I fit them in a fully working amplifier and check them one by one, inc a full power test to see if there is any change in SQ wave response or THD/IMD.
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Follow Ups
- RE: Matched Tubes, What does it Actually Mean - ivan_terrible 01:38:40 10/13/20 (1)
- RE: Matched Tubes, What does it Actually Mean - Nunki 02:04:33 10/13/20 (0)
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