i spent my day today sorting tube bins and ran across this tube. triple mica and looks like a 6sn7 but the structure is rounded off like some 6sl7's i have seen. i have never seen a triple mica 6sl7 though. could this be one of those ruggedized 6sn7's the headphone amp guys are avidly hunting down?
i already tried a magnifying lens and also tried the old timer trick of lightly exhaling on it to try to read something faint off the frosted glass. no dice.
i already tried a magnifying lens and also tried the old timer trick of lightly exhaling on it to try to read something faint off the frosted glass. no dice.
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I'm going to say that what you have is either a 6BL7 or a 6BX7. Both look similar depending on exact vintage. I have both of these numbers packed away in the attic. Perhaps test it as first one and then the other and see which best matches the test.
Both are medium mu with the BX having a slightly lower Rp and amplification factor.
Both are medium mu with the BX having a slightly lower Rp and amplification factor.
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