Matching tubes isn’t that important in a lot of instances, in a push pull amplifier the power tubes should be matched. A preamp that doesn’t share a cathode resistor closely matching isn’t necessary.
My preference for a preamplifier is to closely match gain between the right and left channel tubes.
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The tubes that measure differently did not come from CJ. I was hoping that someone on the forum might be able to chime in for general differences, and if the numbers change over time based on usage or if they stay consistent throughout their lifespan.
So I am confused did you purchase two matched tubes marked 19 and 30, or 2 pairs one pair marked 19 the other 30? If it is the former, they should be returned unless the seller has a meaningful explanation.
The 2nd. One pair was provided with a measurement of 30 for each of 2 tubes. Another pair, that appears to be of the same construction from the same plant, but by a different company, both of these other tubes measure 19
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Then I’d not worry about it.
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