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Old 29th April 2008, 05:34 PM   #1
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Default Any matching in 12AT7 sections? (SimpleSE)

Getting ready to order some more tubes to try in my SimpleSE, and was curious if there needs to be anything special about the sections of the 12AT7 since it is being used for stereo service. Should the sections be balanced? Will that result in better signal integrity?

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Old 29th April 2008, 07:10 PM   #2
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Each side of the triode is there to provide gain, as I understand. I don't see much value in having the two sides matched myself, although some may disagree. For me if one side gives a noticable amount more or less gain, it becomes an tree ornament. A bigger factor in my humble opinion is the manufacturing of the tube.

I've had good luck with 6679's. My favorite being a Sylvania black plate. I have a Tun-Sol grey plate 6679 which is a close runner up. I've also tried a two different Sylvania A2900's, which were pricey, and turned out to be out of spec. Grrrr. The worst I've tried is an Amperex 12AT7. No highs at all.
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Old 30th April 2008, 01:27 AM   #3
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Perfect matching is not needed. However a grossly mismatched tube may cause one channel to be louder than the other. Depending on how the tube sections are "matched" there may be no correlation with performance in the amp.

I have run hundreds of tubes through a SimpleSE amp (enough to wear out the socket). Some were new tubes, some were used, but 200 of them were identical GE five star 6201's from military bulk packaging. I have found some tubes where one or both channels was weak, or distorted, and some that were just dead. It is interesting to note that most of the tubes that didn't work well in the amp tested just fine in two tube testers.
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Old 30th April 2008, 03:34 AM   #4
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Depends on the tester. My knight KG-600 doesn't catch everything. I have a 7868 that has an open grid which it didn't catch. I once tested an RCA black plate 12at7 that I got excited about. It tested 95% on my tester, but no output when plugged into an amp. Retested and it had excessive gas

This explains why the sound was low distorted and 'farty'

I've got one of those blackplate sylvanias..Hmm I'm gonna have to try that in my RH84.
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