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Old 2nd May 2008, 09:35 AM   #1
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Default Expectations of new tube specs

Of my 20 near new Tung Sol 12AX7s, tested for GM, emission, gas and leakage:

3 rated at or above specs
1 rated at or above 90%
2 rated at or above 80%
5 rated at or above 70%
The remaining 9 rated in the 50s and 60s.

What is to be expected for new preamp tubes from Tung Sol?
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Old 2nd May 2008, 09:39 AM   #2
Colt45 is offline Colt45  Serbia
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percent what...
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Old 2nd May 2008, 09:45 AM   #3
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100% emission being 1.2mA iP with grid held at fixed bias

100% gm being 1.6mA/V with 1kHz test signal
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Old 2nd May 2008, 09:57 AM   #4
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Hello d1camero,
in a good triode design is the most importand factor.

Kind regards,
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Old 2nd May 2008, 01:18 PM   #5
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It's a guitar site, but they test new 12AX7s and give variations of 'gain' versus NOS.
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Old 2nd May 2008, 03:53 PM   #6
m6tt is offline m6tt  United States
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I think some of the newer tubes use quite different designs than were used previously. The JJ ec83s looks like an ecc88 or 86, much shorter plate and also has an internal shield. Some of the russian tubes are probably slightly retooled from soviet designs (I may be wrong, not to much experience here). The 12ax7 is a fairly tricky tube to design properly, which is why there is so much variation even in 'golden era' samples.
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