Expectations of new tube specs

[d1camero]

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?

[Colt45]

percent what...

[d1camero]

100% emission being 1.2mA iP with grid held at fixed bias

100% gm being 1.6mA/V with 1kHz test signal

[oldeurope]

Hello d1camero,
in a good triode design µ is the most importand factor.

Kind regards,
Darius

[kstagger]

It's a guitar site, but they test new 12AX7s and give variations of 'gain' versus NOS.
http://www.guitaramplifierblueprinting.com/12ax7.html

[m6tt]

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.