The danger of new untested preamp tubes

[steve25]

I started to re-tube a Vox 15 watt head last night with owner supplyed Ei tubes, 3 ECC83, and in testing them they are all over the place as far as Mu. check this out!
tube 1) 95/134
2) 100/135
3) 88/132
These tubes are known for going microphonic pretty fast in combo amps which this isn`t, but this Vox head has no venting for the preamp tubes but for what heat can find its way out the top thru the unused input jack, or out the front face vent on the output tube side.
This guy plays every weekend and many times both nights, I bet him dinner that at least one of the tubes takes a dirt nap within 6 months!
Anybody else want to give a guess?

[cdw2000]

In the 12AX7/ECC83 family does triode 1 versus triode 2 usually have a disparity like this? I know from reading around that triode 2 is usually lower noise and should be used as the first preamp stage when wiring them. Supposedly its how the wires run inside the glass envelope based on the tube pinout. The triode 2 has a little more isolation from the filament circuit.

I'll have to look at my 12AX7/ECC83S preamps that I got from "Doug's Tubes". They write the mu on the side of the tube after they burn 'em in and characterize them. I honestly don't remember if they were that different, but I don't think so.