Tube warm up proof?

Here is a graph of tube temperature data I acquired today on my Vali 2 with EH 6cg7 that might also be interesting:

 

Awesome! Was it idling during this time, or playing music? I'm guessing that the tube will have a higher temp ceiling while in use that might impact performance (and skew measurements) but right now that theory is untested.

 

Won't make any difference. Heat is a result of power dissipation. The filament of the 6cg7 requires 3.78 Watts (6.3 Vrms x 0.6 A). Vali 2 uses the tube for voltage gain to drive the bases of the output transistors. This requires mW at most. Negligible heat produced by this. So the filament power dwarfs the modulated electron stream between the cathode and plate.