[Amps] Glass tube plate color

[Barrie Smith]

Speaking of class C, I have just completed a nostalgia rig using a push-pull pair of VT-127As (somewhat similar to the 100TL, but looks like a spaceman with grid and plate pins sticking out the sides).

I've been bench-testing it the last few days with a wimpy power supply.  Surprisingly, I'm up to 500 wattts out with 1300 volts on the plates.

I have several tubes, and have tried a couple of different pairs.  In both instances I've noticed that one tube will have a slightly brighter plate glow than the other.

I'd like to have the tubes as closely matched as possible.

My question is:  Which tube is most likely to be the better, the bright one, or the cooler one?

73,
Barrie, W7ALW, DN36au,
QRV 6M, 432 & 1296 EME