I was just curious as to whether the switch is for pentode/triode or 2 tubes/4 tubes.
I assumed it was 2/4 tubes because on the last set of PT's I had in there, only the middle 2 had a blue glow when on 50watts, whereas all 4 had a blue glow on 100watts. But with the new set, all 4 have a blue glow no matter what power their set to.

Also, what's the tonal difference between Pentode and Triode?

My Gear
Cort VX-2V
Stagg BC300
Marshall JCM900 4100 DR
Marshall 1965A
Hartke HA3500 Combo
Not sure of the answer but all I can say is that if all 4 tubes are in there that they are in the 'chain' whether if you are at half power or not. Meaning they should glow. Blue for a 6L6 is cool but what power tubes do you have in there exactly? EL34s?

That said,........then bump.