flash in 12at7

[howardnair]

odd!!  with the mullard cv4024  --i get a flash on turn-on--i do not with the EH 12at7--this occurs with 3 different nos mullards --other than the flash all is well---??????

 

[JC]

This is not uncommon in small European tubes.  It had to do with their filament formulation for "controlled heater warm-up".  I don't know the specifics of their approach, but I see it all the time in guitar amps with Euro tubes.

Kinda scary the first time you see it, though!

 

[Paully]

Yep, mine do it every time.  You're fine.