Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Stereomour => Topic started by: howardnair on September 23, 2010, 08:29:03 AM

Title: flash in 12at7
Post by: howardnair on September 23, 2010, 08:29:03 AM

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---??????

Title: Re: flash in 12at7
Post by: JC on September 23, 2010, 08:35:50 AM

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!

Title: Re: flash in 12at7
Post by: Paully on September 23, 2010, 11:45:16 AM

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