12AT nos , flash at start ?

hi, is normal, when i start nagra pre, tube 12at7 make flash ?

like this

https://www.youtube.com/watch?v=PBjWmeuDurk

mati197904-03-2017 12:05am

noromance Details Discussions Posts This discussion Message User 1,780 posts 04-03-2017 at 01:23am Copy Comment URL Report Comment Edit Delete Yes. It’s fine. Mullards?
baranyi Details Discussions Posts This discussion Message User 664 posts 04-03-2017 at 02:27am Copy Comment URL Report Comment Edit Delete My brimar 6060 (equivalent of 12at7) do the same
swampwalker Details Discussions Posts This discussion Message User 5,132 posts 04-03-2017 at 02:31am Copy Comment URL Report Comment Edit Delete Yep, normal.