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 9,404 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 717 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 5,138 posts 04-03-2017 at 02:31am Copy Comment URL Report Comment Edit Delete Yep, normal.
jedinite24 Details Discussions Posts This discussion Message User 1,503 posts 04-03-2017 at 04:53pm Copy Comment URL Report Comment Edit Delete Agree with the posters above. It is normal with Mullard 12AT7 tubes. I saw the flash when I had a pair installed in my Jolida 502P amp.
mcintech Details Discussions Posts This discussion Message User 128 posts 04-03-2017 at 05:12pm Copy Comment URL Report Comment Edit Delete Perfectly normal in a Nagra preamp. (Full disclosure; am US service center for Nagra)