New Tubes- Need Burn-In?

Zaikesman- All good points. I noticed that the EH KT-88's had improved significantly as I used them. I am hanging onto them for precisely the reasons you mentioned.

Thanks for making me think!

Rumor has it that those GEC clone flat plate KT-88s from Shuguang are incredible. Is that really misguided??

BTW I am late to this thread, the answer is absolutely, you must burn in a new tube to get the best sound it has to offer. They burn in but do not take as much time as many as people say, for an input tube, in particular. They (inputs) will IMHO retain their sonic signature after at most 40hrs. I think people who say 200 hrs are just hearing things.
Output tubes are a different animal altogether they may need 100 hrs or more to settle into their final state they have been quiky in my amps, but they just seem to bounce around. They always seem to start thin and flesh out but even a matched quad will have a tube or two that takes more time and they can go through a really flat sounding period on the way, others flesh out right away.
Can't comment on the 6SN7s burn in every pair I own (may 10 pairs or more- I love tube rolling) is NOS and well burned in.

I've been very happy with the SED flying "C" EL34's in my Dynaco MkIV amps. I also loned a spare quad to a friend with Antique Sound Labs amps which he will be keeping.

Bartokfan...KT-88's and KT-90's are two very different tubes. Compare the KT-88 with the winged C 6550 insted. KT-90's to my ear are much more punchy and a bit more agressive then the winged C 6550. Usually KT-90's have a bit more output as well. What was the tube your Jadis amps were 'voiced' with? BTW as far as I know Jadis does not make their own tubes and buys them from China, Russia, Yugo. etc. G.Garfield

The real term is aging, yes then the cathode emission becomes stable and the tube does not drift. The recommended time is circa 36 hours.Me, vacuum tube gear, late 1950's, Stategic Air Command. Delt with tubes. i'm thinking of doing a online consulting service, does this sound like a good idea, to all? won't be free, but i'll teach audio also to component level including transformers.