Burn-in time for 6550c tubes ?


I have just re-tubed my CJ Premier 8 amps with brand new Svetlana 6550c tubes, having old and rusty Sovtek 6550 tubes before.

I have just droped-in the new tubes, and biased the amp accordingly - sound thru the Premiers is now more linear but constrained.

Is this normal?
Do the new 6550c tubes need of a burn-in phase?
How long?

Please consider that all input drivers are quite new (less than 3 months).

Thanks for your valuable input.

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If you're using them in pentode, about 10 hrs. Triode will take a little longer. The Svetlanas are way better than the Sovteks. The constrained sound is probably more due to the new input drivers, which because they're (relatively) lower power, take a little longer to break in.
My experience with tubes both in my monoblocks and in guitar amps is that they always sound constrained when you first turn them on and they open up after they warm up (the character change of the el-84s in my guitar amp after the first set of warm up is huge). Is the constraint persistant? Another possibility is that you got used to the looser sound of partied out tubes and your ears need to readjust
just looked @ your system pix.
You need to make those LPs upright! they could get warped sooner than you think with them lying on top of each other!
Better yet: before they get warped, I will take those LPs off your hands & save you the trouble!! :-) I can send you my addr off-line.
the LPs are upright Bombayalla, look again!!!

Thanks for the heads-up anyway, I have 500 more in the closet, and spinning them quite frequently!!!


well, these new tubes have now more than 30 hours on them, and sound is really "exploding" out from them.

An interesting note: Due to the perceived additional energy I have now with the new tubes, I needed to re-locate my speakers; now they have NO-TILT and a little closer to the side walls (an inch or so). The speakers just disapear and exhibit a great tonality, dynamics and real textures.

Thanks for your feedback guys!