new tube break in

hi guys,
what is the usual break in period for new tubes for a amp?i have quicksilver v 4`s and i am looking for new kt 88`s
this is an add anyone using penta/shuguang kt88sc`s?what`s your opinion and what`s the breakin time?
My opinion regarding Tube burn in:

24 hours- Noticeable difference
72 hours- You're 90% there
100-200 hours- You're home

This is with the amp playing, not just idling with power on.
About an hour. I have yet to notice a break-in difference with KT88's or 6550's. Input tubes are another story...

I've heard them change right before my very ears...when recently testing out a potential purchase, the seller had mentioned that he had purchased new JJ Tesla kt88's with approx 1 hour's time on them if that. As the amp was warming up with music playing both of us were sitting and remarking at how "hollow" and "cold" the sound was as the same track was repeated itself in the background.

Over the course of about 45 mins as we chatted about birthcities and other irrelevant issues I realized that I needed to make a decision re: the purchase of this amp.

We replayed some of the previous tracks and both heard an amazing amount of difference, the sonic characteristics had changed drastically over the 45mins of additional playtime. So much so that it may have worked against my negotiation tactics.

Now, this could be marked off as amp warm-up vs. break-in but I'm sure the amp was already warm 20 minutes after I had arrived.

With what I heard and continue to hear, that small amount of time made a HUGE difference with sound.

Total play time on the tubes when I heard the difference was approx 2 - 2 1/2 hours...hopefully it gets even better.

I'm still playing with triode vs. pentode but both sound remarkably better than when I first listened to my new baby.

HTH, fwiw I've had no previous experience with tube break-in.

Happy Holidays!
i'm certain that was just amp warm up. 20 minutes is no where near enough to warm the amp. an hour sounds much more realistic. it took my el34 tubes a good 100 hours to burn in.
big difference of opinion,meaning tubes are great out of box vs. 100 plus hrs. to burn in
I'm pretty much in agreement with Fatparrot on this one. The biggest change will be in the first 25 hrs. After that they will settle in slowly. I have the Shuguang KT88 in my VAC PA100 and compared to the Svetlana's they are more mellow, more upper bass and midrange bloom and not quite as solid in the bass.
are they from penta
I like the Penta Lab KT88SC's. The bass is good and tight.
They reveal lots of detail and nuance without ever being harsh or bright. Probably original Tung Sol 6550's are better, but the cost is out of sight. The Penta Lab KT88SC's are my favorite new production KT88 or 6550. I even like them better than NOS Philips ECG 6550. Maybe the Ei KT90's are better, but only type I or II. I won't go near the type III's after several bad experiences. Hope this helps.