[bside123]

As in the case with components, is there a "burn-in" effect with new and unused, new old stock tubes? If so, what can generally be expected: number of hours for sufficient burn-in; changes in timbre or tonal character; dynamics; etc.? I would be interested in hearing peoples experiences. Thanks.

[rollo]

  In my experience with new tubes is that after 30 hours they start to open up. To date I have yet to find a tube thattook less than 100 hours to sound its best. Larger output tubes such as 211s, 845s about 200 hours.
  The most affective method so far has been 5 hours of play five hours off. DO NOT run them 24/7. Break in discs or just the noise from a tuner between stations works just fine. Have fun trying.


charles

[bside123]

Thanks Charles. As I've acquired more tubes, these questions occurred to me. The latest round in particular... While I was in Europe, I purchased 3 different quads of NOS stock 12AT7 variants. I was wanting to compare them in a VTL 5.5 preamp when I returned. As they have never been used, it struck me that I am not really hearing these tubes at there best after only a few hours use. This really doesn't allow for a quickly realized shoot-out conclusion. Even though all three models sound vastly different, I guess I'll have to be patient and really take the time. Should have known, as I continue to run up agains this lesson repeatedly!

[Ericus Rex]

My findings have been in line with Charles.  You should get an overall sense of the tube by 50 hours.  Most of break-in will be done at 100 hours.

What I'd do in your case is listen to the tubes for at least 100 hours and then go back to your original set.  Differences (if any) should be obvious by then.

[dminches]

My experience is that the first change occurs in the first 15-20 hours.  After that there are smaller, albeit noticeable, changes until 80-100.

I have been breaking in a pair of NOS bad boys.  In the beginning it sounded like there were towels hung over my speakers.  Then, somewhere between 15-20 hours the sound opened up significantly.  Things are still changing at 40 hours.

[TheChairGuy]

5-10 hours seem to be right among the many dozens I've had.

I don't hear any break-in changes beyond that.

John