Tube Question - Do they need time to "Break In"

In my experience, my tube integrated sounds its best after about an hour and a half. It will sound great almost immediately, but even better after about 90 minutes. I also would say that the sound of the amp definitely improved over the first 200 hours or so. Do they have to do these things to sound good? No. But they do improve over that time, yes.

>>Thanks everyone for the response...I'm changing tubes for the first time...
02-07-09: Chadlesko<<
>>>>>>>>>>>>>>>>>>>>>>

Chadlesko,
New tubes do require burn-in time to reach their full sonic potential.

Here is an example. Read on page (3) what Cary has to say about burn-in time for tubes in a preamp of theirs.

Check out page (54), A Taste of Tubes

Quote from page 54:
"Their performance initially improves during the first few hundred hours, followed by an extended performance plateau region. Finally, after several thousand hours of use they slowly f-f-f-fade away."

Will you need to wait a hundred hours for your new tubes to sound really good? Probably not.... But they will take a hell of a lot longer than just an hour or so.
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Johnny I have an Audio Research tubed preamp and it has a 45 second power up before you can actually play it, however, the owners manual actually states that the preamp will sound better if warmed up for an hour, which it does!