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

My experience is that tubes do take time to break in. Two years ago, I bought a pair of new Full Music Meshed-plate 300Bs for my SET amp. When I first powered them on, they would not even hold biases. They also sounded muddy and closed. If you looked at the meshed plates long enough, you could see their brightness changed!

After 200-300 hours, they started to open up and hold the bias levels. Now they work perfectly. I really like these tubes!

Do you wait until they're warmed up before playing music? My McIntosh has about a 30-second "tube-warmup" before it'll play. It literally display "tube-warmup" on the front LEDs. My Cary 120S manual says warm-up time is 3 minutes. The tech at Cary Audio said it was ok to start playing pumping music through as soon as the amp is turned on but I take his technical advice with a grain or two of salt.

02-07-09: Cyclonicman
My preamp takes about an hour before it sounds best too. I think the warmup period is not for the tubes, but for the other electrical components within the preamp.

Bingo.

I have some all-tube guitar amps, and once the tubes are up to operating temperature, they're ready. Having been a solid state hi-fi guy for decades, I was really surprised that I could immediately hear the difference when I swapped in some '60s-era NOS RCA grey glass 6V6GTs for the stock Sovteks in my all-tube (including rectifier) Top Hat combo amp. No break-in or settling in required. I think it's the SS components that take awhile to reach optimum operating temp and attendant tolerances. I keep many of my SS components on all the time for this reason.

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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