Does a tube need the break-in hours?

When I swapped the stock 12AX7's in my preamp for Gold Lions, I would say the new tubes did sound slightly better after around 100 hours of use, but the difference was barely noticeable.  By "better", I'd say that acoustic sounds were very slightly "smoother".

We've sold vintage tubes on 'bay for a decade (tekdesinc) and also are designing high-end tube gear. There's 4 categories to this question:

1. raw new modern small signal tubes: definitely breakin for 100-200 hours depending on brand. If cryo'd halve the time. (cryo is a good idea BTW as the thermal exercise also linearizes the raw metal structure).

2.  raw new modern power tubes: this is difficult as you don't want to burn their limited lifespan so breakin for 50 hours until critical listening +/- 50% depending on brand. If cryo'd halve the time.

Next 2 are for vintage tubes as they are rarely unused, typically 95% are used and already 'broken in' per se.

3. vintage small signal tubes: since these have probably been sitting around,  breakin for 10-20 hours depending on brand. Sylvania, RCA, GE require 150-200% more time as they have commercial alloys. WECOs rarely need more than a couple of hours before listenability, but like wine they age nicely.

4.  vintage power tubes: again this is difficult as you don't want to burn their limited lifespan so breakin for and hour or two. Always warn power tubes an hour + before listening to avoid severe stress to the metallurgy.

I just retubed.... and actually changed variety.    That said I think sometimes your brain, ears, and expectations can sometimes play tricks on you.  I had an older quad of Gold Lion KT 66 , with brand new speakers so it was a poor frame of reference to begin with.

I installed a quad of Mullard EL 34 and after letting it settle and checking the bias again I wasnt overwhelmed,   So i let it play and came back a little later and it sounds fantastic....  I think after an hour or so a tube amp is "ready" so to speak

Thanks guys, Mike and tomcy6 !! The tubes were kept properly, of course. And I bough them directly at Manley in Chinos, CA, about 15 years ago (they were not expensive at all). It did not clean the pins (legs), I though, since the problem is not permanent, this may not help. More importantly, i did not think that tubes may also fail because of some problem in the amp. I think now I have enough info to ask to Miss Eva Anna at Manley. Thanks again!
nodari

I’m having trouble understanding your question . If you have multiple failures with new Tubes that have been stored , it sounds like your amp needs service . Some of the newer  Manley’s have changed Tube values due to Tube availability . While power tubes take 100-200 hours to break in , input/driver Tubes also require some time.  Usually less . If your tube pins ( legs ) are oxidized , clean them with De-oxit and a Q-tip . Also contact Manley directly and you will get a more knowledgeable response . Also IMHO NOS Telefunkens are some of the best Tubes on the planet . Unfortunately, their price reflects this .  But I would definitely contact Miss Eva at Manley . Happy Listening , Mike. 

niodari,  unless your old tubes were exposed to extreme conditions like very hot and cold temperatures, they should be OK.  Fifteen years is not much to a tube.  Tubes from the 40s still work fine.  You may need to have your Stingray checked out.  It may be the problem.

I have hundreds of tubes from the 50's and 60's.  No problems.  Much better than most current production.

thanks! then NOS tubes would be the most appropriate (though it should be almost impossible to consider a new tube or one in a good condition from 50s or 60s). 

For any Amperex/Philips/Valvo tubes, the late 50's to mid 60's production are the very best.

Thanks guys for the input!

To my experience, the break-in hours significantly improve the performance of speakers, and the amps as well. For tubes this is not so evident for me (perhaps, because one usually does not replace all the tubes simultaneously). Though some of you argue that there is a technical reason for tubes to improve their performance with working hours.

The 12AT7WC tubes are from preamp section of Stingray together with a pair of 6414 ones. I bough 6 of each type, new, about 15 years ago or so. It is really surprising that none of them are good now (they are falling within 30 minutes of work). Earlier I had to replace the 6414 ones causing noise problems with E 80 CC (Telefunken) ones, which so far are working fine. Long time before that, I have found an excellent substitution for the power EL 84 tubes with Soviet 6P14P military tubes made in 1986. I have replaced Yugoslavian EL84 tubes with these Soviet ones, which have lasted so long (their metallic "legs" are still of the silver color, unlike the other ones that became almost black). Whereas 6414 tubes caused noise, the sound just disappears and comes then back with 12AT7WC ones (with a khhhh... noise) -- quite bothering, you cannot really audition this way.

There may exist European substitution for 12AT7WC (also not sure if these are ECC 81). I would not like to buy another US made Philips ECS series, but, perhaps,  Amperex and Valvo  are better. 

Yes, they do break in. Do they NEED a break in? Not really. Small signal tubes especially will sound good within a few minutes of warming up but they will tend to sound better after a while because everything gets "baked" and molded into shape so to speak. I recommend the JJ tubes for current manufacture or find some New Old Stock (NOS) tubes on ebay. Lots to choose from. You may want to get your tubes from a place like the tube depot or others who test and run them in to make sure they aren't duds and they may even match them for a little more money.

I found any tube requires 100 hrs of burn in .

Uncle Kevvy from Upscale told me the 12au7 and 12ax7 tubes which were NOS would take around 50 hours to break in.

12AT7 tubes can be called different things, but I am not aware of any substitutes.  For example, 6201 is US mil-spec AT and ECC81 is euro designation.  .

I have a bunch of US ATs and a fair number of Amperex/Philips/Valvo.

You might want to post a wanted ad with the specifics of what you are looking for.  The admins don't want us dealing direct.  I would be happy to post a listing if you let me know what you want.

I have found and mfg state 100 hours to fully runin . The new metals need to season or settle in as in any metals they sound a bit bright the first 50 hours or so. Power tubes get hotter faster 
and tend to settle down quicker. Some specialty brands say 200 hours I think 100 hours is pretty safe bet.

"30 minute warmup"

that's the ticket - do it

I wouldn't say they need to break in more that it's they need to be on through their infant mortality stage (first 50 hours or so). If there is anything off about the tube it will fail but after that the chances of living out its full two to ten thousand hours is greatly increased. That means  the tube is healthy and providing its best possible performance. 

I've had a tube preamp for over twenty years and could not tell the difference between a new tube and a "broken in" one after a 30 minute warmup. Same with my 2A3 amp, only that one sounds its best after the 2A3 has been hot for at least four hours, which I am loathe to do because I have the extremely rare RCA Cunningham single plate.

12 series tubes should be plug and play.
12ax7s should last 2000-5000 hours.

@lak, as usual, is absolutely right on

IMO everything sounds better with break-in hours.

in my experience short answer yes, but it varies wildly with diff tubes and diff brands 

Power tubes tend to sound better once played for a number of hours. In my experience that "number" varies greatly. I haven't found break in to be as true with smaller preamp tubes.