[TheChairGuy]

Is there near consensus out there that tubes need break-in time?  Or is this another contested sonic happenstance??

To me, it sounds like capacitor break-ins typically do...only they take less time to flesh out fully.

I just bought some (amazing and heartily recommended for $14 each) gold pin Electro-Harmonix 12AU7's and installed them yesterday (2 each in each mono amp)...and played them all day.  Tho they were immediately quieter than the NOS Sylvania's they replaced...they sounded boxed or closed in and tight.  In fact, throughout the day I heard slight pinging as the tubes broke in/expanded (whatever) and after 6 or so hours that ended while the music just continued to bloom.

Today there is no pinging, just clear and unfettered music - truly wonderful stuff. 

I'm not looking for a contentious debate on this topic a la cable and capacitors....but did I hear what I heard or was this possibly my brain adjusting to them?  The darn pinging I didn't imagine however...and it's not there today (or was there after 6 or so hours yesterday)

I suppose it doesn't matter either way as it's my perception that matters, I just wanted to know what camps existed out there on the subject.

fyi - this has happened each time I install new tubes.....and I have bought used/older tubes that it simply does not occur.

 

[jqp]

Not a tube expert, but I think the break in time may be measured in minutes or hours...also there is a tube warm-up time of about a minute

[PhilNYC]

Not a tube expert, but I think the break in time may be measured in minutes or hours...also there is a tube warm-up time of about a minute

I've found tubes to take much longer than a minute to warm up.  More like a day.

[95bcwh]

I heard break-in in all the 12AU7 tubes that I've tried so far (Mullard 1960s NOS, Brimar, Sovtek).

TheChairGuy, can you tell me if the Electro-Harmonix 12AU7 sound very different from Mullard?

[Dan Banquer]

I hate to tell you this TCG but by the time they come out of the factory they should already be broken in as you call it. When you install them they are on their way to break down. I don't mean to be snotty here, but tubes are not exactly known for their longevity, or for staying the same over the years. If you do a bit of research there should be plenty of material out there that documents exactly that.
              d.b.

[Carlman]

Yes, they change.  I don't know what the consensus is... but what I've seen in preamps is that it take anywhere from 1-2 hours to 'stabilize' and play consistently.  I've also heard tubes get noisier if you left them on continuously for days.... like a bit more hiss after a few days.  If I let them cool for a while, they sounded as good without the hiss after a few hours and for about a day or 2.  I found myself always trying to stay in that window of 'perfect' tube operation range when I had tubed preamps...

Thankfully, most people probably do not suffer my affliction in this regard.  Also, not all tubes acted the same, just the really old ones that sounded the best.  They wore out fastest also.  

[SET Man]

Hey!

  TCG... yes like almost everything else tubes do need time to settled in or break-in. How much? I don't know. But it seem that better made tube have been bench tested/burned longer than some other and this might be less noticeable with that tube. With this IMHO I notice less of tube break-in than say... a capacitor.

   And of cause those sound that you hear from tube when they are turn on and off are normal. Just heat expanding and contracting the components inside the tube. If you think
those 12AU7 pinging is loud, you should hear my KR Audio 842VHDs pinging/bonging when I turn them on and off... you could hear them couple of feet away!

Not a tube expert, but I think the break in time may be measured in minutes or hours...also there is a tube warm-up time of about a minute

I've found tubes to take much longer than a minute to warm up.  More like a day.

   Phil, I agreed that tube need more than a minute to warm up. For me with my own system I would say minimum of 15 minutes and I notice that everything sound great and stabalized in about 45mins to 1 hour.

   I've never left my amps on over night so I don't know but I once left my pre on over night and honestly I don't know much of the difference the next day when I listen compared to my usual warm up time. Than again I don't feel like burning those KR Audio tubes overnight without listen to them.

   
    What I do is turn on my Audio Note M1 tubed pre on than 15 mins later I turn on my SET amps and than wait another 15mins to 30mins before I listen. 

Take care,
Buddy

[rollo]

Buddy,
        Also found it takes about an hour before things sound good.I'd say with breaking in over 100 tubes that %0HRS does the trick.
         I usually wait 15 minutes to let tubes come to operating temp.then let it run for an hour before any critical listening.Works for me
rollo

[TheChairGuy]

I heard break-in in all the 12AU7 tubes that I've tried so far (Mullard 1960s NOS, Brimar, Sovtek).

TheChairGuy, can you tell me if the Electro-Harmonix 12AU7 sound very different from Mullard?

Don't know 95......I only had the 1960 Sylvania's and the original (a mixed bunch) of 12AU7's that came with the amp.  I can say that the EH12AU7's are most agreeably priced and sonically better the Sylvania's.  They are really nice sounding.

I really feel that the excellent new crop of 12AU7's and 12AX7's from Russia and Eastern Europe (and 6V6's...the only other tubes I have history with) eliminate the need for pricey NOS tubes now entirely.

[TheChairGuy]

These 12AU7's 'pinged' for several hours yesterday....then silence.  No pinging today at all.

So, I am puzzled...but not at all displeased 

[Kim S.]

I'm in the middle of a tube break-in experiment now.  I installed a new russian made KT-66 tube to replace a 6L6 tube in my preamp.  At first (after on for about an hour) it sounded thin. (My wife said it sounded "tinny" and asked me to turn it off!)  I've kept the pramp on or 10-12 hours since and we have played the same selection, Four Seasons from  Three  Wishes of the Rose CD byTakako Nishizaki conductor.  While still not up to the 6L6, it sounds noticeably fuller.  Over at audioasylum I was told it might take 100 hours for the tube to break in.  I'll swap tubes then and will see.  I've noticed a break in on new 12Au7 tubes I've installed.  After about 7-8 hours.  The shorter time period makes sense as these are much smaller tubes

[PaulFolbrecht]

These 12AU7's 'pinged' for several hours yesterday....then silence.  No pinging today at all.

So, I am puzzled...but not at all displeased 

I believe this is due to the tube burning off the bit of gas that may be left.  It is *not* break-in per se (at least I wouldn't call it that) and is a much faster process than any cap/wire burn-in.  Like the first few hours of life and that's it.

Whether or not tubes have a break-in period *other* than this particular phenomena, I can't say.

[jt1stcav]

I don't really hear much difference while a new tube is burning/breaking-in...guess my less-than golden ears aren't all they're cracked up to be. But I do let my amp warm-up for 10 minutes before playing music and I hear subtle improvements in overall sonics.

[aerius]

I don't think it's possible to make a definitive answer since there's a million kinds of tubes and countless thousands of different circuits for them.  Some circuits are almost immune to tube changes, others are hyper-sensitive to them, some tubes are really touchy and others are really stable.  For instance ultra-high transconductance tubes such as the Western Electric 437 or the Sovtek 6C45Pi will drift drastically during the first hours of use, the channel balance is fine when the amp's first fired up but 10 hours later and one of the channels is down 5dB.  Then there's the ECC40 which sounds the same whether it's on its first hour or its 1000th.  Other tubes will be somewhere in between, 6SN7's do open up and change a bit as does the 12W6, 6BX7's are pretty much unchanged after the first 15-30 minutes, for all I know they're good as soon as they warm up.

[Kim S.]

Our tube break-in experiment is over with mixed results.  We had the KT-66 tube on for about 30 hours.  It definetly sounds better than it did after the first few hours.  A casual listener might even be tempted to say it sounds "good".  However it still sounds thin and lifeless compared to the 6L6 tube it replaced.  We did not notice any improvement after about the 10 hour mark.  I guess the tube just did not fit our preamp.  It probably sounds great in another application.  No we didn't wait the entire 100 hours.  Could not wait to get back to great music!

[PaulFolbrecht]

Our tube break-in experiment is over with mixed results.  We had the KT-66 tube on for about 30 hours.  It definetly sounds better than it did after the first few hours.  A casual listener might even be tempted to say it sounds "good".  However it still sounds thin and lifeless compared to the 6L6 tube it replaced.  We did not notice any improvement after about the 10 hour mark.  I guess the tube just did not fit our preamp.  It probably sounds great in another application.  No we didn't wait the entire 100 hours.  Could not wait to get back to great music!

KT66s?  Regulators?  This a Supratek by any chance?

[Phil]

Perhaps it depends upon the tube, but 20 - 40 hours for the 6H30 in my universal -- didn't track the time closely but the sound changed from good to really good.  Recently, I had to replace the tube and the replacement (also 6H30) never sounded right to me, so I simply used another after about 50 hours.  The first replacement worked, but the sound was very hard and glassy.   

I find one hour to warm up is sufficient for non-background listening, but there is improvement at the second hour.    After that, everything sounds great for hours.  After a very long time, the sound gets a bit mushy.   The exception is my hybrid Butler amp.  It warms up in about 30 minutes and the sound stays consistent. 

While tubes do degrade, they can last a long time.  The tubes in my Supratek preamp should last 10,000 hours.  That is a very long time.

Phil

[Kim S.]

Our preamp is an ASL 2006, not at Supratek.  We are very happy with it but like all things audio it fun to try to improve things.  The 6L6 tube we're playing with has no markings except the ASL logo.  I'm assuming its of recent Chinese or Russian manufacture.

[Imperial]

Tubes, some of them, will have a coating on some of its metalelements inside
the glass envelope... This has to evaporate, burn of, by the heat...

That's the burn in for ya!!!
Not all tubes are manufactured this way. Or will need this.
So, are there pointers to this? Not really, you'll have to consult the manufacturing remarks ands so on.

If we look at the metallurgical side of things... as long a tube element never reaches the temperature
of "Eutectic..." of that specific metal, or coating, no burn in will apply...
Wikipedia on eutectic:

"When a non-eutectic alloy freezes, one component of the alloy crystallizes at one temperature and the other at a different temperature. With a eutectic alloy, the mixture freezes as one at a single temperature. A eutectic alloy therefore has a sharp melting point, and a non-eutectic alloy exhibits a plastic melting range"


Some of the coatings actually will evaporate, like water on a hot day...
The tubes envelope will become discoloured after some time of use.

Are there heat thresholds that a tube need to reach before the process will start?
hm...

Aluminum (that's aluminuminum for the Bush fans out there... ) will actually change shape in room temperature by pressure alone... meaning the molecules will "float" to a new equilibrium.

All metal elements wish to reach this state of crystalline or non-crystalline grid formation...
So during a heatingprocess, say turning your amp on, there may be going on some changes EVERY time
a given tube heats up...

It will then slowly reach a metal or shape equilibrium on a molecular level...
then you have a reverse process as it cools down.

All of this will depend on the materials used, what level of vacuum is inside the Tube (Torr), the construction, what type, is it gasfilled? ... yup! That's a quick lowdown on the break in of tubes.

Imperial