Tube burn-in?

[Golden Monkey]

Couple of questions regarding tube burn-in...

1) Does it actually exist? I'm assuming tubes would be subject to benefits of burning in like any component, if not moreso.

2) Is it something that gradually changes over time and the life of the tube, or do they reach a state of "broken in"?

3) If yes, how long (typically) does it take for a tube to fully burn-in? Is there an average baseline, or does it vary by tube type?

4) If certain types take different amounts of time, does this variance in amount of burn in differ between different manufacturers (for example, would a Telefunken 6922 take more or less time than an Amperex)?

5) Is there a difference between different vintages, ie: would a 1956 tube take a different amount of time compared to a 1967, given that they were both totally unused up to that point?

6) If a tube is used back in the 1960's long enough to be considered burned in, then shelved for 40 years and sold as used, would it need to be "re-burned-in", or would it still be in the same state, given that everything internal is in a vacuum?

7) Do tubes get burned in simply by being on, or do they need to have signal run through them (like breaking in a pair of headphones)?

I'm sure tube gurus will have differnet opinions/answers on these questions, but I'm just trying to get an idea of how long in general it would take. If I'm going to be trying out different NOS tubes, I'd like an idea of how long I should listen to a tube before I pass judgement on their sound. Thanks for any insight/knowledge you can pass along, O wise sages!

 

[Tridacnid]

1) I think it does. I heard dramatic changes in a pair of WE 6AK5 tubes. One day the midrange was AMAZING, the next day (or couple of hours, really) it was back to good, but not they way I like it.
2) I would say that they eventually reach a plateau, then begin to degrade as they expire.
3) No idea. I run mine for at least 30 hours (if they're NOS).
4) Maybe. Different materials could produce a different reaction.
5) Not unless the design changed, the vacuum was of a different quality, or the materials used were different.
6) Hmmm, I would run it for a couple hours, then just say whatever. I think there is something about how metal gets slightly rearranged after current has been passed through it, but then it reverts to its original order if it goes for long enough without anything passing through it. Don't quote me on this.
7) No idea. I run mine with music.

 

[myinitialsaredac]

Golden,
You and I should know full well not to ask opinions of burn in, cable differences, etc.

However I am also interested in what people are saying on this topic =D.

Dave

 

[Spareribs]

Many afficianados believe that the Western Electric 300B tube should be burned in. I just got mine recently and will try to notice if there are any changes. But fresh out of the box, they sound great like how a quality tube should from my experience.

 

[Golden Monkey]

Quote:

Originally Posted by myinitialsaredac /img/forum/go_quote.gif Golden, You and I should know full well not to ask opinions of burn in, cable differences, etc. However I am also interested in what people are saying on this topic =D. Dave

LOL...true. I'm taking it on faith that there IS a burn-in effect, be it ever so subtle...or maybe not so subtle. Let's say that to my ears there has been a dramatic (or at least very noticeable) change in components like my DAC, my old MKV amp, and the Monarchy DIP, and no noticeable change in any type of cable (power cords thru headphone cables). I'm guessing it's down to capacitors and the like settling down...

 

[pataburd]

There's "run-in" with tubes, IMHE. For example, it takes somes tubes 10+ hours to stop humming after first being fitted to the Darkvoice 336i or 337. My experience with the Mullard 6080 and Svetlana 6H13C suggests that their sound "opens up" and "levels out" after about 20-30 hours. Ditto for many NOS 6SN7s, too.

 

[bergman2]

ditto pataburds comments...usually after a few hours of warm up time most tubes are fine...i find nos, in particular, to be fast warmer uppers...HOWEVER, i have noticed in my dalliances with some nos v new chinese and russian tubes that the new chicom and rusky tubes take a little longer for their harshness to dissipate...after that, whatever edge is left is usually due to inadequate damping which can, and should, be dealt with with the addition of some sort of aftermarket product (eg, herbies, etc.)

 

[myinitialsaredac]

This thread is very interesting, and makes me want my millet max sooner.
However I think the tubes will be burned in before the blackgates xD.

Dave

 

[hew]

My experience mirrors pataburd's. Generally, the changes are pretty subtle and not as evident as in other components.

 

[Skylab]

Yep, I agree. The most notable thing with tube burn in is that most NOS tubes are not quiet at first. Once they run in a little, they usually quiet down totally.

 

[tourmaline]

The tubes also need to warm up a bit, on my system, after an hour or so, the tubes start to sound slightly better.

 

[Golden Monkey]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif Yep, I agree. The most notable thing with tube burn in is that most NOS tubes are not quiet at first. Once they run in a little, they usually quiet down totally.

At first meaning "at first after powering the amp on", or "at first, during the life of the tube"?

 

[bada bing]

Tubes are the only components that can be said to "burn in" without a doubt and it is measurable, not subjective.

Tubes change for the better during the first hours as residual gas from inside the envelope left from imperfect manufacturing vacuum gets scavanged and deposits onto the filaments. At this point they are about as good as they will ever be. It takes anywhere from a couple hours to fifty hours, depending on the tube and the service it is used in.

They then slowly change for the worse as they are used up. Most tubes are rated for a range of several hundred to several thousand hours of useful lifespan. They slowly deteriorate in service, which is easily measured by a tube tester. Hours of use also visibly change tubes - you can see the blackish deposits form on the inside of the glass. The filaments are slowly eroded into a gas which redeposits on the interior of the tube.

 

[bergman2]

Quote:

Originally Posted by bada bing /img/forum/go_quote.gif Tubes are the only components that can be said to "burn in" without a doubt and it is measurable, not subjective. Tubes change for the better during the first hours as residual gas from inside the envelope left from imperfect manufacturing vacuum gets scavanged and deposits onto the filaments. At this point they are about as good as they will ever be. It takes anywhere from a couple hours to fifty hours, depending on the tube and the service it is used in. They then slowly change for the worse as they are used up. Most tubes are rated for a range of several hundred to several thousand hours of useful lifespan. They slowly deteriorate in service, which is easily measured by a tube tester. Hours of use also visibly change tubes - you can see the blackish deposits form on the inside of the glass. The filaments are slowly eroded into a gas which redeposits on the interior of the tube.

"ONLY" ??????

 

[tourmaline]

Quote:

Originally Posted by bergman2 /img/forum/go_quote.gif "ONLY" ??????

If you take caps, resistors etc. out of the equation.lol.