tube burn in


I recently purchased new tubes for my amp I have heard they sound better after XXX hrs. burn in. I leave my amp on 8 hrs. a day while I'm at work. Is letting the amp run without playing anything still burning in the tubes? 
lardawg
I'll be your Huckleberry and try to answer.  Don't leave your power amp on when you're out of the house.  It's not likely, but bad things can happen.  You don't want It takes only a few hours (not hundreds or even dozens) for the tubes to settle in.  Just listening to music will suffice.
There really isn't much in the way of settling in.

The exception might be new power tubes, which will benefit from having their filaments lit but no B+ on the tube otherwise. If left in this state for 3-4 days, this can double the life of the tube and reduce premature failure due to arcing.

Smaller tubes are good to go out of the box.
Ralph, I know your amps provide for filament powering while leaving the B+ off. For the owner of an amp that doesn't, is there a way to do the tube pre-conditioning?
That can be a bit of a trick. If the amp has a B+ fuse that is independent of the filament circuit, you could remove that, but that might be tricky in some amps that don't have the fuse accessible. Another way would be to pull the rectifier tube if there is one, like in a Dynaco ST-70, but that's about it.

 
Okay, thanks. I wish tube vendors would offer your tube preconditioning idea!
Your question can open a can of worms lol. Power tubes from what I have heard can take 100 hrs up to a few hundred from what some people swear by.  I have always been skeptical of long break in times as others above mention. However, who am I to say when some audiophiles have experienced changes and I am sure their ears are decent. 

I tend to always think 25-50 hrs and something else I haven't heard people discuss much. Heat cycles. I would think turning them on and off and getting a few heat cycles like breaking in an engine would help the burn in process. Just my 2 cents :)
The exception might be new power tubes, which will benefit from having their filaments lit but no B+ on the tube otherwise. If left in this state for 3-4 days, this can double the life of the tube and reduce premature failure due to arcing.
Ralph might see it differently but I believe that if you buy the power tubes from Upscale Audio they are matched, cryogenically treated, and burned in for 72 hours. Jim McShane likely does something similar. 
Are you talking about sonic burn in, or testing for reliability?
What's the diff? Unless an expert tells me otherwise, burn-in is burn-in imho. After 72 hours of being on, the tube is stabilized and burned in AFAIK. 
With NOS a first few hours sonic change is an indicator of true NOS Vs used!
No, Ralph recommends running tubes without firing them up with B+ for awhile (I don't recall the exact number of hours), and that doing so significantly extends their useful lifespan. Burning in for sound quality is a separate issue.
Or, you can take the path of just listening to music and not worrying about burn-in…leaving a tube amp on when you’re not around seems wasteful and kinda dangerous, and for me it seems that all the other factors like when you do your active listening relative to your local power grid seem to have more of an impact on the sound, although not a big deal. Trying different tubes also obviously has a real effect, and after a short while (hour or so maybe?) they seem to get where they’re going allowing you to hear the differences between tube types or brands. I do think that a well designed amp should sound great all of the time, and only display sonic variations that are so small to be simply musically irrelevant. Power tubes have lasted a long time for me in amps I’ve owned without any cryo treatment or anything other than simply listing to things…and I roll tubes around often enough that many last a really long time until I deem them unlistenable and replace ’em.
For me, the biggest difference in "burn in for sound quality" comes in brand new, new production power tubes.  Some seem to benefit more than others.  The biggest change from burn in came from Psvane 845 tii.

I just listen and definitely don't leave them running when I leave the house.  After maybe 40-80 hours (usually less), any changes, to me, have pretty much been too subtle or too gradual to really notice or definitively attribute to further burn-in.
Ralph recommends running tubes without firing them up with B+ for a while (I don't recall the exact number of hours), and that doing so significantly extends their useful lifespan
bdp24- IIRC, I believe that recommendation has to do specifically with the 6AS7s that are used in the Atma amps.  Also, I believe he recommends 72 hours. 

Yup swampwater, the power amp output tubes in his OTL’s. But further, Ralph says ALL power tubes will benefit (in terms of their useful lifetime) by pre-conditioning them before fully powering them up with B+. Very few amps allow one to do that.

His recommendation has nothing to do with a tube’s sound quality, only it’s useful lifetime. I believe it has to do with breaking in the tubes gently, rather than hitting them with high voltage out of the box. Sort of like breaking in a car’s new engine, not going over a given RPM until a certain number of miles have been reached.

What's the diff? Unless an expert tells me otherwise, burn-in is burn-in imho. After 72 hours of being on, the tube is stabilized and burned in AFAIK.
The difference might be double the tube life. Pre-conditioning applies to all power tubes, not just ours.
Think about it: you have a thin piece of wire that is being heated up - why not be gentle with it?

metal expands when heated...


I WILL ADMIT that sometimes I just turn the power off on my ARC pre-amp without going thru the volume down, mute on, and only then power off sequence they say to use.  But that may well be to reduce transients going to the amp & speakers, not saving the tube filaments.  
@bdp24 @atmasphere-

I stand corrected.  Now I'll have to find a way to pre-condition the 300bs in my VAC Ren 30/30.  They're a BIT more expensive that the 6AS7s ;-)
Anyone know if the re-branded ones that VAC sells have been pre-conditioned?  I know I can call and ask, but I'm feeling lazy today. 
@swampwalker , I think pre-conditioning does not apply to directly heated tubes.
Thanks, Ralph.