Best Way To Maximize Preamp Tube Life?


I would love to learn how to best maximize tube life. Tubes have a limited lifespan, of course. So when you're not listening for a time, is it best to shut everything off to preserve the "hours" left on the tube's life? OR does the act of powering off/on itself shorten tube length as well? If so, by how much? Something like "powering off/on costs 3 hrs of tube life, so taking a music break of less than 3 hours, better to just leave it powered on." Or 1 hr, or 10 minutes, 6 hours, etc? Where is the tradeoff point?

In my system FYI, I am running a Don Sachs preamp with 4 6SN7s and 1 6BY5 rectifier.  Don says the preamp is only running the tubes at 40% of their rating. I would greatly appreciate some input from people with tube knowledge. Thanks in advance!
sid-hoff-frenchman
I have worked with tube equipment for years, so I will toss in an opinion here.    In general, you want them off, since they don't age in the off condition.   When they are on, you are burning the cathode coating, which is the fundamental part of the design.   In addition, a max'd out plate supply will also wear the cathode coating likewise for max'ing the current flow through it.    Running tubes at reduced power plate supply and current increases the tube life exponentially.   Those are design issues, so once the designer has made all the tradeoffs, the tube life is set for the amount of run time it is on.   The best you can do is turn it off when not using it.

Now, that being said, a lot of turn on and turn offs don't help things either.   So if you are listening, then leaving for a hour or less, and plan on listening when you return, I'd say leave it on rather than do a power down and a power up.   If you are gone for 2 to 4 hours, then a power down and power up starts to make sense.   Certainly, if you are gone for 4 to 6 hours or more, you will probably want it off.     

Remember, tubes burn power, which runs your grid meter, which makes your power company profitable.  Spinning that grid meter when no one is listening uses money that really could be saved to buy new tubes. 

So in general, avoid a lot of power ups and downs in a short time, but don't burn power when no one is listening.  There is no magic rule here but that is a good general one.
I have always had a tube preamp in my system. Out of the 5 I have owned, they all are cycled on and off during use. Most preamp tubes last thousands of hours. Even when I had a AI Modulus3, Modulus3A and Modulus3B, I always shut them down. I got quite a few thousand hours on the tubes, even though the tubes are run hard. I would never leave a tube anything on when not in use. I had a hybrid integrated many years ago made by Yaquin and it caught fire. So, you can appreciate my caution now.
tube info

https://upscaleaudio.com/pages/tube-basics-and-frequently-asked-questions

excerpt

Power tubes like EL34’s and KT88’s are good for about 2500 hours or more. But may go longer in an amplifier with a conservative design. Small signal tubes with numbers like 12AX7, 12AU7, and 6922, and rectifier tubes like 5AR4 may go 10,000 hours.

My experience: they last a hellofa long time.

I test new matched tubes when I receive them, and mark the date and number reached on the meter on the box, confirming just that (and no short). Then I check them annually, around thanksgiving, ready for the holidays. less power on the meter? still ’matched’? typically the same as new, a very gradual decline. Very rarely a short, which you typically find when things start sounding bad, iow, find the one that ’blew’.

My system sounds very good after 20 minutes warm up, listen for a few hours, and I turn them off until next which will be several hours later or the next day. Maybe avg 15 hrs/wk, i.e. 800 hrs/yr. They last for many years, most of my McIntosh mx110z’s were tested good again by Audio Classics this spring. They confirm my thinking, MOST are original tubes. Ryan said "these old tubes last nearly forever".

I cannot understand having tube equipment and not having a simple tester to rule out problems/have confidence/find problems. Just because it was a great find, I bought an Accurate Instrument 257. I just tested my preamp and power amp, using prior 157 and new to me 257. They all reached the same #’s on both unit’s meters. I have a big fancy one, I forget, Jackson or Hickock, the ’toy’ ones always show the same as the big one, I don’t bother with it any more.

I have a large collection of old tubes, used and new. Almost every used tube I test measures ’good’ and reach #’s on the scale equal to or just below new ones. Of course I have found bad ones, but not that many.

Way back when, going to the store to use their big professional testers, I took all the tubes from my Fisher President II, every thanksgiving, AM tuner; FM tuner; Master Control Panel, pair of tape preamps, FM multiplex, pair of RIAA preamps (Fisher came to my uncle’s NYC apt and converted the TT to MM), pair of Mono Amps. Stood there until my feet and back hurt, impatient line behind me: maybe found 2 I decided were ’weak’, a rare ’bad’.
Don Sachs here...   turn them off if you are not going to listen in the next 30-60 minutes.   Honestly, tubes last a LONG time in my gear.  I run them conservatively.   Now and then a tube dies early, but that would happen anyway, no matter what you did.   Leaving things on just creates a lot of heat you don't need over many hours and wears tubes out.   Turning a tube system on 2 or 3 times a day doesn't hurt it all.  My power amp and integrated amp have a very soft turn on sequence that is easy on power tubes.
Just don’t use them, they will last forever..

Read ON..

Kind of like running tubes in a MM or MC phono circuits but you use neither and use and external phono pre amp..

Pull the valves.. It won’t hurt a thing. Save them for when you need new ones.. I’ve done it for years with Macs.. New and old.. Pull the phono section you are NOT using and leave the one you are. Either or but quit burning up valves..

Do you know how many perfectly good Telefunken and RCA prime 12AX7 have just been BURNT UP? Me neither, a BUNCH is a good guess though. :-)

If people new.. now they do...

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Off topic a bit OP I’ll erase it if you want..

Here is a cool one, I can bias up 4, 8 or 12 valves on my V12R Cary. Just depends how LOUD or LOW I want to go..

4 valves total of 6V6 is @ 15 - 20 watts total (2 valves per side).
OR 12 valves of KT88 or 90s at 200 + watts. (6 per side) 100 + watts per side at 8 ohms.

I can get an easy 90db from just 4 valves (about 10 watts per rail or channel) and small planars.. I get a little tube breakup if I REALLY crank it.. Ribbons or small planars aren’t to fond of a goofy wave pattern, you do need to be aware of that..

I bias cool and really get the watts UP, if I’m cranking it. I bias HOT for late night low volume listening.. Nuggets for ALL to share.. They all save valve life and save a few quid to boot.. Electric bills and valve cost...

Regards
It only takes max 5 min for tubes to go into operational heat. Other stories about warming up for hours are just unnecessary hype for unaware and uneducated consumer -- so do your figures.

||Just don't use them and it will last forever||
isn't true at all, because your DC caps will likely dry out and fail often destroying tubes as well.
You can take the advice of the designer/manufacturer or you can take the advice of a random guy on an audiophile forum.  I say leave it on 24/7 and replace the tubes every 12 to 18 months.  This assumes you listen more than four to six hours daily and that the sessions are not continuous.
Turning a tube system on 2 or 3 times a day doesn't hurt it all.
@donsachs 
That sounds about right. Thanks for joining the conversation, Don.



My amps turn themselves off after 30 minutes being idle. So I never tune them off manually. Sometimes I come back to listen within 30 minutes, sometimes I don’t. 
Best way to prolong your preamp tube life is to use a SS preamp. 
Tubes are NOT like fine wine! They DO NOT improve with age! If fact when they are brand new and at 100% cathode emissions that is their peak performance. They only decline with use as the cathode coating gets used up. James Bongiorno pointed this out years ago when he worked at SAE and was asked why he doesn't design with tubes.
Tubes are NOT like fine wine! They DO NOT improve with age! If fact when they are brand new and at 100% cathode emissions that is their peak performance. They only decline with use as the cathode coating gets used up. James Bongiorno pointed this out years ago when he worked at SAE and was asked why he doesn't design with tubes.



They sound better than solid state though
invalid, there are many who think SS electronics sound better.

Transistors can also have a life span especially when used in high current circuits like class A output stages. My Krell KMA 100's lasted 21 years before an output section blew. 

I use a hybrid tube phono stage. It uses three 6922s. It stays on 24/7 in standby mode. The tubes last 5-6 years and it is painfully obvious when one fails. When one does I replace all three. Three Super Low Noise 6922s cost $270.00. Having the phono stage ready to go on short notice is worth it to me. I hate waiting for anything. My Oppo Blu Ray player has been on notice since it was brand new. The transport stinks. It is painfully slow. I am forever wanting to drop kick it out the window. Anyway, 5 years is 44,000 hours. 
good advice from @spatialking on this topic here, hope op listens to it
Pulling tubes and running a circuit without all them in there is absolutely the WRONG thing to do unless you know exactly how the circuit is designed. You can destroy a filament supply (or a tube in it), or overwork a B+ (high voltage) supply if the circuit is designed to have all the tubes in it. I have rebuilt well over 500 pieces of vintage tube gear. On some of it you can pull tubes and there is no effect, on others you better not do that except for a brief few second test on the bench to measure some voltages. If you are not using the phono section in some preamp, then get some bargain basement cheapo 12ax7 (or whatever tube it uses) and plug it in there. If you pull tubes and run things the B+ may be high due to less loading. If the circuit is poorly designed or has parts running close to their max spec, then you could see early parts failure. Again, it all depends on how the unit was designed and built. Many times I have seen things with 475 V on a 500 V rated part. You pull a tube perhaps you are now looking at 490V on that part. I don’t design or build things that way, but I have seen lots of gear that runs parts at the ragged edge. Jim McShane taught me to never run anything over about 70-75% of rating for that reason. Very good advice. You have to take into account the turn on surge as well. A lot of times your B+ may be 420V and the parts are 500V rated, but at turn on before the tubes warm up and conduct you may see 495V and then it drops. Again, if you start pulling tubes you alter that. So you darn well better know what you are dealing with before you run it without all the tubes in it. Rant over......

My experience is that a good tube circuit will sound great in 10-15 minutes after turn on. Leaving it on 24/7 buys you absolutely nothing except very poor tube life. Turning something on 2 or 3 times a day doesn’t hurt it at all unless it is very poorly designed.
Thanks to everyone who has chimed in here. Despite owning all this gear, I am not actually a gear guy - I am a music guy. I don't enjoy endlessly tinkering and swapping out equipment. What I want is the music sound that makes me smile inside and out. So once I have found the sound I love (fingers crossed!) I want to maintain it as long as possible. With tube shortages currently in all directions, including the Northern Electric 6SN7s I am running, I want to squeeze every bit of sonic joy from these tubes as possible.
Man, a fella can learn a thing or two off this forum.  If you don't want to worry about tubes forever, see if you can home audition a Pass Labs preamp, which has that inviting midrange bloom, smoothness of a tube amp, and that lit from within sound; the imaging is layered deeply, which if you like that sort of thing, is nice, but if you're say more an "old Krell" fan (before DD'Ag left) of up-front imaging where music is in the same plane as the speaker's front, then Pass is likely not a good choice.  The front ends configured in the three box set-ups are awfully good, even spanning back to the X0.2, then to the XP-30, and now the current XP-32 front end.  About the current XP front ends, I just bought the current Stereophile most recommended components issue and the XP-22 and XP-32 made the "A" List.  Have a good day all. 
Pulling tubes and running a circuit without all them in there is absolutely the WRONG thing to do unless you know exactly how the circuit is designed. You can destroy a filament supply (or a tube in it), or overwork a B+ (high voltage) supply if the circuit is designed to have all the tubes in it. I have rebuilt well over 500 pieces of vintage tube gear.

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That's why you preface it with Mcintosh, What's WRONG is telling people it's WRONG..  I've yet to work on any Mac valve amp that you couldn't plug and test voltages without valves, add the valves in the circuits and keep on testing.. NO LOAD either, I've NEVER had a problem..

I guess I'm lucky, or maybe ol Mike Samra was right.. I don't know a better tech on Vintage gear anywhere, and MAYBE one Mac tech but he retired. He was a great repairman BUT he wouldn't rebuild Mac gear only repair..

I'm sure Terry Dewick was wrong, TOO.

BOTH guy helped me a few times

BOTH recommended pulling valves.. I wonder who's right?
Hmmm?

OR continue to BURN up perfectly good valve for NO GOOD reason, other than the warm glow at night.

You only get a given number of power ups and a given number of hours. It's all down hill from the first day you flip the switch.. Like I said I have close to NEW Telefunken valve pulls from MM and MC phone section in Macs that are 60+ years old.. C11,20,22,2500, PULL THEM...

You can drive around with your head lights on all the time too.. :-)

Regards
@sid-hoff-frenchman

I want to maintain it as long as possible. With tube shortages currently in all directions, including the Northern Electric 6SN7s I am running, I want to squeeze every bit of sonic joy from these tubes as possible.


don’t worry too much about 6sn7 supply, old stocks are plentiful, not terribly expensive and new production is quite good too
I leave my tube preamp on 24/7 because I have a class A solid state amp that takes a long time to sound it's best.

Power up when listening  power down when through.Depends on the tube and voltage of preamp how long they will last. Amperex is great tube jump on some today.
I have vintage radios that are over 80 years old. The tubes are original and they all work fine.  Those small signal tubes last for ages!
I also run a class A amp (Pass XA25) with a tube preamp. I have a dedicated room and music listening is a session. When I anticipate a session coming on I turn on the amp. It can cook throughout the day if needed. When time for the session I turn it off, wait a minute for the signal path to discharge, then turn preamp on, wait a minute for it to charge, then turn amp back on. The tube pre dos not take long be at capacity. Possibly too much trouble for some.

When session is spontaneous it turn equipment on in proper order and enjoy, the XA25 catches up. 
I have been using tube preamps and phono stages for a couple decades (Audio Research). Now all my equipment is ARC tube. Typically when I head down to listen to listen I turn on my equipment and then go get coffee or wash up or take the dogs out. It takes about 10 - 15 minutes for the equipment to sound great. Most tube life with turning off and on is something like 3,000 hours. That is a very long time. I no longer think about it… even for my amp.

I have had many Pass amps and preamps. They are great, particularly with the XA series amp. But if you really want a compellingly musical and emotionally involving experience tubes by a really great company is the way to go: for me ARC, Conrad Johnson, VAC… etc. 


I done 24h a day on in 2 years tubes are going bad. So now I set it off when not in use. Tubes even good pre ones are getting expensive too.
Befor a listening session of 3 or 4 hours I set the pre amp on one hour befor then it's getting pretty good sounding. 
I really enjoy reading through this kind of discussion. I am new to tube preamp/amp ownership and I honestly had no good information on how to approach the maintenance. I have been turning my system on about 15-20 minutes before I start playing music just to let it warm up. The preamp and amp are usually on for 3-4 hours on average. Some days they will stay on 8-10 if the weather is bad and I am just chilling in the house. 

I definitely need to buy some spare tubes.

Cheers!
Best way to extend tube life is probably going to SS…
I should replace those 20 year old tubes in the preamp. But it sounds pretty good the way it is.
I'd never leave any tube equipment on 24/7. Some have standby mode, in which only heaters are lit, some also have soft start circuits, both minimize wear. The rest you're choosing between wear and tear from being used 24/7 or same from inrush current, voltage. So, sort of depends on how often and how long you listen to music. Daily listening, may as well leave on. Still, I don't like leaving tube equipment on unattended, too many bad things can happen. Preamps slightly less worrisome here, still?

I'd never leave any amp on 24/7, regardless of how often listening. I've always thought ss best for multiple daily listening sessions.
I subject the expensive tubes I prefer to the lightest wear possible, they are not simply disposable items to me.  I'm once a week, long term listening session guy.

I have purchased a spare set of tubes for all my components. In the unlikely need to trouble shoot they are there. Also, when the 3,000 hours are up. Sure, they may last longer.
I also have the DS preamp and the 6by5 and its variants are anywhere from 6 to 20 bucks for NOS that should last 8 to 10k hours...at least.  The 6sn7 tube is not in short supply and aren't very expensive for NOS either.  I happen to like the Shuguang Dawning series WE6SN7PLUS tube and have a spare set.  Unfortunately they are out of production but if you get past 50 hours or so on them they should last you thousands of hours......especially in Don's preamp.  Basically, buy a few spares of the 6by5 and a spare set of the 6sn7 and you'll be good to go for many years assuming you get a reliable set.
No 24 hours on.  No waiting an hour or two for warm up.
Speaking of testers, can someone recommend a simple, cheap unit that I can use at home?  Just recently got several tube units (Schiit pre, Decware amp) and have a bunch of tubes from prior systems.
You should probably leave your space heater on 24/7 too.
I’m surrounded by tubes - many hundreds of them - in gear and in boxes awaiting use. I build/repair tube guitar amps as a hobby, and have built tube mono block audio amps, and repaired tube audio preamps. So, while I’m not an EE or professional technician or designer, I’ve worked with tubes for a long time, so I’ll offer my comments.
I agree with Don Sachs’ comments. In addition, the equipment design is very important. For example, those that run very high plate voltage will wear out tubes quickly. Those with incorrectly high heater voltage will do the same. Preamp tubes will last a long time if they are not run at the upper end of their plate voltage capacity, and if biased properly, will still provide good sound. If biased too cool, distortion will result and if biased too hot, there will be too much current through the tube, increasing heat and reducing life. Some audio designers like to run preamp tubes at their limit in an attempt to maximize gain and headroom, and in the case of many guitar amps, the preamp and output tubes are run well beyond the tube’s specified limit.

NOS and vintage tubes will eventually lose emissions, become gassy, develop leakage, or other problems, even when not in use. I have had to discard many NOS tubes that test fine until placed into service in equipment that pushes them hard.

Pulling tubes, as Don said, is potentially a huge problem. Tubes draw substantial current through the heaters and in passing signals. A power supply designed for all tubes drawing current will, when tubes are pulled, potentially exceed the voltage rating of capacitors or other components, and put more voltage into the remaining tubes. Audible Illusions, as just one example, warns against that practice. I am not a fan of leaving tube gear on all the time, and don’t like equipment that keeps the heaters powered up all the time either. Properly designed circuits together with proper turnon/turnoff procedures will keep your tubes happy.

New preamp tubes are not that expensive, and should last a long time. When they start to fail or emissions fall, replace them with other good quality tubes. You may decide to do some "tube rolling" to hear how different tubes make your preamp sound; in that case, you won’t worry about lifespan in your preamp because you’ll have other tubes. Have fun!
dancub:Most entry-level tube testers are old; the new units tend to be feature-rich and expensive. Cheaper, old tube testers generally have minimal features and capabilities, with emissions being the most common. Better is a transconductance tester, and good ones like my Hickok testers can test for shorts, leakage, gm, remaining life (estimated), gas, and other issues. I have a B&K from the 1930’s that is good for minimal tests on really old tube types, and a cheap Eico emissions tester that is a quick go-to for pass/fail tests.

If you only need to see if a tube is good or bad, a cheap old tester might be OK, but often it’s just best to use "tube substitution", a term all those familiar with working on tube gear will be familiar with. Having a known good replacement, even a marginally-good tube, can be very useful if you suspect a particular tube has gone bad.
My Carver 350s came with a 10 yr warranty on amps and tubes (Bob later raised it to 50 yrs on all of it, long story)  Even his new 275s come with a 5 yr warranty on everything.  He runs them both conservatively and you can touch them even after hrs of playing.Best to allMark
Just do the method you like best 
Any method you pick be ready to take the gas pipe . Don't lose sleep over it 
I can't actualy think of a time tubes wore out, ever.  I've had tubes go bad, but it always happened to a single tube and not the set.  

If the tubes went from use, I would think they (same type/brand used as a pair or more) would burn out roughly the same the same timeframe.  And yet that's not been my experience.

So I'm not sure what the best method is for getting more life out of tubes.

I've turned the amp/pre on after work if I planned to listen in the evening and turn off at bedtime.  On the weekend, I'd turn everything on in the morning and shut off at bedtime, unless I was going to be gone for more than a few hours, in which case I'd shut off then turn back on upon my return.
The more I think about it. The more I think they are such an asset that tube life just should not be a concern. With at least 3,000 hours it’s just not worth worrying about. If your a person that thinks about these things, then replace when it is time.

The fact that tube equipment should not be left on unattended.. pretty well takes care of the longevity issue.