Best Way To Maximize Preamp Tube Life?

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