How should you treat your tubes?

Small signal tubes such as 12AX7's or 6922's are generally best left on 24/7. Quoting from the "TIPS & ADVICE" section of the owner's manual to my VAC Rennaisance 140/140 Mk. III tube amps:

"How long should tubes last? It has long been known in professional circles (and probably now forgotten) that a tube such as the 12AX7 will display BETTER performance characteristics after TWO YEARS of CONTINUAL operation than when it was new. In normal use it is not unusual for a low level tube to last 5 years or longer. Output tubes [i.e., power tubes used in tube power amps] are another story, as they are continuously providing significant amounts of current." (Emphasis original).

The expansion and contraction that small signal tubes undergo as gear heats up and cools down (as a result of being turned on and off) takes a toll over time. In addition, the voltage rush at turn-on is especially hard on small signal tubes. Tube gear with tube rectification is a lot easier on tubes at start-up, and some tube gear has a soft-start feature to soften the blow, while solid-state rectification is hard on them. In summary, while it is to a certain extent model-dependent, it's generally better, for both tube life and for sound quality, to leave tube preamps (and other gear that uses small signal tubes, like DAC's and tuners) on 24/7.

After a few years, the tubes should be replaced, as they do start to "lose their luster" (see Kevin Deal comments above), but they won't fail if used this way -- generally speaking, tubes left on 24/7 either fail within the first 250 hours or so from "infant mortality" or they last forever.

Output tubes cannot be left on 24/7 because they pass a lot of current and will wear out relatively quickly (not to mention wasting a lot of electricity and occasionally dying in spectacular fashion -- best not to leave them unattended).

Raquel,

That is interesting information from a manufacturer. But, how would one keep the small tubes (input, driver, phase splitter) of a power amp, like the VAC 140/140, on while the output tubes are not on? Does it have some sort of standby feature?

Also, while it is generally true that linestages have small signal tubes that don't degrade very rapidly under constant on conditions, that is not always the case. For example, the Counterpoint SA 3000 is pretty hard on tubes.

I might also be a bit leery about leaving on a linestage that had a lot of expensive small signal tubes in them (fortunately for me, my linestage uses cheap 12B4s for signal tubes). Still, I turn it off when not I am out for a long period of time. My phono stage has Telefunken ECC83s in it and uses two 300b tubes as rectifiers, I really hate to leave it on when not in use.

I had a thorough response written and I lost my Internet connection and my text.

Larryi: The VAC 140's have no means of powering up only the 6SN7's. The amp is either on or off, and I turn it off and on as needed. The 6SN7's are not a worry, however, as they are exceedingly hardy tubes that were primarily designed for use in televisions -- it is not unusual to get 40,000 hours out of a 6SN7. The comment in my owner's manual was about small signal tubes generally. Kevin Hayes of VAC is also quick to point out that the studies done in the 1950's established that small signal tubes last much longer and sound better if left on 24/7.

I might be reluctant to leave a tube preamp on that has a lot of tubes in the power supply (or that uses pentodes in the power supply like the ARC Ref 3 or big Jadis two-chassis or a really pricey tube like the 300B). I would be MORE inclined to leave a preamp having expensive NOS tubes in it powered up 24/7 precisely because such use tends to increase tube life.

For the record, I owned Jadis, CAT and Hovland tube preamps, and still have a CAL Audio Labs tubed DAC in the closet that I've owned since 1994. In a combined nine years of running those preamps 24/7, and another six years of running the DAC 24/7, I never lost a tube (the DAC sounded better than ever the last time I had it in the system) and only retubed the preamps when I sold them so that the new owners would have a component with brand-new tubes.

A little common sense goes a long way...if you are leaving the house, or there is a big electrical pull on your system from Air Conditioning or tools that you will be using, or a washer and dryer, sump pump, etc., or there is a thunder storm brewing, by all means turn off the amp first, wait at least 5 minutes, and then turn off the preamp. Under normal circumstances, turning the amp on in the morning and off when you go to sleep doesn't hurt the equipment and will add quality to your listening session.

Ekobesky,

It is a common myth that turning a light bulb on and off shortens it life.

There have been studies showing that turning your light bulb on/off numerous times per day (I can't remember the actual numbers in the test, but it was way more than you would ever do in real life) didn't decrease the life of the light bulb vs. just leaving the bulb on for extended periods.

Basically, it was proven that the light bulb will last longer if you turn it off when it is not needed and not to worry about the number of times it is turned on/off.

I don't know for sure if this also applies to audio tubes (especially NOS ones).

George