Tubes are like light bulbs -- turning them on and off shortens their lifespan.
If you plan to listen later the same day, leave them on. I might turn off my amp if I was listening at, say, 9am and didn't plan to listen to it again until 9pm. But aside from that, you'd just be abusing the tubes by turning them off and then powering up again a few short hours later.
Ekobesky: Thanks for the response. I was feeling guilty either way. Now you make me feel less guilty leaving them on. JBNorth1178
With my tube amp I have a "four hours" rule. Which is, if I'm going to go back listening within "four hours" I leave the amp on. Truth is, when I know I'm going to be listening I turn the amp on for 10 - 15 minutes before hand to warm the tubes up, but I also know it'll generally going take about an hour for the amp/tubes to start delivering their best performance. It really is a case, of patience being rewarded.
Here's some great advice from Kevin Deal @ Upscale Audio (www.upscaleaudio.com):
Tube Life, noise, and do I leave the power on -
We get asked this question a lot. With a power amp
you would typically not leave it running 24 hrs a day. Power amps produce heat, and they use a bit of electricity. Pre-amps, DACs and other products that use small tubes are another question. Regardless of what anyone tells you
I have not found a definitive answer to this question.
Tubes age in a couple ways. One is they lose emissions over their lifetime. In other words, they run out of gas. Or better yet steam
as they dont just "quit" but lose their drive capability gradually. If you figure a tube like a 12AX7 or 6922 to be good for about 10,000 hours, and you leave it on 24 hours a day
you do the math. There are 8,736 hours in a year. So when did the tube go bad? It depends on how picky you are. Its like a tube of toothpaste. Kinda peters out at the end but it seems you can squeeze out a little more. Some products (and audiophiles) are more picky than others. I recommend to folks that want to upgrade to premium new old stock tubes that they do it while their stock tubes are good. That way you have the cheap ones working and available should you decide to sell the pre-amp.
The other way they age is to become noisy. The noise will sound like popcorn popping softly in the background, or it may become a roar, and it can happen to any tube
.including new ones. The most common reason that I have found for tube noise is the coating on the filament becomes compromised. This can be made worse by turning them on and off a lot. Thats the best way to guarantee trouble with tubes. Some products have filaments that are left on even when the product is turned off. This is a good idea and reduces that shock and keeps your pre-amp in a "warm" state. Other than that
.maybe a mixture of a total power off if you will be gone a day or so, and leave it on when you anticipate you will be listening.
Treat them with respect, they get very hot. After a long night of listening always buy them breakfast.
For a stretch of an hour or two, I would not turn off either, certainly not the preamp anyway.
Beyond that kind of time, a lot of different considerations come into play. Not only is the life of the tube at issue. Heat can damage other components, so leaving on tube gear, particularly if the tubes are enclosed or if you are dealing with hot output tubes, can result in shorter life for such components.
Other considerations include whether the equipment has "soft start" circuits (slowly brings up circuits so thermal stress on tube filaments are reduced) or if the power supply employs tube rectification (also results in slow turn on). With such slower turn on, the issue of wear from the turn on part of the cycle is reduced.
Probably the best answer would be that provided by the manufacturer.
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).
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.
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.
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.
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).
A final point: if you search the threads, you'll see that this subject has truly been beaten to death, as well as the more general subject of whether to turn equipment on and off or leave it on 24/7. In those threads, you'll see that repair techs and equipment manufacturers who contribute comments pretty much unanimously advocate leaving all equipment other than tube amps on 24/7 in the interests of longer component life and better sound. If you see the contrary in your owner's manual, it's for liability reasons -- the one component in a million that catches fire is going to result in a lawsuit for the manufacturer, so owner's manuals generally say "turn it off while not in use".
In response to one of the above posters, this is actually a case where the rejection of common sense and reliance upon the basic laws of physics is the way to go -- all matter, whether it is the concrete pavement of a freeway or a vacuum tube or silicon transistor in hi-fi gear, expands as it heats up and contracts as it cools down, and it is repeated expansion and contraction that compromises the physical integrity of these things over time. Keeping gear powered up keeps it at a relatively constant temperature, whereby there is little expansion and contraction -- the only downside in terms of component wear is that it can shorten cap life (capacitors are constantly being beaten by the oscillating 50 or 60 volt cycles of the electrical supply).
It is especially important to leave solid-state power amps and DAC's powered up 24/7. Naim, for example, says that it takes two days for some its amps to reach optimal operating condition (one of my dealers says "Naim amps need a week"). DAC's tend to sound like utter shit without lengthy warm-up (count on 24+ hours for most) and MUST be left on 24/7. I would add one exception to the solid-state amp rule -- Class A biased solid-state amps (e.g., Plinius or Gryphon) burn a hell of a lot of electricity and will turn the average room into a sauna if left on for long periods of time, and should be turned off when not in use as a result.
Of course you want to unplug hi-fi gear when there is an electrical storm or if you go out of town for two weeks, but for day-to-day, leave it on if you don't want it to break and if you want it to sound like the manufacturer intended.
I once watched one of my EL34 tubes 'flame-out'. I still have the wine stain that resulted from my "mad dash...".
EL-34's are used as output tubes in guitar amps and tube amps, and are also commonly used in tube power supplies. As I noted above, tube amps should not be left powered up, if only because output tube failures can be speactacular (I've made a mad dash or two myself -- nothing like that arcing and/or cracking, and the tremendous noise coming from the affected speaker).
If your amp has a standby switch I would use it; if not based on your info I would leave the system on.I would power down when you know you won't be listening until the next day.
Lot of good responses. Seems like it comes down to 2 things. What will make it sound the best and what will make it last the longest. For sound, leave it on 24/7 for a week or even a month, then try cycling it. Decide for yourself if it makes any difference. For longevity it's got to be leaving it on BUT what if the difference was 10 years for on/off or 20 years always on? Do you really think you're going to keep it for 10 or even 20 years? I like Nelson Pass's philosophy: One day it will break and you'll just get it fixed.
For myself, I cycle. Most of us will go thru our whole life without a problem but I do not want to be that one statistic that comes home to see Firetrucks in front of his house. For sure tubes but I've seen evidence of a speaker catching on fire with a very well known SS amp.
Onemug, your concern about fires has application only to tube amps. I have never left my tube amps on when I am not there, even though it typically takes a half hour for them to get up to speed. They are better yet after being on for two hours. I have never turned off any other tube equipment other than when I am out-of-town or lightening threatens.
"For longevity it's got to be leaving it on BUT what if the difference was 10 years for on/off or 20 years always on? Do you really think you're going to keep it for 10 or even 20 years?"
... I respectfully beg to differ from the right honorable contributor and friend Tbg. New-ish hi-fi gear actually breaks all the time and my crusade to get the truth out about this issue is explained mostly by my desire to avoid buying a used product that has been misused through repeatedly being turned on and off, and which is thus much more likely to break in my hands, causing me expense and aggravation.
Don't get me started about other misnomers in this hobby. Ads for gear being sold by the "original owner" that has "only been used thirty hours"??? This means that the seller is either a liar (and, therefore, God knows what he's selling) or an ignoramus (and I'm going to have to run the virgin in question for hundreds of hours with a break-in track before it sounds right). Like I said, don't get me started ... but I WILL say things about:
... People selling preamps and phono stages that their ads display sitting on top of subwoofers.
... "This product is an original Mk. IV, not an upgrade" -- as long as the upgrade has been broken in, totally irrelevant.
... "Reviewed favorably by HP in last month's Absolute Sound" -- every single component or speaker that windbag reviews is the next great step forward in the advancement of reproduced sound (excuse me, I meant the advancement of "continuousness"). For that matter, aside from Cordesman, when was the last time that magazine published a review that contained some real substance and that was not incredibly flattering? The difference between TAS and Stereophile has become striking (Stereophile reviews being much more detailed and, of course, featuring extensive measurements). In my opinion, TAS has become a sham and I've stopped subscribing.
Tbg, I didn't say the SS amp caught fire. It caused a woofer to start burning. I was there, we started smelling something burning. We naturally thought it was the electonics but as we investigated, it was coming from the speaker. The paper woofer had a burn hole in it. I think the explanation was that the amp was leaking DC or something like that. I can't imagine how a SS amp could catch fire. What's to burn? If the woofer had led to the grill cloth ignitig and the speaker was close to curtains, Ba-Da-Bing.
Buying used these days with people modifying, bypassing fuses etc, just be sure you know what you have plugged into your wall. If people want to play golf in a lightning storm, that's their business. I just think you should be aware of the possibilities.