I would THINK (and I may be wrong) that if the suggested bias parameter is given as a value between settings, setting to the lower end might be healthier for the tubes. In other words, as an example, if the suggested bias was given as something like 240 mA to 300 mA going towards the 240 mA end of the deal might be easier on the tubes. But I do not know that for sure.
Also to make sure that they have plenty of ventilation. I suppose one could even set up a small fan.
And if there is a sequence to 'soft start' them for your amp, to always adhere to that.
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And fewer on/off cycles, I suppose ?
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And fewer on/off cycles, I suppose ?
I think that there may be differing opinions on that, @inna . Personally, I do not like to leave output tubes idling when I am not around/in the close by vicinity. The older I get the more neurotic I get.
But the way I listen these days in only once or twice a day . . . it’s ot like I am in and out and turning music on & off. I will say, however, that even back in those days I never left tubes on when I was out of the house.
But: the sort of exception was with my first tube amp before I knew anything at all of what I was doing. It was (and I still own it) a Cary SLA 70 signature and it has a standby switch. With the standby switch in ’on’ the tube filaments are constantly being heated. I’d have to get into the manual to tell you exactly which filaments are heated and glowing, as tubes and electricity is not second nature to me. Anyway, as I was learning the hard way basic stuff that every tube owner should know, I was talking to the service rep guy from Cary (this is back in the ’90s when they had great customer service) and he said it was not his advice to always leave the amp in stand by as I had been doing. Therefore, I then started using the standby switch in sort of a sequence . . . in other words first go to standby for a while before I went to ’ON.’
As far as preamp tubes, I don’t leave my pre on when I am not listening, either, but there have been threads on that subject, and I know that there are some that do.
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I use a variable speed cabinet fan at the lowest speed to pull heat out of my ARC preamp. Can't hear it and it certainly does not hurt. Of course, no data to say the tube life is being extended.
But, I only use the system an hour here and there during the week. 
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Oh no, I never leave it on when I am not in the house, or overnight, for that matter.
Though my VAC has some circuit that shuts it down if power tube runs away.
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I suspect you already had it. Don't leave on and less cycles. My understanding is that tubes become less reliable... as in more likely to blow as well as have the sound quality slowly deteriorate. This is enough for me to change at recommended intervals. Three thousand hours takes a while even at the 2 - 3 hours a day, which I use mine.
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I wouldn't replace expensive and hard to get tubes unless they do something audibly/visibly wrong. But if you use new productions tubes, yeah, why not ?
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This may not apply to your setup, but I have individual bias pots for each output tube. There’s a recommended bias range for each tube type . Running the bias toward the lower end of the bias range can supposedly get more life from them. It’s possible that the tube that runs at the lowest bias setting may last longer in general, but don’t know for sure. There’s no guarantee you’ll have optimal SQ with all bias ranges either, but that’s always subjective anyway.
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Yes, bias is adjusted individually for each tube, and I follow the manual. There is no range stated, there is a black dot you aligned the needle with, that's all.
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Be sure you know what you are doing in setting bias on the low side. If the measurement is in mA, the lower number means running the tube more gently. If the bias is in mV, a higher number means lower current and gentler treatment of the tubes.
Be sure the voltage at your outlet is not too high. I’ve seen 125 volts and higher from some outlets. A variac, or even better, a stepdown transformer, can lower the voltage to something like 115 volts or lower. Running tubes at, or slightly lower than recommended greatly improves life of tubes.
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Be sure you know what you are doing in setting bias on the low side. If the measurement is in mA, the lower number means running the tube more gently. If the bias is in mV, a higher number means lower current and gentler treatment of the tubes.
Thanks for that, @larryi ; I was not aware. I had read some stuff on bias before that had me confused. However, my amp is biased using mA and I do run it a bit low.
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Lower voltage..
I use PS Audio regenerator that outputs 120V constantly, if you believe it.
But I noticed that, yes, input voltage is sometimes above that but never 125V.
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1： do not turning on and off repeatedly
2: well-ventilated spot
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Some amps are designed to drive tubes hard, some will drive tues so gently that they last forever. Generally I have owned amps by designers who don't run tubes hard and I've had very few tubes fail. I've been running 80 and 100 year old tubes lately and still haven't had one fail. I often have my amp on most every hour I'm home. I use it for music and also for powering the front speakers during TV/movies.
If you're having tube failures, I'd look at my amp design.
Jerry
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I make my tubes last longer by turning my second system on. I'm fortunate to have a solid state system that I use 75 % of the time. I have always been told turning amps on for short periods then off is bad for tubes.
I do bias right at or a little shy of amp mfg specs. I don't think it's good to under bias either so if it says 53 ma that's where I usually put it. I use this
https://www.vhtamp.com/avtttt2
Great way to know where you are at.
For me my best bet is to buy matched quads or pairs depending on application from a trusted seller. I seem to have much better luck and durability
Some tubes just last long , some don't. I have a quad of Gold Lion KT88 that I keep as a spare. They have a ridiculous amount of hours. They look nasty, getter is fading , silkscreen is gone. They test strong still, not far from min new and still sound good.
On the other hand I had a quad of new Mullard el34. Did not have then matched / tested and within a month I had one burn up.
So to answer the question, not much you can do but enjoy and not leave em powered up when you're not listening
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Check the heater voltages. If they are above spec, the tubes will fade a lot quicker. Most of the time this is due to high wall voltage above 120V (or 240V) so you can't do much about that other than a transformer. If the wall power is okay then the amp should be serviced. Anything above 6.3 or 12.6 volts on the heaters is either careless designing or fading components. You don't want to stick expensive NOS tubes under those conditions.
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I have always been told turning amps on for short periods then off is bad for tubes.
I would think that repetition would be the key to avoid on this one.
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gs5556, how do I check heater voltages ?
oddiofyl, I could have a second system too with my old SS amp but I just wouldn't listen to it !
Those new EL34 Mullards, are they new reissues or vintage ?
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Balanced power supply. It provides exactly 120 volts at exactly 60 Hz...constantly.
IMO critically important to provide to tube amps...well, if you want your tube amp(s) to sound as it/they were designed to sound, which, sanity indicates you should. Oh, and bias holds better which increases tube performance and longevity,...huh, so I guess the more accurate sound is just a bonus to the longer tube life...funny how that works...
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It is almost always better to turn gear off when not listening and turn it back on when resuming a listening session. Tubes are not light bulbs which are designed to come on instantly so they don’t suffer as much from thermal shock from being turned on. Still, a lot of tube amps do employ some sort of soft start circuit that ramps up slowly and/or heats up the cathode first before the full plate voltage is applied (to avoid “cathode stripping”). An amp with a tube rectifier can have the rectifier act as the soft start feature.
The other practice to avoid is turning off an amp and then turning it back on again after a few seconds; the discharge from the caps can be damaging under these conditions. Wait a minute or two before turning the amp back on.
Amps that don’t need the owner to adjust bias (cathode biased) tend to run tubes more gently. This setup does not allow the circuit to extract quite as much output from the tube, but the reward is often a longer life.
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@xenolith pretty sure your balanced power supply doesn't regulate voltage. Regenerators are the only power supplies I know that do.
My amp has adjustable heater voltage. I do have to adjust it for different driver tubes but I'm using a wide variety of type 10,10Y, 210, 801, and 801A tubes.
Jerry
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If the amp allows, does switching from Pentode to Triode make a difference?
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I always keep a back up set of the full tube complement for each amp. I’m also checking bias every time I run the units --using a Fluke meter-- after the units have fully warmed up using a digital source for the first 45 minute to an hour. I do run them at exactly the recommended setting which is printed on the top plate, next to each tube socket). I often check them at the end of a listening session, too.
I used to never touch the tubes, using white cotton gloves to avoid any fingerprint oil, but abandoned that practice some years ago.
Lamm recommends replacing the driver tube--a 6N6P--every two years for optimal performance. I don’t use the amps constantly. I do know someone--perhaps the oldest Lamm dealer-- who runs his constantly. I get fairly long life from the amp tubes, which I buy directly from Lamm since the 6C33C not only requires burn in (which Lamm does, not sure what the failure rate is) but also has a peculiarity in the output stage*--each 6C33C has a different range in which they properly bias and Lamm matches, by serial number, a tube suitable to the particular amp for that purpose. I thus never tried to buy the tube on the open market. (The particulars for this are not disclosed by Lamm but in talking with another tube amp engineer, he seemed to understand this-- it might be interesting to get somebody else who uses the tube, like Ralph @atmasphere to explain the technical details). Two are in each mono amp- one as the output tube, the other used for voltage regulation. (* I gather that the tube used for the power supply doesn’t require the same degree of matching but since I get them all from the manufacturer of the amp, I am not sure).
One other thing I observed --the only tube I roll in the amps is the 12ax7 and have long preferred an old stock Tele ribbed plate (over the smooth plate). Many of the so-called NOS are, as you likely know, "pulls." I have been using truly never used old stock 12ax7s, a little more money but they seem to last much longer and the bias on the amps seems more stable.
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Really, don’t overthink it. The lifespan will be determined primarily by the amp’s operational parameters (bias, voltage), and quality of the tube. Enjoy your tube amp. Vintage tubes tend to be very good, and long lived. But these days, most of what’s left there are used and will have unknown hours (many???) on them already. Russian power tubes have been very good for me, but they do fail occasionally, and yes "spectacular" failures (catastrophic short) can happen and take out a resistor. Replace those tubes every 2000 hours, at most.
Some of the amps with individual tube bias pots can be run colder or hotter, to get either (maybe) more tube life or more "class A" respectively.
Don’t throw a blanket over a tube amp, but don’t bother with useless tube coolers either. You’d only need a fan if you’re sticking it in a cabinet.
Don’t leave it on for a few hours just to save an on/off cycle. Just turn it on when you’re ready to listen. Unlike some SS amps, it should be at its best in 10 minutes. Any hifi amp you have today should be starting the tube heaters up well in advance of the high voltage, so it’s a safe start for the tubes. You would be hard pressed to find a tube amp anywhere that doesn’t have SOME mechanism for soft start.
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On/off cycling the worst, in rush current at initial startups hard on tubes, rectifier tubes and/or soft start circuits, rectifier tubes may be sacrificial here. Heat is the enemy of all components, my 845 SET amps, nearly 1000V at plates, cooling fans beneath amp to push heat out, 300B amps much less stressed by the heat. Quality tubes with good reputation for reliability.
Some amps just harder on tubes than others, some manufacturers really push with high plate and/or heater voltages. Do your research on amps, determine whether there is history of failures, this is number one with me. For some years I was having failures with a certain tube, replaced loosely spec'd resistor in heater circuit with much higher spec resistor, no further problems.
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I agree that most tube amps sound good after a short warm up, it takes solid state gear more time to sound good so I can see why people keep solid state stuff on all the time. There is no good reason to do that with tubes.
I also agree that many manufactures push tubes hard. I think they do that in order to claim higher output. It seems crazy, to me anyway, to prioritize high wattage ratings with tube gear.
I run some very exotic, and very expensive tubes in my gear. Fortunately, the tubes are run very gently and I have been using the same tubes for close to two decades and the tubes were already old and used before I got them (they tested good). The only tubes that have ever failed on me were twin 300B tubes that are used as rectifier tubes in my phono stage. They failed because a shelf collapsed and dropped a 15 lb turntable motor controller on top of the power supply to the phono stage.
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@whart made a couple of points that I agree with. I check the bias frequently. I don’t have to use a fluke meter as my amp has meters for voltage and current for both the driver tubes and the output tubes. My amp is very stable but I have been rolling tubes a lot lately.
I also agree that there is no need to use white gloves. I’ll admit I’m an outdoor guy who doesn’t use lotion so my skin tends to be dry. but most tubes run cool enough that a little skin oil it isn’t a problem.
Thinking about this thread for the last day, I think the biggest factor in tube failure is running them at the wrong voltage or current. Most amps don’t have as much adjustability as mine. I’ve had amps with no adjustability (cathode bias) and they are designed to be easy on tubes--no action required.
I had a Decware ZMA and it had a great biasing system that I really enjoyed. it accommodates a lot of tubes and the bias current for each tube can be different. to calculate the bias current for a particular tube, look up the maximum plate dissipation on the tube data sheet (watts). Measure the B+ voltage of your amp. The best way is to use some insulated probes clipped to the correct pins (tube slightly elevated) running out to a volt meter. Make sure you don’t create a short to the chassis, turn your amp on, write down the voltage, turn your amp off and remove the probes. This number is important to know. Sometimes OEMs will provide it.
Divide your plate dissipation (watts) by B+ voltage (Volts) will give you amps. You’ll have a decimal. Multiply by 1000 to get milliamps. Now decide how hard you want to drive your tubes--usually a number between 60% and 80%- and multiply that times your current and that is where you set the bias. I have found recommended bias numbers well above what I calculated. I have also know guys who ran their bias purposely higher than recommended because they thought it sounded better. I think this is a myth, the "higher must be better" mentality.
If you have auto bias, you’re out of luck. I’ll never buy an amp with autobias.
Jerry
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I also agree that there is no need to use white gloves. I’ll admit I’m an outdoor guy who doesn’t use lotion so my skin tends to be dry. but most tubes run cool enough that a little skin oil it isn’t a problem.
Agree on the gloves point. Actually, this is something that the engineer in me screams "you're solving the WRONG problem!" about. There is NO risk to tubes from skin oils. Audio tubes are nothing like those awful halogen bulbs from the 1990s. The biggest risk to a tube is DROPPING it. And guess what - those cheesy, cheap white cotton gloves are generally very slick compared to a natural grip. So while purporting to protect tubes from (harmless) oils, they actually introduce a REAL risk to your tube handling. Ugh. These gloves should all be burned.
If you have auto bias, you’re out of luck. I’ll never buy an amp with autobias.
While I do love the ability to manually adjust each tube bias point, the VAC iQ auto-bias system has been very, very good in my use and sounds excellent.
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I'd never own an amp with cathode (auto) bias either.
Also, I don't know what "regulate voltage" means, but I do know that the balanced power supply that I use makes exactly 120 volts.
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As Roger Modjeski well understood, the SOE safe operating envelope for a specific tube is not a few points… hence a deeper understanding of both amplifier design with a dual focus on reliability and sonic engineering… the now ancient RCA SOE diagrams and tables yield much for those who do not think only in terms of points.. see RM-10 for imo a phd “ amp camp “ level demonstration of what is possible in terms of output, reliability and sonics.. RAM tubes and the testing…few if any can do contribute significantly as well… RIP… i miss him, could hardly wish for a better mentor, sensei, spirit guide…
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i find the deep dish pizza to be he$$ on the white gloves….
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Yes, the concern over skin oil has to do with light bulbs, not tubes. The oil deposited on a high intensity, high temperature light bulb will carbonize from the heat. That leaves a black spot on the bulb. The light from the bulb is absorbed by the black spot instead of passing through and that makes the black spot MUCH hotter than the surrounding part of the bulb causing that spot to fail.
Another piece of advice is to grip tubes which have a base by the base and don't push and pull on the glass envelope. The concern is accidentally separating the base from the glass envelope.
Also, if you do a lot of tube rolling, be aware that tube sockets have a limited life in terms of how many insertions and removals before the connection becomes less reliable. An old time technician told me it can be as little as 30 insertions and removals for a socket to fail (i.e., cannot be re-tightened reliably). If you do a lot of trials, consider using socket savers while you are trying to find the right tubes.
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Alright, I will join you in the abandoning the ritual of using white gloves while handling tubes. And the grip is indeed worse than bare hands.
Having extra set of all needed tubes is of course always a good idea, well, some tubes are really expensive and hard to find, at least from reputable sources.
I am not going to use any new reissues, only interested in vintage tubes. I see no reason to just waist money on inferior sounding and less reliable tubes. But if you need 20 power tubes, yeah, you just might be forced into that. I only need a quad.
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I am not going to use any new reissues, only interested in vintage tubes. I see no reason to just waist money on inferior sounding and less reliable tubes. But if you need 20 power tubes, yeah, you just might be forced into that. I only need a quad.
For bigger KT tubes, it’s extremely hard to find good vintage ones anymore. There are still some late make GE 6550s out there. EL34 (like your amp uses) and 6L6GC is much more feasible for sure. The British Mullards are warm (like your SED / Winged C, but better); I preferred Amperex / Holland EL34 for being more a bit more neutral while still sweet sounding. The East German RFT / Siemens are supposed to be quite good too. Electro Harmonix EL34 is a copy of this tube, at least superficially - but the old RFT build quality was much better (straight glass bottles, even!).
I’m quite fond of many of the Russian power tubes so it feels wrong to call the "inferior". But yes, the old power tubes were generally better. The old EL34 were beautifully built.
Also remember - part of VAC’s "secret sauce" is Kevin’s voicing expertise / craft, and it’s usually advisable to stick with tubes that sound at least similar to what it shipped with. What does VAC recommend for an Avatar these days? They were shipping Shuguang KT88 power tubes in 2000s (some with Penta Labs labeling), but Shuguang is long gone. I have a VAC 450S that originally shipped with those Shuguang KT88. They wore out before I got they got. Russian Gold Lion KT88 didn’t sound good in it, but fortunately Tung-Sol KT120 do :) Now that I think of it, might be worth tracking down some Shuguang KT88, sometime.
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It would certainly be interesting to try vintage Amperex EL34 but I am currently on the hunt for Mullards XF2 and getting close to them. XF1 would be much more expensive and even more difficult to find. Then there are first generation Mullard EL34 with metal base that some people consider the best. Well, probably impossible to find a matched quad or at least pairs in excellent condition, so I'll just forget about it. Unless I get very lucky.
Yeah, probably "inferior" was a wrong word not always accurately reflecting the difference.
Of course, SED Svetlana Winged are a copy of Mullard, sound signature should be similar.
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When I bought the Avatar I talked to Kevin about tubes. He recommended selected Chinese 12AX7 for the preamp and phono that he had, Brimar or Sylvanis 12AU7 vintage for driver and, yes, Mullard or Gold Lion vintage for power tubes. But I didn't want to go with any Chinese, I didn't like Brimar 12AX7 in the phono and thought that 12AU7 would not be too different, and Sylvania is thought to be bright by some. So, I disregarded his advice and went with 12AX7 Mullard long plates and 12AU7 RCA blackplates, and I am quite happy with the result. But for power tubes, yeah, Mullards are going to be installed soon enough.
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didn’t like Brimar 12AX7 in the phono and thought that 12AU7 would not be too different, and Sylvania is thought to be bright by some.
Sure - the sonic traits of one make/vintage of 12AX7 generally carry over to the corresponding 12AU7. Sylvania tubes seemed to change a lot from the 60s onwards. Before 1960s: nice clean airy sound, great dynamics, with a beautiful midrange that was romatic and organic while not so thick & warm as Mullard. Afterwards - a more bright and solid-state like sound. Ending with Philips ECG tubes of the 1980s (ugh). The later tubes are certainly serviceable, and even good in some roles, but older Sylvanias with black plates are generally much more desirable and sound good almost anywhere. You might think of older Sylvanias as (sort of) like USA’s Siemens.
XF2's are excellent. I had a quad but they were well worn when I acquired them. They were perhaps a bit more articulate than XF3 and XF4, but don't sleep on the latter - it's far easier to score a really nice quad of those, with a lot of life left.
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I see. Before 60s Sylvania were good, I’ll keep it in mind, thank you. Kevin didn’t specify, by the way, he just said Sylvania and Brimar. Brimar lacks Mullard’s sophistication and has a recessed midrange, both are no-no to me.
No, I’ll get XF2, believe you me. I made a mistake after I bought the amp by getting SEDs instead of seeking out Mullards. I’ll correct this mistake. I should’ve listened to Kevin about that and had more patience.
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Sure, that’s a fine strategy - stick to seeking what you really want. But I’ll say that even XF3 and XF4 Mullards were much much better than SEDs, to me. I didn’t really like SEDs; they came off as a 1-trick pony for lots of warmth, lacking the articulation and 3D holography of British Mullards. That seems to be a common pattern with modern tubes, or Solid State components that try too hard to emulate the vintage "warmth".
You could get some nice XF3 / 4 to use in the meantime, and then they become great spares when you get those XF2’s :) This is how I ended up with tons of tubes lol...
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Right. I wouldn't like to end up with too many tubes.
Yeah, people chase vintage tubes usually for a good reason.
XF3/XF4 as a spare set..that's not a bad idea at all.
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Reducing heat by venting the component or cabinet can extend tube longevity. Suggest that you visit; https://acifinity.com
for a wide selection of component/enclosure heat extraction units. I have one of their units placed directly on top of a Prima Luna EVO 400 integrated amp. It's like they are made for each other. It drops the temp around the tubes by about 12/15 degrees. Btw since these are extraction units rather blowing cool air onto the tubes there is never a risk of thermal shock damage to the hot tube.
Enjoy the music..
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Here’s a little tube porn for ya: 
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@tomic601’s mention of Roger Modjeski leads me to suggest that for longest tube life, they can be installed in any of Roger’s Music Reference amps (RM-9, RM-10, RM-200), in which output tubes last about 10,000 hours. Compare that with ARC amps.
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Yeah, miss Roger Modjeski - what a treasure he was. He was the master of tube conservation. Gave me a good tongue lashing for biasing my RM10 wrong and set me straight for an hour on the phone. Never wore out or shorted a tube in over 10 yrs on my unit. Sorry I sold my RM10MkII. He wrote on his forum "don't worry about handling tubes w/bare hands just get the peanut butter off your fingers". Just got a matched quad of EL34's from RAM tubes yesterday.
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Your bias current is usually measured across a 1 ohm resistor so that mV=mA. The meter measures volts but because the resistance is 1, then the number is the same. So a custom meter will measure volts, but it will say amps.
if your maker didn't order a special meter dial, it may say mV, but is actually reading mA.
There is a post above that contradicts this and I'm not sure what the poster meant.
Jerry
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The 60’s Mac amps also very famous for long tube life… I have some 1965 tubes … Tele that still test well..
@whart I need to copy your dusting rigor…. wow…. i would never get away with photo like that…..
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So you choose particular amps for longest tube life. That's interesting approach, not always works, though.
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