When to power off a tube amp?

So I just got new tubes for my Lyr and really don't want to damage these tubes and want them to last for as long as possible. So I had a few questions and was hoping you guys could help me, thanks.

1) Should I turn off the amp if I am going to away for like an hour or so? Would that decrease the life of my tubes more than leaving it on that whole time I am not using them?

2) Should I let my tubes warm up before using them? If so, how long should I wait?

3) Is unplugging my headphones before turning off my amp necessary?

And just a random question out of curiosity, what if you use two different tubes in a tube amp? lol.

Thank you guys, any help would be much appreciated.
I unplug my 300B SET monoblocks when I'm not using them because they consume lots of electricity, and leave other equipment on 24/7.
Any tube amplifier should never be left unattended. (""More than an hour"") The tube amp could burn down your house in fifteen minutes.. I would say ten minute unattended is max if you do not like taking chances with catastrophe.
Now tube amps blowingup and starting on fire in not common. but still possible and not a good risk to leave unattended.
Hi High roller
Really depends on the types of tubes you have.
I run 300bs, and if I am leaving the house for what I think will be an hour(which is always more) I turn it off.
In contrast, my phono pre has 6dj8s which don't like being turned on and off, so when I flick this unit on, it stays on till I go to bed. I think tubes like 6sn7s could likely be left on 24hrs a day for 5 years before they needed replaced, so again it depends on the tube and its relative characteristics, cost etc.
I think question two is debateable re tube health. I would let the system stabilize(a couple to a few minutes. There is debate re sonic improvements and temperature of components. I don't want to go there since your question was for tube life. Power tubes heat up pretty quick. I also don't think tube amps are generally that fragile. Ie they are designed to be used, not only looked at.
Question 3: I would leave them plugged in and save wear and tear on the plug.

Hopefully Ralph (Atmasphere) or Gary (Hifigeek) will weigh in. My practice, FWIW, is that I will leave my amp on unattended for up to 4 or 5 hours -- never if I am out-of-town.

Seem to recall that it's a bad practice to shut a tube amp off and then restart it unless waiting for at least 5 or 10 minutes. The "wear and tear" of a tube as I understand it is the tube's innards responding to hot and cold, which in turn, causes the innards to expand and contract.

Tube failure also occurs because of arcing. I do not know what user-related factors (if any) cause arcing. I for one would love to hear back from Ralph or Gary.

1) Turn it off
2) Don't need to warm up before playing
3) don't need to unplug headphones
4) You can use different brands of the same type tube without harm
I would agree with Elizabeth. I was listening to music late one night and had fallen asleep in my listening chair. I was using VTL MB250 monobloc amps powering Maggie 1.6's. Something stirred me and when I opened my eyes I saw a shower of sparks coming from behind my right channel amp. It looked like a 4th of July display with all the sparks shooting in the air. I plucked the cord out of the wall and once I regained my senses saw the fuse holder for the B+ was charred.

I sent the amps back to VTL and was told the voltage rating of the fuse holder was too low and had caused the arcing. They replaced both fuse holders with ones that were physically larger at no charge.
1-Turn off when unattended
2-Warm up is usually about 15 minutes
3-unplugging headphones is not necessary
4- Stop worrying and enjoy!
BTW, you can use different tubes as long as they are the same type!
If you go out for just an hour or so leave them on. So long as you home insurance is paid up.

Turning off is not so much the problem, it's the turn on that is the tube deteriorator in most amps.
As nearly all of them bring on the heater supply and the HT(high tension) supply immediately. That means the HT hits a cold tube.

In nearly all the tube amps I've built I bought the heaters on first with the main switch and with a 30sec auto delay circuit then the HT was connected automatically. So there wasn't a sudden shock to a cold tube with the HT.

Cheers George
I think you should have told the folks that your Lyr amp is a headphone amp. Knowing this I think that you might have gotten different responses from folks had they known.

FWIW I see no fire hazard. None. The unit supposedly runs 'hot' but that is a relative term.

I see no need to turn off the unit except on a daily basis or after you are through using the unit each day. That way it will rest at least overnight. Small tubes typically have a long life.

I would not use different brands of tubes. Brands sound different and you would have the left channel with a different tone from the right channel if you don't use the same brand & type.

Turn down the volume to minimum when you turn off the unit. That should be enuf.

Re warm up - it doesn't take much time to warm up this type of unit. 5 to 10 minutes should be enough to take off any rough edges. If it takes more you will hear why when you listen. BTW, if you replace or roll tubes, be sure to get tubes tested for low noise.
Tube failure or arcing (flare up) happens in nearly all cases when the amp is first turned on from cold. This is because the HT comes onto a cold tube.

One way to rectify it is to get a 30sec delay circuit for the HT, so the heaters have a chance to heat the anodes and cathodes first. If you cannot build one yourself then there are many pre-made ones to insert on the HT rail.

Just Google or look in ebay for "Relay Delay Circuit" Do the math as you have high volts small current to give the relay contact amp rating you need. They can be bought for around $10 ready made. In the case of mono blocks you need two.

Or if this is too much bother, then just have another manual switch which breaks the HT so you can bring it on 30sec later, after the tubes have warmed up.

Cheers George

George, what you say sounds reasonable, but I am not EE savvy. I can barely tell the difference between the front and back of the amp. :( Further, any mods to the amp's circuits will adversely affect its resale value.

My linestage and amp have a 12 volt trigger connection. The trigger starts the amp within 10 seconds or so after the linestage is turned on. I suspect this is NOT the same delay circuit you described. Instead, I think delay start-up prevents a linestage turn-on thump from causing a power surge through the amp into the speakers.

Otherwise, I think you and I are on the same page about turn-on/turn-off concerns. I'm not sure if 4 or 5 hours is a good number for my rig, but it's what I have been doing. Thank goodness I never had a Fourth of July problem with my gear -- at least not yet. Hopefully Ralph or Gary will weigh in.


FWIW, a few years ago I installed a brand new quartet of Chinese-made 6SN7 small signal tubes in my VAC amp, that had been provided and tested by a good supplier. After listening to beautifully reproduced music for about 2 hours, all of a sudden there was an eruption of horrific static-like noise from one speaker. I believe it was loud enough, and that it had sufficient high frequency content, to destroy the tweeters in many speakers if allowed to continue for a prolonged period. In this case I had the amp shut down within about 4 seconds, with no damage. I subsequently found that one of the 6SN7's had abruptly developed a short.

I of course have never used any of those four tubes since.

FWIW. Regards,
-- Al
Al, can I assume, therefore, if one leaves their amp on unattended for even a short period of time, they could learn upon resuming their listening session that not only does their amp not work, they may be minus one or two speakers as well?? Al, there is obviously no written rule out there that I am aware of, ... but at the risk of too quick a turn-off/turn-on, what's your rule of thumb about leaving a tube amp on unattended?


1. General consensus is that for safety purposes, it's not a good idea to leave a tube amp unattended for any significant period of time. In my case, that means if I leave the house, I turn it off.
2. Let 'em warm up if you want, but no reason not to listen if you want to. It can't hurt the tbes.
3. If the amp is has tube output tubes, it's not a good idea to run them w/o a load, i.e., headphones.
I've never heard a good reason to leave them on after listening as they warm up within five to ten minutes. I've never had an explosion but there is enough plastic volume in the boards to get a good roaster that could catch a pair of drapes on fire. I'd say even though you can burn down the whole neighborhood on occasion, tubes are worth it.
Many recent vintage tube preamps have a slow start cycle built in. It slowly increases the voltage going to the tubes over a 20 to 45 second interval when you turn the preamp on.

Preamps that I know of with this feature include PrimaLuna, c-j and Aesthetix. If your preamp has this feature, I think you should turn it off if you won't be using it for an hour or so. The life of small signal tubes is being used up even when music is not being played through them, although at a slower rate than when music is being played through them.

I am not a tube or electronics expert, so if i am wrong about this, please correct me.
For my Bellari headphone amp I just leave it on all the time. Since it only uses 1 12AX7 tube I don't really mind if that tubes gets worn down since I have so many. For my Jolida 502P I turn it on and when all the EZ Bias lights turn red I'm ready to listen to music. For my other Response Audio tube monoblocks I leave it on for 45 to an hour first before listening. When I'm done I turn them all off.
"Many recent vintage tube preamps have a slow start cycle built in. It slowly increases the voltage going to the tubes over a 20 to 45 second interval when you turn the preamp on."

I think you'll find that's because they used tube recifiers, not solid state ones they use today.

Cheers George
Thanks for the input guys, greatly appreciate it. I am getting mixed responses as to if I should turn it off when unattended, etc so I will just await more answers I guess.

My Lyr has a 20 second mute relay switch, does that mean it cannot explode or arch when I turn it on cold? Thanks guys.
Most tube gear sounds pretty decent within 10-15 minutes of being turned on so there is no good reason to leave the gear on all of the time--waste of energy and waste of the limited life of tubes. While there is a possible safety issue with leaving tube gear on unattended, the chances of a fire is extremely low, and such risk would apply to solid state gear as well.

Tubes are NOT like light bulbs, which come on instantaneously, so they are NOT as prone to thermal shock from being turned on. The tube may be subject to some damage from "cathode stripping" if the high voltage rail instantly powers up and the cathode is not yet heated enough to be emitting electrons. Better designs utilize a soft start circuit to prevent such problems, or if the amp uses a tube rectifier, the amp will naturally ramp up gradually. Overall, with most tube gear, there is more wear on the tubes from being left on when not in use than from the stress of being turned off and on more frequently.

What I never do is turn off an amp or preamp and then turn it back on without a fairly long interval in between (at least 10 minutes). I have seen tubes, particularly the rectifier, flash when this is done. While I have not noticed any permanent damage, this cannot be a good thing.

I don't know about your Lyr, but, a time delay mute is designed to prevent any output from the amp until it is warmed up and stable. Some tube gear will put out pretty nasty noise as it is powered up so a mute is designed to protect the speakers and your sensibilities while this is going on. The circuit does not necessarily also provide turn-on protection (soft start) for the amp itself; that is a separate feature. But, it is a good sign that the manufacturer is adding such features because soft start protection is even easier to implement.
I agree with Newbee, you do not have what most of us consider a "tube amp". Your Lyr is a tube headphone amp, which uses small signal preamp tubes, not power tubes. My tube preamp is on standby when not in use, there is always power to the tubes, unless I shut it off for extended absences or storms.

I would say that since your "amp" only uses two 6BZ7's or 6DJ8's, it is safe to leave on for an hour or so unattended. Warm up is 5-10 minutes, and you can leave the headphones plugged in when turning the "amp" off.
FWIW for those unaware, the Lyr is a dedicated hybrid headphone amp, the tubes in it do not provide power per se. Most all of the 'dire' consequences of leaving tube power units on unattended just don't exist for this kind of unit, any more than they would for a full sized hybrid power amp, integrated or otherwise.

12-26-13: Bifwynne
Al, can I assume, therefore, if one leaves their amp on unattended for even a short period of time, they could learn upon resuming their listening session that not only does their amp not work, they may be minus one or two speakers as well?? Al, there is obviously no written rule out there that I am aware of, ... but at the risk of too quick a turn-off/turn-on, what's your rule of thumb about leaving a tube amp on unattended?
Hi Bruce,

As you realize, the basic point behind my earlier post is that when a tube component, especially an amp, is left on unattended for significant periods of time, in addition to the very small (but non-zero) possibility of fire (which always seems to get mentioned in this kind of discussion), there is also the presumably much greater (but less often mentioned) possibility that a minor failure of a tube or other part will result in major damage to the equipment, if not discovered promptly.

As the experience I cited illustrates, that can even happen as a result of a problem with a small signal tube, especially if the small signal tube is in a power amp or integrated amp.

It seems clear that a case that is at least somewhat reasonable can be made on all sides of these questions, but FWIW my own practice is that the only equipment I leave on unattended are solid state components having no power switch (which are therefore presumably designed with the expectation that they will be left on all the time), and my solid state CDP.

Regarding your mention of the possible risks of turning on too soon after turning off, I second Larry's comment. I can't base that on personal experience, though, as I've always allowed at least a couple of minutes, and usually more, between those actions. Intuitively it just seems to me to not be good practice to do otherwise.

-- Al
Well apparently turning on the amp is what decreases the life of the tubes? Does it decrease the life more than just leaving it on for that hour of absence? I really want to know as I am buying some Amperex pinched waists 6922 with D-getters which are considered the rarest tube in the 6dj8 family and they are not cheap... So I need to prolong their life as long as possible.

Also, if I don't let the tubes warm up before use, what happens? Decrease in tube life or does it just sound bad?
Highroller -- good question ... good questions all. Let me summarize the opinions given above. Let's see ... uuhhm, exploding tubes, out-of-control tube oscillations taking out speakers, fire hazards, shortened tube live if tubes are turned on and off ....

I finally get it. Boy am I dumb. If you own tube gear, the best way to avoid all of the these hazards and perils is simply not to turn on the system. Or, ... dump the tube gear and get a Phlame Linear 400, or just plain ole' SS gear. Anyone looking to buy ARC ref level gear??

:( :( :(

This thread gets my lowest rating. 3 unhappy faces.


I own a Lyr and love it although it's had about 8 hours of use since it was new. I let it warm up for about 3-5 minutes. You can't hurt the tubes by listening immediately. If I'm getting up to prepare dinner and plan to continue listening later it stays on. If I'm not going to listen for another hour and a half I shut it off.

I personally would not run this headphone amp with extremely expensive and rare tubes. I'd do that with say a high end all tube unit, but not the Lyr. No reason other than why spend half of what the unit costs on tubes? I'm sure there's plenty of great sounding tubes that aren't as rare or expensive. I still run stock only because I barely use the Lyr to justify owning it.
Highroller, whenever this topic comes up there is disagreement. I haven't seen one of these discussions come to an agreement anyway.

Personally, I think the preponderance of the evidence indicates that you should turn your tube preamp off if you are not going to be listening to it within the next two hours.

You want to avoid turning it on and off several times a day also, but to let the tubes burn for hours while not listening is just using them up with no benefit. Turning them on for 10 or 15 minutes of listening doesn't make sense either. If you want to listen for a few minutes use your computer.

If you are using inexpensive current production tubes, leave them on all day and have a spare set handy. Put the new ones in every once in a while and when the new ones sound better than the old ones, leave them in and order another pair.

That's my opinion. I would call the people at Schiit and ask them what they recommend.
I had a NOS JAN Philips 12AT7 flame out in my Jolida last year...harmed nothing, replaced both 12AT7s under warranty (thank you thetubestore) with nice matched CV4024 Blackburn Mullards, and have been living happily ever after. I don't leave the amp on when I'm out, and turn my entire system off at the end of the day or if I'm gone for more than a few hours. The NOS Mullards do provide an entertaining flash on startup, and I don't think new (current repros from New Sensor) ones do that...at least the 12ax7s I have in a guitar amp.