Leaving tube amps on.

This is a question I had for a long time. I know it’s not a good idea to leave tube amps on all the time because of tube life and safety reasons. But sometimes I don’t have the opportunity to listen to my system / music for hours at time at one sitting. Sometimes I can only listen to it 45 min - a few hours at a time during the day / night. So my question is would it be better to leave the amps on all day / evening and listen when I can or turn them on / off every time I listen even if is only  45 min at a clip. But to just clarify when I don’t intend to listen that day/ night they will be off. Does turning the amps on / off throughout the day / night do more harm than leaving them on ? Tube life , wear and tear on amps etc. btw I have the Audio Research Ref 750s. Ea amp has 18 KT150 , 6550WE , 6H30.  

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btw I have the Audio Research Ref 750s. Ea amp has 18 KT150 , 6550WE , 6H30.


Does turning the amps on / off throughout the day / night do more harm than leaving them on ? Tube life , wear and tear on amps etc.

I would be willing to bet the amps have soft start circuitry that limits inrush current to the amp’s power supply. The soft start circuity slightly lowers, reduces, the voltage applied to the power transformer and the secondary windings of the transformer during turn on of the amp. I would think that would address your concerns on harming the tubes and or electronic components in the amps. You could call ARC support and get their thoughts.

JMHO, if you think you may not be listening to the music for several hours, like maybe 4 hours or more, later in the day I would turn them off.


@simao   Ty. I just read it. 
@jea48  Ty. Yes. I have to agree with what u said. Sometimes I don’t listen to music for 4 or more hours later in the day. So it would make sense to shut them down. Anything less I’ll leave on sometimes it’s maybe 2 hours in between listening sessions. But I will tell u that any time I do leave the house to go out even for a short time I definitely turn them off. 

As jea48 says, most decent tube gear has a soft start circuit or if tube rectified, rely on the rectifier to gently bring the power up. It makes sense, from an equipment/tube preservation standpoint to turn off tube gear when not using it.  In particular, your MANY output tubes have a somewhat short lifespan when operating, and heat is not a friend for any of the other components in your gear (which is why their specification include lifetime estimations that are based on differing levels of heat).

As for sound quality, it does take some time for gear to warm up; the good news with tube gear is that it warms up much more quickly than solid state gear and will sound pretty good after a few minutes.

If I will not be listening for anything longer than 30 to 45 minutes, I will turn my gear off.

I would leave them on, assuming that I’m in close proximity to the amps and able to react quickly if a tube event occurred.

 I had an ARC amp that took 45 minutes to warm up and for the sound to bloom and I’ve had that experience with several of the amps I’ve owned. If you’re having short listening sessions, and that’s just the norm and unavoidable, you should be listening to your system delivering peak performance and not hearing the sound of an amp going through a warmup cycle. Your only offset (aside from safety) is that you’re going to be replacing tubes at a higher rate hence you need to decide whether you can justify the extra cost, or not. If not, buy some good solid state amps.

That would be my approach but I can also understand why some might disagree with it.

That is a great question. I got interested enough to read the manual and give it some thought.


My conclusion was simple. Call Audio Research and discuss with the technical representative (I forgot his name).

The new generation of ARC amps have slow startup and there is very very little improvement with warm up. You will have to assess yourself how much fidelity improvement there is as this is a bit older design. Also, that is a massive power amp… with 18 KT 150’s being run hard. So the recommended replacement time is 2,000 hours for those tubes. The small ones 4,000 hours. For me, balancing the above aspects I would turn it off if you were leaving it more than 15 - 30 minutes.

One thing I believe true however is that tube life is longer if left in idle mode with no music going through it… but then you will not be using the hours meter to change tubes at regular intervals, making maintenance more difficult. With ARC, I do what they say as far as tubes.

better safe than sorry. when tube goes bad anything can happen including anything that had been already happening.

leave tube amp on, you are at the fire hazard.

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I would leave them on, assuming that I’m in close proximity to the amps and able to react quickly if a tube event occurred.

leave tube amp on, you are at the fire hazard.

I love the idea of leaving them on, but I cannot park myself near my amps all day long, and a fire is a terrible thing. This seems like an easy one.

Turning amps on and off won’t hurt them due to soft/slow startup cycle.

Calculate the cost of tubes per year makes very little sense. 

@ghdprentice  Thanks for your response. I have to agree now with you. These 750s do have a slow start. And considering the options of leaving them on or off during some of my short listening sessions during the day / night I will now be turning them off. I have about 800 hrs on these KT150s and I also did buy a brand new complete matched set of tubes from ARC when I bought these amps last summer. Also I did already a tube ARC last year when I first got these amps. One of the KT150 tubes must of gotten shaken up during shipping. I think it was the very first time I played them. Scared the FK outta me. I put a post up last year about that. 

@czarivey   Thanks for your response. These are my first tube amps I have ever owned. I went from a Krell FPB 600 to the ARC Ref 750s. My first day of owning them I was listening for about 10 min and had a tube arc from a KT150 tube. It sounded like an explosion with a fire and lots of smoke. Scared the FK outta me. I posted this happening on AG last year. 

This isn’t exactly applicable to your question, and what I do might not fit into the structure of your life, but I generally know, on any given day, when I will be listening, and it usually after I eat dinner. So a couple or three hours before I am going to start preparing my food I turn on my CDP and the power supply section of my pre. about an hour later I turn on the rest of my pre (which lights the tubes up) and then after a few minutes or so I turn on the big power caps of my amp and then when I start making dinner I turn on the rest of the amp which lights up the tubes and when I start eating I put on some background music at a real low level.

By the time I have finished eating and cleaned up my mess my amp is pretty hot and I tell myself that sound degradation is going to be minimal. (I don’t know if it is minimal, but I tell myself so anyway.)

I definitely wouldn’t leave my tube amp on all day or overnight on purpose. Not that it has never happened before. But if you can get it on an hour or so before you start listening, that may make it sound better when you do start listening.


Leave ARC 750’s on 24 hours a day? 36 power tubes total? I find it inexplicable that anyone would even consider such a foolish thing! No offense intended.

ARC power amps are well known to self destruct when even a single power tube blows (ARC doesn't "believe" in fusing tubes). 36 of them? That’s living dangerously.


@bdp24  Who said anything about leaving ARC 750s on 24/7 ? If u are referring to my OP please reread it. 

@immatthewj  I generally warm up my equipment about 15 - 20 min. Then I will listen at about 15db for about 15 min before going up to my usual 28db listening level. But to tell ya the truth the amps sound dam good even from a cold start for listening. 


Ah, okay @tattooedtrackman, I see the difference. Not 24hrs/day, but all day in anticipation of listening that night.

Still, I would not want to leave the 750’s on without someone in the room they are in. That is generally true of all tube amps, none moreso than those of ARC. And with the short life expectancy of tubes in ARC amps I would not want to put non-listening hours on them. The cost of maintaining ARC amps employing 36 power tubes is a daunting proposition!

I never had problems with my ARC power amps, but my dealer (Brooks Berdan) had shelves full of used ARC power amps, many with scorched circuit boards.


Tubes off when listening session end.  SS on all the time.  SS DACs off when listening sessions are not active.  

You really are best taking your advice from the Manufacturer.


When the worse that can happen, does happen, the Home Insurers' will be gathering their info to decide on Payout from that very place.

Output Valve Red Plating is able to occur in an instance.

The following is a Guidance from an individual much more experienced than myself:

Red plating is always a BAD sign and if you ever see it, turn your amplifier off immediately.

If a valve suffers from this overheating for more than a minute or so you should probably consider it written off.

I suggest being present as much of the time the Valves are in service, as this will enable you to turn the Valves of in an Instance.

Those beautiful glowing tubes are not visible for the ambience they can create only.

They are visible to allow heat to not collect in a case, and enable eyes on the prize, when it comes to witnessing changes in their operation that can cause a fire.


Mollycoddling tube amps is silly to me. Although I maybe shouldn’t make a guitar amp analogy in this hallowed audiophile ground (I use tubes for hifi also, but firmly believe nothing is sacred), I’ve owned tube guitar amps that were turned on and off frequently for decades...worked perfectly...same tubes for years and years in some cases. You take your hifi tube amp on airplanes? Blast it on high gain in a club then toss it in your trunk? For years? I don’t drag any of my hifi gear around as...well...nobody does except to audio shows maybe...still...and the answer is turn the damn tube amp off. Tubes warm up in seconds...



Love it! People can get a bit precious about tubes.

There was a time, when everything ran off tubes…

First thing I turn on when I wake up, is the system. Last thing I turn off, is the system. Listen before I leave for work, listen when I get home.

If I leave the house, I turn it off. If I’m going to be working on something around the house for anything over an hour, I turn it off. I listen to radio a lot…

I have a couple of systems here that I switch out (tube and SS pre amps, tube and SS power amps.) with different speakers. I tend to treat SS and Tubes the same.

Turn on if I’m there, turn off if I’m going away.

I have a friend who bought a SE EL34 amp off AliExpress. He never turned it off. It sat in a small area on a shelf, with poor ventilation. One speaker cable had come undone from the banana plug, so left channel was not connected to a speaker. Tubes were original and of very low quality. Nothing bad happened…



I have not owned high-powered tube amps.  None of the amps I’ve owned really required much warm up.  I turn them on and start listening immediately.  If they seem a bit off, that goes away in a minute or so.  If the sound is enjoyable right from the start, even if it is less than optimal, why would you not start listening immediately?  If you sessions are short, it is even more imperative to start immediately.

If high power tube amplifiers are as hazardous as outlined in several post above, then how come they are not banned in the state of California?

Worrying about tube seems a little strange.  You knowingly purchased and expensive amplifier with a large number of tubes.  Do people who buy exotic Italian supercars worry about the cost of an oil change?

Not to derail this topic but I've been thinking of getting a tube preamp. Is there ANY safety concerns leaving them on 24/7 especially the models with tube rectifiers?

Don Sachs had addressed this subject, some time ago. If I remember correctly, he had suggested that it is good to turn the tube gear off, when not listening.

I was first introduced to Valve Equipment in the early/mid' 90's and was quick to move over to the schematics using Valves in place of Transistors and Semi Conductors.

I had my first Valve Amp' Pre and Power commission built, and the EE who at this time had a good few years of working with Valves to produce Audio and Studio Equipment gave me as a newbie a clear warning.

Valve Equipment is not a Turn On and Forget device.

Valves in use need monitoring during use and after Power Off.

I have kept to my side of the Bargain for the best part of 30 Years and see no need to make a change. The same EE remains a friend and has produced further Power Amp commission builds for me. 

Red Plate is common on a Output Valve and is a result of incorrect Bias, where increased Voltage is enabled.

Everything in Valve Talk is about reliability, maintained Bias is extremely important.    

@pindac Thank you for clarity on Red plate. I was just gonna ask how important tube bias is and what can happen if not biased. 

@tattooedtrackman  , on bias and red plating,

a few years ago (I think it may have been some time in '20, I had a coupling cap fail on one side of my Cary V12..  I won't try to explain the science or theory of whatever happened within the circuit, because that kind of stuff is beyond me, but the result that I saw was the bias on that side running away high regardless of the position of the bias pot.  (I could back the bias pot all the way off, but shortly after turning the amp 'on' the bias would start climbing out of control on that side.  The tubes on that side got very hot--red plated--and were never the same sounding after I replaced the cap.  I felt the tubes were getting tired anyway, but that event was the last straw and I bought new tubes.  


@tattooedtrackman A number of years ago I bought a preowned tube amp that according to the manual to set the bias you had to put a tiny phillips head screwdriver in a tiny hole until you blindly felt the phillips head screwdriver engage into the phillips head bias screw.  Then turn the screw until the amp shows proper bias for that channel.  Unknown to myself the previous owner had had a bias pot replaced with one with a normal slotted screw.

Well first time biasing I broke off some part of the bias pot and a second later.  I was met with smoke, smell and a real fireworks show. I hit the on/off button and that did nothing to stop what was happening.  I then pulled the plug and the show was over.

If you really saw and smelled what occurs when something like this happens you would not even want to think of leaving your tube amps on and unattended for a long period of time.

Surprisingly the cost to repair the amp was minimal.

What I generally do with tubed gear, which I've done for eons, is turn the gear on around dinner-time (if I plan to listen to music) and off after listening.  On the weekends I'll turn them on earlier and leave on all day and off before bed.


@jetter   Read my post from last year about when I first bought my Ref 750s. I had a tube arc from a bad KT150. 

@tattooedtrackman  My bad, I did read about it back then but forgot about your personal fourth of July.

If I was not there at the time it could have easily resulted in a serious fire.

Once I turn mine on for the day, it stays on until I’m done for the day; so it’s usually on for 8-10 hours even if I’m only listening for 4-6 hours. 

@immatthewj No need to give a in depth explanation.

It was a reliability issue

My EE will keep a Tube Designed Device under scrutiny for weeks to ensure the circuit is not compromised.

Even when doing general repairs on any Tube Amp' the device is kept back to thoroughly check for reliability. This approach has lost lots of customers who want the device to be sent for servicing / repair returned within a week of having sent it away. 

I recall back in the 90's when Tubes Amp's were becoming quite popular, it was EE's like mine that were the resource selected to repair certain Brands Amp's as the producer did not know how to trouble shoot their faulty circuits.

I know my EE during the 90's has trouble shot a few Brands faulty circuits as a result of receiving Amp's that had multiple failures, usually as a result of extended periods of usage.  I also know some of the circuits worked on were fire risks, due to how the Output Valve / Tranxs could be affected. Maybe he has even more of these circuit corrections under his belt in the 00's ? I have not inquired for a long time. 

ghdprentice Plus 1!

Even with solid state, unless the amps have been unplugged for months, they will sound 99% after 15-30 minutes. My preamp and amps are hybrid, where the input stage (where the tubes are) shuts off, but the rest of the unit is left on. I turn everything one and after 5-10 minutes, they sound swell.😊

teach the children.

turn them and everything else not in use OFF.

It may not make a damn difference to you, but collectively it does, and it is environmentally irresponsible.

@pindac , well, the amp had been in service for many years and caps do occasionally fail, and I think that this failure was due to a mistake I made when I was doing something with the amp.

But, my point was: that if the amp was fully powered on and idling and that cap would have failed and no one was anywhere around, the bias would have climbed and continued to climb until I do not know what then happens. I did have an output tube fail catastrophically a long long time ago (I assume it was an internal short in the tube) and it blew the tube fuse on that side, but I still wouldn’t (on purpose) leave my amp on & unattended for an extended period of time.

Does turning the amps on / off throughout the day / night do more harm than leaving them on ?

in my view, no

You will pi$$ thru tubes leaving it on all the time. Tubes, especially NOS are not cheap. Shut it down when not in use.

Where do most of the world’s KT-150 tubes come from? And where did all the semi-reasonably priced (if compared to alternative) KT-150 tubes come from?

One large altercation later and those tubes aren’t being imported anymore. 
With Russia doing its thing and China redirecting much of its attention to newer tech development / fabrication, the world supply of current production power tubes is quite a bit lower than it was a few years ago.

KT-150 now = NOS unless perhaps you’re buying the costly version produced outside Russia.

I’ve zero interest in anyone making this political - please do not.

But so many of the power tubes that are unhealthy to manufacture come from two nations that are not up to makin’ em like they used to; that probably shouldn’t be something out-of-sight/out-of-mind for the audiophile who likes using tubes. Turn power tubes off when not in use. 

I have a Raven Audio Osprey with NOS tubes and have asked myself this same question many times. The simple solution that I've come to is: if I'm running the amp, I leave it on for at least 1 hour. This is easy to accomplish because most albums are around 45 mins and the amp really needs 15-20 mins of warm up before it's sounding its best. So, 15 mins before I'm ready to put on a record, I turn everything on and let the circuits settle-in. Then, whether I'm there for 1 record or 10, I haven't short cycled the amp. 

Good Luck!

On my Linear Tube Amplifers and pre amp I try to turn them on a few hours before critical listening and turn off after I’m done for the evening.  The LTA circuitry is designed to maximize tube life so I don’t really worry much about it.  

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If I’m stepping away for an hour or two, I leave it on.
Longer than that, it goes off.
The room is so well insulated that leaving them on when not in use heats up the room.