Do you leave CD players with tube outputs on?

I was wondering how many owners of cd players with tube outputs leave their CD players on all the time. I have a Ayon CD-1 with a tube output stage. Based on input I received I've been turning off after listening and let it warm-up at least a half hour before each use. On the other hand, it is my understanding that the electronic circuits for CD players need around 72 hours of being on to reach their full potential. Is there any harm in leaving a CD player with tubes on all the time other than a shortening of tube life?
You have it correct. I would suggest leave it on during a day you are going to or are listening to music and turn it off at night to preserve tube life. If the electronic caps and such are already broken-in in the player then I don't see them requiring much time to reach their full potential.
I am not sure of the technical aspects but I turn mine off when not in use . It only takes about one CD's worth of play to bring it in to its own and sound good .
Living in the lightening capitol of the world makes it dangerous to leave these things on when not in use ! I have already lost a heatpump and microwave oven .

Happy tunes .
Here we go again (these questions come up constantly). Your post and the responses demonstrate a misunderstanding of small-signal tubes (i.e., 12XA7's, 6SN7's, etc. found in tube preamps and tubed DAC's/CD players). In fact, 24/7 operation EXTENDS the life of small-signal tubes in most preamp and DAC circuits. Consider the following 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 [small-signal] 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).

Small-signal tubes pass little current in most preamp and DAC circuits, and thus experience virtually no filament wear. If left on 24/7, they either die within the first 250 hours or so due to "infant mortality" or they basically last forever. What kills small-signal tubes is two things: one, the thermal cycles that result from turning equipment on and off, and two, the voltage rush they see at power on. This occurs if they are in a component with solid-state rectification (i.e., solid-state power supplies), which is almost always the case. The rare component with tube rectification can be a different matter because the tube power supply functions like a variac to apply current gradually (for the same reason, many tube components have "soft start" circuits so as not to decapitate the tubes at power on). This, not 24/7 operation and heat, is the main culprit of tube death. The Colossus computers used in World War II to decipher enemy radio transmissions used thousands of small-signal tubes. The Wikipedia entry for "vacuum tube" has this to say about operation of the Colossus:

"The Colossus computer's designer, Dr Tommy Flowers, had a theory that most of the unreliability was caused during power down and (mainly) power up. Once Colossus was built and installed, it was switched on and left switched on running from dual redundant diesel generators (the wartime mains supply being considered too unreliable). The only time it was switched off was for conversion to the Colossus Mk2 and the addition of another 500 or so tubes. Another 9 Colossus Mk2s were built, and all 10 machines ran with a surprising degree of reliability. The 10 Colossi consumed 15 kilowatts of power each, 24 hours a day, 365 days a year—nearly all of it for the tube heaters."

The Wikipedia entry for the Colossus emphasizes this point:

"Colossus used state-of-the-art vacuum tubes (thermionic valves), thyratrons and photomultipliers to optically read a paper tape and then applied a programmable logical function to every character, counting how often this function returned "true". Although machines with many valves were known to have high failure rates, it was recognised that valve failures occurred most frequently with the current surge at power on, so the Colossus machines, once turned on, were never powered down unless they malfunctioned."

In summary, turn a tube power amp on and off because the output tubes pass a lot of current and will wear out if left on. With regard to most equipment using small-signal tubes, leave it on. For the record, I ran three tube preamps (CAT, Hovland and Jadis) 24/7 for a combined eight years, a DAC 24/7 for five years, and my current CD player, which has six-tubes in its output stage, 24/7 for one year - I have never lost a single tube or had any tube problems. I finally swapped out the tube in my DAC after many years just for the hell of it and it tested like a new tube. People lose small-signal tubes because they turn their equipment on and off.

Regarding your point about leaving digital gear generally turned on 24/7, absolutely leave it on - on/off turns a tolerable technology into a painful technology.
An excellent writeup by Raquel, and excellent advice.

For the record, though, I'd like to cite a couple of minor points that I believe are mis-stated.

Most small signal tubes that are used in audio components, such as the 12AX7's and 6SN7's, use indirectly heated cathodes (meaning that filament and cathode are different elements). The filaments in some designs are powered with low voltage ac supplied directly from a winding on the power transformer, in which case tube vs. solid state rectification has no bearing on the in-rush current to the filaments that occurs at turn-on. Better designs often incorporate dc filament supplies, in which case the design may provide better in-rush control.

In either case, controlled ramp-up of the rectified high voltage that is applied to the plate circuits (that can be provided for in the design of a good solid state rectifier circuit, or that occurs naturally with tube rectification) prevents plate voltage from being applied before some degree of warmup of the filament (and consequently the cathode) has occurred. Application of high voltage to the plate (or screen, or other high voltage elements, if present), prior to establishment of what is called a protective "space charge" of electrons around the cathode, leads to a phenomenon called "cathode stripping," which in the case of some tubes can shorten tube life considerably (although its significance in the case of small signal tubes is controversial).

Cathode stripping occurs, I believe, as a result of stray gas molecules in the tube being positively ionized by collisions with electrons being drawn toward the positively charged plate, the collisions causing electrons in those molecules to be knocked away. The positively charged, heavy, ions are attracted by the cathode due to its low potential, where their impact would damage the cathode's emissive surface over time were it not protected by the space charge.

Again, thanks to Raquel for the excellent writeup.

-- Al
Great posts, thank you! Thanks Raquel for the thorough discussion and to Al for the physics lesson! I previously used a hybrid integrated amp with 7308 tubes in preamp stage and a Consonance 2.2 CD player with tubes in output stage and left those on all the time for a few years without a problem. But when I got the new CD player I was informed to turn it off when not in use. However, I have left the Ayon on for a couple of days now as an experiment, so look forward to listening for changes in sound this weekend.
Thanks a lot Al and Raquel for your informative posts. I have and Audio Aero CDP and it is left in standby all the time which means that the two tubes are receiving power 24/7. I also have an 8 year old OTL which has not had power removed from the driver tubes except for power failures. These driver tubes are all original and still going strong. Don
It would be interesting to compare the cost of 24/7/365 energy consumption to price of new tubes.
The tubes in my Audio Aero Capitol only lasted 2 years because I left it in standby 24/7. Jodi from AA distributor, Globe Audio, recommended I turn the unit off when not in use to extend the life of the tubes.
Most small signal tubes that are used in audio components, such as the 12AX7's and 6SN7's, use indirectly heated cathodes (meaning that filament and cathode are different elements). The filaments in some designs are powered with low voltage ac supplied directly from a winding on the power transformer, in which case tube vs. solid state rectification has no bearing on the in-rush current to the filaments that occurs at turn-on. Better designs often incorporate dc filament supplies, in which case the design may provide better in-rush control.


Pardon my ignorance and I hope you do not mind me asking. I am not looking for a debate, I do not have sufficient knowledge on this topic to hold one, and although my questions are pretty direct, I am just trying to understand what you wrote. So, if you do not want to answer my questions, I do understand.

What if there's a thermistor on the primary winding of the tube amp, for example, what happens to the inrush current analogy? At t=0, caps (in the PSU) are shorted, does the inrush current reach the signal tubes?

I have never encountered a tube failing on preamps because of cathode stripping. Some tubes last for ages, like Telefunken for instance, are they not affected by cathode stripping? How many cycles does it take on the average before cathode stripping is really an issue? Is the decrease in gm be considered as a good measure? Is it safe to assume that cathode stripping only matters on high power tubes where bias voltages are over 1kV and not those tubes whose bias voltage is less?

Again, I apologize for being direct and I hope that you will not take my questions as a challenge to what you have posted.


Hi Abe,

Thank you for the polite nature of your questions, but I'm not able to answer them particularly knowledgeably.

Yes, I would think that a suitable high-current thermistor, suitably placed somewhere in the path between ac inputs and tube filaments, would be an effective means of inrush current limiting. I know that is commonly done in power supply designs, although I don't have a feel for how widespread their use is in audio.

I'm not sure I understand your reference to shorting of caps, but that would seem to only be relevant to designs that incorporate a dc filament supply, not to those that drive the filaments with low voltage ac directly from the transformer.

Re cathode stripping, as I indicated its significance with respect to small signal tubes is a matter of some controversy, and I have no particular feel for its degree of significance myself. But given the possibility of it being significant, it would seem to be good practice to design a tube component to bring up the B+ slowly.

-- Al

Thanks a lot! I am glad that you accomodated my request.
Thanks for your time answering my inquiries. I learned something today!

Best regards,

Tubes reach the point of normal operation faster than semiconductors thus require shorter time to worm up (for the small signal tubes near 2min. Why bother to keep them on??
I think a lot depends on your unit. Some take longer to warm up than others, also some are a little more "blunt" with how they power up. If Telefunken 12ax7s last 10,000 hours, you do the math....
I tend to leave my system on all weekend if I'm listening a lot. But, if I'm not going to listen for a day or two, it gets turned off.
From conrad johnson's web-site........

"To obtain maximum tube life, vacuum-tube products should be switched off when not in use. A good general rule for is that if you will not be listening for more than an hour, turn any tube component off. Conrad-Johnson solid-state preamps (including Sonographe and Motif), on the other hand, are designed to be left on at all times. We recommend switching power amps off when unattended and over night."

How long do tubes last?
A. That varies depending on the type of tube, the number of hours of use and the type of use they have had. Typically tubes should last, on average, about 1500 hours before gradual degradation of performance becomes noticeable. This translates into two to three years if the unit is turned off when not in use. Usually tubes will continue to be functional for a long while after this, but sound quality will be reduced and noise levels will increase. In power amplifiers, the input tubes are most critical for sonic performance. If output tubes are not causing problems, they can be replaced every other time.
Most preamps and CD players/DAC's idle in the 10-30 watt range, and over time, it almost certainly is more expensive to keep gear powered up than to lose small-signal tubes through on/off operation. But retubing with some gear is not convenient, tube failure is often gradual and annoying to listen to because of the tendency of tubes that are dying to act up, and there are other parts in equipment, particularly processors in digital gear, that have to be left powered up if they are to sound right in a high-end two channel system (try listening to cold digital gear through a first-rate triode amp or something like a darTZeel on revealing speakers - it sounds awful). I don't like f'ing with tubes and I hate the sound of cold gear, so I leave everything but my tube amp powered up.
I have left my player on for 72+ hours and do hear improvements in sound stage both width and depth, and a little more detail. The CD player runs quite warm to the touch -- Is heat a concern??
My Audio Aero Capitole has been left 'on' 24/7 for over four years with no drop in quality that I can notice. Until I got my Anthem D2 the Capitole served as my main DAC as all other components, including satellite, streaming audio and DVD player. I also used to play lots of CDs.

My cherished Capitole is now 'off' most of the time as my music library is in my computer and I don't play CDs all that often. Still, it does sound great when I do power it up.

Oh, yes the D2 is 'on' 24/7.
I've been leaving mine on for many years. My tubes tend to last years, not months, too. That makes sense to me, since they are relatively low output.
I have left my player on for 72+ hours and do hear improvements in sound stage both width and depth, and a little more detail. The CD player runs quite warm to the touch -- Is heat a concern??

Hchilcoat -- It's hard to say. I'm not sure which Ayon player you have, but if it is the CD3, with 4 x 6H30 and 1 x 6AX5 tubes, and if it does not have a low-power standby mode, its power consumption is well above average for a CDP, and would easily account for the heat you noted. That would be a bit less true of the CD1 and CD2.

I don't have complete specs on those tubes, but it looks like the filaments alone draw around 5 watts for each of the 6H30's, and around 8 watts for the 6AX5. Factoring in plate dissipations, and power for other circuitry, I suspect that the 50W consumption specified in their datasheet is a bit understated.

Whether or not that would pose a reliability problem in the long-term would be dependent on how well the thermal aspects of the design handle the heat. The 25kg (about 55 pound) total weight of the two chassis, and the fact that the unit is split into two chassis, is suggestive of good design in that respect.

But beyond that I would say that your guess is as good as anyone's, unless the manufacturer can offer specific credible advice.

-- Al
THanks, Al. I have the CD-1. The distributor states that the manufacturer recommends turning off with each use.