I have recently purchased a tube amplifier for home stereo listening, and even though I have MUCH experience with guitar tube amplifiers, I wanted to throw something out there for consideration as it relates to breaking in tubes....
I read everywhere about the length of burn-in time required for pre and power tubes, and there seems to be quite a difference between tubes and various manufacturers. Some people state that they have to burn in their tubes for 10 hours before they "settle down" or some other descriptive word or phrase, while others state 100 or more hours being required. This is a real head-scratcher for me because most tubes are essentially using the same materials in their construction. I understand that the mass and surface area of the plates and getters may be different, but I don't think that this would explain the time required to burn in a tube. Sooo....
I have a theory, and I may not be alone in this or even be the first to posit such an idea. I believe that breaking in tubes has more to do with the number of heat cycles the tubes undergo rather than the length of time they are played. The most physical stress that a tube encounters is when it is warming up or cooling down. When a tube is up to temp and doing it's thing, the only thing that is going on is a transfer of electrons. The path that the electrons are taking isn't creating any type of break-in, or is it?
To test this theory, I have a 12AX7 / 12AU7 pre section in my amp. I played music through the amp for many days before the sound "settled in" and I could start to hear that warm rich bass and mid-range. As is common, I wanted an even better silky mid-range and richer bass, so I rolled some new production Mullards into 12AX7 sockets, and nos Brimars into 12AU7 sockets. Instead of going back through 100+ hours of break-in time, I did the following. In addition to my regular listening of 1 to 2 hours per night, I also power cycled my amp with no-load 4 to 6 times per day - - fully heating the tubes each time (approx :15 to :30 minute cycles). I was astonished after 3 or 4 days of doing this (maybe 20 cycles total) at how rich and warm the bass and mid-range became. And, let me tell you that the nos Brimar CV4003's had an over-the-top amount of air in the mid-range when I first heard them and the bass was not very well articulated and controlled, but now they are just WOW!
Literally, within 4 or 5 short listening sessions over the course of a week, plus 15 to 20 power cycles through full heating and cooling, the tubes are producing such a sweet amount of tonality and richness. Here, a month later and 100+ hours of listening, the sound has not changed at all. Maybe it has improved further, but I haven't noticed any other significant changes in sound.
So, what are some additional thoughts on this theory?
I read everywhere about the length of burn-in time required for pre and power tubes, and there seems to be quite a difference between tubes and various manufacturers. Some people state that they have to burn in their tubes for 10 hours before they "settle down" or some other descriptive word or phrase, while others state 100 or more hours being required. This is a real head-scratcher for me because most tubes are essentially using the same materials in their construction. I understand that the mass and surface area of the plates and getters may be different, but I don't think that this would explain the time required to burn in a tube. Sooo....
I have a theory, and I may not be alone in this or even be the first to posit such an idea. I believe that breaking in tubes has more to do with the number of heat cycles the tubes undergo rather than the length of time they are played. The most physical stress that a tube encounters is when it is warming up or cooling down. When a tube is up to temp and doing it's thing, the only thing that is going on is a transfer of electrons. The path that the electrons are taking isn't creating any type of break-in, or is it?
To test this theory, I have a 12AX7 / 12AU7 pre section in my amp. I played music through the amp for many days before the sound "settled in" and I could start to hear that warm rich bass and mid-range. As is common, I wanted an even better silky mid-range and richer bass, so I rolled some new production Mullards into 12AX7 sockets, and nos Brimars into 12AU7 sockets. Instead of going back through 100+ hours of break-in time, I did the following. In addition to my regular listening of 1 to 2 hours per night, I also power cycled my amp with no-load 4 to 6 times per day - - fully heating the tubes each time (approx :15 to :30 minute cycles). I was astonished after 3 or 4 days of doing this (maybe 20 cycles total) at how rich and warm the bass and mid-range became. And, let me tell you that the nos Brimar CV4003's had an over-the-top amount of air in the mid-range when I first heard them and the bass was not very well articulated and controlled, but now they are just WOW!
Literally, within 4 or 5 short listening sessions over the course of a week, plus 15 to 20 power cycles through full heating and cooling, the tubes are producing such a sweet amount of tonality and richness. Here, a month later and 100+ hours of listening, the sound has not changed at all. Maybe it has improved further, but I haven't noticed any other significant changes in sound.
So, what are some additional thoughts on this theory?
Have you considered the possibility that it is you that is breaking in? You are much more malleable than a tube.
Jan
Moved to the Lounge.
The accumulated stress due to the expansion and contraction of the electrodes may affect the life of the valve, but I'm not aware of any mechanism by which 'power cycling' the valves in the way you suggest would influence the sound of the amplifier.
I'm normally a sceptic about these things but don't some valves such as the 6C33 when used in OTL "settle down" their DC conditions after a bit of use?
In line with Jan's theory, I believe I'm far more malleable than any circuit:
I have an open plan house, so I fitted ceiling speakers in a couple of rooms for sound "reinforcement". When new, I was disappointed by the sound, but now I find it quite acceptable. I'm sure it was my malleability rather than a change in sound of the class D amps, or the mass produced ceiling speakers.
In line with Jan's theory, I believe I'm far more malleable than any circuit:
I have an open plan house, so I fitted ceiling speakers in a couple of rooms for sound "reinforcement". When new, I was disappointed by the sound, but now I find it quite acceptable. I'm sure it was my malleability rather than a change in sound of the class D amps, or the mass produced ceiling speakers.
That may well be the case, but jomac's theory is that switching new valves on, then off, six times a day for a period of 15 minutes each time, over 4 days will improve their sound.
The question is, how well does this stand up as a theory and can it be substantiated by experiment?
Unfortunately, the above quote states that there were two independent variables in play at the same time, i.e. operational time and 'power cycling'. In a proper scientific investigation, only one independent variable is varied while the other is held constant. Only in this way can the effect on the dependent variable, in this case sound quality, be judged.
How do you scientifically define "sound quality"? It is totally subjective and for that trying to give rules for "proper scientific investigation" is leading nowhere.
I agree with your sentiment as well. I read Stockwell's fine article on why tubes sound so good to our ears, and he states that it is very difficult to recall sound quality from what we heard just a few seconds ago, so my ears may be tricking me a bit, BUT (to all the snark-sters above) I know beyond any doubt that the bass and mid-range have changed dramatically, and for the better. Albeit unscientific and highly subjective, I am very pleased with the sound. And no, I don't have a lot of $'s tied up in tubes and this stereo amp. [Ask me about my fender guitar amp, and the answer would be much different, but that is outside of this discussion.] The only nos tubes I bought were the 2 Brimar AU7's at $80 each. The rest are current production Russian tubes which can be bought for $20 to $25 a piece. So....anyways.......
Thank you dhaen for your comment. I was just wondering if anyone had ever put forth the idea of power cycling on tubes as a primary contributor to running them in more quickly.
Burn in on tubes is just a silly hi fi pompous nonsense.
What is there in the tube to burn in ?
The cathode slowly burns away over many years unless it is over driven heavily. Once the cathode is gone then its time to bin it.
nigel, i think schiirn has already pointed this out. his point is that the operating point changes. maybe this = burn-in and has a corresponding change in tone?
Exactly! Sound quality is, indeed, entirely subjective and that is what makes a mockery of jomac's 'theory'.
I was aware of this hole my argument and surreptitiously covered it by using the word 'judged' instead of 'quantified'!
The fact remains that there are too many variables in jomac's 'experiment' to make any form of judgement!
P.S. @ jomac - I don't doubt that you perceive differences in sound quality - it is your theory on 'power cycling' of which I am critical. No personal offence intended.
Thanks for an interesting thread.In valve 'burn-in' three things could be happening:
1. the cathode emissive layer is settling down
2. the getter is mopping up remaining gas
3. the listener is getting used to a slightly different sound
Of course, good circuit design minimises all of them.
I would not expect power cycling to be a factor.
1. the cathode emissive layer is settling down
2. the getter is mopping up remaining gas
3. the listener is getting used to a slightly different sound
Of course, good circuit design minimises all of them.
I would not expect power cycling to be a factor.
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