Amplifier Burn In

[SKR]

Hi,
was just going thru this thread and was surprised to see members discussing and countering claims about audio system burn-in process.
It is beyond doubt an established fact that all audio components and also electrical power cords,wall receptacles, interconnect,catridges, speaker cables,audio tubes, pre and power amplifier etc. etc. need burn-in period which varies for each item.
I am not a technical person so cannot give big descriptions about properties of capacitors, resistors, circuit boards, transformers etc. and that even though their values does not change still there is improvement in sound quality after burn-in.
I am just a music lover and a keen listner for over 30 years and have bought and burnt many systems that i bought in last 30 or more years. In fact a lot of my listening time has gone for burning new systems and cables etc.
I live in Bangkok and here many customers after buying an equipment leave it with seller for 2 to 4 weeks for burn-in.
I EVEN BOUGHT A CABLE BURNER FROM HAWAII ABOUT 5 YEARS BACK TO SAVE ME FROM ACTUAL BURNING TIME ON MY SYSTEM.
Companies like NORDOST and many other are making cable burning equipment for this reason.
And the difference is not subtle after full burn-in, rather there is a huge difference.
One member in the thread correctly cited example of wine tasting. If I am asked to taste a Rs.500 wine and Rs.3000 wine I will most likely not be able to make a correct judgement. Similarly if some one says there is no burn-in differences than he is not being able to differentiate and may not be a very keen listner.( sorry please do not take personally any member )
I again REPEAT the differences are huge and most of us should be able to notice.
Those who know me and have been to my place can vouch for my listening abilities. Moreover in audio world this is an established fact in case you regularly read some of the Hi-end audio magazines.
Still if you have any doubts you can shoot a question to Mr.Robert Harley on AV GUIDE web site by going to FORUM and raising this question and let us see what Mr.Harley has to say. This is a web site of The Absolute Sound Magazine and reviewers inclluding Mr.Harley personally answer the questions of members of audio community.
Or can write to any DESIGNER of high end audio system and take his views on this subject. Some high end auidio capacitors (not electrolytic) like Paper oil or Silver-oil take about 200 hours to give optimum performance. My ANTI CABLES (from USA) interconnects took a very long time to burn in.

WHY IT HAPPENS I DO NOT KNOW. Can take comments of other audiophiles on various audio forums if anybody wants.
So let us not be rigid and should be willing to accept established facts and views of others.
However there always can be a case where some equipment does not need huge burn-in and in some case manufacturer also does partial burn-in of say 2 days or 4 days or in some case may be a week. But these are generally expensive gears.
I just bought a McIntosh 6900 Integrated amplifier about 6 weeks back and talked to their Technical support for a Firmware upgrade to solve a volume control problem. when i asked him about burn-in time he said they run all amplifiers in their factory for 24 hours before final packing. And he told me that with normal usage I will need over a month to get optimum performance.

If any body has doubt in my statement he can call Mcintosh Technical support and check himself. New York USA Tel.No. 00-1-607-723-3512 or 00-1-607-7231545. ISD calls to USA are very cheap now or use e'phone. Voip.

I hope I am not misunderstood by the members who do not agree with me.
Thanks
SKR

 

[SKR]

After posting my last message I re-read the message dated 4th July of Cranky
and fully agree with him. He seems to be technically and musically very experienced.
He has explained so very well and his example of wine tasting is so very appropriate.
Also he is correct when he says there are so many ways to design a 30 watt at 8 ohms amplifier and each designer will have reason to support his way of designing. Also a technically well designed and well measured design on test bench may not sound so good compared to poorly measured tube or solidstate amp.
So measurement is not everything. Generally good designers are very good LISTENERS themselves.
Thanks
SKR

 

[venkatcr]

SKR, at the outset, as I said I do not want to get into any arguments. At the same time, my entire article is based on simple physics and after discussing with a number of amplifier designers. I have not mentioned anything new. All I have written are based on amplifier designs that have been around for years.

You will also be surprised to learn that Robert Harley is right now in the middle of a huge controversy (for want of a better word) where he has called blind listening tests as flawed (Blind Listening Tests are Flawed: An Editorial | AVguide). All I want to say is that amplification is nothing magical but simple physics that can be measured. Even distortion that your ears cannot even discern can be measured and removed. If something is happening beyond these measurements, it is most probably in your ears and not in the system.

Frankly, the only thing that will make me change my mind is if someone scientifically explains to me how a certain usage would make a positive difference that can be measured and repeated. The very essence of science is to create an environment that can be repeated n number of times with the same result.

Cranky has mentioned about the power unit and its parts. And, this is incorporated in my conclusions. But changes in the amplifier circuit? As I have explained, any change in the specifications could only have a adverse effect, not a positive one. I would be happy to be proved wrong.

Cheers

 

[jaudere]

what an exhaustive discussion guys!

Please tell me something

I was missing bass on my open baffle speakers initially. Now after one month, I am not missing it at all. in fact i have stopped using a sub amp for music. Why has this happened?

1)The bass drivers adequately burnt in

2)my ear -drums burnt in( got used to the lower bass).

I think it is my ear drum. I admit that due to my location, i have poor exposure to good systems but when i listen to the CD players in the CD shop, i have started hating the loud bass.

another phenomenon i have observed. when i am listen to music for long hours, i come down on volume a lot gradually. If i start with -40dB, at the end of 2 hours , I am usually down to-55dB. does the volume actually increase after warm up or is it ear fatigue or do my concentration abilities improve over time so that i can pick up minute details even at lower volumes ? These long hours usually start after 12 midnight so no chance of background noise playing any part.

One more thing, I listened to a Denon 1908 with Jamo initially 4 months back and then 1 month back. I was very impressed on the first listening. that was my first exposure to hi fi system. second time, when i listened to it, i did not like it that much. in fact it was burnt in for 4 months(god knows how many hours). Here initially I was comparing Denon to Artis s6600R and second time with Ymaha RXV 361+ home made open baffles. So when i was listening to it at different times, my brain was comparing it to the system which i was listening to regularly at that time. probably this factor is also important.

Lastly, Squarewave has said that he compared same company amp, one burnt in and the other brand new and he found a lot of difference. I just can't argue against the side by side comparison. (i hope that was a blinded trial. in medicine, we hardly give any importance to a clinical trial if it is not double blinded. ). but again 2 different machines, like 2 different individuals do behave differently. that is my personal experience.

So i dont know which part of the argument to favour . what i think is that man as well as machine changes over a period, sometimes for good, sometimes for bad.

 

[Asit]

Hi Venkat,

I have sort of read your report and have tried to understand your line of thought. Thanks a lot for explaining in somewhat detail some of the basic facts of amplifiers, and it is very informative for members like me. I do not want to comment more on the part where you are trying to explain the amplifiers, because I have no expertise in that area. Let other knowledgeable members comment on that part if they want to.

However, I have genuine questions on the other parts (like the conclusions and also the beginning part), and I will not mince my words.

Please note that I shall have nothing to say about your non-observation of an amp break-in. That is your own real experience and I respect that whole-heartedly. I would not relate that to your inability to hear the difference before and after a speculated break-in. Rather, I would like your comments based more on real experiences than anything else. In addition, hearing is a very subjective thing. I may not be able to hear a few things you are able to hear very easily, and vice versa. Believe me, even here I have some solid proof (e.g., once my student was complaining to me about a very shrill sound he was hearing when he booted his laptop. We tried several boots and I was not able to hear anything while many others heard that sound).

Your main argument is based on the following: amplifier performance is in some sense like a ball sitting on the tip of a mountain, and a certain set of parameters are fine tuned for it to be in that position. When one or more of these parameters achieve values other than the desired critical region, the amplifier performance would fall off the tip; for one, the distortions would increase. Based on the above behavior (which I would call unstable criticality), your argument is that if the amps really have to break in and thereby change the values of the parameters from their critical values, its performance would actually suffer rather than improve, in general.

At this point, I have a set of questions and comments:

1) Are you certain that the known number of parameters that are believed to determine the performance of an amp provide a complete set (by a complete set, I mean those independent parameters that would completely specify an amp)? Does such a set exist? We discussed this issue in somewhat depth in my amp thread. My view is that we do not definitely have a complete set. If we did, we did not have to go and hear an amp for its performance, however subjective that may be, people would just take a look at the specs and based on that buy. Nobody buys an amp strictly based only on its specs (specs give the parameter values under certain test conditions). If we had to buy electrons, we did not have to go and inspect them in person, because we know each electron at rest is described by a finite number of quantum numbers (parameters) like its mass, its charge etc and they completely describe the electrons at rest. The amplifier performance is different and we most certainly do not have a complete set of parameters that will fully determine the quality of an amp (yes, they give you a view, but not the complete view).

Now, given the above incompleteness in performance-description of an amp, how can you stick to your view that a break-in, if it has to happen, will certainly deteriorate the performance because of the tip-of-the-mountain scenario? The tip may only be an apparent tip because certain relevant (not yet defined and measured) parameter dimensions are missing (for sure, as I have explained above) and along that yet-unexplored dimension, it's not a fall from the tip, rather a plateau or even a further rise.

2) You seemed to have allowed the possibility of warm-ups (not break-ins). May be I have not read your report carefully enough, and forgive me if your report already explains it (I think not), but then why is a warm-up required at all? Does it not change the sacred parameters that you are basing your whole argument on?

3) Let's assume that the amps are made to specifications that are to be achieved only after a warm-up (I think this is correct). If we accept that, what is in principle stopping us from accepting that amps can also be designed keeping in the break-in in mind? In other words, why cannot the desired specifications be achieved after the break-in rather than before the break-in. Sure things can be designed that way if the characteristics of the break-in is well investigated and therefore known.

Science is not just a profession, neither it is reachable by "academic" endeavors. It is actually a way of living, an attitude towards life which gives one insights, not just an assembly of a number of measurements. Everybody knows that acceleration of a particle is proportional to the force on it, and the proportionality constant is an intrinsic property of the particle, called mass. Everybody also knows that the gravitational force on a particle is also proportional to an intrinsic property of the particle, also called mass. Now how does one know these two masses are the same? They are, and that takes deep insight. That's what basic science (especially physics) is about.

The reason I am bringing this up is that my asking for a scientific answer has apparently upset you and you have made several references to that query of mine and to scientific reasoning. I would request you to go back to the part of your post (# 10) that I have quoted in my post (#17). Firstly, is that only a speculation or does it have a scientific basis? That was my query. Was that an unjustified query? Secondly, even though you mentioned "warm up" there, you were effectively talking about a burn in, I suppose, because a burn-in is a one-time affair and warm-up takes place each time the amp is switched on. Why would a factory warm-up be necessary for each manufactured amp unless they are going to make adjustments for each amp differently, which they don't. The couple of hours you speculated there then must point to a burn-in. My next question (which I already asked in some detail in post #17), if there can be a 2 hour break in, there can also be a 20 hour or a 200 hour break in, it's just a question of scale. We are not investigating how long or how short is a break in, we are actually asking if there is a break-in at all.

No matter how simple you try to make the science of amps, it's not that simple. Even if each sound consisted of a single frequency, amplification is necessarily a non-linear process creating distortions. What makes it almost unfairly difficult is that each sound is actually a wave packet, comprising of many frequencies (you must be aware that even a tuning fork does not strictly produce a single frequency) and that just does not make the amplification part notoriously difficult, it even makes the passive passages of this sound actually quite nontrivial. Most materials respond in general to an electromagnetic field non-linearly (only a linear response of the material to an electric field produces the Ohm's law that is mentioned in your long report) and this non-linearity is further dependent on frequency.

As promised in the beginning, I have not minced my word. My intention is not to disrespect you personally and I think you know that already through my posts and also through whatever personal interactions we have had so far. Also, I respect whatever your observations have been on the amps you owned/borrowd/made. I pay a lot of importance in actual observation in engineering science which the subject of amp falls in, rather than on discussion on theory (although it is very relevant if we know its boundaries) because the theory is not complete or sufficient (as I have tried to explain).

As I have also said a few times on this forum, I have no shame to be corrected because I know much much less than I know.

If we cannot come to an agreement, let us discuss more when I come to Chennai this September.

Regards.

 

[reju]

I only believe in speaker burn ins. Cable/ amp/ player burn-ins don't seem to be logical.

Yes, the speaker cones need to break free to perform optimally, since it's mechanical movement has a direct effect on sound. So burn-in in this case makes sense.

Ears can play games with you. If they are functioning well, you just need to keep them clean. It does make a difference in sound quality after you clean your ears. hyeah:

 

[marsilians]

It is beyond doubt an established fact that all audio components and also electrical power cords,wall receptacles, interconnect,catridges, speaker cables,audio tubes, pre and power amplifier etc. etc. need burn-in period which varies for each item.
I am not a technical person so cannot give big descriptions about properties of capacitors, resistors, circuit boards, transformers etc. and that even though their values does not change still there is improvement in sound quality after burn-in.

SKR, I am OK if you state something very emphatically but then fall well short of providing facts or basis behind it. I am not at the point of "beyond doubt" re: the burnin for recepticles, power chords, etc.

Then you make it worse by saying you are not techical and later on state that the "values" do not change. What value? What changes?

C'mon be ready to assert you position moving forward.

 

[SKR]

Hi Vencatcr,
On the subject of blind testing most of the reviewers do not support it, I think because of the fear that they might be proved wrong. In my view if a reviewer already knows that it is a big brand he or she may already be biased a little bit. After all we know that all these magazines and web site are commercial entities and need to support their advertisers.

I support blind testing and one has to use his ears(not eyes) to evaluate musicality of a system. There has been a lot of discussion on this issue and many audiophliles writing strongly in favour of blind testing but audio reviewers have always opposed it.

I appreciate your argument that you need to be technically convinced for the changes after burn-in. But i think that every thing cannot be explained technically with scientific data's. Listening is a very Subjective thing.
Even from the same system I listen different sound quality at different times which i cannot explain to myself. This could be due to changes in quality of power supply in your home which is not consistent or could be due to use of other equipments on the same line in your house or neighbours house on the same line from the power grid like computers, televisions etc. etc which pollute good power supply.
I think it is difficult to prove this burn-in process technically. Only forum members who have bought new equipments and have observed their equipments performance improving over days or weeks can confirm this and form a consensus to convince about this phenomenon.
When we read a review many times reviewer will write in the start of review that he left the equipment running for say 2 weeks running a FM radio channel
or a CD on repeat mode to burn in the equipment.
I have a BURN IN CD of XLO and another from AYRE (IRRATIONAL BUT EFFICACIOUS). I think every audiophile must have this cd which is a good burn-in tool and ALSO VERY GOOD FOR DEMAGNETISING YOUR SYSTEM.
After continuos use of audio system for weeks we need to demagnetise it and track 7 of this CD does that and you can hear the difference yourself.

THIS CD WAS MADE BY AYRE WITH THE CONTRIBUTIONS FROM GEORGE CARDAS and it says i quote:-
"This disc is designed to enhance the enjoyment of listening to your audio system. The main tool is track seven, a five minute glide tone that when played through your system at a moderately low listening volume will will improve its sound. WHILE WE DO NOT HAVE CONCLUSIVE PROOF OF THE MECHANISM INVOLVED, WE SUSPECT IT FUNCTIONS BY DEMAGNETIZING RESIDUAL FIELDS THAT BUILT UP IN YOUR COMPONENT OVER TIME. WE RECOMMEND PLAYING THIS TRACK ON A PERIODIC BASIS FROM ONCE A WEEK TO ONCE A MONTH. THE OTHER TRACKS HAVE MORE SPECIALIZED FUNCTION.

You can see that even authrities like Ayre owner and George Cardas say that THEY DO NOT HAVE CONCLUSIVE PROOF OF THE MECANISM INVOLVED.
which means that every phenomenon cannot be explained technically.

I will recommend audiophile members to have this CD and use it at regular intervals. Track 7 is for demagnetising and track 4 is for BURNING-IN your system by putting this track on Repeat.
Thanks and regards
SKR

 

[Asit]

I only believe in speaker burn ins. Cable/ amp/ player burn-ins don't seem to be logical.

I will not interfere with your beliefs, because that's personal, but that may be more appropriate in other forums. But when you talk of logic, I would like to know what that is.

People who claim to be custodians of this forum should not discuss beliefs and let us not degrade this forum into a gossip forum like many others.

I also know there is a temptation to take to popular views. For whatever it is worth, I would stay away from it if I do not find a logic for it to take that line.

Regards.

 

[murali_n]

Hai All,

I feel there are lot more parameters that determine the performance of a Audio system.
1. Temperature at which it is played, since temp affects the Resistance of the IC Wires and Speaker voice coil, and speaker cables.
2. Humidity which may affect the Speaker cone movement,
3. Static pressure of the room being played which may impair the cone movement.
4. Room Acoustics may vary based on Furniture placement, drapes etc.

So one does not get to hear the same SQ at all times, there will be subtle difference , it need a very well trained ears and lots of patience to make out.

Thanks,

N.Murali.

 

[reju]

I will not interfere with your beliefs, because that's personal, but that may be more appropriate in other forums. But when you talk of logic, I would like to know what that is.

People who claim to be custodians of this forum should not discuss beliefs and let us not degrade this forum into a gossip forum like many others.

I also know there is a temptation to take to popular views. For whatever it is worth, I would stay away from it if I do not find a logic for it to take that line.

Regards.

If I put forward my opinions how will I degrade this forum? And when you say that, who are you trying to be? An established "custodian"??

Come on Asit, don't target me if you are NOT able to chip in anything concrete.

Just keep the ears clean. I know it's "personal". hyeah:

 

[SKR]

SKR, I am OK if you state something very emphatically but then fall well short of providing facts or basis behind it. I am not at the point of "beyond doubt" re: the burnin for recepticles, power chords, etc.

Then you make it worse by saying you are not techical and later on state that the "values" do not change. What value? What changes?

C'mon be ready to assert you position moving forward.

Hi Marcilians,
When i said values does not change i was quoting other members who are engineers and have written about this. I also agree that a 6.8uF capacitor will not become 7.5uf after burning in.
Every one who drive a car need not be automobile engineer. Even an uneducated car driver knows many things about car. It does not mean he is a technically competent automobile person.
come on let us not try to find out mistakes in each other on such trivial things.
I also said i am a listener for over 30 years in the same post. So naturally i know little bit. I can upgrade my own capacitors and do sholdering and change wires and parts. Make my own interconnects .This does not make me audio technician or electrical engineer.
Warm regards
SKR

 

[Asit]

If I put forward my opinions how will I degrade this forum? And when you say that, who are you trying to be? An established "custodian"??

Come on Asit, don't target me if you are NOT able to chip in anything concrete.

Just keep the ears clean. I know it's "personal". hyeah:

Yes, you have every right to express your opinion. But these opinions better be backed up by your own observed experience and/or logic. Beliefs do not count here, because it may mislead many others. In addition, I also wanted to know your logic because you mentioned something is "not logical". You did not provide it then, and you have not provided it now.

I have not targeted you. Please go and read my other posts in this forum, and you would not find any evidence thereof. On the other hand, I would think being targeted here. I can also document it (I think you know what I am talking about).

Like it or not, can you show me anything in my long post in this thread which is not concrete (I do not know what exactly you mean by concrete, I would interpret that as something with reason, evidence or argument)?

Whatever I am saying, I am saying from the standpoint of the following: I think a contribution is made when one shares one's experience, or when one discusses or asks questions based on some objective thinking (as much as without bias). Please do not get me wrong here, and I am sorry if I came on too strong in my last response, but I would like you to contribute in the way I described above (that's only my wish, I am surely not the custodian, please act according to your own wish). There is a serious discussion going on and please contribute to that. It will enrich us all, including you and me.

Regards.

 

[SKR]

Hi Marsillian,
Just try a good wall receptor and see what difference it makes to sound. And also observe the sound improving after a week or two. Same with power cords. I know it sounds funny to those who have not tried. About 7 to 8 years back like you i never accepted this fact that power cord and receptors could change the sound and needed burning-in time.
What i write is from experience and will request you to please try out for yourself. But when you use a good wall receptor you must use good power cords also otherwise the cords will negate the improvements from the wall receptors if poor quality power cords are used.
Regards
SKR

 

[reju]

Yes, you have every right to express your opinion. But these opinions better be backed up by your own observed experience and/or logic. Beliefs do not count here, because it may mislead many others. In addition, I also wanted to know your logic because you mentioned something is "not logical". You did not provide it then, and you have not provided it now.

I had already mentioned my logic in the initial post.

"Yes, the speaker cones need to break free to perform optimally, since it's mechanical movement has a direct effect on sound. So burn-in in this case makes sense".

I think a contribution is made when one shares one's experience.

I get my beliefs from my experience. If you didn't like word "belief", please don't crucify me for that!

 

[psychotropic]

this thread is great. Privilege to read it. Venkat, thanks for that detailed explanation on how amps work, I am sure many people would find that useful. Asit, I have no knowledge of physics, but I could still grasp your post I think in entirety, and I find it convincing. Personal experiences unfortunately I don't have much, but this sure is fun!

 

[Asit]

Hi Venkat,

(sorry mods for a little out thread talk) I picked up a Nakamichi RX-505 cassette deck yesterday from a used stuff shop. I know how much you care about a Naka deck, that's why I am mentioning it here, later on if I can keep it, I shall a start a thread on it. The sound is sublime, very fullsome and extremely extremely musical. I can listen to it the whole day. But I do not know if I can keep it, because last night it had some problems. This morning apparently the problems are all gone. The shopkeeper said it may have some teething problems initially, because it was not played in a while. Let's just pray I can keep it. And on a lighter side, these teething problems have nothing to do with a break-in of the deck.

Hi Reju,

Yes, I have seen your logic on speaker burn in. Although I am no expert, I think I can agree with you there. But I do not think you can apply the same logic in the case of "cable/ amp/players". Just because these are mostly electronic equipments, it is not automatic that they would not have a break in. If it is automatic, Venkat would not have to dig so deep into his resources to look for and understand the reasons for a negative conclusion on the amp burn-in. Irrespective of whether he is right or wrong, or even partially right or partially wrong, we all got to read his report on the amplifier functioning in relatively simple terms. That is a solid contribution to the cause of this forum. It's not important if I am right or wrong, as I long as I am trying to understand and that's all I am trying to do. If you can put forward evidence/logic against my reasoning, I shall be the first person to appreciate that and would be forever grateful.

Hi Psychotropic,

Thanks for the kind words. I hope I am correct, but that's not as important as finding the facts.

Regards.

 

[venkatcr]

I was wondering whether to submit a reply or not, and opened this dialog while I wondered what to say.

At the outset, I'd like to state that there's no right or wrong, or rather, right and wrong are relative. The world around us is a reality which we try to explain through language, science and theory. The truth is, that we know very little about the way human hearing works but I can tell you that different people hear things very differently.

Therefore, we're treading on very thin ground when we make blanket statements.

Having said that, I appreciate the effort that you've gone through to put all of this together. It is an example to be followed and emulated for sure

First of all, thanks a lot. Yes that post did take a lot of effort. If nothing, it was an education to me (and hopefully to all readers) on how an amp works.

I have clearly mentioned that 'I' am skeptical about amplifier burn in. The human mind is very frail as we are controlled by emotions, My father has always brought me up to only believe in things that I can make sense of in some logical way.

One, that we are dealing with real-world components. Semiconductors drift, capacitors age, and resistors change with time and temperature, and even with the amount of current passing through them. If you can accept the reality of this simple real-world phenomenon, which causes electronics to age (and this is real) why is it so difficult to believe that someone may actually be able to 'hear' these changes?

Very simple actually, and we are discussing three issues here. One; the drift in specifications are known factors that the designer has in his hand, And he designs his circuits within these known limits. Two; I have clearly agreed that electronics do age. My point is that when electronics start working beyond their specified limits, it is more a failure than an improvement. Three; I have agreed that someone can certainly 'hear' some changes. My question is are these changes because of an 'improved' (and non-measurable) performance of the amplifier or your ear getting used to the sound.

Secondly, amplification is simple physics, but only in theory. In reality, implementing an amplifier requires dependence on supply chain and material consistency well beyond the reasonable control of a manufacturer. If it were simple physics, I could swap in practically any device into a circuit and it would sound the same. Depending on the design of the amplifier, a small change in a component somewhere could alter the sonic performance. If you agree with that, and if you agree that components change with time, well, it is possible for components to alter the sonic experience over time, even in a new amplifier.

Sure a change in component WILL alter the sound of the amplifier. And I have already agreed that time will alter the performance of an amplifier. But what I find a little difficult to understand is that a small amount of time (compared to the life of the amp) will 'improve' the sound. Will the designer not have tried for an improvement himself? As I said, a good designer will test his amp to near destruction, and will always find a point of optimal performance. That some uncontrolled factor will further improve the performance is what I find difficult to digest. If designers and manufacturers are so sure of burn-in, should they not burn-in all their products before delivery?

Do look John Atkinson's measurement methods for amplifiers in Stereophile. Note that he preconditions the amplifiers for half an hour at one-third power. If every amp was perfect out of the box, ready to roll, why is this even necessary? Is he crazy? Why is it important to do this? Why would an amp change over the half hour? What would change? Would every amp change? Would every amp not change? Why? Why not?

And I now quote from the Nelson Pass F5 owner's manual:

Quote:
The amplifier requires about 1 hour of operation to reach normal operating temperature, and this warm-up time is appropriate for the most critical listening, but is not otherwise an issue. The amplifiers final adjustments were made after a 2 hours, and the performance difference between that and cold operation is significant.

Why would Nelson Pass design an amp that sounded better after one hour? Would it not be possible to have something that sounded exactly the same through the entire time it was switched on? It's easy to defend this using the term 'warm-up'. Semantics. I switch on amplifier. X sound comes out. After 'n' hours, Y sound comes out. Is X = Y? Is Y = X(func n)? John and Mr. Pass believe it is not a given. It may be, or it may not be.

Let us not get confused between warm-up and burn-in. What is being discussed above by both John Atkinson and Nelson Pass is warm up, I have clearly explained why and how heat (due to warm up) will change the amp's performance. Actually many amps have an optimal performing temperature, or what Nelson Pass calls normal operating temperature. There is no contention here at all.

Will this make me try and convince you? Of course not, you should believe that burn-in makes no difference. Because that's the truth! And SKR, you should believe that burn-in makes a world of difference. Because that's the truth, too!

At the beginning of my post I have said I (also) don't want to get into any argument, All I wanted to do was to explain to people why 'I' am so skeptical about amplifier burn-in.

1) Are you certain that the known number of parameters that are believed to determine the performance of an amp provide a complete set (by a complete set, I mean those independent parameters that would completely specify an amp)? Does such a set exist? We discussed this issue in somewhat depth in my amp thread. My view is that we do not definitely have a complete set. If we did, we did not have to go and hear an amp for its performance, however subjective that may be, people would just take a look at the specs and based on that buy. Nobody buys an amp strictly based only on its specs (specs give the parameter values under certain test conditions). If we had to buy electrons, we did not have to go and inspect them in person, because we know each electron at rest is described by a finite number of quantum numbers (parameters) like its mass, its charge etc and they completely describe the electrons at rest. The amplifier performance is different and we most certainly do not have a complete set of parameters that will fully determine the quality of an amp (yes, they give you a view, but not the complete view).

Now, given the above incompleteness in performance-description of an amp, how can you stick to your view that a break-in, if it has to happen, will certainly deteriorate the performance because of the tip-of-the-mountain scenario? The tip may only be an apparent tip because certain relevant (not yet defined and measured) parameter dimensions are missing (for sure, as I have explained above) and along that yet-unexplored dimension, it's not a fall from the tip, rather a plateau or even a further rise.

An amplifier design is based on a finite number electrical parameters known to the designer given our current knowledge of the laws of physics and mathematics. Frequencies, sound level, and sine waves are all measurebale. It is easy to take an input sound wave and measure it against the output sound wave with lots more accuracy than what our ears can perceive, If this were not so, every amplifier would be an act of randomness every time you switch it on. If you look at an amplifier, the manufacturer will provide a set of specifications (wattage, THD, etc.) which the amplifier will meet. But whether you will like the amplifier's sound or not is a different matter. There is no denying that a decent amp will meet it's specifications under test conditions.

The unknown factor is the designer's 'ear'. He tunes the design to what he thinks is musical. And that is why no two amplifiers sound the same as they have been tuned differently.

2) You seemed to have allowed the possibility of warm-ups (not break-ins). May be I have not read your report carefully enough, and forgive me if your report already explains it (I think not), but then why is a warm-up required at all? Does it not change the sacred parameters that you are basing your whole argument on?

I have explained this in detail. Since an amp passes a large amount of current on a continuous basis, all parts will heat up. When this happens, the behaviour of the internal parts will change in a measurable manner. With heat, for example, resistance will go down and more current will flow. All the electronics parts have a temperature range within which they operate to meet their specifications.

3) Let's assume that the amps are made to specifications that are to be achieved only after a warm-up (I think this is correct). If we accept that, what is in principle stopping us from accepting that amps can also be designed keeping in the break-in in mind? In other words, why cannot the desired specifications be achieved after the break-in rather than before the break-in. Sure things can be designed that way if the characteristics of the break-in is well investigated and therefore known.

As I said in my post above each part has a MTBF. This is the period of time within which, given that their operating temperatures are taken into consideration, they will deliver consistent results. Please pay attention to what the manufacturer says - 'Mean Time Between Failures'. Beyond this time period, the part is only expected to fail. And I have also mentioned that a good designer will run a prototype for the 'burn-in' period to ensure that the results are consistent.

The reason I am bringing this up is that my asking for a scientific answer has apparently upset you and you have made several references to that query of mine and to scientific reasoning. I would request you to go back to the part of your post (# 10) that I have quoted in my post (#17). Firstly, is that only a speculation or does it have a scientific basis? That was my query. Was that an unjustified query? Secondly, even though you mentioned "warm up" there, you were effectively talking about a burn in, I suppose, because a burn-in is a one-time affair and warm-up takes place each time the amp is switched on. Why would a factory warm-up be necessary for each manufactured amp unless they are going to make adjustments for each amp differently, which they don't. The couple of hours you speculated there then must point to a burn-in. My next question (which I already asked in some detail in post #17), if there can be a 2 hour break in, there can also be a 20 hour or a 200 hour break in, it's just a question of scale. We are not investigating how long or how short is a break in, we are actually asking if there is a break-in at all.

I am too old to get upset or excited. You wanted an explanation for the difference between 2 hours and 200 hours, and I found that reasonable. That is the reason I took the effort to explain the difference in detail. When a warm-up happens there is a physical change in many items - metal expands, water evaporates. Once a operating temperature is reached, that object is expected to deliver consistent result afterwards. That is the reason why every amp will be warmed up and put to some finite tests before being packed. If any of those tests fail, that particular amp should be rejected. This also considers the vagaries of manufacture that every single manufactured piece may not be accurate and meet their specifications. This is more a failure of an individual item and not of the design or specifications.

No matter how simple you try to make the science of amps, it's not that simple. Even if each sound consisted of a single frequency, amplification is necessarily a non-linear process creating distortions. What makes it almost unfairly difficult is that each sound is actually a wave packet, comprising of many frequencies (you must be aware that even a tuning fork does not strictly produce a single frequency) and that just does not make the amplification part notoriously difficult, it even makes the passive passages of this sound actually quite nontrivial. Most materials respond in general to an electromagnetic field non-linearly (only a linear response of the material to an electric field produces the Ohm's law that is mentioned in your long report) and this non-linearity is further dependent on frequency.

Strangely Asit, this only solidifies my belief. You have said exactly what I have said - that an amplifier is an unstable device. And to believe that every amp will somehow start performing better after 100 odd hours of use is something I find very difficult to believe.

As promised in the beginning, I have not minced my word. My intention is not to disrespect you personally and I think you know that already through my posts and also through whatever personal interactions we have had so far. Also, I respect whatever your observations have been on the amps you owned/borrowd/made. I pay a lot of importance in actual observation in engineering science which the subject of amp falls in, rather than on discussion on theory (although it is very relevant if we know its boundaries) because the theory is not complete or sufficient (as I have tried to explain).

Have no fear, Asit. Our discussions (including those of Cranky) have been very cordial. I have deep respect for your knowledge and capabalities. And this goes for you also Cranky.

Cheers

 

[jaudere]

How do you guys get so much of time to write so lengthy posts ? of course i must appreciate all the efforts taken by all the members. i won't be able to write that much even if i get all the time in the world.(i accept the fact that i am novice and don't have much to write,so my posts are short).

anyway. i would rather spend all that time for listening to music. are we missing it in the heat of discussion?

 

[SKR]

How do you guys get so much of time to write so lengthy posts ? of course i must appreciate all the efforts taken by all the members. i won't be able to write that much even if i get all the time in the world.(i accept the fact that i am novice and don't have much to write,so my posts are short).

anyway. i would rather spend all that time for listening to music. are we missing it in the heat of discussion?

Joudere i think you are the wise man out there. I am taking your advice and just going to switch on my system and listen to some music. It is 20.15PM here in Bangkok and right time to start listening.
It is good to have technical discussions but here I think we are discussing a issue which is a well established fact. Anyway no harm in exchanging views. But one must not be rigid and must be prepared to accept other's view if substantiated honestly.