Physical explanation of amp's break in?

Recently purchased Moon i-5, manual mention 6-week break in period, when bass will first get weaker, and after 2-3 weeks start to normalize. Just curious, is there ANY component in the amp's circuitry that known to cause such a behaviour?

I can't fully accept psycho-acoustical explanation for break-in: many people have more then one system, so while one of them is in a "break-in" process, the second doesn't change, and can serve as a reference. Thus, one's perception cannot adapt (i.e. change!) to the new system while remain unchanged to the old one. In other words, if your psycho-acoustical model adapts to the breaking-in new component in the system A, you should notice some change in sound of your reference system B. If 'B' still sounds the same, 'A' indeed changed...
Well, I guess sean has checked out, but just as I do not discount knowledge derived from practical experience, he should not discount what's learned in college. As he says,there are no degrees granted in "common sense, problem solving, application of knowledge" but there are most certainly courses in such subjects. Indeed, many specific facts learned in school become obsolete by the time one gets a job, and the real benefit of school is that it teaches you how to learn, which you should continue to do all your life. Also, having a degree does not prevent you from doing all the things that sean does to gain knowledge.

I mentioned Taguchi design philosophy previously: very quickly here is the jist of it.

You build a circuit (or anything else, like a camera lens system) and test it.
You find that some component, say R235, critically affects performance.
It's been suggested that the circuit designer should now begin to tweek R235, and other parts of the circuit to optimize performance.
WRONG! says Taguchi. Send the circuit designer back to the drawing board to modify the design so that R235 does not need to be tweeked.

The purpose of inspection and test of samples of a product as it comes off the production line is it make sure that the design and the production process are producing satisfactory results. If a problem is found, you don't fix the unit before shipping. (That was the old idea of quality control). You junk it, and fix the design or production process.
Until i can get people to stop putting words in my mouth, I'll never be able to get out of this thread : )

Let's clear things up here. I never said that i discounted a College ( or any other type of formal ) education. I have a great amount of respect for the majority of "educated professionals". Anybody that thinks differently has never read any of my posts where i've lauded praise on various designers / engineers / manufacturers or commented on specific products in a positive manner. It was Paulwp that ( effectively ) said that he discounted any form of knowledge outside of College that one doesn't obtain a degree for. His words were that if one doesn't have a degree, one doesn't know what they are talking about. I can't think of a more pompous comment ever being made here on these or any other audio / electronic based forum.

I also never stated that units that have "shifted value" or "broken in" would not meet spec before or after "shifting" or "settling in". Most specs are written in a manner that makes the unit look good on paper yet allows enough variance in production to let "less than optimum" performing units still get by quality control. Those companies that set tolerances phenomenally tight undoubtedly have a far higher amount of unacceptably products. Since the rejection rate goes up, the profit margin goes down.

Since most companies are more worried about the bottom line ( profitability ) rather than the ultimate quality of their products, specs and production techniques become a juggling act in terms of what can be made to pass without having a high quantity of rejects and monetary losses. The end result is that specs are typically "slightly loose" so as to let the majority of products manufactured fly out the door yet "tight enough" to maintain respectability by professionals in that specific field by weeding out the "lemons". As a side note, most of those "lemons" end up getting sold as "factory refurbished" units because most manufacturers don't want ANY loss in profitability. That is, if they can help it.

By the way, anybody that thinks that only tubes begin to deteriorate once they are fired up has very limited understanding of electronics and how / why parts and circuitry fail.

As to El's comments, how many manufacturers follow "Taguchi's rule of mass production and quality control" ? Just because he is aware of these guidelines does not mean that every manufacturer follows them or is even aware of them. Should anyone doubt this, please see the example sited above regarding specifications and factory refurbs. Sean
LOL. I said? My words? Hardly. You said in your first post above, Sean, that "anybody that tells you that components don't break in or 'settle' is either UNEDUCATED [emphasis added] about the subject at hand and throwing out a guess at your expense (IF you believe them ) or knows better and is blatantly lying to you." I ask again, was it unreasonable to ask you about your education with reference to your claiming to know what you're talking about? Not the question of burn-in, but of your claiming to know what you're talking about.

On the subject of burn in, I later said: "Personally, I wouldn't care if someone never got past grade school if he could reference test measurements or a controlled study to support his argument."

Now, absent any measurments or studies, I'll trust my own experience, my own ears. It does happen that I know an ee or two with experience designing and marketing amplifiers who tell me that I don't hear a burn-in effect because there isn't one, but in the end, it's my ears that count. Yours too.

What I take exception to is your statement quoted above. You are saying that, for one example, the designer of some pretty nice equipment is either "uneducated" (that isn't true, he has an ee degree), "throwing out a guess," (nope, wrong there, he has done controlled studies) or "is blatantly lying" (shame on you for saying something like that).

You never said if you were familiar with the Lightstar II.
I have no experience with the Lightstar II. I've been told that the Lightstar amps "might" be slightly more transparent sounding than the Sunfire's but with very similar circuitry. This was told to me by an employee of Sunfire.

As far as your comments about your friend the EE and amp designer, all i can say is that he either needs better test equipment or to run some different tests. Prior to improving the tools that i had to work with, i was not able to measure differences in equipment once a certain threshold was achieved. Even though the equipment that i was previously using was nowhere near "state of the art", i was still able to measure and discern differences in performance above the aforementioned threshold ( which was actually quite low ) with good accuracy. Going to better test equipment simply gave me better resolution. This enabled me to measure and discern the differences in performance between components to an even greater extent. Granted, the increased resolution of the newer test equipment set me back a good chunk of money, but it also opened my eyes / ears / mind to the fact that i was not able to see / measure everything as well as i thought i was previous to the upgrade.

When all is said and done, i guess that we will just have to agree to disagree. Sean

PS... If some of you are under the impression that all audio designers, manufacturers, designers have a full assortment of high quality test equipment at their disposal, guess again. I've seen some of the "test benches" and "design labs" that various "manufacturers" use. Some of the gear that these "techs" and "engineers" are using to design and test their products is equipment that can be found at flea markets. This is NOT to say that the gentleman that Paulwp is referring to is in this boat, but given the point of view being expressed here, it "might" not be far off.

PPS... If gear wasn't changing in a measurable manner as we used it, it would never break down. Parts are shifting and decaying and that is why circuits fail or go out of tolerance. Whether or not you want to call this "break-in" or "settling" is a matter of semantics. Sean
Sean...The design/production philosophy formalized by Taguchi is in general use throughout industry, with the exception of some very small outfits where doing it the old way is a tradition, and this may include most high end audio firms. Good performance can be achieved on a unit-by-unit basis doing things the old way. The consequence of not using the Taguchi approach is high cost, and unreliablity, and that fits high end audio pretty well.

The first example usually cited regarding Taguchi method effectiveness is the camera business in Japan. After WW2 Germany was famous as the maker of the most superb lenses and cameras. They had skilled workers who could grind lenses better than anyone else, and they kept their trade secrets to themselves. Japan realized that they could never match the skill of these workers, and so could not produce cameras comparable to the German product. So, using the Taguchi approach, they figured out which pieces of glass in the lens system were hard to make right, and they designed new lens systems that did not rely on exceptional precision of any of the elements. As a result of this effort Japan became dominant in the camera business.

Example 2 is the superiority of Sony TV sets, vs RCA, GE, Sylvania, etc. I don't think the USA manufactures any TV sets anymore.