Physical explanation of amp's break in?

Sean - Excellent response! From those of us who are ee and still use our test equipment, brains, and ears, thank you. Keep preach'n, even if only to the choir.
As always, just one man's opinion.

Dmitrydr: I know nothing of metalurgy. I can't explain what happens to cables scientifically using test bench equipment taking measurements either or tell you how / why cables "settle" in terms of theory. I do know that i can hear a difference before and after "burning" cables on the various "cooking" devices that i have though. I will not try to pass this off as fact as it is strictly my opinion that i've stated here a dozen times before. Evidently, some people share this point of view while others don't.

Some folks have sent me cables to burn for them and then done A/B comparisons between identical cables ( burned vs un-burned ) once they returned. The differences before and after burning were always quite audible. Some of the identical cables being compared were fresh out of the box whereas other cables had hundreds / thousands of hours of actual use on them. In each comparison, the cables that were cooked were deemed to sound more natural with improved harmonic structure. I've never had anybody tell me that the results of "burning" the cables were anything less than beneficial.

Having said that, those that have an opposing point of view never seem to want to put their money where there mouth is or learn from experience. That is, i've offered to burn cables for them free of charge several times and not one of the "nay-sayers" has ever contacted me once. As such, my guess is that they prefer to spout off rhetoric without doing any form of research on the subject or seeing for themselves what others are talking about. Instead, they chatter away with no personal experience to support their point of view rather than experiment / find out for themselves what the "real deal" is. Kind of hard to argue / debate with someone that refuses to view evidence contrary to their point of view. Actually, it's more than hard to argue or debate with someone like that, it's more like talking to a brick wall. Sean
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PS... My offer still stands to those that are interested. If you really want to see / hear the differences for yourself though, just be prepared to go without the interconnects for several weeks. I can "burn" them for however long you want, but my experience with most cables is that the longer that they are on the burner, the bigger the differences are.

there is no break in...its you getting used to the sound

Sean is right, as a piece ages, the components inside it change value. Resitors changes value, electrolytic caps start to dry out and ALL of them will eventually fail if used long enough, substances such as plastics used as dielectrics change especially when they get hot, and it is indisputable that tubes change as they are used.

I have rebuilt numerous tube guitar amps over the years and the change in sound is quite amazing when the carbon resistors that have risen in value and the old, dried out electrolytics are replaced.

Electronic components have a rated lifetime but they don't have an instantaneous change in value at the end of their life. They change gradually over a period time until finally they are stressed past the point they can withstand or the circuit they are in no longer functions properly.

Solder joints are a very good example. There have been numerous studies about this and volumes of data that support the fact that these joints change over time.

Whether you want to call this "breaking in" or not is up to you. Whatever you call it it is very real.

Sean is absolutely correct--all of the phenomena he mentioned do in fact occur. While electronics changes are perhaps more subtle and gradual than changes in speakers, they happen and are audible for one who has the ears to hear it. His reference to changes in use patterns was particularly interesting. I used a pair of $300 bookshelf speakers for 2 years while looking for new ones. I began pushing them harder and harder as I got closer to replacing them, and listening one day, I had to admit that even after 2 years, they had undergone a major change in sound, and up till then were not truly broken in. I've had my Magnepans for well over a year now, and even with extensive hard use, I have no trouble believing that they are still undergoing changes. In short, believe it!
Chuck