Physical explanation of amp's break in?

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

A few points that were mentioned in the above post and responses:

- manual mention 6-week break in period for the unit (SimAudio)
- component values shift over time (known fact,though this aging process is much longer than six weeks)
- break in or "settle" (Sean) VS breaking-in until it breaks down (Pbb).

The last one is definitely worth my 2 cents. Personally, being an EE, I prefer the term "settling time". And our ears settle to the unit's sonic signature long before any radical change in any passive component value (active components, being bias dependent, are excluded). Of course, no break-down is ever desirable.

"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?"

None of the effects Sean noted are known to cause the behavior Dmitrydr asked about. Hence my original answer.

Sean...I doubt that the normal changes over time/use of resistor and capacitor values can explain what you claim to hear. These changes are trivial compared with the value tolerances of the components (2% is typical for resistors and 20% is common for capacitors). Circuits are designed with such tolerances in mind. Also, if values change, why should they preferentially change in such a direction as to improve audio performance?

Now, about that 6" wire that went to 50 ohms...you know that this wasn't normal It had broken strands or the like.
If it was solid wire, and it wasn't the terminations that were bad, I hope you sent the wire to some research agency for analysis. You discovered the "Sean effect"!

There are obvious reasons for speakers and phono pickups to change with age/use, so those items ought not to be a part of this great ongoing breakin debate.

Eldartford, your logic is flawed. Even though it is true that components are rated at some value plus/minus some percentage, it does not follow that a different value will sound the same even though it is within the rated specification. For example, if you built a crossover with all caps that are + 20% and another with all caps that are minus 20%, they would have decidely different cutoff frequencies and they would sound different.

As to the original weaker bass, stronger bass question, this could have something to do with the capacitors in the amp. The dielectric does change over time as voltage is applied to it. This affects the capacitance as well as the effective series resistance. I have no idea what the topology of this amp is or what type of caps are used, but I would not rule this out. Sean has given sound scientific explanations for his response, Bomarc, I would be curious to hear the reasoning behind your "nope."