What Exactly Does "Burn In" do for Electronics?

The change in the sound a new amplifier sends to the speakers as it gets more playing time is as real as it gets imo. Bass, for example, I've heard change substantially. The way bass loads a room can change and that change can be heard and felt several rooms away.

why is it that burn in always Improves the sound quality. If we were to believe that the sonics of a component do indeed change during burn in, does it make sense that the change would 100% of the time be for the better??? Of course not, ridiculous. 06-15-14: Jaxwired

Sound does not always improve with burn-in/break in. I've complained before that some power cords I've tried have lost bass weight and/or clarity as they had more playing time in my system. This was not a good thing in my book and a deal breaker. I can say too that the bass of some amplifiers I've tried tightened during break to the point that I did not care for it as much. Break in does not always bring about improvements in sound quality.

An ABX Blind Test
Here is but one example. Half got it right, half got it wrong, between highly rated Nordost Valhalla power cords and the cords that come in the box with the equipment.
I am not suggesting sonic differences do not exist between equipment and cables but, like Jaxwired, I believe it is easy in this hobby to perceive tiny sonic changes when the real reasons may be related to other psycho-acoustical influences.
Audio equipment testing
Wiki also provides some interesting discussion about objectivists and subjectivists.

Dragon I completely agree with you. My point is not whether or not the sonic differences are real my point is that we don't know for sure and that there is a possibility that we can be fooled or deceived by our ears. Since this is true, I like to consider more than just "did I hear a difference" when evaluating the worth of a product or concept like burn in. For one thing, I throw common sense into the mix. Certain products and concepts certainly are counter to common sense. For instance, cable risers, expensive feet under components with no moving parts, totem beaks, $1000 / ft cable, etc...

"06-16-14: Jaxwired
Dragon I completely agree with you. My point is not whether or not the sonic differences are real my point is that we don't know for sure and that there is a possibility that we can be fooled or deceived by our ears. Since this is true, I like to consider more than just "did I hear a difference" when evaluating the worth of a product or concept like burn in."

Fine. I agree.

" For one thing, I throw common sense into the mix. Certain products and concepts certainly are counter to common sense. For instance, cable risers, expensive feet under components with no moving parts, totem beaks, $1000 / ft cable, etc..."

Common sense has nothing to do with this. There are plenty of things in science that don't make sense to us, but are still correct. If you want to disagree about what kind of differences you can hear with different cables, fine. But just because something like an expensive cable or tweak doesn't make sense to you, that doesn't mean you are right just because you are basing your answers on common sense. So if you want to get to what the truth really is, I think the only way to get there is with some well conducted listening tests. I've done them before and if carefully planned, I don't see why you can't get accurate results.

The only thing I would add is that you can't just lump everything all together. All cables, all components break in, all tubes, ... that kind of thing. I take everything on a case by case basis. Results vary. Sometimes you can hear a big difference, and some things, small or none.