Break-in

But how do you predict how a component will sound after break-in, if you don't know what causes break-in? How does an engineer design for a phenomenon he doesn't understand? (Answer: He doesn't.)

As for measurements, I think Tom Nousaine once tested speaker drivers before and after "break-in." The differences were so small that they were swamped by the unit-to-unit differences. I would expect the differences to be even smaller for purely electronic devices.

The "Break-in phono-menon" can be easily explained as a function of the ear to adapt to environ-mental sounds. Whereas the eyes, nose, tongue and tactile do not adapt. Since the function of the inner-ear/brain mechanism is to interpret environ-mental sound it has to change its internal physiology to identify source details. Therefore what appears to sound better is actually your ear conforming to provide you with a more accurate "picture" of the vibratory source, making it more understandable. IN OTHER WORDS YOU ARE WHAT YOU HEAR. This explains why the observed "improvement" is unmeasurabe on lab test equipment, and explains why new equipment never sounds worse. The ear is the only "moldable" sense organ, just as new shoes always feel better after they are worn a few weeks "broken in".

I'm not sure I'd go so far as to say that the ear is the only "moldable" sensory organ. You can become accustomed to hot foods, rotten odors, even touching hot or cold items.

The point is that anytime you do a sensory comparison, the biggest variable in the mix is YOU. You can't hold yourself constant.

Bomarc, you're right, you can't hold yourself constant, but you can maintain a reference sample, as Sidssp said.

Sure, and when somebody compares mint and broken-in components in a blind test and identifies them consistently, I'll believe that break-in is a physical phenomenon. Until then, I'd argue that the psychological explanation carries a lot more weight