"Burn in" Are you serious?

Waldhorner's thread is somewhat extreme, but there is a measure of truth within. The ear/brain can deliver the ultimate decision, but it's a system that is easily fooled. My recommendation is accept this as a "fact" and go on about listening to the music. Stop worrying, stop making sense.

Recently replaced my preamp/amp with an integrated unit (a demo, presumably already broken in) and my first impression was that the integrated had slower, more rounded bass and slightly elevated extreme high frequencies than the units it replaced. As the weeks have passed the amp no longer sounds this way. Is it burn-in, or have I acclimated myself to the sound of the amp? I can't really say it's one or the other. Probably a little of both.