Quote Originally Posted by melmar
I bought a used B & K ST 1400 amp a couple months ago. One day, I inadvertantly left the amp on for several hours before I noticed it was on. I then turned my pre amp and CD player on, and I thought I was listening to a different amp. The lows were terrific and the highs were nice and smooth. Is this typical of amps? Does it hurt to leave them on instead of turn them off? Thanks.

Yes, ones perceptions can be dramatic, even if no change has occurred. Tests have shown this time and time again. Interesting why people claim component differences when the same component is presented twice.
Human nature to look for differences, perceive differences when none exists.

The chances are remote or nonexistant that you heard real differences. Perception is different from hearing.

How many times have you asked someone to repeat what they said only to be told nothing was said.