[Grit]

Can someone explain to me how audio equipment sounds different from day listening or night listening?  My audio sounds the same to me no matter what time of day it is.

Sorry, the point I was trying to make was that the sound probably ISN'T different (with the possible exception of power line noise). Rather, I have more distracting factors during the day than at night, which affects my ability to perceive the nuances my system is capable of producing. Essentially, there can be other things when we listen to music that affects our perception.

[Calypte]

For me, the slightest extraneous environmental noise masks the nuances of recorded sound.  I live in a rural area where it's pretty quiet most of the time.  But late at night, noise is nonexistent.  That's when I do most of my listening.