Weather-induced amp performance variation

Pretty dramatic changes in the sound of a system and amp also occur due to variations in the amounts of AC power line pollution and noise during differnt parts of the day and night, especially if you don't use a line conditioner of some kind.
I also heard that changes in the barometric pressure can cause a system, particularly the speakers, sound alittle different on different days.
Also, proper warm-up is essential, especially in solid-state amps and preamps. If they are played from a cold start, there can be huge variations and fluctuations in the sound quality as they go through their warm-up period.

Don't forget that the weather can play havoc with your sense of hearing.

Eldarthford: I guess age of the listener has much too do as age of equipment :-)