Originally Posted by James-uk
I can hear the same setup sound completely different on 2 separate days . Maybe the difference I don't hear is doesn't exist?
Maybe yes, maybe no. It is true that we may "hear" some subtle differences from time to time that are only psychoacoustic. However, consider the following:
Many amplifiers can change as they are initially used (sometimes called "burn in") and it can sometimes take several days for the sound to open up and get a little more spacious and to stabilize. My personal experience was that somewhere in the 100 - 150 hour area, my HDVD800 started sounding more open. However, I never liked the term "burn-in" that everyone uses because for whatever reasons this change in sound is occurring, the process doesn't really seem to be permanent as the term "burn-in" might imply. Turning the unit off for a period of time typically results in some reversal of the initial stabilizing effect, sending the unit backward towards the sound it had when it was new. Since we tend to be using our equipment on and off frequently, the changes from day to day may be very small and not noticed. Also, the reversal seems to happen more slowly than the initial improvements.
However, the more highly resolving a system is and how much it's electronics are susceptible to these changes can determine how likely you might hear a change. For example, frequently, one of the things that might improve as an amplifier is "burned-in" is that some grainy recordings might smooth out a bit. If you happened to leave the system off for a while and then later coming in, turn it on, and immediately put a poorly engineered recording on, it could sound a lot worst that you remembered it being the last time you listened.
This is the reason that many audiophiles with very high resolution, high power class A amplifiers (which tend to run very hot all the time) just leave their equipment turned on all the time so that it's always stable and ready to listen to at its peak performance.
It's also been shown that even a normal amount of wax buildup in a person's ears can have a significant effect on the perceived sound from their systems.
So in any event, there are legitimate reasons that things might sound different from day to day.
Edited by wisemanja - 7/26/13 at 6:30pm