The difference in sound quality that you hear from day to day may not be psychological as another poster suggested . I used to have the same problem and felt the difference was to great to be a matter of state of mind ect . I attributed it to inconsistencies with incoming power . Upgrading to a top notch conditioner seemed to give me consistent sonic qualities . I haven't heard such anomalies since .
Heaven or Hell
After a long day at work I sit down to listen to my stereo and behold the seas part and yes Virginia there is a Santa Claus the Stereo Gods have granted me a rare evening of audiophile heaven but now I ask you why cant I stay in this state of rapture as the following day at the same time listening to the same music the seas refuse to part and Im here in a state of disbelief. Can anyone tell me why its so hard to stay in that elusive zone? Explanations appreciated.