What speakers are you using? I know that sound strange to question and all, but it could be your speakers...or not. Also, what time of the day/evening do you notice this phenominon? Reason I'm asking, is that I used to have a system that sounded WAY WAY different at night than it did during the day. It also sounded different durring week nights than weekend nights till a certain time! I firured it was that my power is WAY higher when everyone goes to bed at night in the neiborhood, and it's lower in the day when everyone's using their power! My voltage went from like 115 during the day to over 124 during the night! I also found out, by accident, not even mentioning the situation, by talkling to another speaker manufacturer, that my speakers (Electa Amators /SF) either sound great or bad, depending on how THE POWER hits them!!!! i'VE FOUND THIS TO BE TRUE WITH MY SPEAKERS SPECIFICALLY FOR SOME REASON.
Anyway, it might be something to consider. Also, I've noticed that some DIGITAL systems tend to get all congested sounding after time, and can use a good DEGAUSING!! This might sound weird as well, but I had a guy do a demagnatizing demo with a CD based Krell system one time, andthe difference was NOT suttle! I'm not sure how that works, but he degaused the system with something called a UFO audio tweek magnetic device, and the system JUST OPENED UP LIKE YOU WOULDN'T BELIEVE. I mean I was a believer (youcan buy em for like $200 or so.
Good luck
Anyway, it might be something to consider. Also, I've noticed that some DIGITAL systems tend to get all congested sounding after time, and can use a good DEGAUSING!! This might sound weird as well, but I had a guy do a demagnatizing demo with a CD based Krell system one time, andthe difference was NOT suttle! I'm not sure how that works, but he degaused the system with something called a UFO audio tweek magnetic device, and the system JUST OPENED UP LIKE YOU WOULDN'T BELIEVE. I mean I was a believer (youcan buy em for like $200 or so.
Good luck