summing noise and hum across the time

Hi
I connect all of my system cables and turn on system.
I listen to music and sound is fresh and live. after some days sound loss ease and high frequency smoothness and definition.
i turn off all system and remove all cables for 15 min. then without connecting cables i turn on system for 15 min. then i turn off system for 15 min and after 15 min i connect all cables and turn on system. now i listen to fresh and pure sound of system. this sound downgrade will happen always and i should repeat this proccess every week. i don't know where is my problem?!
i think my system sum up noise and hum accross the time because in normal mode when i stop sound at high level volume i don't hear any thing after stopping the player but when sound loss in long term and i stop the sound in high level i hear amount of hum sound after stopping the player.

my setup :
accuphase dp-55v CD/Pre
krell kav-300il Power
Dynaudio Audience 82 Speaker
van den hul The Second interconnect
Monster M1.2s speaker cable
Van den hul mainsstream power cord for krell
and i connected earth pin of my system to water pipe.
i had this problem with my last system without connecting earth pin to water pipe(NAD c541i source and c370).

Please help me if you had my problem.

 

what happens if you reverse the direction of the interconnect and switch back on right away?

 

i use xlr cables and i can not reverse them