My MC275 has a clueless sound-change...

I just moved my MC275 from the ground to on top of my rack. Same system and same cables, but the sound changed from musical, well tonal balanced... to thin, noisy, sharp, bottom-less... Anyone of you had such experience and can explain why would this happened? I have the amp sitting close (approx within 2-3 feet from the speakers' mid range section, can the magnetic field affects the operation of the tube amp? or is it that the cables needs to break in again after a few new bends... I am clueless, I switched my interconnect from my Pre to Amp... although it added weight on the bottom end, the mid to the top is still noisy, sharp and forward... please help...