Buzz Hum Problem

Hi, I was wondering if you could give me some input to a slight problem I have been having? The other day I still noticed the very slightest kinda hum buzz going on in both of my channels. It can only be heard at all if the amp gains are past half way up. If you were not listening for it most people wouldn't hear it. I noticed it after playing my Nakamichi cd player, and switching over to my Harman Kardon CDR-26. The Nakamichi is dead silent. All I have to do is turn on the H/K and I get the noise! I don't even half to be on the H/K's input, just turn it on. I'm sure this is some kind of ground loop, but I don't want to put any signal degrading isolation transformer on the H/K outputs. Any suggestion? I was thinking of grounding the Chassis directly to the my Crown IC-150's chassis. The connecting cables between the H/K and Ic-150 are quite old, but then again so are the one's between the Nakamichi and the IC-150. This is the only component giving my a noise issue. Everything else is dead quite! I tried moving the H/K's power cord to a different outlet with no improvement. My Ic-150 is connected to a Crown XTI-2000 power amp.