Ground Issue

I have two McIntosh Amps - MC402 and MC252 - There's a buzz in my system recognized in the midrange and high-end (mostly midrange). Even with the pre-amp off there's still this buzz. A friend suggested I put A/C adaptor on the end of the power cord of each amplifier and the buzz went away. The other way to reduce the noise was to remove both shielded coaxial wires from two source pieces in the system - the noise reduced but not totally eliminated.
Each amp (and my other source equipment) are all plugged into a RG power conditioner. Any suggestions how to eliminate the buzz while using the ground wires of the amplifiers?