Who can help me with a ghost in my system

I have a McIntosh MX135, Marantz DV-9500, Pioneer Elite PDR-19RW and a Linn Ikemi. When no music is playing I get a 'high pitch squeal, almost a ringing squeal, not real loud' heard through the tweeters. This can also be heard between tracks when playing music as well. But, it is only when the pre-amp is switched to the 9500 or the PRD19 but not the Ikemi. The Ikemi is dead silent. This squeal occurs at 25 on the volume setting out of a possible 99. If I disconnect either the Left or Right output on the 9500 or at the MX135 input, just one cable left or right doesn't matter, it drops to dead silence. The cables on the Ikemi and 9500 are Cardas Golden Reference, Pioneer is Audio Magic Excalibur in and out. There is one other ingredient here. Both the 9500 and PDR19 have 2 prong A/C power plugs while the Ikemi is a 3 prong. I have tried ground the 9500 to the MX135 through chassis screws as well as the 9500 to the Monster Power conditioner, no change
I could use some advice from the AG alumi, I hav erubbed a bald spon from scratching my head on this one.