Unsure if those little Ferrite RFI Filters that clip onto an IC would be of help?
One thing you could possibly try, is connecting a ground wire from the Chassis of the Phono Stage to Pre, or even perhaps too, a ground wire from Pre to Main Amp?
The only other things that come to mind here, is trying different Interconnects, but you might have tried this already? That, and perhaps another Pre-Amp? Can someone borrow you one to try?
I'm certainly no electronics guru, and I'm just drawing straws here, but the only logical answers I have is to go through every component associated with, and go through the process of elimination. Mark
One thing you could possibly try, is connecting a ground wire from the Chassis of the Phono Stage to Pre, or even perhaps too, a ground wire from Pre to Main Amp?
The only other things that come to mind here, is trying different Interconnects, but you might have tried this already? That, and perhaps another Pre-Amp? Can someone borrow you one to try?
I'm certainly no electronics guru, and I'm just drawing straws here, but the only logical answers I have is to go through every component associated with, and go through the process of elimination. Mark