I have two dedicated circuits: one for the amps and one for everything else. The second circuit supplies the CDP and the preamp. I would like to find a way to filter the RFI/digital hash from the CDP so it doesn't affect the preamp. I don't know if it does or not right now. Anyhow, a friend of mine mentioned pi filters as a way to do this. Can anyone provide more information as to whether this is appropriate and perhaps recommend a good pi filter for purchase?
Use ac line filters. You know, power strips with extra filtering (more than just spike protection). One for each side of your system. Best if they both plugged into the same outlet. That prevents ground currents via different branches.