My MiniDSP 2x4 HD exibits massive RF interference when connected to my Denon AVR X-4300H's subwoofer outputs (x2) via RCA cable.

MiniDSP is an active crossover/EQ device:
[Link: minidsp.com]

If I disconnect the RCA, then the RF interference goes away.
I've tried two different types of RCA cables and both had the issue.
I tried both RCA outputs on the AVR (sub1 and sub2).
I don't have this issue if I bypass the MiniDSP and plug the RCA from my AVR directly into my amps.
I tried a different PSU for the MiniDSP and still had the issue.

It's caused me to go down to a single RCA instead of two.
That helped a little.
I then ensured the RCA isn't running lengthwise with power cables, which probably helped.
In the end, I had to put the MiniDSP in a really weird position to get the RF interference to be low enough not to interfere with my URC remote's RF.

Do you folks know of any tricks I can use to further minimize the RF interference?
I've already posted on the MiniDSP forum and a 3rd party MiniDSP forum thread but not gotten any help.