In a rich RF environment you might consider really quiet cabling as an important part of your system. I suggest using the very best for this purpose, Canare Starquad L-4E6S microphone cable. It may or may not solve your immediate problem, but it should pay dividends in a blacker background. IMO
RCA connectors. Considering the rest of your system, Switchcraft RCA connectors would be a good choice, inexpensive and very good (from Digikey). Starquad isn’t that easy to DIY, but any tech could help you - but make sure that he solders the shield on ONE end only, and MARKS that end. That’s industry standard for microphone cable and RCA connectors.
When you connect the cables, put the marked ends on the same component. Then try it the other way. One way may be quieter. I use this cabling in a higher end system and have no desire to change.
Good luck!
RCA connectors. Considering the rest of your system, Switchcraft RCA connectors would be a good choice, inexpensive and very good (from Digikey). Starquad isn’t that easy to DIY, but any tech could help you - but make sure that he solders the shield on ONE end only, and MARKS that end. That’s industry standard for microphone cable and RCA connectors.
When you connect the cables, put the marked ends on the same component. Then try it the other way. One way may be quieter. I use this cabling in a higher end system and have no desire to change.
Good luck!