All the components are AC powered off a Tripp lite UPS Conditioner.
With everything plugged into the Tripp Lite, this should reduce/eliminate a ground loop caused by being on different legs of the main panel ...
Also I'm going to assume there are no issues with the cable service ground, but i don't think so, and here's why ...
Generally ground loops "HUM" and your use of the word BUZZ" sounds like you may have loose connection or a broken solder joint. These condition will produce a BUZZ vs a HUM
The broken solder joint could be on the output RCA or input XLR to the Sub.
You may also have a poor/broken solder joint in the cable that has broken from repeated use of installing and removing
I can't help on pin configeration in converting RCA to XLR but that should be checked against Sub pin config.
Once you know pin config. is correct then test cables for continuity ... now you know cables are OK
Then you have to deal with the output RCAs on amp and input XLR on Sub to make sure there are no broken connection. Can you swap another amp in or possible swap another Sub also ??
Ground loops are generrally subtle HUMMINGs where broken or loose connections are louder obnoxious BUZZINGs
Good Luck and Remember ... "Problems that remain persistently insoluble should always be suspected as questions asked in the wrong way."