The mic. cable or XLR should play louder than an RCA they typically rate XLR signal to about double that of RCA on most equipment. If you have any grounding noises the XLR will also help especially with long run. Although the RCA has the same signal as a balanced. Stay away from balanced to non adapter cables, for me I have a 1\4 TRS to RCA "pro cable"{Digiflex} loves to hum as soon as connected.

The best option is shorter shielded RCA if possible and isolate different cables. Especially power and RCA, try to keep 6 or more inches from power cable proximity Basic power cables emit a lot of E.M.I. Another culprit can also be WIFI to close to say a turntable or even equipment rack. My turntable started giving a decent hum went through tidied cables couldn't figure it out. Turns out I moved the router a couple feet from the TT. Took a couple weeks to realize