Have you consulted with REL regarding hum? The high level speakon connection is the ideal way to connect REL subs. I own a pair of REL’s and they are dead quiet using high level connection from my Integrated. You may have too much gain, try ‘floating’ the yellow wire and connect only red wire to positive binding post. Please make sure to mask the exposed yellow wire with electrical tape before turning on the sub and Integrated.
REL .LFE input
I just purchased the Technics SU-G700 integrated and it has a left and right pre-out that can be used for a subwoofer - my REL.
I’m currently using the high level connection but thought about trying the LFE connection as a way to reduce a very low level hum I’m getting in the subwoofer. No amount of connecting he system to one power outlet or grounding has solved it, and it only happens once the speakon connection is connected to the subwoofer.
My only issue with this LFE solution is that there is only one single input on the subwoofer, but the pre-out is in stereo. The question is how much audio low bass information am I losing if I only run one RCA from, say, the right channel on the integrated to the sub.
BTW, this is a dedicated two channel set up, not used for TV.