Buy High Pass Filter or KAB RF1?

Indeed ieales, indeed. I’m going to try the Anthem as driving my Atmos and surrounds in the theater room I am building in the basement, and use an Atoll for the fronts down there.

I also have an Atoll upstairs for my record player driving my two Monitor Audio Golds. Soon I will have the Atoll phono preamp.

I have two Marantz AV7704s, one for each room.

As Al rightly said, the majority who suggested an extension of the phono cables as a test did NOT suffer the hum you describe, or obviously the suggestion would not have been made!

And I do believe the majority suggested as a test not an ultimate end of game fix.

But I will admit I have never owned a Rega so unsure as to how that would have reacted in my system under the same circumstances.
Neither of my two JVC DD tables had any issues with phono cable extensions for testing.

Crap the rumble is back just on the subwoofer, and only when it’s turned up past 10 o’clock. 
I’m assuming if I put a single passive high pass filter on the sub it’s my best option for hurting sound the least other than buying the KAB and getting a Y connector.