some pointers from a previous Bardo owner.

first - you can ditch the RCA box, its clouding the presentation, too much connectors in the way.
a din to rca phono cable from the Brinkman 10.5 to the SUT without going thru the adaptors cable and the RCA switching box are far better to get a better sound.

second - yes! use two phono cables, also from the SUT to your phono preamp. phono cables are builded with care for grounding and shielding and it will be better for
eliminate noises and hums that can surface.

try and switch how the grounding will route, a star - all grounding wire connecting to a single post or (as i preform usually) in a line... every piece are connect to his forward one.
table (phono cable wire) - sut - phono = in line
try to disconnect the table own wire with the special post underneath and use the phono cable wire and vise a versa, try to hear if you got some changes...

another thing i was dealing with when i was a Brinakman user; is the Bardo (and after with the Balance) SS power supply - he was humming (buzzing inside) for itself!
i was contact Helmut back then and he told me to try and "play" a little with the four screws underneath where the legs are and try to un tight them a bit to let the trans inside to loose a bit from the enclosure. it did help a bit with putting it on a slab of slate and some dumping material but not with a 100% success.