Hi, as a newbie to this forum this is my first post , well actually my last attempt failed. Some time ago I carried out a listening test with a variety of SPDIF and AES/EBU cables, using a Musical Fidelity M1 dac and a Shanling dac. I dismissed all the SPDIF cables, off the shelf good quality and custom made ones. At the time I had stumbled on some Neutrik deicated digital XLR connectors, so I made up a couple of cable using the two types available and lengths of Canford Audio BKT-M cable specced as being 110 Ohm. Compared to standard off the shelf xlr cables, other manufacturers XLR connectors made up into custom cables, by far the best sounding were the two types of Neutriks, with a clear difference between the "ordinary" digital type and the full on ones, these are currently available as Neutrik NC3FXX-EMC and NC3MXX-EMC. In the UK a company called Designacable.com supply custom made cables using these connectors at a price for 1m lengths (£27) that is almost as low as the cost of the connectors separately. I don't know if there are any US suppliers who have similar cables available in their catalogs. I would recommend that you investigate this option, as it may be that the RFI that the Neutriks eliminate is the root cause of your dissatisfaction.
