Spdif out to XLR

[hardcore]

Edit: I’m running the inputs from the D via RCA to my Auralic which is driving my HD 800s in balanced mode and I’m hearing a faint 50Hz hum. Not sure if it’s the RCAs picking up mains interference or a ground loop.

First check if there is anything else connected to the Auralic and disconnect that. You could test if it's a ground loop by ground lifting the Auralic using a cheater plug (if it's safe to do so) and see if the hum goes away. If it does, then you confirmed it's a ground loop.

If so, you can try a ground lifter like this ifi GND Defender on the Auralic:
https://www.silentpower.tech/products/gnd-defender

DO NOT ground lift the Devialets though, as the manual specifically says that you should not.

Another option is to try an isolation transformer. These are some of the best.
CI-2RR | Jensen Transformers
I've used their subwoofer version in the past.

Another option if the Auralic has a balanced input with a transformer, is to make a custom RCA -> XLR cable, but do not connect the ground pin on the XLR side.