For closure to my previous post here is Luxman’s feedback on AES48 support.
The M900u / C900u do not support AES48 standard.On well, I may have to spend a little more on long XLR’s since I am getting the m900u.
The engineering team does not recommend using only pins 2 and 3 to conduct signal... without pin 1 in use, the units would be unstable.
The engineer did ask a question: What cables are you trying to use? If he has this information, he may be able to research further.
Also, the Luxman M900u and C900u are Class II devices. As such, they do not employ an earth ground. My understanding is that for AES48 standard, an earth ground is required. I may be wrong about this, but this is what I have been told. I don’t know if this changes your approach or not, but just wanted to pass that along.