Tried to do a comparison of AES and BNC connections on the Yggdrasil yesterday, with music files coming from a Bryston BDP-2. BNC cable is a Black Cat Tombo Tron, AES is High Fidelity Reveal. Ideally, they should be the same make cable, I know, but it's what I've got.
I say tried, because switching between the inputs on the Ygg caused it to lock up. This actually happened once before, attempting the same comparison, and a power off/on fixed it. This time around, I tried to press the input switch less rapidly, but after a while, the switch stopped responding, there was no sound, and the VCO light was blinking. Several power downs, unplugging all connections and power cord didn't help. I left it unplugged for about an hour, tried again... still no luck, but I let it stay powered on, and at some point it just started working again. Weird.
Still, I got some comparison listening in before it froze, and there was a small difference between the two. AES seemed a bit fuller, and more lush, and BNC had a drier but slightly more detailed sound. But they were quite close, and it might simply be down to the different makes of cable. Not sure which I prefer TBH.