Sorry, I'm confused...why do an extra step in converting USB to SPDIF?
AES for me, too. Alternating with BNCx2 on BDA-1. Barely a difference, to my ears.
My DAC has an older USB input that is not asynchronous and it limited to 96k (or 48k, I can't remember).
My converter also provides 3 stages of galvanic isolation, if that matters. A great sounding pairing w/ my MacBook - Bel Canto REFLink and DAC.
Just to split hairs, along the zoom25 discussion in another thread about jitter, the REFLink has a jitter spec measured in femtoseconds. So, I played around with using USB out from the BDP-1 into the REFLink to see if there would be any difference in sound. I flipped back-and-forth on the DAC using both USB-to-SPDIF and AES at the same time from the BDP-1.
Hard to say, of course, as the difference was very subtle. Initially I really thought the REFLink provided a clearer sound, et al., but after a lot of back-and-forth, I decided it was expectation bias and that any difference was so subtle that it wasn't worth the extra step to the DAC.