@debjit_g That seems like logical explanation, I suspect the modified Sonore Opticalmodule within Small Green Computer SonicTransporter Optical I9 would provide better isolation from motherboard. Unfortunately, this doesn't provide for optimal usb out. I want the choice of both optimized fiber and usb with my next server, diy may be only solution for me. I'd have difficult choice between Pink Faun and JCAT.
Also, I presume having to go back through Buffalo switch with fiber vs. direct to dac with usb would have bearing on your preference.