@dekay - From the Schiit Modi 3+ specs page on the Schiit Audio Site:
Inputs: USB, Toslink SPDIF, Coaxial SPDIF
Sample Rates and Bit Depths: 16/44.1 to 24/192 via USB, Coax, and Optical
Input Receiver:
Modi 3+ USB: Schiit Unison USB™
Modi Multibit USB: C-Media CM6631A
SPDIF: AKM 4113