Asus Xonar U1 Quick Installation Manual page 6

For Digital Speakers
SPDIF Out
R
Plug the optical TOSLINK adaptor into the S/PDIF-Out combo connector. Then,
connect your decoder's S/PDIF in port to the optical adaptor with a TOSLINK optical
cable.
Connecting headphone / microphone
R
Xonar U1 Quick Installation Guide
6