Asus P2-M2A690G - Manual (Page 57)

4-9 ASUS P2-M2A690G
We recommend that you connect a high-definition front panel audio module to
this connector to avail of the motherboard’s high-definition audio capability.
9. Digital audio connector (4-1 pin SPDIF_OUT)
This connector is for an additional Sony/Philips Digital Interface (S/PDIF)
port(s). Connect the S/PDIF module cable to this connector, then install the
module to a slot opening at the back of the system chassis.
The S/PDIF module is purchased separately.
8. Back audio connector (20-1 pin Back_Audio Connector)