GIGABYTE 5225 - Manual (Page 72)

Technical Reference - 67 -
English
STEP 1 :
Insert the "SURROUND-KIT" in the back of the case ,
and fix it with the screw.
Advanced 6 Channel Analog Audio Output Mode (using Audio Combo Kit,Optional Device):
(Audio Combo Kit provides SPDIF output port : optical & coaxis and SURROUND-KIT : Rear R/L & CEN /
Subwoofer)
SURROUND-KIT access analog output to rear
channels and Center/Subwoofer channels. It is the best
solution if you need 6 channel output, Line In and MIC
at the same time. "SURROUND-KIT" is included in the
GIGABYTE unique "Audio Combo Kit" as picture.
STEP 2 :
Connect the "SURROUND-KIT" to SUR_CEN on the
M/B.