1. Optical Audio connection.
(TV to STB Connected by HDMI)
a) STB Optical Out to HT Optical in
b) TV Optical Out to HT Optical in
2. Coaxial Audio connection
(Same above procedure)
3. Audio Video connection
(The old system) you may get only 2.1 out
4. HDMI ARC (Audio Return Channel)
Both Your TV & HT should support this feature. Check your HDMI pin, it will be written ARC there. Or refer manual or google it.
STB HDMI to TV HDMI
TV HDMI ARC to HT HDMI ARC
5. In case If your HT have HDMI Input (that means your HT will have more than 1 HDMI pin ( This is the best way)
STB HDMI to HT HDMI (In)
HT HDMI (Out) to TV HDMI