Cant get sound from speakers

Question

hi i have a samsung tx 72 (theatre)& samsung t4671f (LCD). The main problem is I get no sound when i switch to satellite. It does work when DVD is operated.

Im using a direct tv non-HD sat-box, which is connected to the tv with the RCA plugs& S-video cable. When I switched to this set-up, I have sound which is LOUDER from only the TV..

Any Help Would Be Apreciated,

Chris