I bought a DH4130S home theater system, but can't get no sound from it when I try watching a movie from my MAG 254 cable box, even though I changed the TV sound from 'TV speaker' to 'Audio Out'. I've tried using both RCA & HDMI cables to no avail. What do I need to do to get the sound to work? I'd appreciate any help that I can get. Please help me!!