trouble with actual surround sound

Mac is set up with optical cable to a PANASONIC 5.1 home theatre surround system through digital input mode but all I'm getting is stereo when panning surround , all audio channels set to surround. All preferences and audio settings double checked and set to 5.1 surround. Do I need another plug in like SOUNDFLOWER or something similar to get surround? newbie at surround! Thanks