External Audio decoding with a Audigy advanced mb onboard sound card.

Hi.

 

I have a d-9200 with an audigy advanced mb sound card which is connected to an external dolby receiver through the  optical jack.

I selected 5.1 audio in the speaker configuration manager but I only get audio from the left and right front channels. I read on the creative forums that you have to activate  "audio pass-through decoding" or something like that but I can't find that option in the soundcard software.

 

Is there any way to fix this?

 

Thanks.