I have a home theater pc with a 5.1 terratec sound card. It is connected via an optical out to my Sony reciever that has a decoder etc built in. All I want is for the soundcard to output a signal that the receiver can decode into 5.1 - ac3? At the moment my reciever keeps saying - pcm detected - rather than doldy digital 5.1 Any idea what settings I need to enable/disable? I have both versions of ac3 filter but camt seem to make it work The terratec soundcard has spdif enabled.