A common misconception is that S/PDIF digital audio signals will provide a 5.1 channel sound. This is not true. S/PDIF is a 2 channel stereo format, regardless of the medium (optical or coaxial) The exception to the rule is when a form of compression is used. Dolby Digital (AC-3) compresses 6 channel signal into the 2 channel format used by S/PDIF, and can then be read by a decoder. No soundcard apart from the nForce 2 Soundstorm chip so far can encode AC-3. Therefore if you do not have one of these motherboards, the only way to get 5.1 channel sound over S/PDIF is to play a source that is already encoded in the format, such as a DVD video.