This motherboard has onboard sound and video card. So basically you cant have a digital out from a motherboard without a sound card
So in short its from the sound card but only thing is that its onboard and not an add-on soundcard
not really, both serve the same function. you may buy an additional sound card and use both or disable one. if you are particular about the audio processor, this mb i beleive has a regular 192khz/24bit Azalia processor, with 8 channels, jack sensing and multi streaming features. if you buy a sound card be sure you buy something better (creative, auzen, turtle beach etc.) infact asus xonar is recieving high acclaim, and that could be a good hardware marraige for you asus mb.