I'm thinking your soundcard's speaker out is analog right? And I don't think the miniplug optical cable will fit in the slot. You need an optical out. And most of the ones I've seen for computers (Live! Drive IR, Hoontech add on card) use TOSlink. So what I had to do was buy a TOSlink and a miniplug adapter. Cost me around $25 w/shipping. Damn Sony and their proprietary stuff. But in this case, I guess it was for the better since it's smaller than the TOSlink making MD recorder/players smaller in general.