I presume that you will have sinc problems with soundblaster on long ( over 6 or over 12 minutes ) clips.
I have always have that problem with soundblasters with DPS PVR. Try to find some used dat recorder on ebay, like Tascam DA 20. They will do this conversion. ( I am using it for similar purpose for headphones, this tascam passes signal in rec mode without tape in it) Any way you have to pay something and you will end at last on flying cow or something ( but, with tascam you have dat player/recorder that you can also use.)