I've seen sound cards with all kind of glitches such as outputting one of the channels with an inverted phase. I'd be also concerned with whatever audio filters

I've seen sound cards with all kind of glitches such as outputting one of the channels with an inverted phase. I'd be also concerned with whatever audio filters the card may have. Sound cards are just not meant to control precision equipment like that. Including a low cost USB adapter (even an audio one) that is tested and calibrated to work with the printer could prevent a lot of headaches in setting this up.