SB Platinum Live Drive Optical output & MiniDisc optical input

[nghan]

I got an AIWA mini disc that has optical input. When I connected to the optical output on the SB Live Drive I can record, but...when I change the volume in Window, the recorded volume also changes???? I thought "digital - digital" doesn't care about volume, since it's 0 and 1. Can some one explain? Thanks.