The audio delay can't go into the negative range because that would require delaying the video (which would entail buffering the entire video signal in memory for the amount of time being delayed, a much more memory-intensive process than buffering the audio) or doing things to the audio signal that violate some laws against time travel that I think scientists are real serious about us all adhering to. Odds are that any out-of-sync condition you see is related to the video being behind the audio, unless the source itself (the mastering of the DVD or the broadcast being sent to your cable or satellite box) is just simply messed up to begin with.