So, no one answered yet about the differences between the normal and the pro version??
IIRC, there is little difference in the 2 versions. Maybe it was the casing or the audio out (2 phono plugs vs. one 0.125 stereo plug). I believe they both used the same chip, both were powered by a serial pass-thru connector.
The chip is the big deal, supposed to be hard to find.