for MD1, there's no working audio mod yet, except for MD1 VA7 which is a MD2 in MD1 shell, that one can use my sound mod : http://www.fileden.com/files/2008/4/21/1876835/CCAM1.png
Wait, only for YM2612? Would that also capture the PSG sounds? Never mind, I reviewed the diagram and it's there. Also, is there an easy potentiometer-based mod that would allow me to set levels for the 4 PSG channels, and 8-or-so YM2612 channels individually (by channels, I mean voices really)? I am assuming no, but it'd be fun to play with.
all 6 FM channels come from 2 YM2612 outputs, and all 4 PSG channels come from single PSG output... no way to create such mixer as you described :/
I can adjust filtering level to be little higher (to 26KHz range), then you will get all MD can output. Right now filtering point is around 23KHz... 26KHz is highest "normal" condition freq the YM2612 can do, anything above is aliases. if you can solder, I am selling CCAM modules for 20EUR, if you cannot, I can build and install into your machine for 25EUR....