WILOWAR: thanks for the reports!
for mars matrix: edit game inputs (F5), set a key to "volume up" (you may need to scroll down a bit), press OK then start a game & press this key until its at the volume you wish. also make sure "volume down" isn't conflicting with anything else - or just clear input with "clear lock" checked.
for Super-X: exit the game or close/reload FBA, go to "Misc" -> "Options" and uncheck "Use assembly MC68000 core". If this doesn't help and you are using the 64bit FBA, get the 32bit one instead. and/or ctrl-F5 and set the dips to default.
best regards,
- dink