Doug, given that with the M series is a mono output (the other Amulet series are not), but a stereo jack, one could probably hack the preamp and solder in a mic on the ring and share the ground. You'd just need a TRS (stereo) cable and either an TRS A/B female to male Y adapter, or a preamp that accepts a stereo cable. Looking at this photo from their Facebook page, it seems like the connections to the jack are easily accessible.
Amulet M Preamp