From the Synthtech website:
The MOTM-440 offers an updated SSM2040 architecture using matched NPN/PNP pairs and features a switch that adds a second audio feedback path to boost bass response at higher Q levels. This makes the filter “growl and rumble” even more! In addition, voltage-controlled resonance allows for more sweeping effects. The MOTM-440 sports three separate audio inputs and three FM control inputs. The internal gain structure is such that over-driving the filter is possible to get even more nasty sounds. It also self-oscillates at high Q and can double as a 1V per octave sinewave VCO.