A 4-pole multimode filter based on the SSI2140 integrated circuit. Essentially an updated version of the classic SSM2040, the new SSI2140 adds better temperature compensation and a VCA that helps eliminate low frequency damping at high resonance settings. Besides the obligatory 4-pole low pass, MACA adds both 2-pole low pass and 4-pole band pass outputs. There is also a input level control that allows you to easily overdrive the filter core.