The MACA filter is a 4-pole multimode filter based on the SSI2140 integrated circuit. The design is essentially an updated version of the classic SSM2040 (as found in some classic synths eg: Prophet 5 Rev1 & 2, Octave Cat, RSF Kobol)

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 an input level control that allows for overdriving the filter core.

MACA Filter – Build Document

Features

• 4-pole LP, 2-pole LP, & 4-pole BP outputs
• Input level control
• 16hz-16khz range
• “Q” CV input
• Inverting attenuator on “FM” input
• “V/oct” CV input
• Sine wave oscillator at high “Q” settings