The 5089 filter is a voltage controlled, discrete analog, 24 db/oct transistor ladder, low-pass filter, employing hand-matched transistors. Ladder low-pass filter—a subtractive analog sound synthesis foundation—in its lowest FREQUENCY setting removes, or cuts off higher frequency harmonics; its RESONANCE or Q circuit emphasizes those harmonics to the point of “squealy,” giddy self-oscillation, tracking the keyboard in its FULL setting quite nicely if seeking an alternative sine wave.
Seven patch points: 1 V/O, FREQ CV 1, FREQ CV 2, RESO CV, INPUT and 2x OUTPUT direct the deepest manipulation.