176 Triple Resonant Filter

Description

Roland never made a resonator circuit but Korg did, and they put a triple bandpass resonator in the PS3100 of 1977. This module is a re-imagining of this filter for 100M.

The circuit has three vactrol filters, which can be independently adjusted for frequency, resonance and modulation depth. The modulation inputs are usually driven by one or more LFO’s to create band pass sweeps.

The rotary potentiometers (with TR808 style knobs) at the top of the front panel are used to adjust the level of the individual filter outputs (channel 1 and 2). The channel 3 potentiometer pans between the input and output of channel 3. All three channel outputs are mixed together (at unity gain) and available in the MIX output.

The frequency and resonance of each channel is adjusted using slide potentiometers with subtle green LED lighting. The trimmer pots at the bottom of the panel control the level of frequency modulation from two input jacks per channel, typically two LFO’s at different rates.