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The AM8044 module is based around the original SSM2044 Datasheet and is very similar to the circuit used in the Korg Poly 6. The chip delivers a
4-pole voltage controlled low pass filter, with a smooth and controlled resonance. I have added a 2-pole mode which provides a thinner sound by tapping into the cascade of current mirrors which form the "Moog ladder" (via the 2044
pins, not cutting into the substrate!). The switching between LPF modes is electronically switched from the front panel with a red indicator LED.
This dual mode LPF is then followed by a 1-pole HPF with 4 modes;
Bass Boost Flat HPF Cut 1 HPF Cut 2
Those familar with Roland analog synthesizers may recognise this approach.
The front panel has rotary controls for (LPF) Frequency Cutoff and Kybd, which varies the amount of keyboard CV that is applied to the LPF frequency
modulation, connected into the standard Doepfer bus. There are an additional 3x front panel CV inputs, two of which can be varied by front panel slider potentiometers. There are 2x audio signal inmput which also have slide pots, and
a slider pot to control the LPF Resonance, into full and smooth self oscaillation.
The High Pass Filter (HPF) is a simple 1-pole design electronically switched from the front panel with Red, Blue and Green indicator LED's. I am sure
you can work out the colour coding! There is a single audio output for this mazinging flexible and great sounding filter module.
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