LPF with three simultaneous outputs, SSM2040 implementation, one of the best LP filters.
You have probably heard of the SSM2040 filter chip, used in the Prophet-5 Rev 2, Voyetra 8, and others. Although short-lived, the SSM2040 filter had a unique sound different from a Moog, ARP, or other 4-pole lowpass filters. Why? The design used a clever discrete OTA gain cell that responds beautifully as additional gain is added to the input signal.
The E440´s audio input has a drive control that one one hand is a signal attenuator but on the oter hand it can also amplify signals with the factor 2. You can amplify line level signals and distort the filter´s input. Unity gain is approximately at the "4"-position. A jumper on the modules back activates the bass boost enhancement.
The E440 has three filter outputs with slopes of -12dB, -18dB and -24dB/octave, each of them is phase shifted 45° from the prior one. Mixing the filter outputs will generate different slopes, mixing with inversion will result in different frequency response.
For controlling the cutoff frequency there are three CV inputs, the first one working with a characteristic of 1V/octave and tracks over 4 octaves, CV input FM1 has an attenuator, FM2 has a polarizer. The resonance can be voltage controlled as well and the filter can self oscillate at potentiometer position 9. The voltage generated by the resonance pot will be mixed to the external CV.
CV Inputs: -5V to +5V, DC to 10KHz. Res In is 0V to +5V.
Audio input: 50kΩ nominal input impedance, 100mv to 14V pk-pk.
Outputs: -7V to +7V, 20Hz to 18KHz
One audio input, individual outputs for the 2-pole, 3-pole and 4-pole low pass filter.
3 CV inputs for controlling the cutoff frequency. 1x 1V/octave and two controlable FM inputs. One resonance CV input.
3U Eurorack module, 14HP wide, 32mm deep
Current draw: 23mA @ +12V and 23mA @ -12V