The Low Pass Filter, in 4 pole mode, emulates the familiar low pass filter in some analogue synthesizer.
S1's Low Pass Filter expands sonic potential by adding a unique designed 6 pole low pass mode and quasi band pass mode. LPF is characterized by a non-linear transfer function, so-called saturation mode that is affected by the level of the incoming signal. In the audio mixer the red markings on the potentiometer scales show the level at which the filter operates in the saturation mode.
The design quality of LPF's and new features makes the LPF more flexible than any other low pass filter used in analogue synthesizers and results in qualities, such as:
*CUTOFF, Q-PEAK and output level are voltage controlled
*4 and 6 poles low pass mode (24dB/octave and 36 dB/octave)
*Qasi band pass mode (6dB/octave high pass and 24dB/octave low pass
*Saturable, from warm and smooth sound to heavy distorted
*Ideal as effect filter with external signals
CUTOFF controls the filters cutoff- (or corner-) frequency. POLE selects between 4 pole low pass, quasi band pass (that sounds different than the "true" bandpass of the MMF) and 6 pole low pass.
Q-PEAK determines the boost of the corner frequency. From "9" on, the filter starts self-oscillating.
To create useful and interesting sounds, the cutoff parameter has to be controlled dynamically.
This is mostly done by the later described envelope generators and/or by modulating the cutoff with
a periodical signal e.g. an LFO- or an audio signal. This is done with the cutoff modulation section (CM).
CUTOFF MODULATION CM 1 adjusts the corner frequency modulation intensity by ENVELOPE GENERATOR 1. ENVELOPE GENERATOR 1 switch inverts the control voltage of envelope generator 1.
CM 2 adjusts the corner frequency modulation intensity by ENVELOPE GENERATOR 2.
ENVELOPE GENERATOR 2 switch inverts the control voltage of ENVELOPE GENERATOR 2
OSC1/LFO adjusts the corner frequency modulation intensity by the triangle waveform of OSC1 respective to the LFO. Maximum sweep reaching over +/-5 octaves. OSC1 LFO switch selects the triangle waveform of OSC1 or the LFO as modulation source.
In the patch section of the LPF you'll find the HI Z INPUT which is an additional and patchable input.
It is internally pre-patched to the audio output of the Multi Mode Filter. This level is adjustable in the LPF
MIXER section. OUTPUT socket allows the filtered audio signal be coupled to any input. It's destinated to
the audio input of the AMP-section (FILTER MIX).
Here you'll find patchable modulation-inputs for the LPF:
CUTOFF can be used to provide other signals than the triangle waveform of OSC1 or the LFO (to which it is internally routed; see above) as a modulation source for the cutoff frequency. Use the OSC1/LFO knob to adjust the modulation intensity.
LEVEL can be used for gain-control respectively amplitude-modulation of the LPF output signal.
Q-PEAK enables the resonance to be voltage controlled. Again, using audio signals for cv duty can provide interesting results.