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Analogue Modular System A-
Xtreme “MS20” Voltage Controlled Filter (multi mode)
Lowpass: the audio signal is fed to the LP input, HP level control is set to zero, LP level control is set to the desired level
Highpass: the audio signal is fed to the LP or HP input, LP level control is set to zero, HP level control is set to the desired level (in this special case it does not matter if positive or negative amplification is chosen with the polarizer control)
Lowpass/highpass mix with one audio signal: the audio signal is fed to the LP input, LP and HP level controls are set to the desired levels.
special setting 1: if LP and HP are set so that both levels are identical with the same polarity a (slightly imperfect) notch filter is achieved.
special setting 2: if the level controls for LP and HP are set in a way that both levels are identical with the opposite polarity a (slightly imperfect) bandpass filter is achieved.
Remark for settings 1 and 2: The original MS20 circuit was not planned for notch or bandpass applications. Due to the 12dB lowpass and 6dB highpass slopes, this leads to phase relations that do not allow a "perfect" bandpass and notch simply by adding/subtracting signals, but does produce a new type of filter effect.
The variety of controls allows a lot of functions that are not available for any other filter, one of the main effects of the asymmetrical limiting is that in self-