The 4075 LOW-PASS 36A Filter is a faithful recreation of the 24db low-pass filter found in late model Arp Odysseys. The filter topology is almost identical to the Arp 4072 filter module found in later editions of the ARP 2600 synthesizer.
The following two mp3s are examples of the 4075 as a self oscillating sine wave generator being modulated by the
Sequencer 17a and a variety of LFOs,ADSRs and Oscillators.
Self-oscillation1.mp3
Self-oscillation2.mp3
Input 1-3
An on-board mixer sums the three inputs together and the level control knob sets the overall input level to the
filter. Moderate gain settings provide the smoothest sound but higher gain settings are better for high resonance sounds.
1V/Oct Input
Exponential converters track linear voltage input at 1 volt per octave. This input is primarily used for keyboard
tracking and pitch control of filter in self-oscillation mode.
CV Input 1
Control Voltage input with attenuator to control the depth of frequency modulation. When the knob is centered no
modulation occurs. Positioning the knob to the left of zero inverts the incoming voltage (negative) and to the right the
voltage is non-inverted (positive).
CV Input 2
Secondary Control Voltage input with attenuator. CV inputs are used to control the filters cutoff point. The most
common input signal would be from an envelope generator or LFO.
Resonance Control
This knob varies the height of the resonant peak at the cutoff frequency of the filter.
Resonance CV
CV input to control the resonance amount with an attenuator to control depth of modulation
Specs: Wide-range lowpass filter with variable-height
resonant peak at cutoff frequency.
4 pole response
24db/oct cutoff slope
Range:Continuously variable from 16Hz-18kHz
Input impedance: 100K ohms
Output impedance: 1k ohms
Control Sens: 1 volt per octave