Voltage Controlled Low Pass Filter


SW904A Voltage-Controlled Low Pass Filter attenuates frequencies above the fixed control voltage cutoff point at a rate of 24 dB per octave. The cutoff frequency is voltage controlled through the control input jacks. The sum of the applied control voltages doubles the frequency of the cutoff point for each one Volt increase. The regeneration potentiometer varies the amount of internal feedback, creating a resonant peak at the cutoff frequency. This resonant peak will break into oscillation at clockwise settings of the regeneration potentiometer, creating a voltage controlled sine wave generator. The fixed control voltage potentiometer covers a 12 Volt (octave) range. The overall range of the FCV potentiometer is determined by the Frequency Range switch, which moves the frequency cutoff range in twooctave steps.

This Module is based on the original design from 1970

The Voltage Controlled Low Pass Filter is one of the building blocks of analog synthesis. The characteristic upper spectral sweep found in wind instruments articulation is simulated utilizing this filter and the DC voltage supplied by an Envelope Generator with each trigger from a controller. Virtually, every instrumental simulation can use this filter arrangement as part of its overall patch. The lowpass filter is a key module in creating widely varying timbres via subtractive synthesis.
Status - available
Cutoff Frequency fc range:
Signal Input Impedance:9.2 k ohm
Signal Input Level:0 dBm nominal, +10dBm max without clipping
Attenuation slope above Fc:24 dB per octave
Control Input Frequency Response:DC to 50 kHz
Control Input Impedance:100k ohm
Number of control inputs:3
Output Impedance:680 ohms (AC coupled)
Power Requirements: +/-15 Volt at + 75 mA / - 40 mA
Depth:160 mm


  • 75 mA +15V
  • 40 mA -15V
  • ? mA 5V
  • 160 mm deep
  • Ø 5.00 (1 Votes) Average Rating

This Module is currently available.

$377 Price in €
2 HP Filter
submitted Jun 2nd 2013, 18:48 by solitud | last Change Aug 5th 2017, 14:14 by analogdarkside