befaco-bf-22-vcf

Befaco BF-22 VCF

Dual MS-20 Sallen-Key filter with dirty character

17 HP Eurorack module

The BF-22 is a dual Sallen-Key voltage-controlled filter inspired by the early Korg MS-20, offering two independent hi/low-pass filter sections that can be linked in series. It carries the character of the original MS-20 filter — warm, dirty, and capable of aggressive screaming resonance — with added attenuverters for CV control and selectable 6/12 dB slopes.

Features

  • Dual independent Sallen-Key filter sections (A and B)
  • Inspired by the early Korg MS-20 filter circuit
  • Selectable high-pass or low-pass response per filter
  • 6/12 dB per octave slope selection
  • Cut-off CV attenuverters for bipolar CV control
  • Volt/Oct tracking on cut-off CV input across 4 octaves
  • CV inputs for both cut-off and resonance per filter
  • LINK switch connects Filter A output to Filter B input for series operation
  • Eurorack compatible, also runs on +/-15V without modification
  • Banana or mini-jack connector versions available
  • MS-20 character: warm, dirty, and aggressively resonant sound

Controls & Jacks (21)

  • Filter A Cut-off— Manual cut-off frequency control for Filter A
  • Filter B Cut-off— Manual cut-off frequency control for Filter B
  • Filter A Resonance— Manual resonance control for Filter A
  • Filter B Resonance— Manual resonance control for Filter B
  • Filter A LP/HP Switch (6A)— Selects low-pass or high-pass response for Filter A
  • Filter A Cut-off CV Attenuverter (3A)— Bipolar attenuverter for Filter A cut-off CV input
  • Filter B LP/HP Switch (6B)— Selects low-pass or high-pass response for Filter B
  • Filter B Cut-off CV Attenuverter (3B)— Bipolar attenuverter for Filter B cut-off CV input
  • Filter A CV RES (7A)— CV input for Filter A resonance
  • Filter A Cut-off CV Input Attenuated (4A)— Attenuverted CV input for Filter A cut-off
  • Filter A Cut-off CV Input V/Oct (5A)— V/Oct cut-off CV input for Filter A
  • Filter B CV RES (7B)— CV input for Filter B resonance
  • Filter B Cut-off CV Input Attenuated (4B)— Attenuverted CV input for Filter B cut-off
  • Filter B Cut-off CV Input V/Oct (5B)— V/Oct cut-off CV input for Filter B
  • Filter A IN VOL (8A)— Audio input volume for Filter A
  • Filter B IN VOL (8B)— Audio input volume for Filter B
  • Link Switch (11)— Routes Filter A output internally to Filter B input
  • Filter A Audio Input (9A)— Audio input for Filter A
  • Filter A Audio Output (10A)— Audio output from Filter A
  • Filter B Audio Input (9B)— Audio input for Filter B
  • Filter B Audio Output (10B)— Audio output from Filter B

How-To Guides

  • Classic MS-20 Band-Pass Patch
  • Resonant Low-Pass Sweep
  • Inverted CV Cut-off Modulation
  • Parallel Dual Filter Processing
  • Self-Oscillating Sine Wave
  • Resonance Swept by Envelope
  • High-Pass as DC Blocker and Low Rumble Remover
  • LFO Wobble Filter Effect
  • Dual Send-Return Parallel Processing

Explore the interactive BF-22 VCF panel on BleepDex — tap any control to learn what it does.

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