Shop Now

C4RBN

C4RBN module front panel: a narrow 4HP black Eurorack panel with three large knobs (FREQ, FOLD/SAT, FM/RES), a column of HP, BP, and LP filter-mode LEDs, FOLD and SAT LEDs, two buttons, and ten patch jacks arranged in two columns labeled SAT, PING, FM, RES, IN, V/OCT, BP, HP, LP, and 4P.

4/2-Pole State-Variable Filter w/ Wavefolding

1Introduction

C4RBN builds on WMD's history with state-variable filters, adding interface refinements and improved warm-environment stability for live performance and beyond. A novel input saturation circuit and the output wavefolder from WMD's classic SYNCHRODYNE filter pair together to push the timbral flexibility to the next level. C4RBN is the building block to life in your Eurorack.

2Front Panel Overview

Diagram of C4RBN's front panel from top to bottom: a FREQ knob beside a column of HP, BP, and LP filter-mode LEDs and the filter-mode button; a FOLD/SAT knob with FOLD and SAT LEDs and the fold/sat button; an FM attenuator knob; a RES knob; then five rows of paired jacks labeled SAT and PING, FM and RES, IN and V/OCT, BP and HP, and LP and 4P.
C4RBN front panel controls and connections.

2.1Controls

  1. FREQ: Manual filter cutoff frequency control. 2.5 Hz to 10 kHz.
  2. HP/BP/LP (LEDs & Button): Cycle through the four 4-Pole frequency responses. The LED changes immediately, but the audio will wait until the user has made their selection. Holding the button will delay the audio change until release.
  3. FOLD/SAT (LEDs & Button): Press this button to toggle the 4P output wavefolder. The FOLD LED will be lit if it is enabled. Hold this button to cycle through four levels of input saturation. The current level is indicated by the SAT LED.
  4. FM: Inverting attenuator for scaling the signal at the FM input jack. Input is exponential and controls filter cutoff.
  5. RES: Manual and CV control of the filter's resonance. Self-oscillates above 3 o'clock.

2.2Inputs & Outputs

  1. IN: Audio input. Passes through the input saturator before entering the first 2-Pole filter.
  2. SAT: Analog CV input for the input saturator. Offers greater control over the saturation level.
  3. FM: Exponential CV input for filter cutoff, scaled by the FM attenuator.
  4. V/OCT: Calibrated exponential CV input for controlling filter cutoff in the classic keytracking style.
  5. RES: CV input for the filter's resonance.
  6. PING: Sending a gate or trigger into PING generates a fast-decay envelope emulating the response of a vactrol.
  7. LP / BP / HP / 4P: LP, BP, and HP are the respective outputs of the first 2-Pole filter. 4P is the output of the second, series, 2-Pole filter with selectable frequency response and output wavefolder.

3Specifications

Dimensions:

  • Size: 4HP
  • PCB: 112mm
  • Depth: 38mm (with cables)

Power:

  • +92mA, -82mA
  • Memory: 1 save / minute

Inputs:

  • Audio Input: 100k ohm impedance, 20Vpp range
  • V/Oct Input: 82k ohm impedance, Temperature Compensated
  • CV Inputs: >100k ohm impedance

Outputs:

  • Filter Outputs: 1k ohm impedance, 20Vpp range