Our Glasgow shop is currently closed – we are still here to help and you can get in touch by email or phone

WMD C4RBN 4/2-Pole State-Variable Filter w/ Wavefolding

With free UK shipping
C4RBN by WMD is the building block to life in your eurorack.
Email me when available

Temporarily out of stock

Due back in stock in 1-3 days

Order by phone on: 0141 221 9650

14 Day Money Back Guarantee! See our returns policy.

Manufacturer: WMD

Category: Eurorack



C4RBN ("Carbon") is a 4/2-Pole State Variable Filter with input saturation, output wavefolding, and more. It features a wide range of character from nice and clean filter sounds to screaming, squelchy, acidic mayhem.

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 plus the output wavefolder from WMD’s classic SYNCHRODYNE filter pair together to push the timbral flexibility to the next level.


  • HP/BP/LP (LEDs & BUTTON): Cycle through the 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.
  • FM: Inverting attenuator for scaling the signal at the FM input jack. Input is exponential and controls filter cutoff.
  • SAT: Analog CV input for the input saturator. Offers greater control over the saturation level.
  • RES: Manual and CV control of filter’s resonance. Self oscillates above 3’Oclock.
  • LP/BP/HP/4 POLE: LP, BP, and HP are the respective outputs of the first 2-Pole filter. 4P is the output of the 2nd, series, 2-Pole filter with selectable frequency response and output wavefolder.
  • FREQ: Manual filter cutoff frequency control. 2.5Hz to 10kHz
  • 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 4 levels of input saturation. The current level is indicated by the SAT LED.
  • PING: Sending a gate or trigger into ping generates a fast decay envelope emulating the response of a vactrol.
  • V/OCT: Calibrated exponential CV input for controlling filter cutoff in the classic keytracking style.
  • IN: Audio input passes through the input saturator before entering the first 2-Pole filter.




Size: 4hp
PCB: 112mm
Depth: 38mm (with cables)
Power: +92mA, -82mA

Audio Input:
100k ohm impedance
20Vpp range

V/Oct Input:
82k ohm impedance
Temperature Compensated

CV Inputs:
>100k ohm impedance

Filter Outputs:
1k ohm impedance
20Vpp range