A*B+C is a dual, four-quadrant multiplier with VC Offset that can act as Dual Ring Modulator, Dual VCA and Four Channel Mixer. Each section can perform the analog multiplication of two signals (A and B) and add an offset (C).


  • Dual-channel bipolar VCA’s
  • Adjustable VC Offset per channel.
  • AM and Ring Modulation capabilities.
  • Output normalization allows it to work as a four-channel mixer.


  • Current needs: +12V: 40mA, -12V: 40mA
  • Width: 6 HP
  • Depth: 25 mm (including power connector)
  • Aluminium, heat-treated front panel
  • Designed, kits prepared and completed modules assembled in Barcelona,


*This iBOM is meant to be used together with Befaco’s Assembly guide.

B inputs are routed to an attenuverter that multiplies the signal between -2 to 2, while the offset inputs (C) route through a unity gain attenuverter (multiplies the signal between -1 and 1).
B and C inputs are normalized to 5v and 10v respectively, so the A inputs can be processed using just the potentiometers.
The output of the first block is normalized to the second one, so the second output can act as a master to get (A1*B1+C1) + (A2*B2+C2).