CG Products
design — construction — sound

Eurorack Module


4-Quadrant Multiplier

X front side view
Front view
  • Ring or amplitude modulation
  • Voltage controlled amplification
  • Exponential conversion
  • Wave shaping
  • Dynamic expansion
  • One input with adjustable level and offset control
  • Works both with audio and CV signals
  • Red LED for overdrive indication
  • Easy to use
  • Width: 6 HP
  • Dimensions: 128,5 mm x 30,2 mm
  • Depth: 35mm
  • Supply voltage: ±12V
  • Current consumption: ≈25mA
  • Optionally with banana or 3,5mm minijack
The amplitude multiplier module X is multiplying the two applied input voltages X in and Y in. A multiplication of 2 both positive or both negative input voltages will result in a positive output voltage, while a multiplication of 1 negative and 1 positive signal input will generate a negative output signal (phase inversion). The results are ring/amplitude modulated sounds or control voltages.

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One of the input, X in, is equipped with several manual control options: A switchable exponential converter for VCA-like applications etc.; a Level knob to amplify or attenuate the input signal, an inversion switch and an adjustable Offset voltage, which can be added to this input. The offset knob is also allowing a ‘dry/wet’ style control over the Y input and the modulated signal, or may be used to shift the multiplier’s working point. In addition, there is a little red LED indicating when this input is becoming overdriven.
In comparison with the 1st input X in, the 2nd input Y in has no extra features or controllers – to reduce the complexity and keep the handling more simple.
The output (W out) is internally attenuated to ensure that the product voltage of X×Y is almost in the range between the ±12V voltage supply.
4-quadrant means: In comparison to a common VCA (2-quadrant operation), a multiplier is processing both positive and negative (control) voltages, causing a ± polarity inversion of the modulated signal for input voltages with unequal polarities (≙ 4-quadrant operation).

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  • X drawing


  • X right side view

    right side

  • X left side view

    left side

  • X banana version

    Banana version

  • X banana version left side view

    Banana version left


Ringmodulation of synthesizer and rhythm machine
X in: Korg MS-20 filtered VCO and noise with different filter settings;Y in: Rhythm machine

Ringmodulation of rhythm machine and trumpet
X in: Rhythm machine; Y in: Preamplified trumpet; different X Offset settings

Ringmodulation of rhythm machine and cymbals
X in: Rhythm machine; Y in: Preamplified cymbals; different X Offset settings

Stereo panorama control with 2 X modules X in 1: triangle/squarewave, X in 2: triangle/squarewave inverted;
Y in 1+2: Rhythm machine / VCO

Envelope shaping with 2 X modules X in1+X in2: trianglewave; Y in 1: VCO; Y in 2: Noise
In exponential mode, depending on X Offset and X Level settings, different modulation waveforms can be achieved.

Noise modulation with 2 X modules and Delay1022 Xin1+Xin2 (exponential mode): pink noise, Yin1: white noise; W out1: Delay In
Y in2: +10V DC voltage W out2: Delay time CV input
Multiplier 1 (modulating white noise) is followed by the delay (delay time modulated by multiplier 2)

Or listen on

Block Diagram

X svg Block Diagram

Examples (linear mode)

Linear mode: switch ‘lin/exp.’ in upper position
X in or Y in = 0 ⇨ W out = 0 X in polarity ≠ Y in polarity ⇨ W out = negative
X in 0 ± + +
Y in ± 0 + +
W out 0 0 + +


X Offset X in Y in W out
0 X in: sinewave Y in (linear mode) W out Offset: 0
+2 X in: sinewave Y in (linear mode) W out Offset: +2
+4 X in: sinewave Y in (linear mode) W out Offset: +4

Examples (exponential mode)

X Level: ≈3 (≙ X in amplification ≈ 1); exponential mode: switch ‘lin/exp.’ in lower position
X Offset X in Y in W out
+3,5 X in trianglewave Y in exponential mode W out exponential mode
Due to the rectifying characteristic of the exponential mode, with different settings of the X input level and X offset several modulation shapes can be achieved for Y in (Y in: +10V DC voltage)
X Offset X in Level X in (ca. 8V pp) W out
+3,5 1 X in trianglewave W out Offset: +3,5
+2,5 2 X in trianglewave W out Offset: +2,5
0 4 X in trianglewave W out Offset: 0
-4 7 X in trianglewave W out Offset: -4