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: +12V: ≈33mA; -12V: ≈31mA
  • 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
Please note: The panels of the modules are made from untreated natural aluminium, hand printed and varnished. Due to this manufacturing process, their surface may have little scratches or unregularities or may slightly differ in their color appearance.


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