Rachael – Ring Modulator

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Rachael is an analogue ring modulation effects module from Black Corporation. It is based on the Yamaha CS-80 ring modulator circuit and has additional features such as a fully operation analogue Oscillator (VCO/LFO) with the famous CSaw waveform and an Envelope Generator (EG).

Table of contents:

  1. Video replay
  2. Downloads
  3. Tech notes

Video replay:

Content downloads:

Functions Diagram:

Input/Output connections:

Tech notes

Overview and Specifications

  • Dimensions:
    • Size: 14 HP (eurorack format)
    • Depth: 38mm
  • Power:
    • +12/-12V DC – Eurorack standard (5V not used)
    • Consumption: +12V 150 mA and -12V 100 mA (5V not used)
  • Module Functions:
    • Ring Modulation (analogue)
    • Oscillator (VCO/LFO) with Square, CSaw (Saw in LFO mode) and Sine waveform outputs
    • Envelope Generator (EG) – ADSR format
  • Inputs & Outputs:
    • Input for audio source (signal input)
    • 1V/Oct input for VCO/LFO (-5V/+5V)
    • Input for external reference audio (REF IN)
    • ADSR EG (0-10V) with external CV inputs for control over Attack, Decay, Sustain and Release
    • CV Input for Depth that controls balance of modulation amount
    • EG Out (sends envelope generator CV out)
    • Output for modulated signal (effects out)

Ring Modulation

Ring modulation is well known for it’s bell-like sounds, tremolo effects and extreme metallic-like sounds. It is an effect where an audio signal is modulated by a reference signal and then outputs their sum and difference while subtracting the original frequencies. Here’s an example using 2 sine waves – one as the carrier, the other as the modulator and the results combined:

Image courtesy Wikipedia

For more information about what ring modulation is – check out a very good article over on WikiPedia here.

It is important to note that the internal oscillator modulates the audio signal using only a sine wave. This is irrespective of the waveform selection switch (which can only be used with the OSC OUT jack).

The ring modulation effect can be controlled by Speed (Frequency) and Depth. You can also modulate the effect with the internal EG and EG Amount control. In addition there are CV Inputs for Depth and 1V/Oct for pitch controls.

Oscillator (VCO/LFO)

The Oscillator can be used as a standard VCO or LFO. You can access the waveforms at the OSC Out socket. You can select waveforms of Square, CSaw* and Sine. When in LFO mode Saw is produced instead of CSaw.

About CSaw. This is a unique sawtooth waveform which originated from the Yamaha CS-80. It has a glitch in the design that caused the ramp to be led with a thin pulse. This adds to the character that the CS series synthesizers are reknowned for. The CSaw can only be heard from the OSC OUT jack when the Oscillator speed is set to VCO.

Envelope Generator (EG)

The EG produces a 0-10V envelope shaped by the Attack, Decay, Sustain and Release sliders on the front panel. The EG can be used to shape the ring modulation signal as well as an external EG control.

There are also CV inputs that can modulate the Attack time, Decay time, Sustain level and Release time of the Envelope Generator. This is a powerful feature and makes the module quite unique.

Further notes

Black Corporation made the Rachael module as a companion to the Deckards Voice module. The Deckards Voice module is a complete synthesizer voice with a stack of features.

For more information about Rachael, head on over to the Black Corporation website.