GPrackmodules
Stereo Chorus
Stereo Chorus is a module in the GP plugin for VCV Rack 2
Features
The Chorus effect adds complexity to signals by duplicating input signals and applying pitch modulation to them.
- Four internal LFOs to control four Stereo voices.
- Left and right channels of one voice are modulated from the same internal LFO, but with a 90-degree phase offset.
- Additional or exclusive external modulation of all eight independent circuits is available through modulation inputs.
- CV inputs with attenuverters can control most parameters.
Sockets
- One or two audio inputs can be fed into the IN sockets in the lower left corner of the front panel. The IN sockets will accept all signals from polyphonic cables and sum them together before going into the monophonic signal processing.
- The processed signal is provided in the OUT section in the lower right corner. If both audio IN and OUT are stereo, there is no audio crossfeeding between channels, so Stereo Chorus can be used as a dual Mono Chorus with a shared set of parameters. The OUT sockets provide a monophonic signal.
- MODULATION inputs 1 through 4 accept voltages for external modulation of the voices. Each modulation input can accept polyphonic cables and will use a signal on channel 2 for independent modulation of the right channel of each voice. Modulation input 1 is marked 1/P, since it can also be used to modulate all eight circuits with one polyphonic cable. The polyphonic cable must carry exactly eight channels, regardless of the number of voices selected in Stereo Chorus. You can use the VCV MERGE module to combine eight modulation sources into one cable and plug that into modulation input 1/P. Channels 1 through 4 control the left side if the voices, channels 5 through 8 control the right sides. Set the number of channels in the MERGE modules to eight.
- The RATE, DEPTH, TONE and WET control voltages are multiplied with the respective attenuverters and then applied to parameters in addition to the values adjusted with the front panel knobs. See below for details.
Parameters
Main Parameters
RATE
The RATE parameter controls the frequency of the internal LFOs in a range from 1 to 10 Hz. If you turn the RATE knob all the way down, the internal LFOs will be deactivated and only external modulation will take place. Please note that switching to “External Modulation Only” and back will lead to a sudden jump in delay with a little click. Therefore, this LFO deactivation is not accessible through the RATE control voltage.
DEPTH
The DEPTH parameter determines the amount of pitch modulation taking place. Normally this also depends on the frequency of the modulation signal, but for the internal LFOs this gets compensated, so regardless of the RATE setting pitch variation at the maximum DEPTH setting will be about +/- one semitone.
TONE
The TONE parameter controls the frequency content of the wet signal. If turned to the left (values -100% to -1%) a lowpass is applied to make the signal sound darker. If turned to the right (1% to 100%) a highpass will cut away some of the low frequencies to provide a clearer, less muddy signal.
VOICES
The VOICES parameter determines how many voices are active. More voices give a more complex signal. If more than one voice is activated, the internal LFOs are detuned against each other by a few percent.
WET
The WET parameter defines the mix between the input signal and the processed effect signal.
Attenuverters
The four attenuverters determine the amount of CV control for their respective parameters. In the middle position the CV input is inactive. They are applied as a factor to the control voltages between -1 (displayed as -100%, inverts the CV) and 1 (100%, no inverting).
To be able to sweep the whole range of the RATE, DEPTH and WET parameters with a 0 to 10 V control voltage, set the knob for the parameter to the minimum position and turn the attenuverter to 100%. For inverted control turn the parameter knob to its max position and set the attenuverter to -100%.
For the TONE parameter, set the TONE knob to the middle position and set the attenuverter to -100% or 100% to be able to sweep the full range with CV.
Smaller percent values than +/- 100% reduce the parameter changes by the CV inputs accordingly.
External Modulation
The internal LFOs and the parameter ranges were chosen to achieve musical results. Especially the limitation of pitch changes based on the LFO frequency makes it impossible to do really outlandish things. While the internal LFOs are active, external modulation is also reduced by 50% to achieve a complex mix of internal and external modulation.
If you want to explore wilder sounds, turn the RATE knob all the way down, RANGE all the way up and use external modulation only. In this mode a 1 Hz sine wave modulation will create about +/- one semitone of pitch modulation, higher modulation frequencies can result in much higher pitch changes.
Sample Applications
CV Control with MIDI Modulation Wheel
External eight channel modulation using the VCV MERGE module