BogaudioModules

Modules for VCV Rack, an open-source Eurorack-style virtual modular synthesizer:

• Oscillators
• LFOs
• Filters
• Envelopes and Envelope Utilities
• Mixers, Panners and VCAs
• VCAs and Dynamics
• Noise/Random, Sample and Hold
• Sequential Switches and Sequencers
• Visualizers
• Polyphony Utilities
• Pitch CV Utilities
• Other Utilities
• Miscellaneous

Most Bogaudio modules support VCV Rack's polyphony feature; see <a href="#polyphony">Note on Polyphony</a>.

Some modules have expanders; see <a href="#expanders">Note on Expanders</a>.

Many modules support bypassing in a non-default way; see <a href="#bypassing">Note on Bypassing</a>.

The modules have two <a href="#alternate_panels">alternate panel designs</a>, "Dark":

And "Dark (low-contrast)":

Builds/Releases

Mac, Linux and Windows builds of the latest version are available through the VCV Rack Library. Find release notes on the releases page.

Building

You'll need to be set up to build VCV Rack itself. Under the Rack build directory, switch to plugins/, and then:

git clone https://github.com/bogaudio/BogaudioModules.git
cd BogaudioModules
make

The master branch of this module currently builds against Rack 2.0.x.

Modules

<a name="oscillators"></a> Oscillators

<a name="vco"></a> VCO

A standard VCO featuring:

• Simultaneous square, saw, triangle and sine wave outputs.
• Traditional exponential and linear through-zero FM.
• Pulse width modulation of the square wave.
• Hard sync.
• Slow (LFO) mode.
• Antialiasing by a CPU-efficient combination of band limiting and oversampling.

The main frequency knob is calibrated in volts, from -4 to +6, corresponding to notes from C0 to C6. The default "0V" position corresponds to C4 (261.63HZ). Any pitch CV input at the V/OCT port is added to the knob value to determine the oscillator frequency. With CV input, the pitch can be driven as high as 95% of the Nyquist frequency (so, over 20KHZ at Rack's default sample rate). The FINE knob allows an additional adjustment of up to +/-1 semitone (100 cents, 1/12 volt). In slow mode, the output frequency is 7 octaves lower than in normal mode with the same knob/CV values.

In linear mode, the frequency 1000HZ times the pitch voltage (as determined by the knob plus V/OCT CV) -- at 0V, the frequency is zero, and the oscillator stops. In slow mode, it tracks at 1HZ times the pitch voltage. Negative voltages will realize the same output frequency as the corresponding positive voltage (the oscillator runs backwards). Use with with an FM input to create strange waveforms.

The context menu option "DC offset correction", on by default, removes DC offset from the outputs. Presently, this only affects the square output when the pulse width is set to anything besides 50%. When this is enabled, and viewing the output on a scope, the waveform will move up and down relative to 0V as the pulse width is changed -- this is the DC offset removal in action. When disabled, the waveform stays centered on 0V, which is useful if using the output as CV.

Polyphony: <a href="#polyphony">polyphonic</a>, with channels defined by the V/OCT input. The poly port can be changed to the FM input on the context menu.

When <a href="#bypassing">bypassed</a>: no output.

<a name="lvco"></a> LVCO

A 3HP subset of VCO, designed as a compact general-purpose oscillator. The waveform is selectable between sine, triangle, saw, square and 25% and 10% duty-cycle pulses. FM and linear modes are selectable on the context menu.

Context menu option "Reset phase on wave change", if enabled, causes the waveform phase to be set to zero when the waveform is changed. By default the continues to advance from wherever it was.

Polyphony: Same as VCO.

When <a href="#bypassing">bypassed</a>: no output.

<a name="sine"></a> SINE

A 3HP subset of VCO, designed in particular for use making synth drums. The waveform defaults to sine but is selectable on the context menu, with the same options as LVCO, with the addition of a ramp (inverse saw) wave.

Additionally, there is a phase control with CV borrowed from XCO (if CV is used, the input is attenuverted by the PHASE knob). This sets the initial position of the wave when the module is synced (if you're not using sync, changing the phase won't meaningfully alter the output). This can be used to alter the harmonic content of sync sounds, and for transient shaping for drum synthesis.

Polyphony: Same as VCO.

When <a href="#bypassing">bypassed</a>: no output.

<a name="pulse"></a> PULSE

A 3HP subset of VCO, oriented toward pulse-width modulation. The only output waveform is square/pulse, and there is no FM. However, the PWM CV input has a dedicated attenuverter, and unlike VCO, the result CV value is summed with the PW knob position.

Polyphony: <a href="#polyphony">polyphonic</a>, with channels defined by the V/OCT input.

When <a href="#bypassing">bypassed</a>: no output.

<a name="xco"></a> XCO

Includes all the features of VCO, adding:

• An onboard wave mixer with output at the MIX port.
• For each wave type:
  • A wave modifier (pulse width for square; saturation for saw; a sample-and-hold/step-function effect for triangle; FM feedback for sine).
  • A phase knob/CV controlling the phase of the wave in the mix.
  • A mix knob/CV to control the level of the wave in the mix (waves are output at full level at their individual outputs). The mix knob/CV responses are linear in amplitude.
• A CV input for FM depth.

The context menu option "DC offset correction" works as documented on <a href="#vco">VCO</a>.

The context menu option "Mix output processing" sets how the mix output is scaled or clipped. VCV Rack modules generally should not output signals exceeding +/-12 volts, and oscillators typically output +/-5 volts. However, XCO's mix output combines four oscillators, and can easily exceed these values. "Mix output processing" sets how to deal with this:

• "Scaled to +/-5V" (default): the output is directly scaled down to +/-5V (like a regular oscillator) when it would otherwise exceed that range (it will not scale up; it is possible to reduce the output below this range with the MIX controls). The scaling is updated once per oscillator cycle, and abrupt parameter changes can confuse it; in this case hard clipping takes over.
• "Saturated": a saturator (soft clipper) keeps the output within +/-12V.
• "Hard clipped": the output is simply clipped at +/-12V.
• "None": no scaling or limiting is applied to the output, ignoring the voltage standards. This was how XCO always behaved prior to version 2.*.41. Older patches should restore this mode if affected by the addition of these options.

Polyphony: <a href="#polyphony">polyphonic</a>, with channels defined by the V/OCT input.

When <a href="#bypassing">bypassed</a>: no output.

<a name="additator"></a> ADDITATOR

An additive oscillator, where the output is the sum of up to 100 individual sine/cosine waves (partials). Various parameter knobs/CVs allow control over the number, frequencies and amplitudes of the partials:

• PARTIALS: sets the partial count.
• WIDTH: sets the spacing of partials in frequency; at the default position each successive partial is pitched an octave higher than the one before.
• O-SKEW: adjusts the spacing of odd-numbered partials up or down relative to WIDTH.
• E-SKEW: adjusts the spacing of even-numbered partials up or down relative to WIDTH.
• GAIN: Sets the level of the output by adjusting an internal amplitude normalization parameter.
• DECAY: applies a positive or negative tilt to the amplitude decay of the partials; at the default position, amplitudes decrease proportionally with increasing frequency.
• BALANCE: cuts the amplitudes of the odd or even partials.
• FILTER: manipulates the partial amplitudes to simulate low or high-pass filter effects.

Polyphony: <a href="#polyphony">polyphonic</a>, with channels defined by the V/OCT input.

When <a href="#bypassing">bypassed</a>: no output.

<a name="fmop"></a> FM-OP

A sine-wave oscillator and simple synth voice designed to allow patching up the classic FM algorithms (using multiple instances). Features:

• Linear through-zero FM response.
• CV-controllable FM depth.
• CV-controllable FM self-feedback.
• CV-controllable output level. The LEVEL knob and CV have a linear-in-decibels (exponential in amplitude) response; a context-menu setting makes this linear in amplitude.
• An on-board ADSR, controlled by the GATE input, with selectable routing to output level, feedback and depth, with CV control over the sustain level.
• A main frequency knob calibrated for setting the frequency as a ratio of the frequency dictated by the V/OCT input - assuming a single V/OCT CV i