Essential Building Blocks Included with Rack

Fundamental is Rack’s starter pack of sound generators and processors for creating simple synthesizers, routing and analyzing signals, complementing other plugins, and building not-so-simple patches using brute force (lots of modules).

VCO-1 & 2 Manual

A Voltage Controlled Oscillator generates raw tones at a particular frequency controlled by a voltage signal. The VCO-1 module is a traditional analog/digital oscillator with four output waveforms: SIN (sine), TRI (triangle), SAW (sawtooth), and SQR (square). VCO-2 is an oscillator that allows morphing between these four waveforms.

With the ANLG/DIG switch in the ANLG position, analog-modeled waveforms are used. In most cases, like subtractive synthesis, analog waveforms are often preferred due to their imperfect and “more musical” harmonics.

Fundamental VCO sine wave Fundamental VCO triangle wave Fundamental VCO sawtooth wave Fundamental VCO square wave

In the DIG position, mathematically-perfect waveforms are generated instead. In some cases, a digital sound is preferred, like FM synthesis for example, to emulate the classic 80’s FM style.

The pitch of each oscillator is controlled by the FREQ knob, with a range of 9 octaves, and the FINE knob (only on VCO-1), with an additional range of 2 semitones. In digital mode, the FREQ knob snaps to exact semitones in the chromatic scale. In their initial states with FREQ and FINE at 12-o’clock positions, the note C4 (middle C) is generated. Like all parameters in Rack, you can right-click a knob to reset it to its initial position.

To control the pitch externally, use the V/OCT input (only on VCO-1) or the FM input. The V/OCT input tracks at 1V/octave, meaning that an increase of 1V increases the pitch by one octave, doubling the frequency. This is the standard used in all MIDI interfaces, quantizers, and some sequencers in VCV Rack.

The FM input applies an additional pitch adjustment with an included FM CV attenuator knob. With the FM CV knob hard-right, the FM input functions similarly to the V/OCT input. In fact, this is the only way to achieve 1V/octave tracking on the VCO-2 module. At lower knob positions, a smaller adjustment can be made to the pitch, for subtle vibrato, for example.

The SYNC input applies hard-syncing to the waveforms by resetting the phase of the waveform when the sync signal passes upward through 0V. If an audio-rate signal is patched into the SYNC input, the result is a waveform having characteristics of both the internal and sync frequencies. By toggling the HARD/SOFT switch to the SOFT position, soft-sync is used instead, which reverses the direction of the waveform when the sync signal passes through 0V. This results in a “softer” effect with fewer harmonics than hard-sync.

The P. WIDTH knob adjusts the pulse width (aka duty cycle) of the square waveform, and the PWM input and its PWM CV attenuator knob allow external pulse width control. The following are examples of a digital square wave with 1%, 25%, 50%, and 75% pulse width.

Fundamental VCO square wave 1% pulse width Fundamental VCO square wave 25% pulse width Fundamental VCO square wave 50% pulse width Fundamental VCO square wave 75% pulse width

On the VCO-2 module, the WAVE knob and CV input selects a waveform to generate at the OUT port. As the knob is increased, the output morphs between sine, triangle, sawtooth, and square. Intermediate values are blended, so it is possible to have a half-triangle, half-sawtooth wave, for example.

VCF Manual

A Voltage Controlled Filter removes a range of frequencies from an audio signal, with its cutoff frequency controlled by an external voltage. Fundamental VCF models a 4-pole transistor ladder filter with saturation at each stage.

Note: The high-pass output of Fundamental VCF is currently non-functional. This feature will be added in the future.

More coming soon

VCA Manual

A Voltage Controlled Amplifier allows the level of an audio or CV signal to be controlled by another CV signal. Fundamental VCA includes two VCAs with both exponential and linear response, and an attenuator knob.

A signal passing through IN to OUT is attenuated with the LEVEL knob with a gain ranging from 0 to 1.

If a CV signal is patched into LIN, the signal is also attenuated based on this control voltage, or “enveloped” by the control voltage ranging from 0V to 10V. A CV of 10V applies a gain of 1, while a CV of 0V (as well as negative CV) mutes the signal completely.

The EXP input gives an exponential response for more exaggerated and faster envelopes.

Fundamental VCA envelope In this figure, a constant sine wave is being attenuated by an ADSR envelope CV signal (pink), using a VCA to combine the signals into the enveloped output (blue).

Ideally, linear VCAs obey the equation out = in × (CV / 10V) for positive CV, and out = 0V for negative CV. For example, a CV signal of 2.5V applies a gain of 0.25 to the input signal. The golden rule of VCAs: “It’s just multiplication.”

LFO-1 & 2 Manual

Coming soon

Delay Manual

Coming soon

ADSR Manual

Coming soon

VC Mixer Manual

Coming soon

8vert Manual

An “attenuverter” is an attenuator that can also reach negative values. 8vert is utility module with 8 inputs, 8 attenuverters, and 8 outputs.

Each attenuverter can apply a gain ranging from -1 to 1. In its initial position at 12-o’clock, a gain of 0 is applied, resulting in a silent output signal. Positioned hard-right, the input signal passes through without modification, and positioned hard-left, the input is inverted, flipping its value.

The top input of 8vert is normalized to 10V, meaning that a constant 10V signal is used instead when no cable is patched. All other inputs are normalized to the input above it, allowing inputs to “copy” their signal downward.

When no inputs are patched into a channel and all channels above it, these inputs are all effectively normalized to 10V. This turns 8vert into a constant voltage generator with voltages set by each of the attenuverters from -10V to 10V.

As another example, if a cable is patched into the first input only, all channels below receive the same signal and can attenuvert it independently based on each attenuverter’s position.

Unity Manual

Coming soon

Mutes Manual

The Mutes utility module contains 10 channels of switches which allow quick control over muting a signal. Click a button to toggle the mute state of each channel.

Each input is normalized to the input directly above it. In other words, all inputs “copy” their signal to the channel below it. For example, Mutes is able to function as a multiple module that copies one input to up to 10 outputs, with additional mute control for each output.

Like other modules, randomization and initialization from the module’s context menu can affect the state of the mute buttons.

Scope Manual

Coming soon

SEQ-3 Manual

Coming soon

Sequential Switch 1 & 2 Manual

Coming soon