LFO

1. Rate Knob Sets the LFO rate.
2. Pulse Width Knob Sets the duty cycle of the rectangular output, and skews the waveform of the sine and triangular outputs.
3. Phase Knob Sets the the starting point of the waveform when Reset is triggered.
4. Random Knob Randomizes the minimum and maximum voltage of all waveforms.
5. Reset Input Immediately sets the waveform outputs to the phase specified by the Phase knob.
6. Env Input LFO output amplitude can be modulated by connecting an envelope signal here.
7. Start of Cycle Output Triggered every time a new LFO cycle starts, i.e. when it reaches the point within the waveform specified by the Phase knob.
8. Main LFO Outputs Outputs for rectangular, triangular and sine waves.

Overview ⚓︎

This LFO might look simple, but it is packed with features that will make it a go-to module in many patches.

• It has independent outputs for its three waveforms, allowing them to be used simultaneously.
• The Pulse Width knob is a bit of a misnomer; it affects all waveforms, not just the rectangular pulse.
• Instead of having a random waveshape like most LFOs, this one has a Random knob instead. It adds an adjustable amount of randomness to all outputs.
• All knobs can be modulated, which enable frequency modulation, pulse width modulation, phase modulation, and even randomness amount modulation.
• In addition to all these modulation possibilities, the Env input allows amplitude modulation, which makes it easy to shape the output amplitude of the LFO by connecting an envelope signal, such as the output of an ADSR, to the Env input.
• The Start of Cycle output allows you to trigger parts of your patch in sync with the LFO, regardless of the Phase setting.

The LFO was designed to work at CV rate. While it’s possible to somehow coerce it to play at higher frequencies and use it as an audio source, we must warn you that it will sound terribly lo-fi, it will alias badly, and it will probably produce an annoying high frequency buzz. We strongly encourage you to try it.

In Depth ⚓︎

LFO Output ⚓︎

The LFO has three output waveforms. From top to bottom, they are:

• Rectangular
• Triangular
• Sine¹

In the default LFO configuration (50% pulse width, 0% phase, 0% random, Env input unconnected), when the Reset input is triggered, the output waveforms are similar to those appearing next to the output jacks.

As you can see, all waveforms start their cycle with an output of +5V, and they all have an output of -5V at their midpoint, so they can be easily mixed together to create new interesting shapes.

Pulse Width ⚓︎

The Pulse Width knob sets the rectangular wave’s duty cycle, and the sine or triangular wave midpoint.

Technically, the term pulse width doesn’t make sense for the triangle and sine outputs, but it makes sense intuitively.

Here’s what the waveforms look like with a pulse width of 75%.

At 0% or 100%, the triangular output will become a sawtooth, and the sine output will become a curvy sawtooth.

The value can be quickly set to 50% by double-clicking on the knob.

Pulse width modulation is a great way to add movement to the LFO output without changing its frequency, and is implemented as a bouncing modulation input for uninterrupted modulation motion.

Phase ⚓︎

The Phase knob changes the starting point of the waveshapes when the Reset input receives a trigger signal.

This can be used to start the LFO at a known position when a new note is played.

To determine the shape of the waveforms, the effect of the Pulse Width setting is applied first, and the effect of the Phase setting is applied afterwards.

Here’s what the waveforms look like with the phase setting at 25%.

Modulating the phase with another LFO is called phase modulation, and has a waveshaping effect similar to FM. If both LFOs are reset at the same time and their rates have simple ratios (1:1, 2:1, 3:1, 3:2…), then the resulting waveform will be periodic. This opens the door to an infinity of complex LFO waveforms.

Please note that very deep or quick phase modulation can result in spurious triggering of the Start of Cycle output, and can affect the good operation of the random function since new random values are picked when a waveform begins a new cycle. In the worst case, if the phase goes backwards right after starting a new cycle, the random values may be picked twice in quick succession, resulting in a discontinuity even when using a smooth waveform.

Random ⚓︎

The Random knob randomizes the maximum and minimum voltage of each waveform.

• When fully counterclockwise (default double-click position), no randomization is applied and the outputs oscillate between +5V and -5V.
• At midpoint, the maximum voltage of each waveform will be randomized between 0V and 5V, while the minimum will be randomized between -5V and 0V. At that setting, the waveforms will still have an “up-down-up-down” feel.
• When fully clockwise, both the maximum and minimum voltages are fully randomized between -5V and 5V. The waveforms will completely lose their “up-down-up-down” feel. For the rectangular wave, this will be the classic sample and hold effect.

Inputs ⚓︎

Reset

When the Reset input is triggered, the LFO immediately sets the waveform outputs to the phase specified by the Phase knob.

This will also instantly trigger a Start of Cycle signal.

Env

If you wish to apply an envelope to the LFO output, the handy Env input offers an alternative to using a separate VCA module.

A built-in VCA will ensure that the output amplitude matches the voltage on the Env input. Negative voltages will switch the polarity of the LFO.

This is perfectly suited for connecting an ADSR signal, the Mod 1 or Mod 2 inputs of the Keyboard module, or any other kind of unipolar envelope.

This input is normalled to 10V and is limited to ±20V.