Modular Add-On: Intellijel Rubicon: Thru-Zero FM VCO Module by Softube

The core of Rubicon is a high precision emulated triangle oscillator. Its thru-zero frequency modulation can be switched between linear and exponential modes, with a linear index VCA for dynamic control of modulation depth. Softube notes that the exponential TZFM option is a first for any module of this kind.

Symmetry control runs from normal at full clockwise, through centered where the VCO sits at 0 Hz, to reversed waveforms at full counter-clockwise, and it accepts CV. Pulse-width modulation and exponential FM each have dedicated attenuators.

Rubicon provides 12 primary waveform types, including sine, sigmoid, double sigmoid, triangle, saw, double saw, zigzag, square, and three pulse variants. A suboctave circuit adds outputs at -1 and -2 octaves, and those outputs respond to FM in the same way as the main signals.

For sync, soft sync (also called reversing sync) comes with an attenuator, and hard sync offers a selectable reset direction. That setting controls whether the triangle starts moving up or down after a reset, which the developer notes is especially useful in LFO mode.

Softube Modular is required to run this add-on.