Opto Phase is an analog-modelled phaser effect, based on a custom-designed phaser circuit. The phaser circuit functions using a light-source (e.g. an LED) driven by a low-frequency oscillator (LFO), which is then coupled to a series of light-dependent resistors, which in turn control the cutoff frequencies for a set of allpass filters, thereby creating a modulating "phasing" effect.

In this effect, the dynamics of the opto-couplers are modelled using a physically-informed differential equation solver, while the rest of the circuit is modelled using Modified Nodal Analysis. The "Rate" knob controls the speed of the LFO driving the phaser effect.

The "Feedback" knob controls the amount of signal being fed-back from the output of the effect back into the phaser circuit.

The "Frequency" knob controls the "base" cutoff frequency for the allpass filters, and the "Range" knob controls how far the cutoff frequencies are allowed to be modulated.

The "Stages" knob controls how many allpass phasing stages are in the circuit. A 2-stage phaser corresponds to a "45 degree" phase shift, 4 stages corresponds to 90 degrees, and so on.

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