Circuit - user manual

Circuit has a colour-coded interface, with crossover filter and waveshape modelling elements in blue, input signal and envelope follower in red, LFO in orange, and Lorenz attractor in yellow.

A simplified schematic diagram of Diffusion's internals is presented below:

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Crossover

When the sound enters Circuit, it is split into three frequency bands. The crossover frequencies between band 1 and 2 can be adjusted from 100 to 400 Hz, and between band 2 and 3 from 800 Hz to 4 kHz. This is done by vertically dragging the frequency handles with labels, located between the bands:

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An on/off switch on each of the three bands defines whether it's being processed or is passed dry into the output. Band output level slider is in effect in both cases.

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Signal processing

Each band lets you choose one of 12 processing models.

The first row has six different waveshape transformer algorithms which change the signal shape using sine-based transfer functions and make the sound very synthetic:

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Non-linear distortion turns the signal into a square wave:

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Foldback distortion warps the signal into a harsh-sounding waveform:

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Circuit-bent low-pass filter produces an extremely raw, buzzing sound:

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Sample rate reduction resamples the signal at a rate of 100 Hz to 22 kHz:

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Bit depth reduction changes the bit depth of the signal from 12 to 1 bit:

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Ring modulator multiplies the signal with a sine wave with frequency from 50 Hz to 5 kHz.

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A waveform scope above the algorithm selector shows approximately how each harmonic partial of the sound will be changed:

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The band output level is adjusted by this staircase-style slider:

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The band model parameter is adjusted by this arrow-style slider:

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Beneath this slider are three bipolar modulation sliders which define the parameter modulation depth from the envelope follower (red), LFO (orange) and Lorenz generator (yellow):

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Input & envelope

The input level is adjusted by the staircase-style slider. It affects the character of the bands which are set to waveshape or distortion models.

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The input section features an envelope follower, which detects the average energy of the input signal and allows you to use it as a modulation source. Envelope follower sensitivity is adjusted with this slider:

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Envelope follower smoothness is adjusted with this slider:

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LFO

The low-frequency oscillator generates a repeating modulation signal and is always synchronised to the host sequencer tempo and position. It can be set to one of four waveforms: triangle, saw, square and pulse:

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The current LFO phase is indicated by a rotating arc around the rate display:

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The rate can be set from as fast as 1/64 note to as slow as 4 bars, using the arrow-style slider:

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Lorenz attractor

Lorenz attractor is a dynamic chaos system typically used for modelling the flow of air. It generates a continuous signal which is smoothly fluctuating and never repeating. The Lorenz chaos generator's approximate output is displayed as a two-dimensional shape:

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It has a variable rate which is adjusted using this slider:

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