PolyBrute - Voice Architecture

Yes. Some aspects of the PolyBrute are digitally controlled, but it uses VCOs (voltage controlled oscillators), analog filters, and has a fully analog signal path except for the effects (chorus, phaser, flanger, ring modulator, delay, and reverb), which are digital.

Each of the Polybrute’s six voices of polyphony offers two VCOs plus a noise generator.

Both are continuously variable between sawtooth and triangle. In turn, the sum of those two waveforms can be blended with a pulse wave with variable width.

The Metalizer in VCO1 adds intense and non-serial harmonics to the triangle component of the waveform output. It does this via a process called wavefolding.

• Imagine folding the peak of a triangle so that it points towards the opposite side. On top, you’d now have an upside-down W shape with two peaks.
• Repeat with the negative phase of the waveform.
• Now, fold all the new peaks again … and again … and again.

Turning the Metalizer knob up further increases the number of folds, resulting in increasingly “jagged” harmonics. Gentle settings add a bit of edge to the sound that’s different from distortion or clipping. Extreme amounts can add a character reminiscent of early digital wavetable synths.

VCO2 features a sub-oscillator that produces a sine wavean octave below the fundamental pitch.

The Sub knob blends between the main waveform and sub-oscillator such that if you turn it all the way up, you only hear the sub-oscillator.
At 12 o’clock, you hear equal parts sub-osc and main waveform.

That and more. The Sync 2>1 knob progresses smoothly from no sync at all to full hard sync in which the pitch of VCO2 is locked to that of VCO1.
This allows for much more harmonic variation than a traditional on/off option for sync.

Yes. The FM 2>1 knob modulates the frequency of VCO 1 with that of VCO2 in linear fashion.

There are two: a 12db-per-octave Steiner filter inspired by the vintage Steiner-Parker Synthacon, and a 24-db-per octave classic Ladder filter inspired by a world-famous monophonic synth.

Each VCO (and the noise) can be routed to either or both filters via buttons in the Mixer section:

VCF1 is continuously state-variable between lowpass, highpass, and bandpass modes.

Notch filtering is even possible about midway between lowpass and highpass. It also has Brute Factor.

This Arturia exclusive was introduced with the MiniBrute synth. On the PolyBrute, it’s a feedback circuit in the Steiner filter and VCA. Since it’s taken post-VCA, it can add a little grunge, aggressive overdrive, or anything in between. It interacts with the cutoff, resonance, and other settings in non-linear ways, so be sure to experiment!

Yes. Either filter self-oscillates at high resonance settings, meaning you will hear sound with no VCOs in the mix.
This will further be affected by the Key Track setting, cutoff, and Filter FM.

The PolyBrute has a knob (VCO2 > VCF1) to modulate VCF1 (Steiner filter) with the pitch and waveform of VCO2.
Varying the amount in conjunction with other VCO and filter settings can produce unexpected and interesting harmonics and sidebands, from gentle to clangorous.

In addition, the noise source can modulate VCF2 (Ladder filter), with the Noise Colour knob varying the sonic result.

Both. A knob in the Ladder filter section can actually blend between series (VCF1’s output into VCF2) and parallel. Either filter’s output may be panned in stereo as well, by setting its pan as a modulation destination.

You can also hold the Settings button and move the Stereo knob to bring up a menu with the option Voice + Filter Pan.
When this is selected and the filters are in parallel, they are gradually distributed across the stereo field as the knob is turned clockwise.

The PolyBrute was designed around the idea of placing almost no limits on modulation possibilities.
You can modulate virtually any parameter with multiple sources.

Read our section on the Matrix for details.