The analog filter · MicroFreak guide

6.1BasicsManual §7 p.53, §7.1 p.53, §7.1.1 p.54, §7.1.2 p.54, §7.1.3 p.54, §7.1.4 p.55

Filter types and cutoff

The MicroFreak pairs its digital oscillator with an analogue filter. A filter emphasises some of a sound’s harmonics and suppresses others, which changes its timbre. Picture a searchlight passing over the oscillator’s sound, with a beam that can be wide or tightly focused, picking out some harmonics and leaving others in the dark.

Three filter types

LPF — low-pass: Attenuates frequencies above the cutoff. Lower CUTOFF and the highs fade first, then the mids, until nothing is left. It’s the core of subtractive synthesis and the filter you’ll use most.
BPF — band-pass: Attenuates frequencies above and below the cutoff, so only a band around it gets through. RESONANCE sets how wide that band is.
HPF — high-pass: The opposite of the low-pass: it attenuates frequencies below the cutoff. With CUTOFF fully up everything is removed. As you lower it, more and more of the sound passes, from the top harmonics down.

Key combinations

FILTER TYPE: Switches between the low-pass, band-pass and high-pass filter.

FILTER · FilterTurn CUTOFF and RESONANCE; press FILTER TYPE to choose LPF, BPF or HPF.

Cutoff

The frequency where the filtering takes place. Fully anticlockwise it is about 30 Hz; fully clockwise it is above 15 kHz.

CUTOFF knobRange About 30 Hz to over 15 kHz

6.2BasicsManual §7.1.2 p.54, §7.1.4 p.55, §7.1.5 p.55

Resonance

Early filter users found that feeding a filter’s output back into its input creates a peak around the cutoff frequency. RESONANCE controls that peak. You’ll also see it called emphasis, or Q, for the quality of the filtering.

As you turn it up

Frequencies close to the cutoff get louder and the filter becomes more selective.
The sound starts to ring, and anything passing through is strongly coloured.
At the top of its travel the filter self-oscillates.

In band-pass mode RESONANCE sets the width of the band. Fully anticlockwise, everything passes. As you turn clockwise the band narrows. Fully clockwise the filter self-oscillates and blocks the digital oscillator completely, leaving the filter’s own tone.

From the community

Use the filter as a second voice: HPF, CUTOFF around 25%, RESONANCE fully up, Key/Arp → Cutoff at +100 so it tracks the keys, and CycEnv → Cutoff for movement under a sample or pad. via VolcaNiced on YouTube (1:15)

MicroFreak 5.0: How could I have overlooked THIS before? (Filter Osc + Cycling Envolope Pairing)
VolcaNiced
Uses a self-oscillating high-pass filter tracked by Key/Arp and driven by the cycling envelope as a second bass voice.

6.3IntermediateManual §7.2 p.55, §7.2.1 p.56, §7.2.2 p.56

Animating the filter

Sweeping CUTOFF by hand shows you what the filter does, but the filter really earns its place when cutoff and resonance move on their own. On the MicroFreak the envelope, the LFO and the arpeggiator can all do the moving.

Cutoff modulation: An envelope is the most musical way to move the cutoff, so the MicroFreak’s envelope is wired to it permanently. FILTER AMT, next to SUSTAIN, sets how far it moves. Turn that knob and the matching matrix point lights up; you can fine-tune the amount there too.
Resonance modulation: More emphasis focuses the filter on the frequencies near the cutoff and boosts them. Modulating it varies how sharp and ringing the filter sounds.

Where to take it next

The envelope — the envelope and FILTER AMT, including a classic slow filter sweep to try.
The LFO — LFO to cutoff is a ready-made matrix route, ideal for sweeps and wobbles.
The cycling envelope — a looping envelope with shapes an LFO can’t make.
Resonance — resonance needs to be assigned before it can be modulated.

From the community

FILTER AMT is bipolar with zero at the centre. Fully left sends −100 to the cutoff and can silence a patch — it catches many new owners out. via LeSynth on YouTube (5:29)