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Supercritical Synthesizers Demon Core Oscillator & Expander

Eurorack Modules By Rory Dow
Published January 2020

Supercritical Synthesizers are a new company from Finland and their first product is the wicked-sounding Demon Core Oscillator. It’s an analogue oscillator with a remarkable 16 voices, which can be spread and detuned, but perhaps more importantly, and with the help of the Demon Core Expander module, played polyphonically. So, a cloud oscillator with benefits.

Demon Core Oscillator.
Size: 12HP. Current: +12V 120mA, -12V 20mA.Demon Core Oscillator. Size: 12HP. Current: +12V 120mA, -12V 20mA.The base module contains the oscillator itself. This will work without the Expander and will provide you with 16 sawtooth or pulse waveforms which can be detuned and spread with unison and octave stacking. The oscillator can be tuned using coarse and fine controls, and there is a handy LED indicator to show when you hit a C note (it also doubles up to show MIDI activity when the Expander is connected). The Spread control adjusts the detuning, allowing anything from subtle unison detune to complex equally spaced microtuning. Another control labelled Core Stability will introduce pitch drift per voice, which can sound like anything from a gentle chorus effect to a swarm of angry bees.

In terms of connectivity, there is of course a 1V/oct input, which is joined by FM, Spread and Stability CV inputs. The Spread input can also double up as a PWM control when the oscillator is set to pulse wave. An input labelled Sync Trig will, when triggered, re-sync all the oscillator voices. This is useful for sounds where you might want a very consistent attack transient (feed the same trigger you use to trigger your Amp envelope). Typically this is used on bass sounds, but you can get some interesting rhythmic effects by sequencing it too. The last connection socket is the mono audio output.

The number of voices used by the oscillator can be adjusted with a single button and a star of 16 LEDs shows you just how many voices you’re currently using. Successive presses of the Voices button rotate through 1-2-3-4-5-6-8-10-12-16 voices. As well as choosing the number of voices, you can also decide the octave stack value. For example, if you had eight voices and a stack value of two, you would have two sets of four voices an octave apart. Eight voices in a four-octave stack would give you four octaves of two voices each. You can even combine numbers which don’t divide precisely, the oscillator will simply do the maths for you and assign the voices as best it can. It’s a very visual, flexible and easy way to allocate the voices in different ways.

Demon Core Expander. Size: 8HP. Current: +12V 130mA, -12V 30mA.Demon Core Expander. Size: 8HP. Current: +12V 130mA, -12V 30mA.The Demon Core Expander connects to the main module via a supplied ribbon cable. Power is transferred from the main module, so no additional power cable is required, although will draw more power from your system. The main feature on the Expander is the addition of polyphony, by allowing a MIDI input on TRS mini-jack. This means you can play the 16 voices just like a normal synth. MIDI channel can be set from the front panel, as can other MIDI-related functions such as pitch-bend range, a hidden LFO you can use for vibrato via modulation wheel, and even variable polyphonic portamento.

The Expander also gives you 16 VCAs with ADSR for each voice, effectively making it a complete synthesizer voice, minus the filter. The behaviour is altered using the Stream/Gate mode button, with Gate mode employing the ADSRs and VCAs and Stream mode acting more like a normal oscillator with each voice droning indefinitely. In this mode, you might utilise the Gate output, which will output a trigger or gate signal for each MIDI note, allowing you to use other VCAs and envelopes in your system to create a paraphonic synth voice. It’s a neat solution which turns almost any existing modular into either a full polyphonic or paraphonic powerhouse. Furthermore, the voices can be divided up to form various combinations of polyphony and stacking. For example, you might have seven-note polyphony with two voices per note, using up 14 voices in total. Or you might choose four-note polyphony with four-voice stack. As long as the total doesn’t exceed 16, you can come up with almost any combination. Not only that, but you can also add octave stacking to the mix. For example, four-note polyphony, two voices per note and a two-octave stack per note would use up all 16 voices.

The ADSR works with only two front-panel controls, Attack and Release. Pressing the Function button on the main oscillator module will turn these into Decay and Sustain controls. It’s not quite as nice as having dedicated controls for all four stages, but it works well enough. One nice touch is that you can switch the VCAs to work in legato or re-trigger mode.

If you don’t want to use MIDI, you can still get four-voice polyphony using the four FM inputs. This will control the first four voices. If are using MIDI, however, these inputs aren’t wasted and can be used to control other parameters: Sync Time, Sync Random, Octave Stack Size and Octave Stack Interval. One neat feature of having both main module and Expander is that the MIDI input and main 1V/oct input work together. So with the Expander in Stream mode, use the MIDI input to play a chord, and then use the 1V/oct input to transpose that chord. Ta-da! Instant chord memory. Now patch in some control voltages to the four individual FM inputs on the Expander and you can further transpose the individual notes of the chord. Perhaps you could add a sequencer which transposes each note up or down an octave.

The possibilities of the Demon Core Oscillator and its Expander module are many. I think it would make an excellent heart to a polyphonic or paraphonic modular setup. You could use the MIDI input on the Expander and the Gate mode envelopes to give you a traditional polysynth. Adding in an external filter would make it paraphonic. Alternatively, you could set the polyphony to four and use the four FM inputs on the Expander to control four voices via 1V/oct pitch CV giving you direct analogue control over four voices at once.

Do you need the Expander? Well, if you want to do polyphony, then yes. The main oscillator module is still an excellent cloud oscillator, but I feel that having the combination and being able to play 16 voices polyphonically will be the biggest selling point for most people. Occasionally it can feel complex, there is a reliance on button combos to enable modes. Frequent checking of the excellent manual is probably going to be unavoidable until it’s committed to muscle memory. Overall, though, the Demon Core Oscillator is an impressive debut from Supercritical Synthesizers. It represents another step towards truly polyphonic modular systems and sounds really rather excellent. The build quality and styling are equally impressive. I look forward to more from Supercritical Synthesizers.


Oscillator £415.99 & Expander £237.99

Oscillator $510 & Expander $410