Vannes Devices - Obsidian

West Coast wavefolding meets traditional subtractive synthesis in Obsidian, a Dutch semi-modular analog synth with a distinctly old-school look to it. The black-and-white panel, with its long rows of sliders, has a touch of early ARP about it. We definitely have a soft spot for that sort of thing!

The sound starts with two oscillators that have quite different jobs. OSC1 is a simple sine-wave oscillator, useful both as a sound source and for modulating OSC2, where most of the shaping takes place. Here you can move between sine, saw and square waves, feed them through a wavefolder and add cross-modulation from OSC1. There's oscillator sync and a sub-oscillator too, so plenty to work with before the signal even reaches the filter. And the filter is worth a closer look: a resonant 12 dB/oct design that recalls the original Oberheim SEM in one respect — you can sweep smoothly between different filter modes. Only here, the sweep runs from low-pass through band-pass to high-pass, rather than through notch as on the SEM. A two-channel mixer also lets you bring external audio into the equation.

Modulation comes from two analog envelopes, a conventional ADSR and a simpler AD(R) envelope with separate rise and fall controls, both with voltage control over their stages. There's also an LFO with separate pulse and random outputs, and a tape/BBD-style digital delay with voltage-controlled time and feedback. Then we come to the sequencer. Five steps! A familiar sight to anyone who's spent time with the classic Buchla Music Easel, and a nice nod to the West Coast side of Obsidian. You can use it for melodies, of course, but perhaps it's even more interesting as a modulation source. Let an external keyboard handle the notes while those five sliders control the amount of wavefolding or move the filter between its different modes. You can also switch to four steps, and the sequencer, LFO and delay can all follow tap tempo, external clock or MIDI clock.

Despite all the patch points, Obsidian works as a complete synth without connecting a single patch cable, thanks to its internally normalled connections. The panel is clearly divided into sections, with the patch connections gathered along the bottom and just about everything else available on a slider or knob. It's a wonderfully old-school approach to an instrument with quite a few modern conveniences. Naturally, this being a semi-modular synth, the normalled connections are a courtesy, not a set of instructions ;)

Features:

• Semi-modular analog synthesizer combining East and West Coast synthesis
• Two independent analog oscillators with 1V/oct tracking
• OSC1 sine-wave oscillator for audio and modulation
• OSC2 with variable sine/saw/square waveshaping and wavefolding
• Cross-modulation, PWM and oscillator sync
• Sub-oscillator one octave below OSC2
• Two-channel mixer with external audio inputs
• 12 dB/oct resonant multimode filter with continuous low-pass, band-pass and high-pass morphing
• CV control over filter cutoff, resonance and mode
• Patchable VCA with CV input
• Two analog envelope generators: ADSR and AD/R, with voltage-controllable stages
• LFO with selectable waveforms, separate pulse and random outputs (0.01–100 Hz)
• Tape/BBD-style digital delay with CV control over time and feedback
• Five-step CV sequencer, switchable to four steps, with manual and external reset
• Tap tempo, external clock and MIDI clock synchronisation for sequencer, LFO and delay
• Extensive Eurorack-compatible CV and audio patching
• MIDI via USB and DIN, including note, gate, velocity and pitch bend
• Internal signal routing for standalone operation
• Black-and-white panel with dedicated sliders, knobs and patch points