Michigan Synth Works - MSW-820 Euro

The MSW-820 is a fader-heavy analog monosynth from Michigan Synth Works — here in its Eurorack version, a whole voice in 46 HP instead of a desktop box. While the spec sheet lays out a fairly classic two-VCO architecture, the more interesting story is what's actually inside. The oscillators are AS3340-based, the filter core is AS3109 — the same chip family that powered the Roland SH-101, MC-202 and CMU-810 — and the result sits firmly in that lineage of immediate, characterful Roland-style mono synths. MSW's earlier MSW-810 was a faithful CMU-810 recreation; the 820 takes the same circuit DNA and builds on it, with more oscillator features, a second envelope, a much bigger filter section, and a syncable digital LFO.

The headline is the filter. Sixteen modes — all analog — built around an AS3109 in a pole-mixing arrangement, the same circuit used in the Caveman Totem filter module (Caveman Modules being a collaboration between Michigan Synth Works and Neutron Sound). Two banks of eight, switched by a toggle and a rotary, covering 24dB and 12dB low-pass, high-pass, band-pass, notch, allpass, and a generous series of hybrid responses — well beyond the usual mono-synth menu. Just above the cutoff sits a small attenuverter labelled "THIS": turn it up and VCO1's triangle routes straight into the filter frequency at audio rate. Filter FM, right there on the panel, no patching required.

A few other clever moves keep the rest of the layout manageable. The LFO's Rate, Fade and Shape controls double as the editor for both the noise generator and an optional digital third oscillator (where you get eight choices of oscillator flavours with names like Hillagator, Hypnotoad and Hexperc..). The external input can run through the filter or through a second envelope-controlled VCA. And in this version the whole thing runs off your case, drawing a modest +12V/100mA and -12V/80mA from the bus — while V/Oct, Gate, Clock, two CV inputs and audio in/out sit ready to be wired into the rest of the patch, with MIDI over TRS or USB still on board.

MSW-820 is a complete mono voice imbued with Roland-flavoured DNA, some new ideas — and a filter section that gives you a lot more to chew on than the rest of the spec sheet lets on.

Features:

• Complete analog monosynth voice in 46 HP Eurorack format
• Two analog VCOs (AS3340) with saw + pulse waveforms and continuous PWM
• Range switch per VCO (16'/8'/4'), hard sync (two modes), VCO reset trigger options
• Sub oscillator tied to VCO1: 1 octave, 2 octaves, 2 octaves PWM
• 16-mode analog pole-mixing filter (AS3109-based), two banks of eight modes selected by toggle and rotary
• Filter modes include 24dB and 12dB low-pass, high-pass, band-pass, notch and allpass shapes, plus several hybrid pole configurations
• Resonance up to self-oscillation
• "THIS" attenuverter: audio-rate filter FM driven by VCO1 triangle
• VCF modulation mixer with bipolar attenuverters: Mod Env, LFO, Pitch CV, Ext CV / Accent
• Two discrete ADSR envelopes (Mod and VCA), with manual trigger button
• Digital LFO: 0.1–22 Hz, eight crossfading waveforms (sine, pulse, ramp, triangle, saw, exponential decay, random, smoothed random), multiple reset and fade modes including one-shot behaviour, MIDI clock sync
• Digital noise generator with multiple flavors and per-type editable parameter
• Optional digital third oscillator with eight voices (Hillagator, Donk, Fattner, Batsaw, Hypnotoad, Pseudo Reso, Formic, Hexperc), each with editable parameter
• Five-channel mixer: VCO1, VCO2, Sub, Noise/DiOSC, External Input
• External audio routing: through filter, or through a secondary envelope- or CV-controlled VCA
• Accent (5V trigger or MIDI velocity > 100), with switchable VCF-only or VCF + VCA behaviour
• Portamento control
• Built-in A440 tuner function
• Connections: 3.5mm TRS MIDI input (PSIMIDI, TRS A or B), Clock In, Gate In, V/Oct In, Ext CV In, CV2 In, Audio In, Audio Out
• USB-C for USB MIDI
• Extensive MIDI CC implementation and SysEx control (channel select, calibration, root octave, note priority, factory reset)
• Also available as a desktop version