AMSynths AM8111 VCO & VCF (2023–)

A Eurorack love letter to a Roland prototype that never was—now reborn with SH-101 soul and Monopoly fire.

Overview

You can almost hear the ghost of 1978 in the AM8111: a synth module that should’ve existed but didn’t, until now. Roland’s System 100M launched with eight modules, including the dual VCO 112 and the VCO/VCF/VCA combo 110—but there was a third, forgotten concept: the 111, a VCO and VCF in one. Only a few prototypes were ever built, and Roland quietly shelved it, likely because the 112 already covered the territory with more flexibility. Fast-forward to 2022, when AMSynths’ designer stumbled upon photos of that rare 111 prototype and decided to resurrect it—not as a museum piece, but as something new. The result? The AM8111 VCO & VCF, a 16HP Eurorack module that channels the spirit of the original but swaps in modern silicon to deliver a sound all its own.

This isn’t a straight Roland clone. Instead, it’s a hybrid beast: the VCO core is based on the Coolaudio V3340, a reissue of the legendary CEM3340 that powered the SH-101, while the filter uses the Coolaudio V2044A—a faithful replica of the SSM2044 ladder chip found in the Korg Mono/Poly. That pairing is deliberate and inspired. The SH-101’s oscillator brings its snappy triangle core, precise pitch stability, and that iconic sub oscillator one octave down, while the Mono/Poly’s filter contributes a rich, musical 24dB/octave slope with built-in Q compensation and the ability to self-oscillate across nearly the full audio range. Together, they create a voice that’s warmer and more aggressive than the original 100M’s OTA-based filters, with a low-end heft and resonance character that feels more like a late-’70s polysynth than a modular oddity.

The module’s layout borrows from Behringer’s 100M reissues—familiar to modern Eurorack users—with rotary controls for octave range and fine pitch, illuminated sliders for filter cutoff and resonance, and a clean, logical jack arrangement. But beneath that accessible surface lies serious engineering. The VCO uses the Alfa Rpar tuning method, which trades a few extra trimmers for far better temperature stability and easier calibration. The filter includes a Q compensation circuit lifted from the SSI2144 datasheet, using a V13700 chip to maintain consistent output level as resonance climbs—something many clones skip, resulting in volume drops at high Q settings. It’s these thoughtful touches that elevate the AM8111 from “cool idea” to “daily driver.”

Specifications

Key Features

The V3340 That Actually Works Right

The Coolaudio V3340 is a godsend for DIYers and boutique builders, but it’s not a drop-in replacement for the original CEM3340. Early implementations often struggled with pulse width control and waveform glitches—especially around the 40% width mark, where the leading edge of the pulse wave can collapse. AMSynths didn’t just copy a reference design; they dug into the datasheet and solved it. By adding a 1.2MΩ hysteresis resistor (pin 4 to pin 5) and a 10kΩ buffer before pin 5, they eliminated the glitch and sharpened up the pulse edge across the entire width range. They also tweaked the Alfa Rpar tempco circuit, reducing a key resistor from 24k to 20k to stabilize the 0V reference point. This isn’t just engineering for engineering’s sake—it means the VCO tracks accurately, stays in tune, and delivers the crisp, stable PWM that made the SH-101 so expressive.

Monopoly-Style Filter With Real Q Compensation

Many SSM2044 clones cut corners on Q compensation, letting the filter’s output level drop as resonance increases. The AM8111 doesn’t. It uses a proper external circuit based on the SSI2144 datasheet, incorporating a V13700 chip to maintain consistent amplitude even at screaming resonance. The result is a filter that doesn’t just get louder when you crank the resonance—it stays balanced, letting you push it into feedback howls and sine waves without losing mix presence. The 3.3nF capacitor between the two signal inputs adds a subtle high-end lift, giving it that characteristic Mono/Poly “sheen” that cuts through a dense patch. And yes, it self-oscillates cleanly from 16 Hz all the way to 20 kHz, making it just as useful as a sine wave LFO or FM target as it is for shaping VCO tones.

Smart Normalization and Workflow Tweaks

The AM8111 isn’t just a pair of circuits slapped together—it’s designed to play nice with the rest of your rack. The VCO’s sawtooth, pulse, and sub outputs are normalled to the three VCF audio inputs, so you can patch the full mix into the filter with a single cable. The keyboard CV input is normalled to the first filter CV input, enabling key follow without extra patching. The third filter CV input has a polarity switch, so you can invert an ADSR envelope without needing an external inverter. Even the illuminated sliders are thoughtfully implemented: the resonance slider uses a reverse log taper, just like the original System 100, giving you finer control at lower settings where you need it most. These aren’t flashy features, but they’re the kind of details that make a module disappear into your workflow—until you try to live without them.

Historical Context

The System 100M was Roland’s first serious foray into modular synthesis, released in 1978 as a compact, semi-modular alternative to the Moog and ARP behemoths. It was never as flexible as a 5U system, but it was affordable, portable, and musically coherent—thanks in part to its distinctive OTA-based filters. The 111 module was meant to be a streamlined voice generator: VCO and VCF in one, perfect for a compact setup. But with the 110 already combining VCO, VCF, and VCA, and the 112 offering dual oscillators, the 111 was redundant before it even launched. It faded into obscurity—until Behringer’s 2020 reissue of the 100M brought renewed interest in Roland’s modular past. AMSynths didn’t just follow that trend; they dug deeper, asking what might have been. The AM8111 answers that question with a modern twist: what if the 111 had been built not with 1978 tech, but with the sonic DNA of Roland’s most beloved monosynth and Korg’s most underrated poly? It’s a “what-if” machine, and it sounds like nothing else in the 100M family.

Collectibility & Value

The AM8111 isn’t vintage yet—it started production in late 2023—but it’s already carving a niche among Eurorack enthusiasts who value both heritage and innovation. Priced at £149 new, it’s positioned as a premium boutique module, not a budget clone. It’s not the cheapest way to get a VCO and VCF, but it’s one of the most musically satisfying. The build quality is solid, with tall trimmers for precise calibration, M3 mounting hardware included, and a PCB layout that maximizes space on a 16HP panel. Failures are rare, but early adopters should be aware of one quirk: the original prototype had LED driver issues that caused slight pitch drift due to power rail sag. This was resolved by switching to low-current LEDs (1–2mA instead of 10mA), so current production units are stable. If buying used, check that the VCO holds pitch under LED illumination—especially during long note holds.

There’s no kit version of the full module, though AMSynths does offer partial kits for DIYers. Given the SMD components (V3340 and V2044A are both surface-mount), this isn’t a beginner build. Stick to factory-assembled units unless you’re comfortable with fine-pitch soldering. On the used market, expect to pay £100–£130 depending on condition. It’s not a flipping target like some limited-run modules, but it’s also not disposable. Owners report it as a “set and forget” module once calibrated, making it a reliable voice in a larger system. Pair it with a standalone VCA, and you’ve got a complete Roland-inspired voice with a character all its own.

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