AMSynths AM8111 VCO & VCF (2023–)
A Eurorack module based on a Roland prototype that never shipped, rebuilt with SH-101 and Monopoly parts.
Overview
The AM8111 is a module that should have existed in 1978 and didn't. Roland's System 100M launched with eight modules, including the dual VCO 112 and the VCO/VCF/VCA combo 110. There was a third concept, the 111, a VCO and VCF in one. Only a few prototypes were ever built, and Roland shelved it, likely because the 112 already covered the territory with more flexibility. In 2022, AMSynths' designer found photos of that rare 111 prototype and decided to resurrect it as something new. The AM8111 VCO & VCF is a 16HP Eurorack module that follows the spirit of the original but swaps in modern silicon.
This isn't a straight Roland clone. The VCO core is based on the Coolaudio V3340, a reissue of the CEM3340 that powered the SH-101. The filter uses the Coolaudio V2044A, a faithful replica of the SSM2044 ladder chip found in the Korg Mono/Poly. The SH-101 side brings a snappy triangle core, precise pitch stability and a sub oscillator one octave down. The Mono/Poly side brings a 24dB/octave slope with built-in Q compensation and the ability to self-oscillate across nearly the full audio range. Together they sound warmer and more aggressive than the original 100M's OTA-based filters, with more low-end weight and a resonance that feels closer to a late-'70s polysynth than a modular.
The layout borrows from Behringer's 100M reissues, with rotary controls for octave range and fine pitch, illuminated sliders for filter cutoff and resonance, and a clean jack arrangement. Under that is some serious engineering. The VCO uses the Alfa Rpar tuning method, which costs a few extra trimmers but gives far better temperature stability and easier calibration. The filter has a Q compensation circuit lifted from the SSI2144 datasheet, using a V13700 chip to keep output level steady as resonance climbs. Many clones skip this and the volume drops at high Q settings.
Specifications
| Manufacturer | AMSynths |
| Production Years | 2023– |
| Original Price | £149.00 (inc. tax) |
| Format | Eurorack |
| Width | 16 HP |
| Depth | Not specified |
| Power | 10-pin to 16-pin Eurorack power cable (+12V, -12V) |
| VCO Core | Coolaudio V3340 (CEM3340 reissue) |
| Filter Type | Coolaudio V2044A (SSM2044 replica), 24dB/oct transistor ladder |
| Waveforms | Triangle, Sawtooth, Pulse |
| Sub Oscillator | Yes, one octave below main oscillator |
| Sync | Hard and soft sync (switch-selectable) |
| CV Inputs | 3 VCO CV inputs (1V/oct, mod, PWM), 3 filter CV inputs (cutoff modulation) |
| Audio Inputs | 3 VCF audio inputs (normalled from VCO outputs) |
| Outputs | VCO OUT, SUB OUT, 2 VCF outputs |
| Filter Cutoff Range | 16 Hz to 20 kHz (self-oscillating) |
| Cutoff CV Range | ±90 mV |
| Resonance | Adjustable, with Q compensation |
| Indicators | Red/green LED on VCF for signal and overload |
| Weight | 325 g |
Key Features
The V3340 That Actually Works Right
The Coolaudio V3340 is a great find 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 dug into the datasheet and fixed it. A 1.2MΩ hysteresis resistor (pin 4 to pin 5) and a 10kΩ buffer before pin 5 removed the glitch and sharpened the pulse edge across the whole width range. They also tweaked the Alfa Rpar tempco circuit, reducing a key resistor from 24k to 20k to stabilize the 0V reference point. The VCO tracks accurately, stays in tune, and gives the crisp, stable PWM the SH-101 was known for.
Monopoly-Style Filter With Real Q Compensation
Many SSM2044 clones cut corners on Q compensation and let the filter's output level drop as resonance increases. The AM8111 doesn't. It uses an external circuit based on the SSI2144 datasheet, with a V13700 chip to hold amplitude steady even at screaming resonance. Crank the resonance and the filter stays balanced instead of just getting louder, so you can push it into feedback howls and sine waves without losing presence in the mix. The 3.3nF capacitor between the two signal inputs adds a subtle high-end lift, giving it the Mono/Poly "sheen" that cuts through a dense patch. It self-oscillates cleanly from 16 Hz to 20 kHz, so it works as a sine wave LFO or FM target as well as a filter for VCO tones.
Smart Normalization and Workflow Tweaks
The VCO and VCF are meant to work with the rest of your rack, not just with each other. The VCO's sawtooth, pulse and sub outputs are normalled to the three VCF audio inputs, so one cable patches the full mix into the filter. The keyboard CV input is normalled to the first filter CV input, which gives key follow without extra patching. The third filter CV input has a polarity switch, so you can invert an ADSR envelope without an external inverter. The resonance slider uses a reverse log taper, just like the original System 100, which gives finer control at lower settings.
Historical Context
The System 100M was Roland's first serious move 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 was meant to be a streamlined voice generator, VCO and VCF in one, for a compact setup. But the 110 already combined VCO, VCF and VCA, and the 112 offered dual oscillators, so the 111 was redundant before it launched. It faded into obscurity until Behringer's 2020 reissue of the 100M brought renewed interest in Roland's modular past. AMSynths followed that interest and asked what might have been. The AM8111 is their answer: a 111 built not with 1978 tech, but with the SH-101 oscillator and the Mono/Poly filter.
Collectibility & Value
The AM8111 isn't vintage yet. It started production in late 2023. Priced at £149 new, it's positioned as a premium boutique module, not a budget clone. The build is solid, with tall trimmers for precise calibration, M3 mounting hardware included, and a PCB layout that makes good use of a 16HP panel. Failures are rare, but early adopters should know about one quirk: the original prototype had LED driver issues that caused slight pitch drift due to power rail sag. That was fixed 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. The V3340 and V2044A are both surface-mount, so 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. Owners report it as a "set and forget" module once calibrated. Pair it with a standalone VCA and you have a complete Roland-inspired voice.
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