AMSynths AM8120 VCF & VCA (2023–)
A Eurorack module that revives a Roland prototype that never made it out of 1978, now with Jupiter-8 filter DNA and Q compensation that works.
Overview
The AM8120 is AMSynths' take on the Roland 100M 120, a prototype that never saw production. It combines the VCF from the 121 with the VCA from the 130. AMSynths changed a few things, though. The filter now comes from the Jupiter-8's 24dB OTA design, and the Q compensation uses half of an AS662 OTA chip, so you don't lose level as resonance climbs.
At 16HP, it’s not the slimmest module on the rack, but it earns every millimeter. The front panel is powder-coated in a subtle Pantone Mid Grey 5U with crisp white silkscreen—minimalist, yes, but with a tactile presence that feels more boutique than budget. The slide pots for cutoff, resonance, and VCA gain have a smooth, deliberate action, and the green LED indicators under each give just enough feedback without screaming for attention. It’s a module that looks like it belongs next to a vintage Roland System 100M, but functions like a modern Eurorack citizen. The normalized connection between the VCF output and the first VCA input is a thoughtful touch—patch cables are minimized for basic use, but full flexibility remains for complex routing.
The 24dB mode has that classic Roland growl - think Jupiter-8 basslines or SH-101 leads with a little extra throat. The 12dB mode opens up for smoother, more organic textures. The VCA, pulled from the Roland 130, offers both linear and exponential response, giving you precise amplitude control or the punch of classic synth envelopes. It's not a "character" module in the way some boutique filters are. It's a reliable, consistent tool.
Specifications
| Manufacturer | AMSynths |
| Production Years | 2023– |
| Original Price | £220 (assembled), £150 (kit) |
| Format | Eurorack |
| Width | 16HP |
| Depth | 35mm |
| Current Draw | 120mA @ +12V, 30mA @ -12V |
| VCF Type | OTA-based 24dB/oct low-pass, 12dB/oct selectable |
| VCF Modes | 12dB, 24dB |
| Resonance | Voltage-controlled, Q-compensated, self-oscillation at maximum |
| VCA Type | OTA-based, linear and exponential response |
| VCA Inputs | 3 audio inputs, 3 CV inputs |
| VCF Inputs | 3 audio inputs, 2 CV inputs for cutoff, 1 CV input for resonance |
| Outputs | 2x VCF outputs, 2x VCA outputs |
| Normalization | VCF output → first VCA audio input |
| Filter IC | AS3109 |
| VCA IC | AS662D (half used for VCA, half for Q compensation) |
| PCB Design | Dual PCB: front PCB for jacks and pots, main PCB for circuitry |
| Front Panel | Grey powder-coated aluminum, white silkscreen |
| Mounting | M3 screws, included |
Key Features
The Filter That Roland Never Made
The original 100M 120 prototype used the 121's filter. AMSynths based theirs on the AS3109 chip found in the Jupiter-8 instead. The 24dB/oct slope is thick and handles rounded pads and snarling leads alike. The 12dB mode is softer and warmer, suited to string machines or early analog polys. The Q compensation is the key feature. OTA filters usually lose volume at high resonance, but the AM8120 uses the second half of the AS662 OTA to compensate and keep levels consistent. You can crank the resonance into self-oscillation without the sound disappearing or distorting unpredictably.
Two-in-One Efficiency Without Compromise
The VCA is a direct replica of the Roland 130's design, using half of the AS662 OTA chip. It keeps both linear and exponential response modes, which is rare in modern modules, where exponential is often the default. Linear suits precise amplitude shaping, and exponential gives classic synth envelope behavior. The three audio inputs and three CV inputs per section let you mix multiple sources before filtering, or modulate the VCA with multiple envelopes or LFOs. The normalization from VCF out to VCA in cuts cable clutter for basic subtractive patches, and it's easy to break if you want parallel or feedback routing.
Dual PCB Design for Reliability and Serviceability
Inside, the AM8120 uses a dual-PCB layout. The front board holds the jacks and slide pots, and the main board carries the core circuitry. That makes servicing easier. If a jack gets loose or a pot wears out, you're not desoldering through a dense main board. SMD op-amps handle signal and CV mixing and keep the front board compact. The main board packs in the filter, VCA, and LED drivers. The 80mm-wide PCB is densely populated with 1/8W resistors and SMD components, but the layout is clean and well-documented. Trimmers for signal and CV calibration are accessible from the front, though they need a small screwdriver. You don't have to disassemble the module for alignment.
Historical Context
The Roland 100M system came out in the late '70s as a compact, patchable modular designed for studio integration. The 120 module, a VCF/VCA combo, was prototyped in 1978 but never released. By pulling the filter design from the Jupiter-8, AMSynths sidestepped the limitation of the original 100M's single filter type. Behringer was reissuing the entire 100M line at the time, and AMSynths went its own way with modules that improve on the originals, like adding Q compensation where Roland didn't, or using modern components for better reliability.
The AM8120 is one of the "replicant" modules in Eurorack that blend accuracy with practicality. Some clones prioritize exact circuit replication at the expense of usability. The AM8120 makes concessions, like using the AS662D instead of the original BA662, which is harder to source. It's for people who love Roland's sound but don't want to wrestle with 40-year-old engineering trade-offs.
Collectibility & Value
The AM8120 isn't a vintage item yet, but it's already a favorite among Roland purists and Eurorack minimalists. Assembled units typically sell for £220 - £250, while the kit version goes for £150. AMSynths' production runs are limited and the module's appeal is niche, so prices are likely to hold steady, if not appreciate slightly. Condition matters. With slide pots and SMD components, units with damaged sliders or cold solder joints can be a hassle to repair. Look for clean panels, smooth pot action, and consistent LED brightness.
Failures are rare but not unheard of. The most common issue reported is misalignment of the VCA's linear and exponential modes, which requires trimming the internal LIN1, LIN2, EXP1, and EXP2 trimmers. That isn't user-serviceable without removing the panel, so buy from a trusted seller or test before purchase. The AS662 and AS3109 chips are still in production, so replacements aren't a concern. The kit is well-documented, but the SMD components on the main board demand decent soldering skills. If fine-pitch work isn't your thing, stick to the pre-assembled version.
If you're building a Roland-heavy Eurorack system, especially with Behringer's 100M modules, the AM8120 fills a gap they left open. It's also a solid choice for clean, musical filtering without the quirks of more esoteric designs. Don't expect it to scream like a Moog or swirl like a SEM.
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