AMSynths AM8171 (2024)
A modern Eurorack take on a forgotten Roland 100M sequencer switch. Clean, precise, and built for stepping voltages in rhythm.
Overview
The AM8171 Sequential Switch doesn't shout like a screaming filter or a detuned oscillator stack. It sits in the rack and does its job. It is a reimagining of the Roland 173 module from the System 100M, a rare bird that only saw a few hundred units made back in 1983 before Roland pulled the plug on the entire 100M line. The AM8171 brings that logic back with modern reliability for today's Eurorack systems. The function is the same as the original: it routes control voltages or audio signals through four stages in sequence, advanced by a clock or trigger.
AMSynths refined the circuit rather than just cloning it. The original Roland 173 was part of the third and final wave of 100M modules, introduced just as analog modular was being steamrolled by the digital tsunami of the DX7 and D-50. It never got the chance to become a classic, but the design had promise: a quad analog switch that could step through stages with precision, useful for anything from rhythmic panning to morphing filter cutoffs or sequencing multiple oscillators. The AM8171 makes that potential accessible as a useful tool in modern patching workflows. It turns static sounds into evolving sequences with minimal effort.
Specifications
| Manufacturer | AMSynths |
| Production Years | 2024 |
| Original Price | £195 GBP |
| Module Format | Eurorack |
| Width | 12HP |
| Depth | 35mm |
| Current Draw +12V | 40mA |
| Current Draw -12V | 10mA |
| Inputs | 4x Signal Inputs, 1x Clock/Trigger Input, 1x Reset Input |
| Outputs | 1x Sequential Output, 1x Step Indicator Output (Gate per step) |
| Switching Type | Analog CMOS Switch |
| Control Voltage Range | 0–10V |
| Signal Type | DC-coupled (supports both CV and audio) |
| Stepping Modes | Forward only (sequential cycle) |
| Reset Function | Resets sequence to Step 1 on trigger |
| Step Indicator | Gate pulse per active step |
| Panel Material | Black anodized aluminum |
| Mounting Type | M3 screws, standard Eurorack |
Key Features
Four-Stage Analog Switching with Eurorack Integration
The AM8171 is built around a quad analog switch IC, replicating the signal routing behavior of the original Roland 173. Each of the four inputs can accept either control voltage or audio signals. The DC coupling matters here, because it lets the module sequence modulation sources like LFOs, envelope shapes, or sample-and-hold voltages as well as notes. When clocked, the module steps through each input in order, sending the selected signal to the common output. The concept is simple, but it opens up complex modulation possibilities, like cycling through four different filter cutoff voltages on each beat, or rotating a panning control across four positions in a quadraphonic setup. The switching is clean and silent with CVs. With audio, the transitions are crisp and glitch-free, with no pops or clicks if your signals are DC-balanced.
Precision Clocking and Reset Control
The clock input accepts 5-10V trigger signals, so it works with most sequencers, drum modules, or LFOs. A dedicated reset input forces the sequence back to Step 1, handy for syncing to song position or restarting a pattern on the downbeat. The step indicator output sends a gate pulse corresponding to the active stage. That pulse can light LEDs (if panel-mounted) or trigger other events in your system, like activating a different effect on each step. It can drive multiple processes in lockstep.
Compact and Reliable Modern Build
The original Roland 173 lived in a fragile, aging ecosystem. The AM8171 is built for modern modular use. It is 12HP wide and 35mm deep, compact enough for dense systems. The circuit uses modern CMOS switching technology, which is more consistent and less prone to leakage than vintage discrete designs. Power draw is modest (40mA on +12V, 10mA on -12V), and the module is manufactured with attention to longevity, something AMSynths emphasizes across their lineup. The black anodized aluminum panel feels solid, with clearly labeled jacks and an intuitive layout. There's no onboard clock source or direction control (it only steps forward). That's by design, since this is a utility module and not a full sequencer.
Historical Context
The original Roland 173 never had the chance to matter, and that is why the AM8171 exists. Released in 1983 as part of the final wave of System 100M modules, it arrived just as the music world was pivoting hard toward digital synthesis. The Yamaha DX7, Roland's own D-50, and Korg's M1 were rewriting the rules, offering preset-based, polyphonic sounds that modular systems couldn't match in convenience. Roland discontinued the 100M line in 1984, leaving modules like the 173 as obscure footnotes. Few were made, fewer survived, and even fewer found their way into documented patches. The concept of a simple, clocked analog switch was sound, though. It filled a niche between passive switching and full sequencing, offering a way to automate signal routing without complex programming.
AMSynths, led by designer Rob Keeble, specializes in resurrecting forgotten ideas with modern engineering. Keeble's background in vintage synth restoration and modular design (including work with Behringer on their 2600 and 2500 replicas) gives him a sharp eye for what works in practice. The AM8171 brings the 173's functionality into the Eurorack era.
Collectibility & Value
As a 2024 release, the AM8171 isn't vintage in the traditional sense, but it's already gaining traction among modular enthusiasts who appreciate its niche utility and historical lineage. New units sell for around £195 directly from AMSynths. Given the small production runs typical of the brand, resale prices on the used market could climb if demand outpaces availability. Condition is straightforward. Being a modern module, there's little to go wrong beyond damaged jacks or power issues from incorrect cabling. The CMOS switches are robust, but like any analog switch, they can degrade over decades if exposed to high-voltage or DC-offset signals. Buyers should check for consistent stepping and clean signal transfer across all four stages.
Failures are rare, but the most vulnerable points are the input protection circuitry and the clock/reset input conditioning. A malfunctioning clock input might ignore triggers or double-step, while a failed reset could leave the sequence stuck in a loop. These are typically repairable with basic soldering skills. For collectors of Roland 100M history, the AM8171 is one of the few ways to experience the 173's functionality without hunting down a fragile, expensive original.
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