AMSynths AM8131 Audio Mixer ()
A Eurorack copy of Roland's 1978 131 mixer, built for stereo imaging, visual feedback, and the System 100M workflow.
Overview
The AMSynths AM8131 Audio Mixer puts a piece of the Roland System 100M in a Eurorack case. No hunting eBay for NOS modules, no rebuilding vintage power supplies. It is a direct replica of the Roland 131, re-engineered for modern modular setups, and it keeps the original's four-channel, AC-coupled mixing architecture. It is part of AMSynths' 100M ecosystem. You get individual channel level controls, panning, and a master volume on a clean, professional 3U panel that would look right next to a TR-808.
It does one job: mixing 10V peak-to-peak audio signals into stereo outputs. Use it as a final summing stage before your audio interface, or as an internal mixer inside the rack. Bouncing sequences between oscillators, blending filtered outputs and layering noise sources all work. Unlike many minimalist Eurorack mixers, it has LEDs on every slider and output, so you get real-time visual feedback on signal flow.
Specifications
| Manufacturer | AMSynths |
| Model | AM8131 Audio Mixer |
| Dimensions | 16 HP, 30 mm deep |
| Current Draw | 30 mA +12V, 30 mA -12V, 0 mA 5V |
| Price | £99 incl. VAT |
| Inputs | four AC coupled inputs |
| Input level potentiometers | 30mm level potentiometers |
| Outputs | Stereo Left & Right Outputs, Mono Output |
| Output connectors | three 3.5mm jack sockets |
| Rear PCB jumpers | three jumpers that set whether the outputs are at normal Eurorack level or attenuated |
| Included accessories | a set of M3 mounting screws and washers, and a standard Doepfer power cable |
Key Features
Pan, Level, and Master Control with Vintage Flair
Each of the four channels has a 30mm level potentiometer and a high-quality rotary pot for panning. The knobs are not tiny and the layout is not cramped. The panning is smooth and precise, so each signal can be placed in the stereo field where you want it. The master volume, also a rotary pot, is the final gain stage. It makes it easy to feed a healthy signal to your interface or recorder without clipping. The topology is simple: level → pan → sum → master.
Visual Feedback That Works
Behind each channel's slider indicator sits a subtle green or red LED. They are not flashy, but they are bright enough to show signal presence and relative strength at a glance. All three outputs - Left, Right, and Mono - have their own green LEDs to monitor output levels. That lets you catch clipping or imbalances before they hit your DAW, which helps when mixing complex patches or running feedback loops.
Built Like a Eurorack Citizen
The AM8131 uses 2mm multi-colour anodised aluminium panels, which AMSynths treats as a hallmark of its build quality. The panels resist scratching, feel solid in the hand, and have a professional, almost industrial look. The module is compatible with the Doepfer standard, so power and mounting are plug-and-play in any Eurorack case. Power supply protection fuses sit on the PCB as a safeguard against shorts or power spikes. It draws a modest 30 mA on both ±12V rails and nothing on 5V, so it won't tax your power supply even in densely packed systems.
Knobs That Feel Like Home
The rotary pots wear Roland TR-808 style control knobs, the tall, ridged kind that are easy to grip and satisfying to turn. They also give real tactile feedback, which makes fine adjustments intuitive. Anyone who has spent time on vintage Roland gear will know the feel.
Flexible Output Level via Jumpers
On the rear PCB, three jumpers set whether the outputs run at normal Eurorack level or are attenuated. You can tailor the output to downstream gear that might be sensitive to hot signals, or pad it down for use in semi-normalled configurations. Many modern mixers overlook this kind of flexibility.
Kit or Assembled — Your Choice
The AM8131 is available both as a fully assembled module and as a DIY kit. Builders get a chance to get inside the circuit and learn from a faithful reproduction of a classic design. Anyone who just wants to patch can rack it and run. Either way, it comes with M3 mounting screws, washers, and a standard Doepfer power cable.
Warranty You Can Trust
AMSynths backs the module with a two-year warranty against product defects. Boutique modules sometimes come with no safety net, so the warranty signals a professionally manufactured product rather than a one-off build from a garage operation.
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