ADDAC System 511 (2025–)

A 20HP module for stochastic voltage, with memory, motion and mood.

Overview

Patch in a clock, turn a knob, and the sequence starts to hesitate and skip ahead. The 511 is not a plain random source. It works in probabilities, interpolates between states, and remembers what it was doing three minutes ago. At 20HP it is compact enough for a travel case. It is also deep enough to need its own sketchbook of patch notes. This is not a set-and-forget module. It wants attention and it rewards experimentation.

The 511 traces back to ADDAC's long interest in stochastic processes, including the 2013 ADDAC501 Complex Random. It is a full reimagining, not a simple upgrade. There are four independent channels of voltage generation. Each can morph between continuous random voltages, quantized melodies or envelope-like shapes. All of it runs through a menu-driven interface with a screen and dual encoders. Deep editing stays fluid, so you can tweak distributions on the fly and save snapshots. Each channel also has a 32-step sequencer. The sequences can evolve independently or lock into sync, which gives you shifting backdrops.

It’s also a control hub. Those eight CV inputs aren’t just modifiers—they’re puppet strings. Map them to probability curves, smoothing amounts, or clock dividers, and suddenly your filter cutoff is modulating the *rate* at which randomness unfolds. The four gate inputs let you trigger mutes, holds, or state changes, making it stage-ready. And the three logic outputs? They turn internal comparisons—“is channel 2 higher than channel 1?”—into triggers, clocks, or gates, enabling feedback loops that feel like the module is arguing with itself. It’s rare for a voltage generator to double as a brain, but the 511 doesn’t just respond—it reasons.

Specifications

Manufacturer	ADDAC System
Production Years	2025–
Original Price	520€ / $599.99
Format	Eurorack
Width	20HP
Depth	4.5cm (45mm)
Power Consumption	200mA @ +12V, 100mA @ -12V
Channels	4 independent
CV Output Type	Bipolar (-5V to +5V)
Gate Output	Per channel, +5V
Clock Input	Per channel
Sequencer Steps	32 per channel
Quantization	Per channel, with custom scales
Distribution Curves	Adjustable per channel
Smoothing	Interpolation control per channel
Probability Control	Per channel event likelihood
Time Control	BPM ranges, clock dividers/multipliers per channel
Memory States	3 per channel
CV Inputs	8 assignable
Gate Inputs	4 assignable
Logic Outputs	3 configurable
Average CV Output	Sum of all four CV outputs
Display	OLED screen for parameter editing
Controls	2 encoders, push buttons for menu navigation

Key Features

A Four-Voice Mind for Modular Improvisation

Each of the 511’s four channels is a self-contained stochastic engine, capable of generating voltages, envelopes, or acting as a quantizer—all with independent clock inputs. That independence is key: you’re not just randomizing a single parameter across your system; you’re running four parallel experiments. One channel might be slowly drifting through a minor pentatonic scale, another firing off rapid gate bursts with 30% probability, a third smoothing through a sawtooth-like ramp, and the fourth holding steady until triggered. The ability to mute or hold any channel on command makes it ideal for live performance, where you can freeze a chaotic passage or drop a layer out entirely with a single gate. And because each has its own 32-step sequencer, you’re not limited to static randomness—you can program evolving sequences that change their behavior over time, like a melody that gradually detunes itself or a rhythm that stutters into silence.

Stochastic Intelligence: Where Random Meets Strategy

The 511 gives you control over the randomness itself. You don't just pick "more random" or "less random." You choose a distribution curve: Gaussian, uniform, biased or custom. Each one shapes how voltages cluster or scatter. Smoothing interpolates between steps, from jagged jumps to slow, undulating waves. Probability settings set whether a step fires and how likely it is relative to others. Time control gives you BPM-synced clocks or free-running rates, with dividers or multipliers per channel. The module can also tune a VCO directly from the menu.

Expandable Architecture: CV as Intent

The eight assignable CV inputs and four gate inputs transform the 511 from a source into a system. You’re not just feeding it control voltages—you’re giving it instructions. That LFO from your oscillator? Patch it to modulate the *probability curve* of channel 3. The envelope from your kick drum? Use it to trigger a state change on channel 2. The gate inputs can activate mutes, holds, or cycle through the three memory states per channel—each a full snapshot of that channel’s settings. Want to shift from a smooth, ambient drift to a jagged, atonal burst with the press of a button? That’s what the states are for. And the three logic outputs let you build conditional responses: output a gate only when two channels cross a threshold, or generate a clock pulse when a sequence resets. It’s modular meta-thinking: using the module’s internal logic to drive the rest of your system.

Historical Context

The ADDAC 511 lands in a Eurorack market already crowded with random sources. For years, randomness in modular was an afterthought: a single noise source, a sample-and-hold, maybe a shift register. Then came modules like the ALM Busy Circuits or Xaoc Batumi, which showed that generative sequencing could be deep, musical and performable. The 511 sits in that lineage. Where some modules focus on rhythm or melody, the 511 treats randomness itself as the instrument. It is a successor to the ADDAC501 with much more flexibility and integration. It was released in 2025, as modular synthesis leaned harder into hybrid digital-analog designs with screens and menus. Competitors like the Intellijel Metropolis or Make Noise Mimeophon offer generative textures, but none match the 511's four-channel autonomy and internal logic. It is not a synth voice or an effects processor.

Collectibility & Value

At launch, the ADDAC 511 retailed for €520 or $599.99, which is the premium tier. As of 2026, it's still in production and available from ADDAC's direct store and authorized dealers like Perfect Circuit or Thomann. Used units are rare, given its recent release. When they appear, they command 80-90% of retail, typically €450 - €500 depending on condition. There are no known manufacturing defects or common failure points. The module has a black anodized aluminum panel and through-hole components. The OLED screen is the only potential long-term concern, though no widespread issues have been reported. Firmware updates are available directly from ADDAC, and the module supports preset backup. The manual is excellent, but the depth of control means you'll need hours to unlock its full potential. It's not a plug-and-play random source.