ADDAC 511 VC Stochastic Voltage Generator (2025–)
A four-channel stochastic voltage generator where the randomness is shaped, not left to chance.
Overview
The ADDAC 511 is not the kind of random that gives you jagged, aimless noise. It has memory and structure. It works less like rolling dice and more like a machine improvising inside a set of rules. It can shift a sequence from a tight minor pentatonic into a dissonant whole-tone drift, on its own, at the moment you wanted it to.
The 511 is a four-channel voltage generator. Each channel runs independently or together with the others, and can produce continuous control voltages, envelopes, or quantized pitch data. All of it is governed by probability, distribution, and timing parameters. It builds on ADDAC’s 2013 ADDAC501 Complex Random, which was the sketch to the 511’s finished painting. You can define the shape of the probability distribution and the jitter in the gate timing. You can set it to walk through a scale like a drunkard, skip notes with weighted odds, or interpolate smoothly between voltages.
Recall and performance control set the 511 apart from the other “random” modules in Eurorack. Each channel has three user-definable “states,” which are snapshots of all its parameters, and dedicated front-panel buttons toggle them instantly. One channel can shift from a tight arpeggio to a sprawling atonal run with a single press while another flips from smooth glides to stepped randomness. Across four channels that makes twelve possible configurations. There is also a 32-step sequencer per channel, and yes, that means per channel.
The interface centers on an OLED screen and two rotary encoders, with a grid of buttons that do double duty through short and long presses. It is not a knob-per-function design, and anyone expecting to tweak everything without menu diving will be disappointed. ADDAC kept the menus shallow: most parameters are no more than two layers deep, and the screen shows active modes, voltage ranges, quantization scales, and distribution curves. CV inputs sit on the right, outputs on the left, clock inputs below, and the main controls are grouped together. Keep the manual nearby, at least for the first dozen sessions.
Specifications
| Manufacturer | ADDAC System |
| Production Years | 2025– |
| Original Price | €520 / £519 / $659 |
| HP | 20 |
| Depth | 4.5 cm (45 mm) |
| Current Draw +12V | 200 mA |
| Current Draw -12V | 100 mA |
| Channels | 4 independent |
| CV Outputs | 4 bipolar (range configurable) |
| Gate Outputs | 4 |
| Clock Inputs | 4 |
| CV Inputs | 8 assignable |
| Logic Outputs | 3 programmable (AND, NAND, OR, NOR, XOR, XNOR) |
| Average CV Output | 1 (sum of all four CV outputs) |
| Sequencer Steps | 32 per channel |
| Preset Storage | 16 user presets |
| States per Channel | 3 |
| Quantization | Custom scales, transposition, note probability |
| Internal Clock | Yes, with divider, multiplier, delay |
| Display | OLED screen with menu navigation |
| Encoder Controls | 2 |
Key Features
Four Channels of Deeply Programmable Randomness
Each of the 511’s four channels is a self-contained stochastic engine, and it can generate either continuous voltages or gate signals. The voltage section selects between continuous output and envelope generation. It also has polarity (unipolar or bipolar), range limits, and range-locking so external CV can shift the whole span up or down. The quantization engine lets you assign any scale - major, minor, chromatic, or fully custom - and then adjust the probability of individual notes appearing. A diminished fifth can be set to show up only 20% of the time. The root note can be muted entirely.
The gate output section controls gate length, probability, and step skipping, which suits unpredictable rhythmic patterns. “Walk” mode creates a “drunken walk” effect where each new voltage is a small random offset from the previous one. The smoothing function acts as a tunable slew limiter, with adjustable resolution for smooth glides or stepped transitions. It can morph between harmonic centers or add portamento-like movement to sequences.
Time, Clock, and Sequencing Intelligence
The 511 treats time with the same scrutiny as voltage. Each channel has its own time parameters, including clock source selection (internal or any of the four external inputs), tempo range, and time distribution curves. You can lock a channel into a 32-step sequence where each step modulates a parameter, such as probability or voltage range. These sequences run independently or synchronized across channels, so patches can evolve over minutes, not seconds.
The internal clock is robust, offering multiplier, divider, and delay functions, so you can generate polyrhythmic relationships directly within the module. The four external clock inputs can be freely assigned, meaning you can drive different channels from different sources—say, a steady 16th-note pulse for one and a triplet-based clock for another. This flexibility makes the 511 not just a source of randomness but a conductor of generative systems, capable of tying together disparate rhythmic elements into a coherent whole.
Assignable Modulation and Logic Outputs
The 511 has eight CV inputs and four gate inputs. Each CV input can be mapped internally to any parameter on any channel. An LFO could modulate the probability curve on Channel 2, or a sequencer could shift the quantization scale on Channel 4. That makes the 511 a modulation matrix as much as a voltage generator, with external sources shaping the randomness itself.
The three logic outputs compare any combination of CV inputs, clock signals, or internal states using standard Boolean logic (AND, OR, XOR, etc.), and output a gate when the conditions are met. An AND condition can trigger when two channels hit their peak voltage at the same time. A reset pulse can fire when a sequence reaches a certain step. These outputs let the 511 drive other modules with complex conditional events.
Historical Context
Early random sources, such as sample-and-hold circuits and noise-based triggers, were blunt instruments. Later modules like the Make Noise René or Intellijel Metropolis added sequencing and logic, but still treated randomness as a secondary effect. The 511, along with contemporaries like the ALM Busy Circuits SIG or the Qu-bit Electronix Melodicer, belongs to a newer class of modules where generativity is the primary function.
ADDAC has been exploring stochastic processes since its early modules, and the 511 is its most ambitious statement yet. It is positioned against full compositional tools, not simple random generators. Compared to the SIG, which excels in live improvisation, the 511 leans toward preparation and structure, with its three states per channel and deep preset system. Against the Melodicer, which offers elegant simplicity, the 511 trades immediacy for depth: fewer “happy accidents,” more “intentional surprises.”
The 511 follows ADDAC’s usual design approach: understated front panels, serious functionality, and no oversimplifying. The black panel, minimal labeling, and reliance on menus are choices made for users who prioritize precision over instant gratification.
Collectibility & Value
As of 2026, the ADDAC 511 is too new to be considered “vintage” in the traditional sense. The original price is around €520, which puts it in the upper tier of Eurorack modules - not as expensive as a dual analog filter or a full voice, but not an impulse buy either. Given ADDAC’s reputation for solid build quality and long-term firmware support, it’s unlikely to depreciate quickly. Limited availability and high demand could push secondary market prices upward, especially for early production units.
Condition matters when buying used. The OLED screen is durable but can suffer from burn-in if left on static menus for extended periods. The encoders and buttons are high-quality, but heavy use may lead to wear, so check for smooth rotation and positive tactile feedback. Firmware updates are available from ADDAC’s website, and owners are advised to keep their units current. There are reports of crashes under high-load conditions, such as fast clocks with wide voltage sweeps. These crashes are infrequent, but they suggest early firmware may have stability issues, so buyers should confirm the module is updated.
For collectors, the value is in functionality, not rarity. The 511 is not a flashy centerpiece. It is a workhorse. It pairs well with modules like the ALM Busy Circuits SEQ-3, the Intellijel Steppy, or the Mutable Instruments Marbles (a spiritual predecessor in concept, if not implementation). A full system with the 511 at its core can work as an autonomous music generator, producing evolving pieces with minimal human intervention.
A simpler and cheaper module will do for someone who only wants random notes now and then. The 511 suits people who compose with probability and want patches that surprise them without betraying them.
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