ADDAC System ADDAC506

A four-channel modulation beast that turns randomness into orchestral motion—like a weather system for your modular rack.

Overview

If you've ever wanted your modular synth to make decisions on its own—beautiful, unpredictable, evolving decisions—the ADDAC506 isn't just another envelope generator. It's a stochastic brain, a digital-analog hybrid that breathes like a living thing. Officially licensed from Teia’s long-discontinued Stochastic Function Generator (introduced in 2013), this module takes the original concept and rebuilds it from the ground up with a reprogrammed MCU, giving it a new nervous system while keeping the soul intact. What you get is a Eurorack-sized laboratory for controlled chaos: four independent analog envelope and slew generators, each capable of generating smooth voltage curves or jagged, random stair-steps, all under digital command.

It’s not just an envelope module—it’s a modulation powerhouse. The ADDAC506 excels in drone soundscapes, where its ability to produce long, slow sweeps—up to six minutes in duration—creates tectonic shifts in tone and tension. But don’t let the slow stuff fool you: in Trigger + Loop mode, it can push into the audio range, hitting speeds up to 1kHz, making it capable of generating actual pitched content or rapid-fire modulation for FM and wavefolding experiments.

This is a module for self-patching addicts, the kind who love to wire outputs back into inputs and watch systems evolve. With three gate outputs per channel (End of Rise, End of Fall, and standard Rise Gate), plus dedicated attenuverters for amplitude and offset on each CV output, it invites complex feedback networks. And because it’s part of ADDAC System’s 500 Series, it fits neatly into a larger ecosystem of hybrid digital-analog modules that blend precision with warmth.

Specifications

Manufacturer	ADDAC System
Model	ADDAC506
Type	Eurorack Module, VC Stochastic Function Generator
Width	20 HP
Depth	40 mm
Current Draw	200 mA +12V, 150 mA -12V, 0 mA 5V
Expansion Module	ADDAC506B (2 HP, 10 mA +12V, 10 mA -12V)
Channels	Four
Original Price	$401
Audio Range	Up to 1kHz in Trigger + Loop mode
Max Sweep Time	Up to 6 minutes

Key Features

Quad Analog Core with Digital Intelligence

At its heart, the ADDAC506 is a quad analog envelope and slew generator—but calling it just that undersells its complexity. Each of the four channels features independent Rise and Fall generators, all analog-core but under digital control. This hybrid approach lets it maintain the warmth and smoothness of analog voltage shaping while benefiting from the precision and repeatability of digital logic. The result? Envelopes that can be tightly controlled or wildly unpredictable, depending on how deep you want to dive into the random engine.

Built-In Random Generators with Full Control

What sets this module apart is its deep integration of randomness. Each channel has built-in random generators for both Rise and Fall times, each with Minimum and Maximum controls. That means you’re not just getting noise—you’re getting *shaped* noise. You can set a narrow band for subtle wobble or open it wide for chaotic, unpredictable timing. Global controls for maximum and minimum rise/fall times let you scale the behavior of all four channels at once, making it easy to shift from snappy staccato bursts to languid, drifting swells with a single adjustment.

Three Gate Outputs Per Channel

Each channel doesn’t just give you one gate—it gives you three. The standard Rise Gate output behaves like a traditional envelope gate, but the End of Rise and End of Fall triggers open up complex sequencing possibilities. Imagine chaining envelopes so that the end of one rise kicks off the next fall, or using the End of Fall to reset a sequencer only after a full decay. These outputs encourage interdependent patching, where modules respond to each other in cascading chains of cause and effect.

Dedicated Attenuverters for CV Shaping

Every channel’s CV output comes with dedicated [Amplitude] and [Offset] attenuverters. This isn’t just a convenience—it’s a design philosophy. Instead of needing external mixers or attenuators to shape the output, you can directly scale and shift each voltage right at the source. Whether you’re sending CV to a VCO, filter, or another modulation target, you’ve got immediate, hands-on control over the range and center point of the modulation.

Sum and Average CV Outputs

Beyond the four individual channels, the ADDAC506 provides two additional CV outputs: one for the Sum and one for the Average of all four voices. These are gold for generative patches. The Sum output can create dense, evolving control voltages by layering all four channels together, while the Average output smooths everything into a single, slowly shifting master control. Patch either into a master filter cutoff or overall amplitude control, and you’ve got a macro-level expression of the module’s internal chaos.

Expansion via ADDAC506B

The ADDAC506 isn’t a closed system. With the optional ADDAC506B Expansion Module (a mere 2 HP), you unlock four trigger inputs for the random engine and four additional CV random outputs. This turns the 506 into an even more powerful modulation hub, allowing external triggers to influence the random behavior or letting the module’s internal randomness drive other parts of your system. The expansion draws minimal power (10 mA on both rails), making it an efficient upgrade for those who want deeper integration.

Slew Mode for Portamento and Glide

In Slew Mode, the ADDAC506 transforms into a sophisticated portamento processor. Feed it a quantized pitch CV—say, from a sequencer—and it’ll generate smooth, variable glide between notes. But because each channel has independent randomization, you can create polyphonic glide effects where each voice slides at a slightly different rate, producing a lush, chorused pitch shift that feels organic rather than mechanical.

Historical Context

The ADDAC506 exists because the original Teia Stochastic Function Generator, introduced in 2013, became a cult favorite—and then vanished. ADDAC System stepped in with an officially licensed recreation, but they didn’t just clone it. They took the concept, rebuilt the microcontroller unit from scratch, and expanded it into a fully featured four-voice system. Positioned within the ADDAC500 Series, the 506 reflects the company’s broader mission: fusing digital control with analog warmth to create hybrid instruments that feel both precise and alive. While the original Teia module is now a footnote in modular history, the ADDAC506 keeps its spirit alive, updated for modern Eurorack systems.