ADDAC System ADDAC506B (—)
A 2HP expander for the ADDAC506 VC Stochastic Function Generator. It does nothing without it.
Overview
The ADDAC506B isn't a standalone synth module. On its own in a rack it does nothing. It's a little black 2HP expander for the ADDAC506 VC Stochastic Function Generator, and it lets you shape and trigger the structured randomness on demand. It's officially licensed from Teia's Stochastic Function Generator, a cult favorite from 2013 that vanished when Teia stepped back. It isn't a straight clone. The original concept was rebuilt in fresh code on a new microcontroller, and ADDAC System reprogrammed the MCU from the ground up.
The ADDAC506B exists to unlock more of what the main ADDAC506 can already do. That module is a 4-voice, dual-stage envelope and slew generator with built-in randomization for rise and fall times, multiple gate outputs per channel, and CV outputs for sum and average of all voices. The 506B adds four trigger inputs that let you poke the internal random engine at any point in the envelope cycle, not just at the start. Want to jitter a falling slope halfway through? Trigger it. Need a sudden burst of CV chaos during a sustained phase? There's an input for that. It also adds four CV random outputs, each feeding unpredictable voltages back into your system to modulate filters, pitch, panning, whatever you like.
This is part of ADDAC's 500 Series, a family of modules built around generative and stochastic control. The 506B is a specialist and a sidecar. It doesn't generate envelopes or gates on its own. It doesn't even draw power from the 5V rail (0 mA, to be exact). It depends entirely on its host.
Specifications
| Manufacturer | ADDAC System |
| Dimensions | 2 HP |
| Current Draw | 10 mA +12V, 10 mA -12V, 0 mA 5V |
| Power consumption | 10mA @ +12V / 10mA @ -12V |
| Inputs | Four trigger inputs for the random engine. |
| Outputs | Four CV random outputs from the random engine. |
Key Features
Expansion, Not Independence
The ADDAC506B is an expander, pure and simple. It has no envelope generation, no slew limiting, no gate logic of its own. Everything it does piggybacks on the ADDAC506. The four trigger inputs let you interrupt or reseed the random engine mid-cycle, which helps if you're trying to avoid predictable patterns. Most random sources reset on trigger. This one lets you interact with the randomness while it's running, so you can get evolving textures, glitchy transitions, and generative sequences that don't sound canned.
Four Flavors of Chaos
The four CV random outputs are where you collect the randomness. Each one gives a different stream of unpredictable voltage, all derived from the same engine but statistically independent. You could route one to oscillator pitch, another to a filter cutoff, a third to pan, and the fourth to a sample-and-hold clock. The main ADDAC506 already offers CV outputs with amplitude and offset control (up to 10V peak-to-peak, configurable as 0-10V or -5V to +5V), so the 506B's outputs slot right into that setup. You can attenuvert and scale them to taste.
Form Follows Function
At 2HP, the 506B is barely there. It's a sliver of black front panel, ADDAC's current standard color, with just enough space for eight jacks (four inputs, four outputs) and a tiny label. No knobs, no lights, no menus. ADDAC offers colored panels on request, so a neon green 506B in a sea of black is apparently an option. The depth behind the panel isn't listed anywhere, so assume it's standard for ADDAC's 500 Series.
Collectibility & Value
Pricing is all over the map. The ADDAC506B isn't discontinued or ultra-limited, at least not that we know of. Recent listings have run from $99 to $626.33, which is a wild spread for a 2HP expander. More commonly you'll see it around $119 - $139, with some sellers asking $129. One Reverb listing declared the unit "Absolutely MINT Condition!!" There's no original MSRP on record, so there's no saying whether it's holding value or inflating. Since it's an expansion, its resale appeal is tied to the ADDAC506's user base. If you don't own the main module, it's a paperweight. There are no reports of common failures or maintenance issues, which makes sense with so little to break: no moving parts, just a microcontroller and some jacks. No reflash guide is known if the MCU ever dies.
eBay Listings
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