ADDAC System 107 (2023)

A happy accident that became a full acid voice in just 9 HP. Squelch on tap, distortion built in, and a smiley face etched on the panel.

Overview

Plug in the ADDAC 107 and turn the resonance up past 12 o'clock. You know what comes next. It's a gurgling, wet, unstable snarl, and the module makes no attempt at subtlety. It wasn't supposed to be this, either. It was originally pitched as a complex percussion source, but during development the Lisbon-based team at ADDAC realized the circuit had a different personality. It was an acid machine. So they leaned in. The result is a complete, self-contained analog voice - VCO, filter, VCA, envelope - in a 9 HP Eurorack module. It takes the TB-303's legacy and adds modern flexibility.

The voltage-controlled oscillator offers sawtooth or triangle waveforms, switched with a small toggle. That signal is blended with a square wave before it hits the filter. The filter is multimode, with lowpass, bandpass and highpass modes, and you're going to live in bandpass. Resonance is where it gets interesting. Crank it and the cutoff starts to scream, wobble and self-oscillate in the classic resonant peak that defines acid. CV control is standard, but the 107 adds an attenuverter for the cutoff modulation, so you set how much external movement gets in. The VCA stage is where things get clever. Instead of a traditional envelope generator, it uses an AD (attack-decay) contour with a fixed short attack and a decay time you can adjust by hand or via CV. The VCA's input also doubles as a gain stage that can push signals past unity gain, up to double amplification. That brings in harmonic saturation and soft clipping, which turn clean acid lines into gnarled, overdriven growls. Patch in a gate, trigger, or CV above +5V and the 107 distorts, so the VCA shapes tone as much as it shapes amplitude.

And then there’s the accent input. A feature more common on drum modules than synth voices, it lets you dynamically boost the amplitude of individual notes, adding punch and variation to sequences. It’s a small thing, but it makes the 107 feel more alive, more musical, especially when paired with a sequencer. The module also includes a CV output that mirrors the internal slewed envelope signal, letting you route modulation to other parts of your system—say, to modulate a second filter or pan position. It’s a thoughtful touch, turning the 107 into not just a sound source, but a modulation hub. Even the faceplate has personality: a tiny smiley face etched near the bottom, a wink to the genre’s rave roots. This isn’t sterile engineering—it’s gear with a sense of humor, built by people who’ve clearly spent time in dark rooms with loud music.

Specifications

Manufacturer	ADDAC System
Production Years	2023–present
Original Price	$249 (assembled), €202 (DIY kit)
Format	Eurorack
Width	9 HP
Depth	40 mm
Power Consumption (+12V)	80 mA
Power Consumption (-12V)	80 mA
Power Connector	Standard Eurorack 16-pin ribbon cable
VCO Waveforms	Sawtooth, Triangle (switchable), Square (mixed)
VCO Range	4 octaves
Filter Types	Lowpass, Bandpass, Highpass (3-position switch)
Filter Resonance	Voltage-controlled with manual knob
VCA Type	AD envelope (fixed attack, variable decay)
VCA Gain	Adjustable up to 2x amplification (unity gain + boost)
Inputs	VCO CV, Filter Cutoff CV, VCA Input (Gate/Trigger/CV), Accent CV
Outputs	Audio Out, CV Out (slewed envelope)
Normalizations	CV Out normalled to VCO and Filter CV inputs; jumpers allow de-normalization
DIY Option	Available as SMD/through-hole hybrid kit (SMD-Kit-2, medium difficulty)
Weight	Approx. 150 g (assembled)

Key Features

A Filter That Knows How to Misbehave

The 107's multimode filter is the heart of the module. In bandpass mode it gives that squelch with a liquid, almost vocal quality. Turn up the resonance and it oscillates, warbles and breathes. The cutoff CV input with attenuverter sets how much external modulation moves the filter, whether that's a subtle wobble from an LFO or a full dive from a sequencer. The filter sits after a mixed VCO stage (triangle or saw blended with square), so there's plenty of harmonic material before the sound reaches the resonance knob. It's not a 303 clone, but it shares the same unstable, expressive behavior, and it goes from polite to unhinged with a single turn.

VCA as a Sonic Weapon

Most synth voices treat the VCA as a simple gatekeeper for volume. The 107 turns it into a distortion stage. The input gain knob can push signals past unity, adding soft clipping and harmonic saturation that thickens the sound a lot. Feed in a clean gate and you get a punchy note. Feed in a hot CV or overdrive the input, and the VCA saturates, adding grit and growl that feels more like a stomp box than a modular component. The AD envelope is simple by design, with a short fixed attack and a variable decay. If you want more control, patch in external envelopes or mod sources. The accent input takes a CV to boost note velocity, which gives sequences human-like variation, like a drummer hitting harder on the offbeats.

Hidden Modulation & DIY Flexibility

Flip the module over and you’ll find jumpers on the side that let you de-normalize the CV output from the internal VCO and filter CV inputs. It’s not the most accessible design—those jumpers aren’t on the front panel, so you’ll need to power down and remove the module to tweak them—but it’s a smart compromise between clean front-panel layout and deep customization. The CV output itself is a goldmine: it sends out the slewed envelope signal from the VCA stage, which means you can use it to modulate other modules in your system. Want to sync a filter sweep or panning effect to your acid line? Patch it in. It turns the 107 into a mini modulation hub. And for tinkerers, the DIY kit option is a major draw. It’s rated as medium difficulty, combining SMD and through-hole parts, making it accessible to intermediate builders. For the price, it’s a rare chance to get hands-on with a module that sounds this good.

Historical Context

The 107 landed in 2023. ADDAC didn't just drop another utility module into a market already flooded with oscillators, filters and voices. They went after self-contained, characterful voices that don't eat up rack space. The 107 sits in a lineage of compact acid modules, like the Intellijel Polaris or the XAOC Batumi, but with its own personality. It's not trying to be a full synth. It's trying to be the best acid voice in 9 HP. It's also a product of ADDAC's broader philosophy of hybrid instruments that blend analog sound with digital control, though in this case they went fully analog. Competitors like Doepfer and Erica Synths offer acid-style modules, but few package VCO, filter, VCA, envelope and distortion into such a tight footprint.

Collectibility & Value

As of 2026, the ADDAC 107 is still in production and available from retailers like Perfect Circuit, Reverb, and Exploding Shed. The assembled version lists for $249, while the DIY kit goes for €202. On the used market, prices hover between $200 and $230 depending on condition, with mint units from careful owners sometimes fetching closer to retail. It's not a rare module yet, but it's gaining a reputation as a "must-have" for acid enthusiasts and minimal techno builders. Completed kits are more common in the wild than unbuilt ones. Failures are rare, but owners should be aware of the SMD components if repairing. Reflowing solder joints on the filter or VCA stage may be needed after years of use, though no widespread reliability issues have been reported. Many users run multiple units for layered acid lines. When buying used, check that the toggle switches (waveform and filter mode) are clean and crackle-free, and verify that the accent input responds dynamically. Power up slowly with a current-limited supply if the module has been stored for years. No known firmware or revision changes affect performance.