ADDAC104 VC T-Networks ()
Four gritty, voltage-controlled drum voices that crackle with the raw character of vintage rhythm boxes—patch one and you’ll feel it in your ribs.
Overview
The ADDAC104 VC T-Networks isn’t trying to be a polite synth voice. It’s a percussive beast, built for kicks that thump like a basement floor giving way and toms that snap like dry twigs underfoot. Made by ADDAC System—a boutique Eurorack outfit out of Lisbon, Portugal—this module leans hard into analog chaos, resurrecting the Twin T-Network circuits that once powered the heartbeat of classic drum machines. If you’ve ever chased that unnameable grit in an 808 or CR-78, this module doesn’t just nod in that direction—it cranks it up and hands you the patch cables.
It’s a Eurorack module, squarely aimed at modular heads who want more than just another VCO. Instead of smooth sine waves and pristine sweeps, the 104 trades in resonance, decay, and that slightly unpredictable analog wobble that feels alive. It’s not a full drum module—no dedicated snare or hi-hat circuitry—but it excels where punch and character matter most: kicks, bass pulses, and toms with attitude. Owners report it’s “great for kicks, basses, and toms,” and one reviewer put it bluntly: “it was love at first patch for me.” That kind of instant chemistry isn’t something every module can claim.
What sets it apart from its siblings and competitors is its foundation. The circuit design pulls directly from Twin T-Network topologies, a clever but often overlooked analog trick that uses twin RC networks to create sharp, resonant notches in the frequency response—perfect for percussive transients. These circuits were tucked inside some of the most iconic drum machines of the ’70s and ’80s, and ADDAC didn’t just copy them—they voltage-controlled them. That means you can modulate the frequency of each voice in real time, opening up everything from rhythmic pitch sweeps to chaotic, skittering textures.
And there are four voices here, each independent but housed in a single module. You get individual outputs for each, so you can process them separately—send one kick through a spring reverb, another through a distortion pedal, no problem. There’s also a mix output with its own volume knob, which is a small but meaningful convenience when you’re jamming and don’t want to patch out to a mixer right away. It’s the kind of detail that suggests ADDAC was building this for actual use, not just spec-sheet completeness.
Specifications
| Manufacturer | ADDAC System |
| Product Type | Eurorack module |
| Number of Voices | 4 |
| Outputs | Four individual outputs as well as a mix output with dedicated volume control |
| Controls per Voice | Frequency control with CV input and attenuverter; Frequency Range Switch, Low/Mod/High |
| CV Input Calibration | The CV inputs are not calibrated to 1v/octave |
Key Features
Circuitry Rooted in Drum Machine History
The ADDAC104 VC T-Networks doesn’t just simulate vintage drum tones—it rebuilds the actual circuit architecture that gave them life. Twin T-Networks were used in a number of legendary rhythm boxes to generate sharp, resonant percussive hits without the need for complex filtering or sample playback. ADDAC’s implementation stays true to that spirit, but adds modern modular flexibility. Each voice is a self-contained T-network oscillator with a tunable frequency, letting you dial in anything from subby thumps to metallic clicks. The result is a sound that feels both retro and immediate—like it’s been pulled straight from a ’70s service manual and dropped into your rack.
Evolution from the ADDAC103
The 104 takes that foundation and adds CV inputs with attenuverters for each voice, giving you real-time control over pitch. That might not sound like a huge leap, but in practice, it transforms the module from a static sound source into something that can breathe and evolve. You can sequence pitch changes, modulate them with LFOs, or even use random voltages to create unpredictable rhythms. The CV inputs aren’t calibrated to 1V/octave, which means you can’t reliably play it like a melodic instrument from a keyboard—but that’s not the point. It’s about motion, texture, and surprise.
Four Voices, Four Personalities
Having four voices in one module gives you a compact but powerful drum voice engine. Each voice has its own frequency knob, CV input, attenuverter, and a three-position range switch: Low, Mod, and High. These switches let you jump between broad frequency zones, making it easy to set one voice to a deep kick, another to a mid-range tom, and a third to something snappy and high-pitched. The lack of 1V/octave tracking means you’ll spend more time tweaking by ear than by scale, but that’s part of the charm. It forces you to listen, to experiment, to patch and repatch until you find that sweet spot where the sound locks into your groove.
And because each voice has its own output, you’re not stuck with a summed signal. You can send each one to different effects, different channels, or even different mixers. That kind of flexibility is rare in a module this focused. but the 104 treats each voice like a first-class citizen. The mix output with its own volume control is a nice fallback—perfect for quick jams or when you’re short on mixer channels—but the real magic happens when you start processing each voice independently.
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