Four voices of raw, uncalibrated analog chaos that crackle with the spirit of vintage drum machines—patch it once and fall in love.
Overview
There’s something instantly addictive about the ADDAC104 VC T-Networks—not because it plays nice, but because it doesn’t. It’s a four-voice Eurorack module that throws out the rulebook on pitch stability and instead leans into the gritty, unpredictable nature of Twin T-Networks circuits, the same ones that powered the guts of classic drum machines. This isn’t a synth voice you tune for melodies; it’s a percussive beast built for clicks, knocks, and resonant thumps that feel alive. Portuguese manufacturer ADDAC System didn’t try to polish the rough edges—they doubled down on them, adding voltage control to each voice to open up a world of modulation that feels both nostalgic and wildly modern.
Owners report it was “love at first patch,” and it’s easy to see why. Each of the four voices delivers a distinct character, with the top two channels tuned for higher frequencies and the bottom two sitting in a lower, meatier register. That split alone makes it a natural for drum racks—think snappy hi-hats up top and boomy toms below. But what really sets it apart is its flexibility: thanks to a gate-to-trigger converter on every input, you can feed it anything. A sequencer gate? Sure. A random burst of noise? Even better. And if you route an audio signal into a trigger input? That’s where the magic turns destructive—each voice can act as a brutal, resonant filter that mangles your source into something unrecognizable. It’s not a feature you find in manuals; it’s something you discover mid-patch, and once you do, you can’t unhear it.
And despite its wild nature, it’s surprisingly practical. The summed mix output with dedicated volume control means you can blend all four voices and send them out through a single cable—ideal for live setups where cable spaghetti kills the vibe. One reviewer noted it “fits perfectly in a live case for maintaining live manageability,” which says a lot for a module that could easily have gone full chaos mode. At 8 HP and 25 mm deep, it’s compact without sacrificing usability, and with no 5V draw, it plays well with skimpier power supplies. It’s not trying to be everything—it’s trying to be *this*, and it nails it.
Specifications
| Manufacturer | ADDAC System |
| Dimensions | 8 HP |
| Depth | 25 mm |
| Current Draw | 50 mA +12V, 50 mA -12V, 0 mA 5V |
| Price | $179 |
| Number of Voices | 4 |
| Features | Frequency control with CV input and attenuverter, Frequency Range Switch (Low/Mod/High), Trigger Input, Audio Output (per voice) |
| Features | Summing Mix output with Volume control |
| Features | CV inputs with attenuverters for each voice Frequency |
| Features | Gate to trigger converter at each voice input |
| Features | Audio inputs can be used as input, enabling destructive filter behavior |
| Features | CV inputs are not calibrated to 1v/octave |
| Design | Inspired by Twin T-Networks circuits used in many legendary drum machines |
| Design | Top 2 channels feature a higher frequency range, bottom 2 channels feature a lower frequency range |
Key Features
Four Voices, Four Personalities
The ADDAC104 gives you four independent voices, each with its own frequency control, CV input with attenuverter, trigger input, and audio output. But don’t expect keyboard-style tuning—the CV inputs aren’t calibrated to 1V/octave, a deliberate choice that keeps the module affordable and frees it from melodic expectations. Instead, it encourages experimentation. The lack of calibration means every patch is a negotiation, a dance between control and chaos. And that’s where the fun lives. Each voice has a Frequency Range Switch with three positions: Low, Mod, and High. These aren’t subtle trims—they’re dramatic shifts that can take a voice from subby thud to metallic ping in one flick. The top two voices are biased toward higher frequencies, making them ideal for hats and clicks, while the bottom two are tuned lower, perfect for kicks and toms. It’s a smart layout that turns the module into an instant drum brain.
Voltage Control Meets Analog Anarchy
The “VC” in the name isn’t just for show. Each voice’s frequency can be modulated via CV, and with attenuverters on board, you can scale and invert the incoming signal for dynamic, expressive movement. Want a snare that tightens up as it decays? Route an envelope into the CV input and tweak the attenuverter until it snaps just right. The gate-to-trigger converter on each input means you don’t need a dedicated trigger source—any gate signal will do, and it’ll be converted to the right timing to fire the voice. This opens the door to using sequencers, clocks, or even random logic signals to drive the module. But the real dark magic happens when you feed an audio signal into the trigger input. Because of the gate-to-trigger circuit’s behavior, the voice starts reacting to the waveform’s zero crossings, effectively turning it into a resonant, self-oscillating filter that can chew up audio in real time. It’s not clean. It’s not predictable. But it’s incredibly musical in the right context.
Summed Output for Live Simplicity
One of the most practical touches is the summed mix output with its own volume control. In a world where mixing four separate drum voices usually means patching through a mixer or using multiple outputs, this is a small luxury that pays off big. You can blend all four voices internally and send a single stereo or mono mix to your interface or PA. It’s a huge win for live performers who need to keep patch count low and workflow tight. Reviewers have called out how this feature makes it easy to “get 4 drum sounds with only one output,” which might sound minor until you’re on stage with 15 modules and a tangle of cables. It’s a reminder that good design isn’t just about sound—it’s about how the module fits into your system, your set, your headspace.
Collectibility & Value
The ADDAC104 VC T-Networks isn’t a rare unicorn—yet—but it’s holding steady in the used market with prices clustering between $175 and $217.46, slightly above its $179 retail price. That suggests demand is healthy, likely driven by its unique character and live-friendly design. There’s no data on common failures or maintenance issues, and no reports of circuit-specific weaknesses, which is reassuring for a module built around somewhat obscure analog topology. Since it draws no 5V current, it’s also less likely to cause power supply headaches in crowded cases. It’s not a museum piece, but it’s not disposable either—owners clearly value it enough to keep it in rotation and pay a small premium to get it. If you’re building a compact, percussion-heavy system, this one’s worth tracking down.
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