Four voices of raw, uncalibrated analog chaos that crackle like vintage drum machines. Patch it once and you're hooked.
Overview
The ADDAC104 VC T-Networks is a four-voice Eurorack module that skips pitch stability and goes for the gritty, unpredictable side of Twin T-Network circuits, the same circuits used in classic drum machines. You don't tune it for melodies. It's built for clicks, knocks, and resonant thumps. Portuguese manufacturer ADDAC System left the rough edges alone and added voltage control to each voice, which opens up a lot of modulation.
Owners report it was "love at first patch." Each of the four voices has its own character. The top two channels are tuned for higher frequencies and the bottom two sit in a lower, meatier register. That split suits drum racks: snappy hi-hats up top, boomy toms below. Every input has a gate-to-trigger converter, so you can feed it a sequencer gate or a random burst of noise. Route an audio signal into a trigger input and each voice acts as a brutal, resonant filter that mangles the source into something unrecognizable. You won't find that in a manual. You find it mid-patch.
It's also practical. The summed mix output has a dedicated volume control, so you can blend all four voices and send them out through a single cable. That helps in live setups with too many cables. One reviewer noted it "fits perfectly in a live case for maintaining live manageability." At 8 HP and 25 mm deep, it's compact, and with no 5V draw it plays well with skimpier power supplies.
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. The CV inputs aren't calibrated to 1V/octave. That's a deliberate choice that keeps the module affordable and frees it from melodic expectations, so every patch is a negotiation between control and chaos. Each voice has a Frequency Range Switch with three positions: Low, Mod, and High. These are dramatic shifts, not subtle trims, and can take a voice from subby thud to metallic ping in one flick. The top two voices are biased toward higher frequencies, which suits hats and clicks. The bottom two are tuned lower, for kicks and toms.
Voltage Control Meets Analog Anarchy
The "VC" in the name means each voice's frequency can be modulated via CV. The attenuverters let you scale and invert the incoming signal. Route an envelope into the CV input and tweak the attenuverter, and you can get a snare that tightens up as it decays. The gate-to-trigger converter on each input means you don't need a dedicated trigger source. Any gate signal will do, and it gets converted to the right timing to fire the voice. Sequencers, clocks, or random logic signals can all drive the module. Feed an audio signal into the trigger input and, because of the gate-to-trigger circuit's behavior, the voice reacts to the waveform's zero crossings. That turns it into a resonant, self-oscillating filter that can chew up audio in real time. It's not clean and it's not predictable.
Summed Output for Live Simplicity
The summed mix output with its own volume control is one of the most practical touches. Mixing four separate drum voices usually means patching through a mixer or using multiple outputs. Here you can blend all four voices internally and send a single stereo or mono mix to your interface or PA. That keeps patch count low for live performers. Reviewers have called out how this makes it easy to "get 4 drum sounds with only one output," which matters more when you're on stage with 15 modules and a tangle of cables.
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 healthy demand, 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. Owners clearly value it enough to keep it in rotation and pay a small premium to get it.
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