ADDAC System ADDAC103 T-Networks ()
Four little thumps in a 6HP space, born from the same analog witchcraft that powered classic drum machines — simple, weird, and ready to crack open.
Overview
The ADDAC103 T-Networks doesn’t announce itself with fanfare. No flashy lights, no menu diving, no patch memory — just four knobs stacked twice, each paired with a switch and an input. But that simplicity hides a lineage. This module taps into the same analog soul as the Twin T-Network circuits found in some of the most iconic drum machines ever made, the kind that gave many legendary drum machines their snappy, organic snap. It’s not a sample player or a digital emulation; it’s a compact Eurorack homage to that analog resonance, distilled into a 6HP block of pure percussive potential.
It’s a four-voice percussion module, meaning you can generate four separate drum-like tones — think toms, snares, kicks, or even metallic clicks — each with its own frequency control and trigger input. The top two voices lean toward higher frequencies, ideal for snappy hats or tight toms, while the bottom two dig into lower territory, capable of rounder thuds and deeper booms. Each voice has a Frequency Range Switch with three positions: Low, Mod, and High, letting you jump between registers on the fly. Trigger it with a gate, tweak the knob, and you’re in business. It’s about as straightforward as synthesis gets — no envelopes, no VCAs, no modulation routing. What you turn is what you get.
But here’s where it gets interesting: the ADDAC103 doesn’t just make noise — it can mangle it. Each voice accepts audio-rate signals at its trigger input, thanks to a gate-to-trigger converter on board. Feed it a waveform, a burst of noise, or even an external audio source, and the twin-T circuit starts behaving like a “very destructive filter,” as one retailer put it. It’s not clean. It’s not predictable. It’s more like running your signal through a rusty spring and lighting it on fire — but in a good way. If you're into gritty, unpredictable textures or want to add a bit of analog chaos to your patches, this module delivers.
And yes, it sums all four voices to a single output with its own volume knob, so you can treat it as a complete drum voice section without needing an external mixer. It’s compact, self-contained, and designed to be immediate. No firmware updates, no calibration routines (at least none documented), just plug, patch, and play. That immediacy is part of its charm — it feels like a tool, not a toy.
Specifications
| Manufacturer | ADDAC System |
| Dimensions | 6 HP |
| Depth | 25 mm |
| Current Draw | 40 mA +12V, 40 mA -12V, 0 mA 5V |
| Number of Voices | 4 |
| Features per Voice | Frequency control, Frequency Range Switch (Low/Mod/High), Trigger Input, Audio Output |
| Output | Summing Mix output with Volume control |
| Frequency Range Characteristic | The top 2 channels feature a higher frequency range, the bottom 2 channels feature a lower frequency range |
Key Features
Four Twin-T Circuits, One Purpose
The ADDAC103 uses four twin-T circuits — one per voice — directly inspired by the analog topologies that gave vintage drum machines their character. These aren’t modeled in software or approximated with op-amps in a new way; they’re faithful recreations of a classic passive filter network that can self-oscillate when triggered, producing sharp, resonant percussive tones. It’s a simple trick, but when done right, it feels alive. Each circuit responds quickly to triggers and decays naturally, giving you that organic “thwack” that’s hard to replicate digitally.
Gate Inputs That Double as Audio Processors
Each voice’s trigger input includes a gate-to-trigger converter, so it responds reliably to standard Eurorack gate signals. But because the input can accept signals well into the audio range, owners have found that feeding audio directly into the trigger input transforms each voice into a kind of filter — albeit a “weird” one. It doesn’t behave like a standard low-pass or band-pass; instead, it interacts unpredictably with incoming waveforms, creating distortion, resonance peaks, and strange cancellations. It’s not for cleaning up your mix — it’s for tearing it apart and seeing what’s underneath.
Smart Voice Layout with Built-in Summing
The division between high and low frequency voices isn’t arbitrary. By dedicating the top two voices to higher ranges and the bottom two to lower ones, the module encourages a natural layout: place your snares and hi-toms up top, your kicks and floor toms below. It makes patching intuitive, especially when you’re building a full drum voice setup. And with the summed mix output — complete with its own volume knob — you can send all four voices out through a single cable. That’s a small convenience, but in a crowded rack, every patch cable saved is a win.
Collectibility & Value
The ADDAC103 T-Networks holds steady in the used market, with one listing showing a price of $149 on Reverb and ModularGrid. Another retailer, synthCube, lists it at a range of $99.00 to $112.00, suggesting that new or NOS units may still be available at or near original pricing. It’s not a rare grail, but it’s not disposable either. With an average rating of 4.27 out of 5 based on 11 votes on ModularGrid, it’s well-regarded among users, though detailed reviews or owner testimonials haven’t surfaced in the research. There’s no data on common failures, repair costs, or long-term reliability — which could mean it’s trouble-free, or just that no one’s talking about it breaking. Either way, it’s a module that seems to do its job and stay out of the way.
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