ADDAC System ADDAC103 T-Networks ()
Four little thumps in a 6HP space, built on the same analog circuit idea that powered classic drum machines. Simple, weird, and ready to crack open.
Overview
The ADDAC103 T-Networks has no flashy lights, no menus and no patch memory. It has four knobs stacked twice, each paired with a switch and an input. The simplicity hides a lineage. The module uses the same Twin T-Network circuit found in some of the drum machines that gave many classic drum sounds their snappy, organic snap. It's not a sample player or a digital emulation. It's an analog Eurorack take on that resonance, in a 6HP block.
It's a four-voice percussion module, so you get four separate drum-like tones - toms, snares, kicks, or even metallic clicks - each with its own frequency control and trigger input. The top two voices lean toward higher frequencies, good for snappy hats or tight toms. The bottom two go lower, for rounder thuds and deeper booms. Each voice has a Frequency Range Switch with three positions: Low, Mod, and High. Trigger it with a gate and turn the knob. There are no envelopes, no VCAs and no modulation routing. What you turn is what you get.
The ADDAC103 can also mangle sound. 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 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 and it's not predictable. Think of running your signal through a rusty spring and lighting it on fire. If you want gritty textures or a bit of analog chaos in a patch, this does it.
All four voices sum to a single output with its own volume knob, so the module works as a complete drum voice section without an external mixer. There are no firmware updates and no calibration routines (at least none documented). You plug in, patch, and play.
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, based on the analog topologies behind vintage drum machines. They aren't modeled in software or approximated with op-amps in a new way. They're recreations of a classic passive filter network that can self-oscillate when triggered, producing sharp, resonant percussive tones. Each circuit responds quickly to triggers and decays naturally, giving an 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. The input can also accept signals well into the audio range, and owners have found that feeding audio into it turns each voice into a kind of filter, albeit a "weird" one. It doesn't behave like a standard low-pass or band-pass. It interacts unpredictably with incoming waveforms, creating distortion, resonance peaks, and strange cancellations.
Smart Voice Layout with Built-in Summing
The split between high and low voices is deliberate. The top two voices take higher ranges and the bottom two take lower ones, so the layout suggests itself: snares and hi-toms up top, kicks and floor toms below. That keeps patching intuitive when building a full drum voice setup. The summed mix output, with its own volume knob, sends all four voices out through a single cable. In a crowded rack, every patch cable saved counts.
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. It has an average rating of 4.27 out of 5 based on 11 votes on ModularGrid. Detailed reviews and 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.
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