ADDAC System ADDAC103
Four little analog thumpers in a 6HP slot, each one ready to crack open like a snare shell or rumble like a tom—if you know how to flick the switch.
Overview
This is a Eurorack module for people who like their percussion dry, immediate, and slightly unhinged. It’s not a drum machine, not really. It’s more like a drum machine’s nervous system laid bare: triggers in, frequencies twisting, outputs spitting out clicks, knocks, and booms that feel less synthesized and more *excavated*.
It’s categorized as a four-voice percussion source, and that’s accurate, but it’s not pretending to be a Roland TR-808 in miniature. Instead, it leans into its simplicity. Four voices, each with a frequency knob and a range switch (Low/Mod/High), give you just enough control to dial in a kick, a snare, a rimshot, or a tom fill. The top two channels favor higher frequencies, the bottom two dig deeper—so there’s a built-in hierarchy, almost like a mini drum rack. You don’t patch in samples or sequences; you patch in triggers, and the ADDAC103 responds with a burst of tuned resonance, like plucking a spring or hitting a drum head that forgot how to ring.
And then there’s the weirdness: each voice has a gate-to-trigger converter at the input, which means you can feed in any signal—not just triggers. That’s where things get unpredictable. Feed an audio signal into a voice input, and due to the gate converter’s behavior, the voice doesn’t just respond—it *distorts*, *clips*, *destroys*. Some users exploit this to turn the module into a set of four extremely aggressive filters, mangling external sounds into something unrecognizable. It’s not clean. It’s not musical. But in a system full of pristine oscillators and smooth VCAs, that kind of controlled chaos can be exactly what a patch needs.
It’s part of the ADDAC100 series, a line that values hands-on design and analog immediacy. Later modules like the ADDAC104 VC T-Networks and ADDAC105 4 Voice Cluster are described as following in its footsteps, drawing inspiration from its stripped-down approach. But the ADDAC103 stands apart for its rawness. There’s no voltage control over pitch, no envelope shaping—just frequency, range, and trigger. What you get out depends entirely on what you put in, and how much you’re willing to abuse the inputs.
Specifications
| Manufacturer | ADDAC System |
| Model | ADDAC103 T-Networks |
| Product Type | Eurorack Module |
| Number of Voices | 4 |
| Dimensions | 6 HP |
| Depth | 25 mm |
| Current Draw | 40 mA +12V, 40 mA -12V, 0 mA 5V |
Key Features
Four Twin-T Circuits, Straight from the Drum Machine Graveyard
The ADDAC103 doesn’t simulate classic drum tones—it resurrects the actual circuit topology used in vintage drum machines for kicks and toms: the twin-T network. The ADDAC103 uses four of them, one per voice, giving each its own tuned decay and character. There’s no digital modeling, no sample playback—just analog resonance born from resistors, capacitors, and the right kind of trigger pulse.
Gate-to-Trigger Conversion: Open Input Policy
Each voice has a trigger input with a gate-to-trigger converter, meaning it doesn’t care what kind of signal you send—just that it sees a rising edge. This opens the door to all kinds of timing sources: sequencers, clock dividers, logic modules, even random gates. But the real flexibility comes from the fact that *any* input source can trigger a voice. That might sound obvious, but in modular, not all inputs are created equal. The ADDAC103 doesn’t demand precision; it responds to anything that crosses a threshold. That makes it forgiving in a patch, but also unpredictable—especially when you start feeding it audio.
Audio Inputs as Destructive Filters? Sure, Why Not
Here’s where the module stops being just a drum voice and starts becoming a sound mangler. Because of the gate-to-trigger converter’s behavior, feeding an audio signal into a voice input doesn’t just trigger it—it causes the circuit to react erratically. The result? Each voice can act as a “very destructive filter,” chopping and distorting the incoming signal in ways that aren’t musical but are undeniably *textural*. Run a sine wave through it and it comes out square, clipped, and buzzing. Run noise through it and it fractures into bursts of static. It’s not a feature for every patch, but in a system short on aggressive processing, it’s a sneaky way to add grit without adding another module.
Frequency Control with Range Switching: Low, Mod, High
Each of the four voices has a frequency knob and a three-position range switch: Low, Mod, High. This gives you coarse control over where each voice sits in the spectrum. The top two channels are tuned for higher frequencies—ideal for snares, rims, or hi-hats—while the bottom two are optimized for lower tones, perfect for kicks and toms. The switch lets you jump between ranges quickly, so you’re not endlessly turning the knob to find a usable pitch. It’s a small thing, but in a live patch, that kind of immediacy matters. You want a deeper kick? Flip it to Low. Need a snappy clap? Crank it to High and tweak.
Mix Output with Volume Control: One Knob to Rule Them All
All four voices feed into a summed mix output, complete with a volume knob. It’s not a full mixer—no individual level controls, no panning—but it’s enough to send a composite drum signal to your audio interface or effects chain. If you’re using the ADDAC103 as a standalone percussion module, this is your main output. If you’re routing each voice separately, the mix becomes a preview bus. Either way, the volume control is welcome, especially since the raw outputs can be hot. It’s a practical touch on a module that otherwise refuses to overcomplicate things.
Collectibility & Value
The ADDAC103 isn’t rare, but it’s not generic either. Current market listings show prices ranging from $119.36 on eBay to $149 at retailers like Perfect Circuit and Reverb, with some listings at $129—suggesting mild price variance depending on seller and condition. It’s not a grail module, but it’s respected, with an average user rating of Ø 4.27 based on 11 votes on ModularGrid. That’s solid for a niche percussion module with no frills.
There’s no data on common failures or long-term reliability, but an Assembly Guide PDF is available from ADDAC System for a DIY kit version, which suggests the design is straightforward enough for hobbyists to build themselves. That also means repair is feasible for those with soldering skills—no proprietary chips, no firmware. If a voice stops working, it’s likely a passive component or a power connection, not a black-box IC. For collectors, the black panel version appears to be the standard, and there’s no indication of limited editions or color variants. It’s a “buy it, patch it, forget it” module—until you need that one weird snare sound, and suddenly it’s indispensable.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.