ADDAC 702 VCF (2015–)

A dual-filter beast that snarls like a rewired MS-20 and thinks in stereo—patch it once and you’ll forget you ever needed just one filter.

Overview

Flip the switch and the ADDAC 702 wakes up with a guttural hum, like an old synth rack in a damp basement finally getting juice after years unplugged. It’s not clean, it’s not polite—it’s two filters in one module, one high-pass and one low-pass, each with its own voice, its own attitude, and its own distortion circuit that can turn a sine wave into a chain-saw buzz with a flick of a toggle. This isn’t just a filter module; it’s a sonic demolition derby packed into 16HP of Eurorack real estate. Born in 2015 as ADDAC’s first foray into voltage-controlled filtering, the 702 wears its Korg MS-20 inspiration on its sleeve, but don’t mistake it for a clone. It’s more like a reimagining—same raw DNA, but built for the modern modular world, where patching is everything and subtlety is optional.

What makes the 702 stand out isn’t just that it gives you two filters, but how they talk to each other. You can run them completely independent, processing two separate signals with surgical precision. Or stack them in series—high-pass feeding into low-pass—for that classic band-pass sweep, perfect for carving out vocal-like formants or tightening up a muddy drone. There’s even a coupling mode inspired by the obscure Oscar synthesizer, where the low-pass cutoff tracks the high-pass with an offset, letting you sweep a resonant window across the spectrum with a single control. And if you’re into stereo processing, the voltage-controlled mix output lets you blend the HP and LP outputs dynamically, turning a single CV into a spatial and tonal morphing tool. It’s rare to find a filter module that feels this flexible, this alive.

And then there’s the dirt. Both filters come with their own post-filter distortion stage—switchable between clean, diode clipping, and LED clipping—so you can add grit after the filtering, which is where the real magic happens. Run a resonant sweep into the fuzz and it doesn’t just get louder—it tears, it growls, it spits harmonic fire. The distortion isn’t an afterthought; it’s baked into the signal path like a second personality. Combine that with phase inversion switches on each output, and suddenly you’re not just filtering sound—you’re warping it, canceling parts out, reinforcing others, building textures that shift and breathe in three dimensions. It’s the kind of module that rewards deep patching, that turns a simple oscillator into something unrecognizable, something dangerous.

Specifications

Key Features

A Dual-Channel Mindset

Most filter modules give you one flavor and expect you to work with it. The 702 laughs at that. It doesn’t just offer two filters—it forces you to think in stereo, in layers, in interaction. The high-pass and low-pass aren’t mirror images; they’re partners in crime. You can route a kick through the LP and a hi-hat through the HP, then sweep both with linked CVs to create a dynamic filter gate effect. Or feed a single drone into both and use the mix control to crossfade between spectral extremes. The module’s architecture assumes you’ll be patching creatively, not just inserting it into a signal chain. Even the way the CV inputs are laid out—separate for each filter, each with its own attenuverter—tells you this isn’t a one-trick module. It’s a filter *system*, and it wants to be at the center of your patches.

Resonance with a Bite

Turn up the resonance and the 702 doesn’t just whistle—it bites back. The resonance circuit is modeled after the MS-20’s famously aggressive filter, but ADDAC added a twist: a three-position switch that changes how the resonance clips. In “diodes” mode, it’s warm and snarling, like a tube amp pushed into breakup. “LEDs” adds a sharper, more chaotic edge—perfect for industrial textures. And “none” gives you clean resonance for when you want precision over character. This isn’t just a tone switch; it fundamentally changes the behavior of the filter under high resonance, making it one of the few modules where resonance isn’t just a parameter but a timbral tool. And because resonance is voltage-controllable, you can modulate not just how much, but *what kind* of resonance you’re getting, if you’re willing to patch in some clever logic.

Smoother Than It Looks

Buried in the panel is a tiny switch labeled “Smooth,” and it’s one of the 702’s secret weapons. Engage it and the cutoff control takes on a soft, vactrol-like glide, smoothing out stepped CVs and turning sharp envelopes into languid sweeps. It’s not a dedicated slew generator—it’s baked into the filter’s response—so it feels organic, not processed. This is especially useful when using sequencers or digital LFOs that can sound too precise; the Smooth circuit reintroduces a bit of analog slop, the kind of imperfection that makes a filter sound alive. It’s a small feature, but it bridges the gap between the clinical and the human, letting the 702 sit comfortably in patches that mix digital and analog sources.

Historical Context

The ADDAC 702 arrived in 2015, right when Eurorack was shifting from boutique curiosity to mainstream staple. Modules were getting smarter, more complex, but a lot of them were also getting cleaner—more digital, more precise, more sterile. Against that backdrop, the 702 was a statement: a reminder that filters could be raw, unpredictable, and full of character. It tapped into the same nostalgia that fueled the MS-20 reissues and Behringer’s clones, but instead of rehashing the past, it built on it. The MS-20 filter was legendary for its aggression, but it was also limited—single filter, no CV control over resonance, no stereo operation. The 702 kept the attitude but gave it a modern chassis: full voltage control, patchable topology, and that brilliant dual-channel design.

It also arrived at a time when modular users were starting to treat effects and processors as instruments in their own right, not just add-ons. The 702 wasn’t just for cleaning up signals—it was for mangling them, for turning simple waveforms into evolving soundscapes. Competitors like the Mutable Ripples or Intellijel Morgasmatron offered more polished, refined filtering, but they didn’t have the 702’s punk-rock edge. This was a module for people who wanted their synths to sound like they’d been dragged through a junkyard and lit on fire. And with ADDAC’s reputation for bold, expressive design—see the 604 Quad LFO or the 712 Vintage Pre—the 702 fit perfectly into a lineup that valued character over conformity.

Collectibility & Value

The ADDAC 702 has never been rare—ADDAC kept production steady, and it’s still available new—but it’s become a cult favorite, the kind of module that shows up in high-end racks and DIY skiffs alike. On the used market, prices hover between €250 and €320 depending on condition and whether it’s the original silver panel or one of the limited dark or custom-colored versions. The dark panel variant, with its black finish and red accents, tends to fetch a slight premium, not because it sounds different, but because it looks like it belongs in a horror movie synth lab.

Condition is key. These units are generally robust—no delicate pots, no flaky jacks—but the toggle switches, especially the phase and distortion toggles, can get noisy over time if not cleaned. The LEDs are also known to dim or fail after years of use, though that’s more cosmetic than functional. The biggest red flag? Any sign of overvoltage damage. The 702 draws a fair bit of current, and if a user plugged it into a poorly regulated power supply, the filter cores can get fried. There’s no user-serviceable repair for that—only a full board replacement. So when buying used, always ask for a demo video showing all modes, all outputs, and both filters under resonance sweep.

Maintenance is relatively straightforward. The distortion circuits are passive—just diodes and LEDs—so they’re unlikely to fail. The vactrols in the smooth circuit can degrade over decades, but we’re not there yet; most units from 2015 are still behaving. Recapping isn’t a common need, but if you’re restoring one that’s been in a hot rack for years, fresh electrolytics won’t hurt. The real cost isn’t in repair—it’s in opportunity. At nearly 16HP, the 702 isn’t small, and in a crowded system, that’s a trade-off. But for what it does, few modules deliver this much character in a single slot.

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