ADDAC System ADDAC807C (2017–)

Four more channels of analog summing for a Eurorack console that wasn't quite big enough.

Overview

It starts with the realization: your ADDAC807A and 807B are already a command center, a full-featured analog console in Eurorack clothing, but it’s not enough. You’re running out of channels, and the mix is getting crowded. That’s when the ADDAC807C shows up—not as a standalone solution, but as the final piece of a modular dream. This isn’t just another mixer; it’s a 38 HP expansion that pushes the entire ADDAC807 system from five to nine stereo channels, transforming an already powerful console into something closer to a studio centerpiece. The moment you patch it in, the layout clicks: the same intuitive controls, the same LED feedback, the same hands-on routing flexibility, now extended with surgical precision. There’s a certain thrill in stacking these modules, watching your case swell with analog infrastructure, knowing every knob and switch was designed to make complex routing feel natural.

The ADDAC807C is for the system builder, the patcher who treats a rack like a recording console and wants CV control over pan, volume, and sends across multiple stereo channels. Each of the four new channels mirrors the base ADDAC807A: volume and pan knobs with LED metering, attenuverters for modulation, dedicated send and pre/post switching, mute buttons, cue/mix toggles, phase inversion, and synth/line level switching. The send section supports three independent stereo busses (Send 1, 2, and 3), each with pre/post switching. Because it's part of the ADDAC807 system, the 807C inherits the whole signal flow: matrix routing, cueing, master level control, and integration with the ADDAC807B input console.

Standalone mixers like the WMD Performance Mixer or Intellijel Mixup offer excellent summing in compact forms. The ADDAC807 series, especially with the 807C expansion, goes for console-style signal management instead. Volume and pan can be modulated via CV inputs (±5V), every control has a dedicated attenuverter, and there's LED feedback on level and pan. The 807C itself doesn't include master outputs or cueing. Those live on the 807A. The build is industrial: a thick black anodized aluminum faceplate, precision potentiometers, and a dense layout that makes every HP count. At 4.5 cm deep and drawing 250mA per rail, it's not skiff-friendly.

Specifications

Manufacturer	ADDAC System
Production Years	2017–
Original Price	€620
Format	Eurorack
Width	38 HP
Depth	4.5 cm
Weight	0.6 kg (1.3 lb)
Max Current Draw	250mA on +12V, 250mA on -12V
Power Connector	8×2 IDC (Doepfer style)
Power Supply Compatibility	±12V and ±15V
Channels	4 stereo channels
Per Channel Volume Control	Knob with Level LED
Per Channel Pan Control	Knob with Left/Right LED
Attenuverters	Volume, Pan per channel
Send Controls	Send knob (Send 1, 2, 3), Pre/Post switch per channel
Mono Routing	Mono Pre/Post switch per channel
Mute	Button per channel
Cue/Mix	Switch per channel
Phase	Switch per channel
Input Level Switching	Synth / Line switch per channel
Inputs	Stereo Input (Line level), Left Input, Right Input per channel
CV Inputs	Volume CV, Pan CV per channel
Outputs	Mono Output per channel

Key Features

Console-Grade Expansion, Not Afterthought

The 807C is a full channel expansion that matches the 807A functionally. Some mixers add channels with reduced feature sets. This one gives you the complete toolkit: full CV control, LED metering, sends with pre/post switching, and individual mute and cue routing. It keeps the same signal path, control layout, and visual feedback as the 807A, so there's no learning curve. It also integrates with the 807B input console, so jacks and CV inputs stay logically grouped and cable clutter stays down.

CV-Controlled Summing with Analog Character

Many Eurorack mixers focus on passive summing or basic VCA control. The ADDAC807C is part of a system built around automation. Every volume and pan knob has a corresponding CV input with attenuverter, so levels and stereo position can be modulated from LFOs, envelopes, sequencers, or random sources. A sequence could fade channels in and out while panning across the stereo field, with no hands on a knob. The sound is clean and transparent, with low noise and high headroom. There's a subtle warmth to the analog summing that softens the edges of digital oscillators and crisp digital effects, and the mix comes out cohesive, almost "glued." It doesn't color the sound aggressively like a vintage console emulation.

Integration-First Design

The 807C isn't meant to stand alone. It has no master outputs or cueing, by design. Those functions live on the 807A, and the 807C assumes they're already there. It connects to the 807A via internal bus routing, which handles signal transfer and power distribution. The system scales in order: start with the 807A and 807B, then add the 807C when you need more channels. There's also a follow-up expansion, the ADDAC807C+, which adds individual post-fader stereo outputs for each channel. That helps anyone tracking to a DAW or using external effects sends.

Historical Context

The ADDAC807C arrived in 2017, as Eurorack was moving from experimental sound design toward structured, console-style workflows. At the time, most mixers were compact, utility-focused modules, simple VCAs or passive summing buses. The ADDAC807 series, with its big footprint and studio-console layout, was a bold statement. It suggested modular could be a serious music production environment. Competitors like A-Designs (with their outboard gear) or even Behringer's then-upcoming DeepMind series offered integrated mixing, but nothing in Eurorack matched the 807's control and expandability. The 807C, as an expansion, doubled down on that. It also suited hybrid setups, where modular interacts with external synths, effects, and DAWs. The line-level inputs and level conversion made it a hub for non-modular gear, a role that modules like the Intellijel Rainmaker or MakeNoise Shared System also explored, but with less physical immediacy.

ADDAC System, based in Lisbon, had already built a reputation for high-quality, thoughtfully designed modules focused on performance and usability. The 807 series, announced at Superbooth 2017, was their most ambitious project yet. It drew comparisons to classic analog consoles, not in sound but in workflow: the long faders (simulated via knobs), the matrix routing, the dedicated cueing and monitoring. Some dismissed it as overkill. Others saw it as the missing link for making modular a primary production tool. The 807C, as the expansion, completed that vision.

Collectibility & Value

The ADDAC807C isn't a rare module, but it's not common either. It was built in limited batches and sold primarily through direct pre-orders or select dealers, so it's found its way into high-end modular setups rather than the general market. As of 2026, used units trade between €450 and €550, depending on condition and whether they include original packaging or documentation. The original price was €620, so depreciation has been minimal. Because it's part of a larger system, it rarely sells alone. Most listings include the full ADDAC807A+B+C stack, which can fetch €2,000 or more in excellent condition.

Reliability is generally excellent. The 807C uses standard, high-quality components: Alps potentiometers, durable jacks, and a power design compatible with both ±12V and ±15V systems. There are no known design flaws or recurring failures. The most common reported issue is misalignment during installation. At 38 HP wide, it can be tricky to fit in densely packed cases, especially next to modules with large connectors or heatsinks. Users also note that the lack of individual channel outputs on the 807C itself is a limitation unless it's paired with the ADDAC807C+ module, which adds post-fader stereo outs for each channel at 2 HP. That module is often overlooked and can be harder to find.

For buyers, the real challenge is compatibility, not condition. The 807C only makes sense if you already own or plan to buy the ADDAC807A and 807B. It's not a standalone mixer, and using it without the main console defeats its purpose. Check that the case has enough space (38 HP is substantial) and enough power headroom (250mA per rail is not trivial). It's also worth checking whether the unit was part of a factory order or a custom build. ADDAC System has offered red faceplates on request, and these command a small premium among collectors.