ADDAC 213B (2017–)

A passive module that carries eight signal lanes between cases. No power needed.

Overview

The ADDAC 213B makes no sound, has no LEDs and generates no melody. If your Eurorack setup sprawls across multiple cases, it may be the most practical module you'll install. A pair of these 3 HP modules links up with a single ribbon cable and carries eight CV or audio signals across your case, or between cases, with no jumpers. No power draw, no firmware, no calibration. It's passive signal routing, and the first time a gate crosses the rig through the 213B and syncs a VCO on the far end, it feels a little like magic.

The 213B is the expansion sibling to the ADDAC 213A. It can stand alone or bolt onto the 213A to extend its bridging capacity. On its own, a pair of 213Bs gives you eight lanes for signals, which suits a master clock, modulation buses, or audio outs going from one zone of your case to another without cluttering the front panel. As an add-on, one or two 213B pairs plug into the back of a 213A and scale it from 8 to 24 channels of inter-case communication. That's enough for entire synth voices, complex modulation bundles, or bidirectional control data between racks. Because it's passive, there's no latency and no coloration, and no risk of ground loops or signal degradation, provided you stick to reasonable cable lengths. Forum reports and manufacturer testing both confirm that even 30-meter runs show negligible voltage drop, so it works for live rigs or studio islands separated by meters of floor space.

What really sets the 213B apart isn’t just function—it’s flexibility. The modules install in either normal or 180-degree flipped orientation, letting you adapt to tight spaces or odd rack configurations. They’re also sold exclusively in pairs, with a 50cm ribbon cable included (100cm available on request), and the option to request custom lengths directly from ADDAC. That ribbon cable isn’t some proprietary connector; it’s standard 10-pin IDC, easy to source or replace. And if you’re the DIY type, a kit version is available with through-hole components and a clear build guide—ideal for those who want to save a few euros and don’t mind a weekend with a soldering iron. It’s not flashy, but in a world where Eurorack setups keep growing, the 213B solves a real, tactile problem: the moment you realize you’ve spent 45 minutes repatching for a single set, and your fingers keep knocking knobs because the cables are everywhere.

Specifications

Manufacturer	ADDAC System
Production Years	2017–
Original Price	€90 (assembled pair), €61 (DIY kit, excl. VAT)
Format	Eurorack
Width	3 HP
Depth	25 mm (2.5 cm)
Power Requirements	None (passive module)
Signal Channels	8 (per pair)
Signal Type	CV or audio (passive)
Ribbon Cable Length	50 cm (included), 100 cm (available), custom on request
Cable Type	10-pin IDC ribbon cable
Mounting Orientation	Normal or 180-degree flip
Included Accessories	Two modules, one 50cm ribbon cable (two included if used with 213A)
DIY Availability	Yes (THT kit)
Weight	Approx. 40 g (pair)
Panel Color	Black aluminum (standard), custom colors available on request
Compatibility	Designed for use with ADDAC 213A or standalone bridging
Expansion Capability	Up to two 213B pairs per 213A (max 24 channels)

Key Features

Passive Signal Highway with Zero Power Draw

The 213B's biggest strength is also its simplest: it doesn't need power. There's no circuitry and no chips, so there's no risk of noise injection or ground hum. It's a routed connection, eight signal paths carried through a ribbon cable from one module to its twin. It won't load down your power supply, won't generate heat, and won't fail from voltage spikes. In a format where every milliamp counts, adding eight signal lanes without touching your bus board is a rare win. There's no signal processing either. What goes in comes out unaltered, which suits clock signals, gate triggers, or control voltages where timing matters.

Modular Expansion for the 213A Bridge System

The 213B works solo, but it was clearly designed as a companion to the 213A. The 213A acts as the primary bridge between two Eurorack cases and handles eight signals out of the box. Plug one or two 213B pairs into the back of the 213A and you double or triple that capacity, up to 24 channels total. Users with large, multi-case systems report using this setup to link entire performance rigs, where one case holds sequencers and controllers, another hosts oscillators and filters, and a third manages effects and outputs. Because the expansion connects via the rear, your front-panel patch points stay free for actual patching.

Compact, Reversible Design for Tight Spaces

The 213B is 3 HP wide and 25 mm deep, so it fits into small gaps in a case. You can install it right-side-up or flipped 180 degrees, which helps when you're working near power supplies, case edges, or other modules with awkward cable exits. That means you can place a 213B pair at the top and bottom of a tall case and route signals vertically without long patch cables crisscrossing the system.

Historical Context

The ADDAC 213B arrived in 2017, as Eurorack was shifting from boutique curiosity to mainstream studio staple. As musicians built larger, multi-case systems, the limits of front-panel patching became obvious: cables stretched across racks, signals degraded over distance, and live setups required painstaking repatching between songs. The 213B and its sibling 213A were part of a quiet wave of utility modules focused on system management instead of sound generation. It wasn't the first attempt at internal signal routing, since some builders had long used custom ribbon cables or breakout boxes. It was one of the first commercially available, modular-native solutions that felt integrated and reliable. While many Eurorack companies were chasing the next big sound engine or digital wizardry, ADDAC went the other way: quieter, simpler, more functional. It also fit a broader trend in the modular community toward hybrid workflows, where digital sequencers, analog voices, and external gear all needed clean, stable interconnection.

Collectibility & Value

The ADDAC 213B isn't a collector's item in the traditional sense. Nobody's hoarding it for resale, and it doesn't age like a vintage synth with sought-after components. A new assembled pair sells for around €90 directly from ADDAC, with DIY kits available for €61 (excluding VAT). On the used market, prices vary: pairs in good condition with original cables typically go for $80 - $120 on Reverb or eBay, though listings sometimes spike to $150 when demand outpaces availability. The module is passive and has no moving parts or ICs, so failure points are minimal. Most issues stem from damaged ribbon cables or bent pins, both easily replaceable. When buying used, check that the IDC connectors are intact and that the included cable is present and undamaged. Replacement cables are standard and inexpensive, so even a "missing cable" listing isn't a dealbreaker. The kit is straightforward, with through-hole components, clear documentation, and a build time of under two hours for experienced solderers. The only long-term consideration is availability: ADDAC doesn't stock custom panel colors, so if you want a red or bronze faceplate, expect a 4-6 week lead time and a premium. The standard black panel is more than sufficient for most.