ADDAC System ADDAC213C (2023–)
A silent module that cleans up modular cable clutter with ribbon cables and straight signal routing
Overview
The ADDAC213C is not flashy, makes no sound, and won't win any beauty contests. It changes how you use your rack anyway. You don't notice it when it's working; you only miss it when it's gone. It sits in a 1U row as a pair of passive bridge modules, and it lets you route eight CV or audio signals across distant corners of your case with a single ribbon cable. No power draw, no settings. Just signal transfer.
It was originally designed as an expansion for the ADDAC213A, the Eurorack Bridge that links multiple cases. The 213C found its own use as a standalone utility. The 213A handles bridging between cases. The 213C handles the mess inside one case: the sequencer is on the far left, the filter stack is on the right, and you're burning patch cables just to send a gate or a pitch CV across the gap. Two 213C modules, connected back-to-back with a ribbon cable, carry signals behind the modules. Because they're passive, there's no coloration, no noise and no added complexity.
Simple doesn't mean limited. Use it to isolate rows and keep your modulation cables contained. Route audio between stacked 1U effects without cluttering the front panel. In a multi-case system, plug a 213C into the rear expansion port of a 213A to add eight more channels, stacking up to three pairs for a total of 24 bidirectional signals. Most Eurorack solutions are either all-in-one or piecemeal. This one is modular in concept and simple in execution.
Specifications
| Manufacturer | ADDAC System |
| Production Years | 2023– |
| Original Price | 90€ (pair, assembled) |
| Format | 1U Eurorack |
| Width | 22HP |
| Depth | 2.5 cm (25 mm) |
| Power Requirements | None (passive) |
| Channels | 8 bidirectional |
| Signal Type | CV or audio |
| Ribbon Cable Included | Two 50cm cables |
| Cable Compatibility | 40-pin ribbon (2x20) |
| Expansion Capability | Up to two ADDAC213C per ADDAC213A |
| DIY Kit Available | Yes (61€, THT-only) |
| Mounting | Standard Eurorack screw holes |
| Panel Material | Black anodized aluminum |
| Custom Panel Options | Red, Green, Blue, White, Silver Gray, Yellow, Gold |
Key Features
No Power, No Problem
The ADDAC213C draws zero current—no power cable, no bus board strain, no risk of ground loops. It’s a passive signal bridge, meaning it doesn’t amplify, attenuate, or process anything. What goes in comes out, clean and unchanged. This makes it ideal for routing sensitive control voltages where even minor noise or offset could throw off tuning or timing. In a world full of overengineered solutions, the 213C’s lack of electronics is its greatest strength. It’s like a high-quality audio snake in a live rig: invisible, reliable, and mission-critical.
Ribbon Cable Routing, Done Right
The included 50cm ribbon cable connects the two 213C modules with a 40-pin interface, carrying eight signals in each direction. The ribbon is flexible and low-profile, and it terminates in IDC connectors that snap securely into place. Some users report minor crosstalk with long runs or high-impedance CV, though most find it negligible in practice. ADDAC offers custom cable lengths, including 100cm versions for deeper cases. The cable runs behind the modules, so the front panel stays clear of cables.
Scalable Expansion for Multi-Case Setups
The 213C is also an add-on for the ADDAC213A. Each 213C can plug into the rear expansion port of a 213A and add eight more channels to the bridge. With two 213Cs per 213A, you go from the base 8-channel link up to 24 channels between cases. That's enough for full sequencer data, multiple audio paths, clock, reset, and modulation across a dual or triple case system. There are no proprietary hubs and no daisy-chaining.
Historical Context
By the early 2020s, Eurorack had grown into a sprawling ecosystem where signal management became as critical as sound generation. Cases expanded vertically into 1U rows and horizontally into multi-rack systems, and cable routing got harder. ADDAC System, a Lisbon-based boutique known for hybrid designs, saw the gap. Their 2021 launch of the ADDAC213A addressed inter-case linking, but users quickly asked for internal solutions. The 213C, released in 2023, answered that.
It arrived as 1U became a serious format. No longer just for power conditioners or blank panels, 1U began hosting complex utilities, effects, and processors. The 213C fit that trend: compact, efficient, and practical. While other companies chased DSP-heavy modules or flashy sequencers, ADDAC went after infrastructure, and found a growing demand for "silent utilities," modules that don't make sound but make everything else work better. Competitors like Intellijel and Doepfer offered patch bays or distribution modules, but none matched the 213C's blend of passive simplicity, ribbon-based routing, and expandability.
Collectibility & Value
The ADDAC213C isn't a collector's item, at least not yet. It's too new and too utilitarian to be hoarded. It still has value. On the used market, a pair in good condition trades between €60 and €80, depending on included cables and whether it was purchased assembled or as a kit. The DIY version, priced at 61€, is popular among builders, especially since it uses only through-hole components and requires no surface-mount soldering. Documentation is thorough and the build is straightforward, which makes it a solid first kit for beginners.
Failures are rare, but they happen. The most common issue is ribbon cable damage, either from improper insertion or repeated flexing in tight cases. The IDC connectors are sturdy, but forcing the cable can crack the housing or misalign pins. A few users have reported intermittent connections after heavy use, usually fixed by reseating the cable or replacing it with a custom-length version. Since the module is passive, there are no capacitors to dry out and no ICs to fail, just traces on a PCB.
When buying used, check that both modules are present, the ribbon cable isn't frayed, and the IDC connectors haven't been pried open. Test all eight channels with a multimeter for continuity if possible. If you're pairing it with a 213A, confirm that the expansion port is functional, since some early 213A units had grounding quirks when daisy-chaining multiple 213Cs. It's a low-risk purchase, especially if you're drowning in cables or planning a multi-case setup.
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