4ms RCD Breakout (2010–Present)
No power, no noise, just six switches that open up the clock divider.
Overview
The 4ms RCD Breakout makes no sound and draws no power. What it does is change how the Rotating Clock Divider (RCD) gets used. Mounted beside the RCD in a Eurorack system, this 4HP expander is a front-panel interface for what were once soldered jumpers on the main module's circuit board. Before the Breakout, changing the RCD's core behaviors, like maximum division ratio, counting direction, or reset behavior, meant flipping tiny physical jumpers with tweezers or a screwdriver. You picked a setup once and rarely changed it. Six switches now put those settings on the front panel, so you can change them on the fly like any other performance control.
Say you want to flip from counting up to down mid-sequence. There's a switch for that. Say you need Gate or Trigger mode, depending on whether your downstream modules prefer sustained pulses or sharp spikes. That's a switch too. You can also set the maximum divide-by value (up to /64) without reprogramming or repatching. The Spread mode, introduced in firmware v1.1 (2012), works differently from the normal sequence. Instead of stepping through divisions sequentially, the outputs "spread" evenly across the full range, which gives staggered, polyrhythmic pulses that feel organic rather than mechanical.
The Breakout isn't a standalone module. It's physically and electrically passive, and it connects directly to the RCD via a 16-pin ribbon cable. It draws no power from the Eurorack bus - the +12V, -12V, and +5V rails are all unused. Its depth is 1.14" or 29mm, so it tucks behind the RCD without straining panel alignment or case clearance. The original RCD PCB versions (1.0 and 1.0.1) required firmware updates to unlock full Breakout functionality, particularly Spread, Auto-Reset, and Up/Down counting. Any unit updated to v1.1 or later (or manufactured post-2012) supports all features out of the box. The Breakout kit, sold by 4ms as a DIY project, is rated beginner-friendly and needs only basic soldering skills and common hand tools.
Specifications
| Manufacturer | 4ms Company |
| Production Years | 2010–Present |
| Module Size | 4HP Eurorack format module |
| Depth | 1.14" (29mm) |
| Power Consumption (+12V) | Not used |
| Power Consumption (+5V) | Not used |
| Power Consumption (-12V) | Not used |
| Inputs | None (connects directly to RCD via 16-pin ribbon cable) |
| Outputs | None |
| Controls | 6 SPST switches: Max Divide (16/32), Gate/Trigger, Counting (Up/Down), Spread, Auto-Reset |
| Firmware Requirement | RCD PCB v1.0.2+ with firmware v1.1 or later for full functionality |
| Compatibility | 4ms Rotating Clock Divider (RCD) only |
| Connection Type | 16-conductor ribbon cable (included in kit) |
| Kit Components | Front panel, 6 switches, ribbon cable, hardware |
| Assembly Level | Beginner DIY kit |
| Weight | Light (primarily aluminum panel and switches) |
| Mounting | 2 M3 knurled screws (included) |
| Original Kit Price | $45.00 USD |
Key Features
Six Switches, Infinite Timing Variations
The Breakout has six front-panel switches, each mapping to a jumper setting that used to be buried on the RCD. The Max Divide switch selects between /16 and /32 (or /64 with the firmware update). That sets the upper limit of clock division across the module's eight outputs, and it shapes the density and complexity of the rhythmic patterns. The Gate/Trigger switch determines whether the RCD outputs sustained gate signals (useful for holding envelopes or VCAs open) or short trigger pulses (ideal for initiating drum hits or sample-and-hold events). That lets the RCD work with a wider range of modules without patching workarounds.
Directional Counting and Performance Flow
The Counting switch toggles between Up and Down modes. In Up mode, the RCD cycles through divisions from /1 to the maximum set value. In Down mode, it reverses, stepping from max down to /1. That can change the feel of a sequence completely. Live performers use it to create call-and-response patterns or rhythmic reversals without touching a patch cable.
Spread Mode and Rhythmic Texture
Spread mode, introduced in firmware v1.1, changes how the RCD allocates divisions across its outputs. Instead of stepping sequentially (e.g., /1, /2, /3...), it distributes the divisions evenly across the full range. The result is overlapping, staggered pulses that act like polyrhythms or humanized timing. The Spread switch turns it on. It works well when feeding multiple sequencers or envelope generators, since a single clock source can produce evolving, non-repeating patterns. The Auto-Reset switch does something different: when enabled, the RCD resets its sequence upon receiving a new clock signal, which keeps things tightly synchronized when restarting patterns or switching tempos.
Historical Context
The RCD Breakout came out in 2010, from 4ms's DIY-friendly approach, as Eurorack was shifting from boutique curiosity to mainstream modular revival. The original RCD (introduced earlier) was already a favorite for its rotating division concept, which assigns different /N values to each of eight outputs in sequence. But the need for physical jumper changes limited its live use. The Breakout fixed that by putting the advanced features within easy reach. At a time when many manufacturers were adding CV control to every parameter, 4ms took a different path: mechanical switches, no power draw, total reliability.
Competitors like Doepfer and Intellijel offered clock dividers, but few matched the RCD's rotating output scheme or its expander model. The Breakout's release coincided with the rise of complex sequencers like the Make Noise René and Intellijel Metropolis, which benefited immensely from the RCD's ability to generate multiple interlocking clock divisions. The 2012 firmware update (v1.1) added Spread mode and kept backward compatibility with older PCBs. Owners of pre-1.0.2 boards had to flash new firmware, a process 4ms documented openly.
Collectibility & Value
The 4ms RCD Breakout has never been a flashy module, and its collectibility comes down to utility and condition. As of 2026, factory-assembled units sell for $95-$120 on the secondary market, while the DIY kit remains available new for $45. Used prices vary widely. Mint-condition assembled modules command premium prices, especially if paired with an RCD, while incomplete or damaged kits (missing switches or panels) can be found for $30-$50. The most common failure point isn't the Breakout itself, since it has no active components, but the 16-pin ribbon cable, which can fray or disconnect over time. Owners report that misalignment during installation can bend pins on the RCD's header, leading to intermittent switch behavior. When buying used, check all six switches for consistent tactile feedback and an audible click.
Firmware compatibility is the other thing to check. Units sold before 2012 may require a firmware update to access Spread mode and Up/Down counting. 4ms provides free hex files and clear instructions, but buyers unfamiliar with AVR programming may find this a barrier. Technically, the Breakout works with any RCD, but PCB version matters: units with v1.0 or v1.0.1 boards have different pin mappings, requiring either rewiring or a firmware upgrade for full functionality. Service technicians observe that many "faulty" Breakouts are simply mismatched with outdated RCD firmware. For collectors, a complete, tested set (RCD with v1.1+ firmware and Breakout) is the sweet spot, with full functionality and no DIY hurdles. Given its passive design and lack of wear-prone electronics, a well-maintained Breakout should last indefinitely.
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