4ms Micro Modular Recorder (2019–)

A tiny stereo recorder that fits in your synth rack but sounds like a studio machine — if you can survive its cryptic menu system.

Overview

You’re knee-deep in a patch, the modular is breathing, evolving, doing something magical you’ve never heard before — and you realize you forgot to hit record on your interface. Again. That’s the moment the 4ms Micro Modular Recorder earns its keep: it lives in your rack, runs off your case power, and captures whatever’s happening with near-flawless fidelity, no computer required. At just 6HP, this unassuming Eurorack module is a full-featured stereo WAV recorder that tucks into even the tightest systems, letting you document sonic accidents, layer live loops, or fly in field recordings without breaking your flow. It’s not a sampler in the traditional sense — no pitch-shifting, no slicing, no envelopes — but it’s a recorder in the purest form: press a button, capture sound, play it back later, all in pristine 24-bit/96kHz quality.

What makes the Modular Recorder stand out isn’t just its size or specs, but its philosophy. It’s designed to feel like an analog cassette deck from the '80s — tactile, immediate, but with modern digital reliability. You can record from line-level sources, headphone outs, or direct modular signals, thanks to a gain knob that boosts low-level inputs up to +20dB. The dual LED meters give you a clear visual of your input levels, and the red/green push-button tells you at a glance whether you’re armed, recording, or playing back. It’s disarmingly simple until you need to do something slightly more advanced — like pick a different file or change the sample rate — and that’s when the charm starts to fray. The interface relies entirely on LED patterns and knob-twisting rituals, with no screen or labels to guide you. Want to browse recordings? Hold the play button and turn the gain knob while watching LEDs blink in binary semaphore. Want to switch from stereo to mono? Dive into a system menu that requires a five-second button press and careful tapping. It works, but it’s not intuitive — and in a live set, it can feel like you’re decoding hieroglyphs instead of making music.

Despite its quirks, the sound quality is exceptional. Recordings are captured in lossless WAV format to a microSD card (Class 10 or better recommended), with selectable settings of 96kHz/24-bit, 48kHz/24-bit, or 44.1kHz/16-bit. Owners report that the audio is indistinguishable from direct computer recordings — a rare win in the modular world, where digital modules often cut corners on converters or power filtering. The inputs are normalized, so a mono signal plugged into the left input automatically routes to both channels, making it easy to record single sources in stereo. A trigger input lets you start or stop recording or playback via external clocks or sequencers, and if you stack multiple units, you can mult the trigger to build a crude multitrack setup. It’s not meant to replace a DAW, but it’s perfect for sketching, capturing happy accidents, or looping ambient textures that you can then mangle with filters, delays, or granular processors downstream.

Specifications

Key Features

Studio-Grade Recording in Eurorack Clothing

The Modular Recorder punches far above its size class when it comes to audio quality. Unlike many digital Eurorack modules that use cost-reduced ADCs or share power rails with noisy digital circuits, this unit delivers clean, transparent recording that holds up in professional contexts. The 24-bit/96kHz capability ensures dynamic range and frequency response that match modern studio standards, and the low-noise design means you won’t hear hiss even when boosting quiet sources. This makes it ideal not just for capturing modular patches, but for recording vocals, acoustic instruments, or field recordings directly into your case. The inclusion of a gain knob with up to 20dB of boost is a thoughtful touch — it means you can plug in a guitar, a mic preamp output, or even a line-level drum machine and record at optimal levels without external gear. The normalization of inputs also simplifies mono recording, eliminating the need for a separate splitter cable when you only have one source.

Triggered Operation for Seamless Integration

One of the most practical features is the trigger input, which allows you to start and stop recording or playback via external CV/Gate signals. This opens up creative possibilities: you can sync a recording to a specific sequence, trigger playback of a loop at a precise moment, or use a clock divider to create delayed overdubs. In playback mode, each incoming trigger restarts the most recent recording, making it behave like a one-shot sample player. While it doesn’t support random access or CV-controlled file selection (a limitation compared to modules like the Make Noise Morphagene or the 4ms Stereo Triggered Sampler), the simplicity ensures reliability. There’s no loading time, no buffering — just immediate playback. For live performance, this immediacy is a strength, even if it lacks the sophistication of more advanced samplers. The trigger input also works in record mode, letting you begin recording on the downbeat of a sequence, which is especially useful when documenting generative patches that evolve over time.

MicroSD Management and File Browsing

The use of microSD cards is both a blessing and a curse. On one hand, storage is cheap, expandable, and hot-swappable — you can yank the card out (when the busy light is off) and plug it into a computer to back up or edit files. On the other hand, file management happens entirely within the module’s opaque interface. To browse recordings, you hold the play button and turn the gain knob, with LEDs indicating which file is selected. With more than eight files, the system uses a combination of blinking patterns and color shifts that can be confusing under stage lights. There’s no delete function on the module itself — if you record a bad take, it stays on the card until you remove it and erase it on a computer. Some users work around this by labeling files sequentially and keeping a mental note of which ones are keepers, but it’s far from ideal. Firmware updates have improved stability and added features over time, but the core interface remains stubbornly minimal. It’s clear 4ms prioritized reliability and low part count over user-friendliness — a trade-off that pays off in durability but frustrates in daily use.

Historical Context

The Modular Recorder arrived in 2019, a time when Eurorack was shifting from purely analog signal generation to hybrid systems that embraced digital recording, sampling, and effects. Modules like the TipTop Audio One, Erica Pico Drums, and MTM Radio Music offered basic playback capabilities, but few focused on high-fidelity recording with flexible I/O. The Modular Recorder filled a niche: it wasn’t trying to be a sampler or a looper, but a no-compromise recorder that lived in the rack. Its design philosophy echoes early digital portastudios and DAT machines — tools meant to capture ideas quickly, without the overhead of a computer. At the same time, it reflects 4ms’s reputation for building utilitarian, no-frills modules that prioritize function over flash. Unlike the company’s more experimental offerings like the Spectral Multiband Resonator or the Dual Looping Delay, the Modular Recorder is deliberately straightforward — almost austere. It doesn’t try to impress with features; it just records well, runs reliably, and stays out of your way. In an ecosystem full of modules that do ten things poorly, this one does one thing very well.

It also arrived alongside 4ms’s Listen series of mixers, which share the same modular-level I/O philosophy. The Listen Four, for example, accepts both line and modular signals, making it a natural partner for the Modular Recorder. Together, they form a self-contained recording ecosystem: patch your synth into the mixer, monitor through headphones, send a feed to the recorder, and capture your performance — all without leaving the case. This integration potential is part of what makes the module more than just a novelty. It’s a building block for standalone modular rigs, ideal for buskers, live performers, or anyone who wants to work untethered from a laptop.

Collectibility & Value

The Modular Recorder isn’t a rare module — it’s still in production and widely available — but it has developed a loyal following among modular users who value high-quality audio capture. On the used market, prices typically range from $180 to $220 depending on condition, with mint units still in original packaging commanding closer to $250. It’s not a speculative collector’s item, but a functional tool, so most units in circulation are well-used. That said, it’s a robust design with few failure points: no moving parts, minimal surface-mount components, and a simple power draw that won’t stress most cases. The most common issue is microSD card corruption, usually caused by removing the card while the busy light is on. This can brick the module temporarily until a formatted card is inserted, but it rarely causes permanent damage. Some early firmware versions had bugs with file indexing, but these have been resolved through updates.

When buying used, check that the gain knob turns smoothly and that both input jacks are secure — loose jacks are the most frequent mechanical failure. Test the trigger input with a clock source to ensure recording and playback can be externally controlled. Also verify that the LED meters respond correctly to input signals and that the module recognizes a known-good microSD card. Because the interface is menu-driven, it’s worth asking the seller if they’ve used the browsing or settings functions successfully. A unit that only records and plays back the most recent file might be hiding a deeper firmware or card issue. For long-term ownership, keep a spare microSD card on hand and consider labeling it with a permanent marker to avoid mix-ups. While the module doesn’t require regular maintenance, storing it in a dry environment will prevent corrosion on the contacts, especially if used in humid or live settings.

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