4ms LD ()

Name: 4ms LD
Brand: 4ms

A compact loop machine that turns your modular into a self-contained echo chamber, with hands-on control and no menu diving

Overview

That first time you crank the regeneration on the 4ms LD and watch a simple sine wave bloom into a swirling cloud of self-oscillating texture—it feels like discovering a secret. There’s no screen, no presets, no digital obfuscation. Just two knobs, a couple of switches, and a single button that starts and stops the loop like flipping a light switch. It’s brutally simple, but in the best way: this module doesn’t invite tweaking, it demands performance. You play it. You feed it audio, hit record, and then wrestle the feedback into something alive. It’s not a delay pedal shrunk into Eurorack—it’s a looping instrument, more akin to a tape machine with a mind of its own than any digital stompbox.

The LD doesn’t try to be everything. It’s a single-channel, analog bucket-brigade loop with a maximum delay time of around 2.5 seconds—short by modern standards, but long enough to build dense, evolving textures if you’re patient. What it lacks in duration it makes up for in character. The BBD circuit imparts a warm, slightly degraded smear to repeats, especially as you push the feedback past 50%. At high regeneration, the repeats don’t just fade—they mutate, gaining low-end thickness and high-end fizz, until the whole thing collapses into a controlled roar. It’s unstable in the most musical way possible. Turn the delay time down and you’re in slapback territory, perfect for rhythmic stuttering. Crank it up and you’re in ambient drone country, layering fragments into something that feels almost orchestral.

Compared to its more famous sibling, the Dual Looping Delay (DLD), the LD is the stripped-down, no-frills cousin. No MIDI, no voltage control over loop length, no separate record and playback heads. Just input, output, record button, feedback, and time. That simplicity is its strength. There’s no learning curve. You patch in, press record, and immediately start shaping sound. It’s the kind of module that ends up permanently installed in your rack not because it does everything, but because it does one thing—looping—and does it with such immediacy that you reach for it before anything else.

Specifications

Manufacturer	4ms Company
Production Years	Unknown
Original Price	$275
Form Factor	Eurorack
HP	8
Depth	40mm
Current Draw +12V	80mA
Current Draw -12V	20mA
Audio Input	1/8" (3.5mm) TS
Audio Output	1/8" (3.5mm) TS
Max Delay Time	2.5 seconds
Delay Type	Analog Bucket Brigade (BBD)
Feedback Control	Manual knob, up to self-oscillation
Record Control	Push-button, momentary
Delay Time Control	Manual knob
Power Requirements	±12V

Key Features

Analog Looping Without the Fuss

The LD’s magic lies in its immediacy. There’s no patching required to start looping—just feed it a signal and press the button. The lack of voltage control over loop length might seem limiting, but in practice, it forces a performance mindset. You’re not programming a sequence; you’re reacting in real time. The moment you release the record button, the loop is fixed, and from there it’s all about sculpting with feedback and external processing. Patch a filter after the LD and you can sweep the repeats into oblivion. Add a VCA and duck the loop under new material. The module doesn’t do those things itself—it invites you to build the system around it.

BBD Character That Ages Like Vinyl

Digital delays are clean. The LD is not. Its BBD circuit introduces a subtle chorusing effect on repeats, especially at longer delay times, as clock noise and slight timing inconsistencies smear the signal. Some might call it a flaw; owners call it soul. The degradation isn’t harsh—it’s warm, almost tape-like, with a high-end roll-off that softens transients and a low-end bloom that builds with feedback. At maximum regeneration, the loop doesn’t just repeat—it resonates, feeding back in a way that feels physical, like a room starting to ring. It’s unpredictable, yes, but that’s the point. You’re not after pristine repeats; you’re after texture.

Compact Design, Big Presence

At just 8HP, the LD is a space-saving workhorse. It doesn’t demand attention on your rack, but once you start using it, it dominates your patches. The front panel is minimal: two large knobs (time and feedback), a single push-button, and the input/output jacks. No LEDs, no status indicators—just pure analog interface. That simplicity means fewer points of failure, but it also means you’re flying blind. You can’t see the loop level or know if it’s recording without listening. For some, that’s a dealbreaker. For others, it’s part of the charm—a reminder that this isn’t a computer, it’s an instrument.

Historical Context

The LD emerged during the mid-2000s Eurorack renaissance, when boutique builders like 4ms were redefining what modular could do—not by mimicking vintage synths, but by inventing new forms of sonic manipulation. While most companies focused on oscillators, filters, and envelopes, 4ms went sideways, building modules that behaved more like instruments than components. The LD fit perfectly into that philosophy: it wasn’t a utility, it was a performance tool. At a time when looping was still largely the domain of guitarists with Boss RC units, the LD brought that capability into the modular realm with zero compromise on sound quality or responsiveness.

It arrived before the wave of digital looping modules with infinite memory and MIDI sync, and that timing mattered. The LD wasn’t competing with those—it was offering something different. Where digital loopers aimed for transparency, the LD embraced coloration. Where others offered endless undo/redo, the LD forced commitment: once you recorded, that was your loop. No take-backs. That limitation fostered creativity, pushing users to think compositionally, to treat each loop as a one-shot performance. It shared DNA with tape loops and analog echo units, but without the maintenance headaches of motors and heads.

Collectibility & Value

The LD isn’t rare, but it’s not common either. It never had the profile of the DLD, so fewer were made, and fewer still have survived heavy use. On the used market, prices hover between $200 and $300 depending on condition—slightly below its original $275 MSRP, which is unusual for sought-after Eurorack gear. That might suggest it’s underrated, or that its limitations keep it from being a must-have. Either way, it’s a bargain if you value hands-on looping over digital precision.

Failures are rare but not unheard of. The most common issue is degraded performance from aging BBD chips, which can manifest as increased noise, loss of high end, or dropout in the delay signal. These chips are not user-replaceable and require skilled soldering to swap. The momentary push-button for recording is another weak point—after years of heavy use, it can become intermittent or fail entirely. There’s no backup; if it dies, the module is unusable unless repaired. Power issues are uncommon, but always check for cold solder joints around the power connector, especially on older units.

When buying, test thoroughly: feed a steady tone, record a loop, and listen for consistent repeats. Crank the feedback and verify it self-oscillates smoothly without dropouts. Check that the delay time knob sweeps cleanly from short slapbacks to the maximum 2.5 seconds. If it’s silent at long times, the BBD may be failing. Also, inspect the jacks—3.5mm jacks are less robust than 1/4", and wiggling a cable shouldn’t cause crackling. A working LD is a joy; a faulty one is a repair project, not a performance module.