4ms LD ()

A compact loop machine for the modular, with hands-on control and no menu diving

Overview

Crank the regeneration on the 4ms LD and a simple sine wave blooms into a swirling, self-oscillating cloud. There's no screen, no presets, no digital menus. It has two knobs, a couple of switches, and a single button that starts and stops the loop. 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, closer to a tape machine than to 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. That's short by modern standards, but long enough to build dense, evolving textures if you're patient. The BBD circuit gives the repeats a warm, slightly degraded smear, especially as you push the feedback past 50%. At high regeneration the repeats mutate, gaining low-end thickness and high-end fizz, until the whole thing collapses into a controlled roar. Turn the delay time down and you're in slapback territory, good for rhythmic stuttering. Crank it up and you're in ambient drone country, layering fragments into something that feels almost orchestral.

Compared to its sibling, the Dual Looping Delay (DLD), the LD is often described as the stripped-down, no-frills cousin. Reportedly, it has no MIDI, no voltage control over loop length, and no separate record and playback heads. It has input, output, record button, feedback, and time. There's no learning curve. You patch in, press record, and start shaping sound. It's the kind of module that ends up permanently installed in a rack because it does one thing, looping, and does it with enough immediacy that you reach for it first.

Specifications

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

Key Features

Analog Looping Without the Fuss

The LD needs no patching to start looping. 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. Once 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, so you build the system around it.

BBD Character That Ages Like Vinyl

Digital delays are clean. The LD is not. Its BBD circuit adds a subtle chorusing effect to the 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 resonates, feeding back in a way that feels physical, like a room starting to ring. It's unpredictable, and you're after texture rather than pristine repeats.

Compact Design, Big Presence

At just 8HP, the LD is a space-saving workhorse. The front panel is minimal: two large knobs (time and feedback), a single push-button, and the input/output jacks. Reportedly there are no LEDs and no status indicators. That 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 appeal.

Historical Context

The LD emerged during the mid-2000s Eurorack renaissance, when boutique builders like 4ms were inventing new forms of sonic manipulation rather than mimicking vintage synths. While most companies focused on oscillators, filters, and envelopes, 4ms went sideways, building modules that behaved more like instruments than components. The LD was a performance tool, not a utility. 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. 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 pushed users 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 reportedly hover between $200 and $300 depending on condition. That's 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.

Failures are rare but not unheard of. The most common issue is degraded performance from aging BBD chips, which can show up 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 sturdy than 1/4", and wiggling a cable shouldn't cause crackling.