4ms Dual Looping Delay Black (2016–)

A 20HP digital delay and looper that holds up to three minutes of whatever you feed it. Getting the most out of it means getting into its memory.

Overview

Plug in a signal and wait for the Dual Looping Delay (DLD) to hand three minutes of your past back at you in clean digital sound. This isn't a delay that echoes and fades. It remembers, rearranges and resurrects. The 4ms DLD stores what you played, loops it, scrambles it, and returns it in ways you didn't ask for. It doesn't try to be warm or degraded. It doesn't whisper like tape or wobble like bucket-brigade chips. It's sharp and unapologetically digital, like listening to your sound through a freshly polished window.

The black-panel DLD is a Eurorack module that takes up 20HP and draws 180mA from the +12V rail. Two fully independent delay channels, A and B, share a common clock but otherwise go their own way. Each can run up to 174 seconds (nearly three minutes) of delay in 16-bit mode. Flip a jumper to 24-bit recording and you get 88 seconds per channel, with more resolution and less quantization noise. Most users never bother. The 16-bit sound is already pristine, with a frequency response from 0Hz (DC) to 24kHz and a maximum deviation of just -1.7dB. There's no audible roll-off and no digital harshness. The repeats are clean and transparent and don't color your source, unless you want them to.

The DLD doesn't impose a character of its own. You supply it. Patch the send into a filter to smear it with resonance. Reverse the playback while modulating the clock to glitch it into pieces. Lock one channel to a subdivided clock while the other runs free for polyrhythms. The module also takes CV well. Time, Feedback, Mix, Delay Feed, Reverse and Hold all have a CV input. The Time knob can reach audio rate when clocked fast, so the DLD can generate textures, tune resonant feedback networks, and even make Karplus-Strong-style plucked string sounds by feeding noise into a tightly tuned delay loop.

Newcomers often miss that the DLD isn't a looper in the traditional sense. You don't press record, play and stop. It's always recording. The memory buffer is a rolling timeline, and your "loop" is a window into that stream. Engage Infinite Hold and the window freezes. Feedback stops, no new material gets written, and the loop plays back endlessly. Turn the Feedback knob while holding Infinite and it no longer sets volume. It scrubs the start and end points of the loop, digging backward into older recordings and pulling up fragments you forgot you played.

Specifications

Key Features

Time as a Playable Parameter

Most delays treat time as a fixed setting. The DLD treats it as something to play. With the Time knob mapped to beat divisions (via the +16, =, 1/8 toggle), you can dial in rhythmic delays that lock to your sequencer. Hold the Infinite button and turn the Time knob, and you enter Unquantised Time Mode. The delay time becomes continuous and drops off the grid. Patch a VCO square wave into the clock input, set the Time knob to an eighth-note division, and the delay becomes a resonant cavity. In this mode the Time CV input also shifts to a 1V/octave response, so you can play the delay time like a pitch.

The Send/Return Trapdoor

Every delay has sends and returns. Patch the Send output to a filter, a second delay or a wavefolder, then route it back into Return. The feedback path now processes your signal recursively, in real time. Every repeat gets darker, brighter, noisier or more distorted, depending on what's in the chain. Because the DLD is always recording, those processed repeats get written back into the main buffer. When you exit Infinite Hold or switch modes, you hear the original loop plus every effect that ever touched it. It's like leaving a message on a voicemail system that keeps re-recording itself through a distortion pedal. The results are unpredictable, sometimes beautiful, sometimes alarming.

Clock Independence via Ping Lock

Both channels share the same clock source. Firmware v5 added Ping Lock. Engage it on one channel and that channel freezes its timing reference to the current Ping value, even if the actual clock changes. That lets you run Channel A at 1/16th note while Channel B crawls at 4-bar phrases, all from a single tempo source. It isn't full dual-clock independence, but it's close enough for most polyrhythmic experiments. The loop clock outputs are also available, so you can feed them into dividers, multipliers or other modules to build more complex timing.

Historical Context

The DLD arrived in 2016, when Eurorack was shifting from analog obsession to digital experimentation. Before then, digital delays in modular were either cheap PT2399-based modules with lo-fi charm or expensive, closed-box processors. The DLD sat between them. It offered professional-grade digital clarity without giving up patchability or control voltage integration. It made no attempt to emulate the past, with no tape wobble and no BBD warmth. It leaned on the precision of modern DSP, inspired more by the clean repeats of the Lexicon Prime Time or the Eventide H3000 than by the Echoplex or Space Echo.

Looping was having a renaissance at the same time. Artists like Tim Exile and Robert Henke were pushing live looping with software, but hardware loopers were still mostly stuck in guitar pedal territory - record, overdub, play, stop. The DLD rejected that model. It made looping a subset of delay behavior, tied to clock, modulatable and always recording. It wasn't for singer-songwriters. It was for sound designers, ambient composers and rhythm hackers who wanted evolving textures that unfolded over minutes, not measures.

The firmware matters too. The DLD shipped with v3, and v5, released a year later, changed a lot. It added 24-bit recording, de-jitter modes for cleaner clock handling, and Quantised Change Mode, which prevents abrupt parameter jumps by syncing changes to the next clock pulse. Updating wasn't plug-and-play. You had to play an audio file into the input while rebooting, and some older power supplies couldn't handle the boot loader. This was a hacker's tool, not a consumer product.

Collectibility & Value

The DLD has never been rare, since 4ms has kept it in steady production since 2016, but it's never been cheap either. New units still sell for around $415, and used ones typically fetch $300 to $375 depending on condition. There's no vintage premium and no collector markup. Demand comes from working musicians who need what it does.

The black anodized panel is scratch-resistant and the PCB is solid, but the real risks are firmware and power. Units that have never been updated to v5 work but are missing key features, so buyers should verify the firmware version before purchasing. Some early adopters also reported boot loader issues with underpowered or noisy power supplies, especially older Doepfer units. It isn't a common failure, but it's a known quirk. If a DLD won't update, try it with a clean, high-current supply before assuming it's bricked.

There are no electrolytic caps to dry out and no fragile pots. The module is densely packed with surface-mount components, though, so DIY repairs are tricky. If a jack breaks or a chip fails, it's not a simple fix. Because the DLD is always recording, a malfunctioning memory buffer could cause glitches, dropouts or corrupted loops. These are rare, but they're showstoppers when they happen.

When buying, test it live if possible. Check both channels, verify clock sync, try a long loop with windowing, and patch in some CV modulation. Make sure the Infinite Hold and Reverse functions behave as expected. A good unit has a 174-second memory span.

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