4ms STS (2018–)

A dual-channel sampler with the feel of a tape deck and the precision of a lab instrument. It comes with no map.

Overview

Power up the 4ms STS and the buttons give a brief purple glow. Then nothing. No screen, no menu, no welcome message. Just a panel of knobs, jacks, and colored LEDs that look like hieroglyphs at first. The first hour goes to squinting at it like a fuse box and learning that holding Reverse and Bank together trims output levels, and that pressing Play and Record at once arms monitoring. It's not unfriendly. It just assumes you've read the manual, twice.

Once you crack the code, the STS is one of the most expressive sampling engines in Eurorack. It's not a multitimbral workstation or a groovebox clone. It's a stereo-triggered sampler built for texture, manipulation, and real-time recombination - two full stereo playback channels, each with independent CV control over pitch (1V/oct), sample selection, start position, and playback length. You can play two different stereo samples at once, pitch them across a 14-octave range (yes, fourteen), reverse them on command, or slice them into 8ms grains for granular storms. The module ships with a 16GB microSD card preloaded with over 600 samples from artists like Richard Devine, Moor Mother, and Daedelus - field recordings, glitches, vocal fragments, synth stabs - so you're never starting from zero.

The workflow is where it gets good. The STS lets you record samples live, directly into the module, without a computer. Patch in any audio source, hit Record, and it captures a stereo WAV file straight to the SD card. That means you can bounce your entire patch - filters, delays, modulations - into a single sample, then replay it, reverse it, or loop a fragment of it. It's a feedback engine disguised as a sampler. The microSD card is hot-swappable, so you can swap libraries mid-performance and pull in new banks without powering down. To use your own samples, copy folders to the card - no renaming needed. Folders named "Red Percussion" or "Blue Drones" auto-load into their matching color banks. Elegant? Not quite. But effective.

The STS demands patience. There's no display and no file browser, and the only way to see what sample you're on is to count blinks of the Bank LED. Flashing red twice is Bank 2. Three times is Bank 3. Steady purple is Bank 7. It works, barely, but feels archaic next to modern modules with OLED screens or MIDI integration. The firmware has improved since launch (including a jump to 0.7ms playback latency), though early adopters reported bugs around sample reloading and SD card handling. Most of those are ironed out now, but the learning curve remains steep. This isn't a "plug in and jam" module. It's built for people who want control, not convenience.

Specifications

Manufacturer	4ms Company
Production Years	2018–
Original Price	$450
Module Size	20HP
Depth	0.98" (25mm)
Power Consumption	+12V: 145mA, -12V: 39mA, +5V: not used
Audio Inputs	20Hz–20kHz (-7.6dB rolloff), 21V peak-to-peak max
Audio Outputs	0Hz–22kHz (-1.8dB max deviation), ±10.5V max output
Sample Formats	WAV, up to 96kHz/32-bit/stereo
Maximum File Size	4GB per file (~6.7 hours at 44.1kHz/16-bit stereo)
Recording Resolution	44.1kHz/16-bit or 24-bit stereo (96kHz not yet available)
Simultaneous Playback	Two stereo samples
Sample Capacity	Up to 600 samples active at once (60 banks × 10 samples)
MicroSD Card Support	Hot-swappable, class 10 or UHS Speed Class 3 recommended
Trigger Inputs	Latency: 0.7μs, +2V to +12V trigger range
Trigger Outputs	+10V pulse, 13ms typical width
CV Inputs	1V/oct pitch (-10 to +4.3 octaves), Sample Select, Start Position, Length, Reverse
Recording Time	Unlimited (card-dependent); 256GB card ≈ 18 days continuous
Included Accessories	16GB microSD card, SD adapter, 10-to-16 pin power cable, M3 screws

Key Features

Dual Independent Stereo Channels

The STS is two samplers in one. Each channel operates independently, with its own sample bank, playback controls, and CV inputs. You can trigger them separately, layer them in stereo, or route them to different effects chains. In practice, that means a reversed ambient pad can play in the left channel while the right fires off a pitched-down drum hit, each responding to different sequencers or LFOs. The module supports both stereo and dual-mono output modes. In stereo mode, both samples are mixed and sent to the L and R outputs. In mono mode, each channel outputs a summed mono signal. Switching between them means holding both Bank buttons for five seconds - another hidden combo that feels cryptic until it clicks.

CV-Controlled Sample Manipulation

Every parameter that matters is CV-addressable: pitch, sample selection, start position, playback length, and reverse. The 1V/oct input gives full chromatic tracking, and the pitch range is absurdly wide - down to -10 octaves, enough to turn a snare crack into a sub-bass rumble. The Start Position and Length CVs are 0-5V, not bipolar, which can trip you up with a symmetric LFO. Half your modulation cycle does nothing. Fix it with a DC offset, or live with the asymmetry. Modulating playback length down to near-zero values is where the STS slips into granular territory. At 8ms or less, you're no longer playing samples. You're scanning across them like a needle on a broken record, creating stutter, smear, and texture. Add CV-controlled start position and you have a real-time granular scrubber that responds to voltage like a synth engine.

Onboard Recording and Resampling

Unlike most samplers that need a computer for sample loading, the STS records directly into the module. Hit Record, and it creates a new WAV file on the microSD card. You can capture external sources or bounce your own modular output, say a filtered drone or a sequenced arpeggio, and play it back right away. The module records at 44.1kHz/16-bit or 24-bit (user-selectable). It doesn't yet support 96kHz recording despite playback capability, but the fidelity is excellent. You can also resample your own manipulations: play a sample, reverse it, modulate its start point, then record the output back into a new slot. Remember to disarm recording when you're not using it. There's no undo, and accidental takes pile up fast.

Historical Context

The STS arrived in 2018, late in the first wave of Eurorack samplers, after pioneers like the Make Noise Morphagene and the Qu-Bit Nebulae had already carved out niches in granular and spectral manipulation. Where those modules leaned into abstraction, the STS went the opposite direction: high-fidelity, immediate playback, and a focus on traditional sampling techniques, with full modular integration. It was also one of the first to offer dual stereo channels with full CV control, which made it a favorite with performers who wanted to layer or switch between sound banks on the fly.

Its two-year development cycle showed. By the time it shipped, the market had moved. Modules like the ER-301 and later the Mutable Instruments Clouds (before discontinuation) offered deeper sample manipulation, more intuitive interfaces, and built-in effects. The STS felt built for a slightly earlier era, one where computerless operation and SD card swapping were still novel. It found its audience anyway: live performers, sound designers, and anyone who wanted a no-compromise stereo sampler that could record, play, and resample without leaving the rack. And unlike many boutique modules, it was built to last - no flimsy PCBs, no overheating chips, just solid engineering from a company that had already proven itself with the Dual Looping Delay and Quad Clock Divider.

Collectibility & Value

The STS has held its value well, trading consistently between $400 and $500 depending on condition and included accessories. Used units with the original 16GB card and packaging command a premium, especially since 4ms no longer includes sample-loaded cards with new units. No widespread hardware failures have been reported - no capacitor plague, no SD card socket issues, no overheating. The biggest risk is firmware. Early units required audio-file-based updates, which could brick the module if interrupted. Current firmware (v1.5 as of 2022) is more stable, but owners still recommend keeping a backup SD card with the latest update file just in case.

When buying, check that the microSD card slot clicks firmly and that the module boots with the expected purple LED flash. Test both recording and playback, and verify that CV inputs respond correctly, especially pitch, which should track chromatically across multiple octaves. Some users report slight gain mismatch between channels, but this is usually correctable via the internal trim pot accessed through the Reverse + Start Position menu. Avoid units with bent jacks or cracked faceplates. The FR4 board is sturdy, but the panel is unforgiving if over-tightened.

The STS is not the easiest sampler to use, nor the most feature-rich. But for raw, voltage-controlled access to stereo sampling, without MIDI and without screens, it's still one of the best tools in the rack. It won't replace a DAW.