4ms QCD (2010–Present)

Name: 4ms QCD
Brand: 4ms

A tap tempo button that feels like striking a match in the dark. Suddenly everything in your rack has a heartbeat.

Overview

Patch in the 4ms QCD, tap in a tempo with a few quick taps, and the whole modular system snaps to attention. It isn't flashy and it isn't trying to be a sequencer or a brain, but it *organizes*. It does more than distribute clock. Four channels of voltage-controlled clock division and multiplication, each with its own reset, CV control, and independent clock input, give you precise control over rhythm. You can chain them, cross-patch them, and modulate them into stuttering polyrhythms or smooth, cascading subdivisions. It makes you realize how messy your timing was before - ghost triggers, drifting sync, clocks that never quite locked. The QCD fixes that. It's not a rhythm generator the way a sequencer is. It's more like a master timekeeper that can spawn complex, interlocking patterns from a single pulse.

The tap tempo button is mechanical and clicky, like a metronome with attitude. Press it a few times and the module locks in with rock-solid consistency, sending that tempo to five outputs: the tap clock itself and one per channel. The LED indicators pulse in time, each at its own rate, so you can see at a glance which channel is dividing by three and which is multiplying by five. The normalization chain - Tap to Red to Black to Blue to Green - means you can start simple and expand outward, daisy-chaining multiple QCDs or syncing in external clocks without rewiring everything. It was designed by people who actually use modular systems.

The QCD gets interesting when you patch it back into itself. Send a divided clock from channel 3 into the reset of channel 1, modulate a multiplier with an LFO, or patch in a random voltage to shift divisions on the fly, and you're breeding rhythms. It's generative, unpredictable, and deeply musical. It outputs 5V clock pulses, fully buffered and stable, so it can drive just about anything: drum modules, envelope generators, sample-and-holds, other clock dividers.

Specifications

Manufacturer	4ms Company
Production Years	2010–Present
Original Price	$239
Module Size	10 HP Eurorack
Depth	26 mm
Power Consumption (+12V)	88 mA max
Power Consumption (-12V)	40 mA max
Power Consumption (+5V)	Not used
Clock Outputs	5 (Tap, Red, Black, Blue, Green)
Clock Input Normalization	Tap → Red → Black → Blue → Green
Division Range	/32 to /1 per channel
Multiplication Range	x1 to x16 per channel
CV Control	Divide/Multiply CV input per channel
Reset Inputs	One per channel (trigger resets clock phase)
Tap Tempo Button	Manual tempo input with LED feedback
LED Indicators	One per channel, blinks at output clock rate
Output Signal	5V pulse, square wave (default)
Expandability	Compatible with QCD Expander for pulse width, inversion, and envelope generation
PCB Header	For connection to Quad Pingable LFO (QPLFO)

Key Features

The Tap Tempo That Thinks

Most tap tempo functions feel like an afterthought, something you use to match BPM and then forget. On the QCD it's central. Tap in a tempo and the module locks to it, and the tap clock output stays active regardless of how the individual channels are clocked. So one channel can run off an external clock, another can divide a random pulse, and a steady master tempo still goes out to your DAW or another module. The LED blinks in real time for immediate visual feedback, and the mechanical switch has just enough resistance to feel deliberate, not twitchy.

Self-Modulating Rhythm Engine

The QCD is often described as a "clock distributor," and that label undersells it. Each channel is a full voltage-controlled divider/multiplier with CV input, reset, and independent clock input. You can patch channel 2's output into channel 3's clock input, modulate channel 1's division with an envelope, and reset channel 4 from a snare hit, all at once. The result is a rhythm generator that can create evolving, non-repeating patterns without any external sequencer. It's a system you *play*, like a drum machine with no pads. The detented knobs snap to integer values, so you're not guessing at divisions, but the CV input lets you glide between them for rhythmic sweeps or glitchy stutters. That balance of precision and chaos makes it a favorite among experimental and live performers.

Expandability as Philosophy

The QCD was designed to grow. The optional QCD Expander adds pulse width control, inversion, and the ability to generate four independent envelopes via the QPLFO header. It turns the QCD from a clock module into a full rhythmic control center, able to shape timbre and dynamics as well as timing. Even without the expander, the module's PCB includes a header for connecting to the Quad Pingable LFO. It's built for tinkerers who want to push beyond standard clock distribution.

Historical Context

The 4ms QCD arrived in the early 2010s, when the Eurorack scene was exploding but clock management was still a mess. Most racks relied on basic clock dividers, DAW sync, or drum machines with limited outputs. Studio musicians had used master clocks for decades, but a compact, voltage-controlled Eurorack version was new. The QCD wasn't the first to offer multiple clock divisions, but it was among the first to make them musically flexible, with CV control, reset inputs, and intelligent normalization. It arrived just as modular users were moving beyond simple looping sequences into generative, reactive systems, and it became a staple in racks that valued rhythm as much as melody.

Its closest competitors at the time, like the Doepfer A-160 series or the Intellijel Metropolis, offered division and multiplication, but few matched the QCD's combination of tactile control, expandability, and clean signal integrity. The QCD didn't try to be a sequencer or a brain. It stayed focused on timing. It also reflected 4ms Company's broader design approach: no frills, maximum utility, built for the long haul. It found its way into experimental setups, live performance rigs, and studio racks where reliability and flexibility mattered more than flashy visuals or preset storage.

Collectibility & Value

The 4ms QCD has never been a "rare" module in the collector's sense. Production has been steady since 2010, and it's still available new from the manufacturer and dealers. A used QCD in good condition typically sells for $180-$220, while new units hold close to the original $239 MSRP. There's little price inflation because supply meets demand, and because the module hasn't been discontinued or reissued in multiple revisions that create scarcity.

Condition still matters. The tap tempo button is mechanical and, while durable, can wear out with heavy use. Owners report that sticky or unresponsive buttons are the most common failure, usually fixable with contact cleaner or replacement. The power draw is 88mA on +12V and 40mA on -12V. That's modest but not negligible in a large system, so check your case's headroom before adding one. The module uses no +5V, which is a plus for older or budget power supplies. There are no known circuit-level failure points beyond standard electrolytic capacitor aging, and given the digital-heavy design, there's little to "recap" anyway. The real maintenance is mechanical: keeping the jacks tight, the knobs secure, and the front panel free of stress cracks from over-tightened screws.

When buying used, test all four channels with a scope or logic probe if possible. Verify that the tap tempo locks consistently and that the LEDs respond correctly. Check for firmware updates. The QCD doesn't have a traditional firmware chip, but 4ms has released minor PCB revisions that improve stability and expand functionality. Confirm whether the QCD Expander is included, since standalone expanders can cost nearly as much as a used QCD and the two are often bought together. A full QCD + Expander setup commands $400-$450 on the used market.