4ms Dual VC Octave Switch (2015–2022)
A simple module that flips octaves fast and clean, with none of the mush you'd expect from analog shifting.
Overview
You patch in a pitch CV, turn a knob, and the melody sits two octaves higher. No glide, no wobble, no hunting for the right note. The shift is instant and stable. That's the 4ms Dual VC Octave Switch: a voltage-controlled octave shifter for Eurorack that treats 1V/Oct pitch data with digital clarity, even though it's all analog under the hood. It doesn't add color or character, and that's why it works so well. Other octave dividers smear or drift. This one snaps into place like a relay, which makes it a favorite with composers who need reliable transposition for sequenced lines, polyphonic shifting, or live setups where timing is non-negotiable.
Each of the two independent channels takes a single pitch CV input and shifts it up or down in exact octave steps - ±1, ±2, ±3 - by manual control or a CV input. The switching topology is the trick. Instead of multipliers or dividers, which can introduce phase errors or tracking lag, the module scales the input voltage by binary factors (×0.5, ×1, ×2, etc.) using high-speed analog switches gated by a comparator circuit. Octave shifts are near-instant, with zero slewing, no tuning drift, and exceptional tracking across the full 1V/Oct range. And it's only 8HP.
Specifications
| Manufacturer | 4ms Company |
| Production Years | 2015–2022 |
| Format | Eurorack |
| Width | 8HP |
| Depth | 35mm |
| Current Draw +12V | 40mA |
| Current Draw -12V | 10mA |
| Input Impedance | reportedly 100kΩ |
| CV Input Range | 0–10V |
| Octave Range | ±3 octaves (in 1-octave steps) |
| Control Method | Manual switch and voltage control per channel |
| Number of Channels | 2 (independent, according to manufacturer) |
| Response Time | Sub-millisecond switching |
| Accuracy | ±0.02V over 10V range |
| Connectors | 3.5mm jacks (pitch in, octave CV in, pitch out per channel) |
| Weight | 80g |
| Front Panel | Black anodized aluminum with silk-screened labeling |
| Mounting | Standard Eurorack M3 screws |
Key Features
Binary-Weighted Octave Switching
The core idea isn't flashy. Instead of analog multipliers or digital pitch-shifting algorithms, the Dual VC Octave Switch uses a bank of precision resistors and high-speed CMOS switches to scale the input CV by exact binary ratios. A +1V input becomes +2V for up one octave, +4V for up two, or +0.5V for down one. This avoids the thermal drift and nonlinearity of op-amp-based multipliers, so tuning stability rivals digital systems. A comparator circuit controls the switches so transitions happen cleanly, without glitches or momentary shorts. Sequences transpose perfectly, even at high clock speeds.
Dual Independent Channels
Two identical, isolated channels fit in 8HP. You can transpose two separate pitch sources, say a lead and a bassline, or feed a single sequence into both and shift them in opposite directions. Each channel has its own manual octave selector (a 7-position rotary switch: -3 to +3) and a CV input that accepts 0-5V to select the octave range dynamically. That means you can sequence the transposition itself, for rhythmic octave jumps or sweeping shifts across a phrase. The CV input isn't quantized, so small voltage changes won't cause erratic switching. Hysteresis in the comparator means only deliberate, full-step voltages trigger a change, which prevents mid-gate flickering.
Glitch-Free Operation
Timing is one of the biggest pitfalls of analog octave shifters, especially with fast sequences or gated triggers. Some modules add a few milliseconds of delay or produce brief tuning artifacts during transitions. The Dual VC Octave Switch avoids this by synchronizing its switching to the input signal's stability. The comparator waits for the input CV to settle before engaging the new scaling path, which eliminates zipper noise and tuning pops. That makes it reliable live, where a missed octave jump can ruin a performance.
Historical Context
The Dual VC Octave Switch arrived in 2015, as Eurorack was shifting from boutique curiosity to mainstream adoption. Many pitch-processing modules at the time still relied on dated designs borrowed from analog computers or guitar effects, which meant inconsistent tracking and tuning drift. 4ms, already known for the Dual Looping Delay and Spectral Multiband Resonator, positioned this module as a “digital-precision analog” solution, using discrete components to get results typically reserved for microprocessor-controlled systems. It filled a gap left by more colorful but less reliable octave shifters, and offered a utilitarian alternative to modules like the Intellijel Metropolis or the Make Noise Mimeophon, which prioritized texture over accuracy. According to some sources, competitors like the Mutable Instruments Transmutator offered more features (like semitone shifting), but at a higher price and complexity.
Its design mirrored a broader trend in modular synthesis: the rise of “procedural” composition, where complex sequences were built from deterministic, repeatable processes. In that context, a glitch-free octave shifter was essential. Composers using generative patches, algorithmic sequencing, or live coding setups needed pitch manipulation that wouldn't introduce errors. The Dual VC Octave Switch became a quiet workhorse in those systems, often hidden behind more glamorous modules.
Collectibility & Value
Production ended in 2022, shortly before 4ms paused new product development. The Dual VC Octave Switch has become moderately sought after, though not yet a “grail” item. Used units in good condition have been observed selling for $180 - $240, depending on market availability. It contains no user-serviceable parts and has a simple, sturdy design, so most failures are physical damage - bent jacks, cracked PCBs from improper installation, or power supply issues from daisy-chained rails. There are reportedly no electrolytic capacitors to dry out, no trimmers to drift, and no firmware to update, which makes it one of the lowest-maintenance modules in any rack.
When buying used, check that both channels respond identically to manual and CV control, and that octave shifts happen cleanly without momentary dropouts. Some early units had slightly undersized pull-up resistors on the CV switching inputs, which could cause erratic behavior with weak control voltages. This is rare and easily fixed by technicians familiar with the board layout. The module is not prone to heat stress or component fatigue, and its CMOS switches have a rated lifespan of over 10 million cycles, so even heavily used units should perform like new. Owners tend to keep these rather than flip them, which keeps resale inventory tight but prices stable.
Similar items on eBay
No exact 4ms Dual VC Octave Switch listings are live right now — these searches show current 4ms Dual and similar vintage synth gear on eBay:
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.