2hp VCA (2010–Present)

Name: 2hp VCA
Brand: 2hp

Two HP of uncolored voltage control. It is small and clean, and it stays out of the way.

Overview

The 2hp VCA does one thing quietly. It has no flashing lights, no exotic waveforms and no gritty character. It is a dual linear VCA built for precision, not personality, and it has found its way into thousands of Eurorack systems since its release. Use it to duck a signal, gate a noise burst, or modulate amplitude without adding color.

Under the brushed aluminum faceplate is the SSM2164 VCA chip, a workhorse from the golden age of analog ICs, known for ultra-low distortion and wide dynamic range. The audio path is clean, transparent, and stable across voltage swings. There is no softening of transients, no low-end sag, no high-frequency roll-off. It is just amplitude control.

At just 2HP wide, it's one of the most space-efficient dual VCAs ever made. It exists to fill awkward gaps between larger modules without giving up functionality. The trade-offs are real. The knobs are tiny, the jacks are close together, and with thick cables or densely stacked modules, reaching the attenuators can feel like threading a needle. Some builders avoid it for exactly that reason, especially in skiff builds where every millimeter counts. For many others, the compactness is the whole point.

Specifications

Manufacturer	2hp
Production Years	2010–Present
Type	Synth Module
Format	Eurorack
HP Size	2HP
Depth	42mm
Power Supply	Requires Eurorack case and power supply
Power Consumption	21 mA +12V, 26 mA -12V, 0 mA 5V
VCA Architecture	SSM2164 (dual)
Topology	Dual linear VCA
CV Input Attenuator	Yes, per channel
Coupling	DC-coupled inputs and outputs
Inputs	2x audio/CV inputs (per VCA)
Outputs	2x audio/CV outputs (per VCA)
CV Inputs	2x CV inputs with attenuators (per channel)
Color	Silver (standard), Black (variant)
Mounting	Skiff-friendly
Weight	Approx. 40g

Key Features

SSM2164 Fidelity in Miniature

The SSM2164 was originally developed by Solid State Music and later used in high-end consoles and VCAs. It offers a dynamic range and linearity that few modern alternatives match. In the 2hp VCA it delivers less than 0.01% THD under typical operating conditions, which makes it one of the cleanest analog VCAs available in Eurorack. That matters in mixing, sidechaining, or anywhere signal integrity counts. Unlike VCAs with logarithmic response or inherent saturation, this one doesn't sweeten the sound. It preserves it. Some users find that clinical neutrality a drawback when seeking warmth or vintage character.

DC-Coupled Flexibility

Both audio and CV signals pass through the 2hp VCA thanks to full DC coupling. That opens up routing beyond simple volume control, such as modulating LFO depth, scaling random voltages, or using it as a bipolar attenuator in utility patches. The CV input attenuators let you fine-tune modulation depth, so you're not stuck with full-scale swings when a subtle nudge is needed. It lacks the offset or polarizer controls found on more complex VCAs, which keeps the design lean and the signal path short.

Space-Saving Design Philosophy

The design goal is to maximize utility and minimize footprint. In a format where 4HP is considered compact, 2HP is tiny. Skiff users in particular praise how it squeezes into corners and gaps that would otherwise go unused. The density has limits, though. Patching and adjusting get fiddly when it is flanked by other narrow modules, and some users report accidentally unplugging adjacent cables when reaching for the knobs. It suits static patches and systems where re-patching is infrequent.

Historical Context

When 2hp launched the VCA around 2010, Eurorack was still a niche within a niche. Most manufacturers focused on oscillators, filters, and sequencers. Utility modules were often bulky and feature-light. 2hp treated utility as a design problem: how small can a functional dual VCA be? The answer was 2HP. At a time when even basic mixers consumed 6HP or more, that was a big step. It arrived alongside other compact designs, including Doepfer's A-100 utilities, Ladik's compact designs, and later Intellijel's µ-series.

The SSM2164 chip, though decades old, remained a gold standard for clean gain control. Competitors like Mutable Instruments' Veils offered more features, including mixing, coloration and envelope generation, but at 8HP and higher cost. The 2hp VCA didn't compete on features. It competed on density and fidelity.

Collectibility & Value

The 2hp VCA has never been rare, and production has remained steady since its debut. It has also never been cheap for its size. New units typically sell for $120 - $140, which some consider steep for two VCAs in a sliver of metal. Used modules hold value well, often trading for $80 - $100 in good condition.

Failures are uncommon. The most frequent issue reported is power rail damage from reversed cabling or case faults, which is unsurprising given the tight PCB layout. The SSM2164 chips themselves are sturdy, but replacing them requires surface-mount skill. Cosmetic wear is more common: scratched faceplates from patching, loose knobs from frequent adjustment, or bent jacks in densely packed racks. When buying used, check for consistent response across both channels and make sure the attenuators sweep smoothly without crackling. Units with silent channels or erratic CV response likely have damaged ICs or cold solder joints.

There’s no “vintage premium” here—no sought-after revisions or color variants that command double the price. The silver and black versions perform identically. What you’re paying for is consistency and build quality, not collectible scarcity. For restorers, the module is straightforward to service: no complex firmware, no delicate trim pots, just a clean analog path. If you’re assembling a minimalist rack or filling gaps in an existing system, the 2hp VCA remains one of the most reliable ways to add dual linear control without bloating your footprint.