2hp EG (2008–Present)

Two knobs, two stages, and a time range so wide you'll wonder if your patch is frozen or evolving.

Overview

Turn the attack knob clockwise and the envelope stretches from a snappy 3 milliseconds to 11 minutes of rise time. That's the 2hp EG: a two-stage envelope generator in a Eurorack case, just 2HP wide. It isn't an ADSR. There's no sustain stage, only attack and decay. You get linear or exponential curve selection on the fly, CV control over both time parameters, and a built-in attenuator on the output that doubles as a manual level knob. It lets you build patches that would otherwise take three times the real estate.

The range is the headline feature. Need a percussive blip for a kick drum? Turn it down. Want a slow filter sweep that unfolds over several minutes? It does that too. Switching between linear and exponential curves mid-patch helps: exponential for natural-sounding decays, linear for clocked precision or metallic zaps. It has quirks. Some users report a slight volume drop when using the EG to control amplitude directly, especially with certain VCAs. That comes from the minimalist signal path, and from users assuming perfect unity gain. The knobs work, but they've been described as wobbly or cheap-feeling, a trade-off for the ultra-slim front panel.

Still, the EG’s value isn’t just in its specs. It’s in its role as a Swiss Army knife for timing. Use it as a gate delay, a slow LFO substitute, a trigger stretcher, or even a rudimentary sequencer when patched into a comparator. Its attenuator isn’t just for scaling CV—it lets you manually offset the envelope’s peak, useful for shaping filter sweeps without touching your keyboard. It’s the module you reach for when you want to add motion without clutter, when your case is full but your patch feels static. In a world of bloated, feature-saturated envelopes, the 2hp EG is a reminder that sometimes two stages are enough—if they go deep enough.

Specifications

Manufacturer	2hp
Production Years	2008–Present
Original Price	$97 USD
Width	2HP
Depth	42 mm
+12V Current Draw	26 mA
-12V Current Draw	7 mA
Envelope Type	Two-stage (Attack/Decay)
Time Range per Stage	3ms to 11 minutes
Curve Selection	Linear and exponential (switchable)
CV Control	Attack and Decay (normalled to attenuated inputs)
Attenuator	Integrated output attenuator with manual control
Inputs	Gate/Trigger, Attack CV, Decay CV
Outputs	Envelope CV
Module Type	Eurorack Envelope Generator
Front Panel Material	Aluminum

Key Features

Time Range That Defies Practicality (And That’s the Point)

The 2hp EG’s most talked-about feature isn’t just its wide time range—it’s how absurdly wide it is. From 3ms to 11 minutes per stage, it spans the gap between human reflexes and geological time. In practice, this means you can use it for anything from tight snare transients to glacial ambient swells that evolve over entire tracks. The lower end is crisp and reliable, perfect for rhythmic modulation, while the upper end opens doors to experimental sound design. Patch it into a filter cutoff and let a single note bloom over five minutes. Use it to modulate a wavefolder’s intensity so subtly that the change is almost subconscious. The range isn’t just a spec sheet flex—it’s a compositional tool. And because both attack and decay are CV-controllable, you can dynamically shift the envelope’s character in real time, morphing from staccato to legato with a single control voltage.

Minimalism as a Design Philosophy

At 2HP, every millimeter counts, and this module respects that. There are no displays, no multiple outputs, no loop modes or retrigger options. Just two knobs, a switch, and a handful of jacks. The front panel is clean and austere, with basic controls. The attenuator doubles as a manual output level knob, so simple patches don't need a separate attenuator module. The lack of a sustain stage might seem limiting, but in many patches, especially drum voices or one-shot effects, an AD envelope is all you need.

Curve Switching for Expressive Shaping

The ability to switch between linear and exponential curves on the fly is more than a convenience—it changes the character of your sound. Exponential curves mimic natural decay, making them ideal for emulating acoustic instruments or creating smooth, organic fades. Linear curves, on the other hand, offer mechanical precision, perfect for rhythmic modulation or digital-sounding effects. The switch is small but decisive, and it’s normalled to exponential, which means if you leave it unpatched, you’re getting the warmer, more musical response by default. This kind of thoughtful default behavior speaks to 2hp’s user-centric design: it assumes you want musicality unless you say otherwise.

Historical Context

The 2hp EG emerged in the late 2000s, just as Eurorack was moving from niche curiosity to mainstream synth culture. Module widths were still fairly generous then - 8HP, 10HP, even 16HP wasn't uncommon. 2hp, founded by Tony Rolando (also behind the original Buchla 200e firmware), challenged that with a line of modules built around extreme space efficiency. The EG was one of their early standouts. It arrived alongside other minimalist modules like Intellijel's µ-series and Make Noise's tiniest utilities, but stood out for its range and its built-in attenuator. Competitors like Doepfer offered ADSRs with more stages, but none matched the EG's time span in such a narrow footprint. It offered an alternative for cases already bursting at the seams.

Collectibility & Value

The 2hp EG has never been a collector's item in the traditional sense. There were no limited runs and no special editions. It's too common and too utilitarian for that. As of 2024, new units sell for around $97, unchanged from the original price for years, which is rare in the modular market. Used units typically go for $60 - $80 depending on condition, with little fluctuation. There are no known production runs or revisions to track. Failures are rare, but when they happen they're usually power-related or tied to the curve selection switch, which has a small but noticeable failure rate over time. The knobs are a common complaint: they feel loose and can wobble under frequent use, though they rarely fail outright. Buyers should test the switch and both CV inputs. Make sure the curve selection clicks cleanly and that CV modulation responds smoothly across the full range. There's no need to recap or refurbish these units; they're solidly built for their price point.