2HP Zlob (2016–2018)

A small analog module that fits in the gaps between your other modules. It has noise, random voltages, and sample-and-hold in 2HP.

Overview

The 2HP Zlob is a sample-and-hold module with a built-in noise source. It doesn't play melodies or hold chords. It adds unpredictability to rigid sequences and makes a robotic arpeggio twitchy and a little nervous. It's about as compact as analog circuitry can get. At just 2HP wide, it's the module you install because you ran out of space but still needed one more source of controlled randomness.

Onur Kalaycıoğlu originally designed it under the Złob Modular name, and 2HP later acquired and rebranded it. The Zlob was never meant to be a flagship. It was a way to squeeze random voltages into a format where every millimeter counts. It debuted around 2016, when Eurorack was exploding in popularity and skiff-builders were fighting over every half-inch of panel space. It does one thing, with a minimal footprint.

Sonically, it's raw. The noise generator produces white, pink, and brown (also called red) noise, all analog and slightly gritty, the way discrete circuits tend to be. It isn't pristine like a digital noise source. It crackles, like an old AM radio tuned between stations. That noise feeds directly into the sample-and-hold circuit, which can be clocked externally or left to free-run. The output is a stepped random voltage, good for modulating pitch, filter cutoff, or pulse width. A trimmer on the PCB adjusts the gain of the white noise, which in turn changes the voltage spread of the S&H output. Turn it and you can go from subtle wobble to full stochastic madness.

A lot of function is packed into a narrow space. The panel is laser-cut acrylic, available in multiple colors. It looks delicate, but it holds up fine with basic care. The module draws 15mA from both the +12V and -12V rails, with no 5V requirement, which was standard for its era. It was sold both as a DIY kit and pre-assembled. Early versions had components that slightly overhung into the third HP, so tight module spacing could cause mechanical interference. Some users solved this by mounting it with a 3HP panel instead, though the original 2HP version still fits if you leave a little room.

Specifications

Manufacturer	2HP (originally Złob Modular)
Production Years	2016–2018
Original Price	$90
HP Size	2HP
Depth	62 mm
Current Draw +12V	15 mA
Current Draw -12V	15 mA
Current Draw 5V	0 mA
Noise Types	White, Pink, Brown (Red)
Sample and Hold	Yes, with internal noise normalled to input
Outputs	Noise Out, S&H Out, Smooth Random CV Out (0–5V)
Inputs	Clock In (for S&H)
Panel Material	Laser-cut acrylic
Adjustments	PCB trimmer for white noise gain, PCB trimmer for smooth CV offset
Availability	Discontinued
Form Factor	Eurorack
DIY Option	Yes, available as kit
Manufacturer Website	http://zlobmodular.com

Key Features

Analog Noise with Character

The noise generator is also a tone source. White noise here isn't flat and clinical. It's slightly colored, with a warm top end and a low-end thump that feels more organic than most discrete designs. Pink and brown noise give progressively darker textures. Brown noise has a rumbling, almost subsonic quality that suits slow-moving parameters or atmospheric pads. Because the noise is analog and unfiltered by design, it keeps harmonic complexity that digital noise sources often lack.

Sample-and-Hold with Normalled Chaos

The sample-and-hold circuit is where the Zlob gets its name (Polish for "rage" or "tantrum"). Clock it, and it grabs a voltage from the internal noise source and holds it until the next clock pulse. The S&H input is normalled, so with nothing plugged in it automatically uses the internal noise. You can drop the module into a patch and start modulating without a single extra cable. To randomize VCO pitch, patch the S&H output to a 1V/oct input. To make a filter squirm, route it to the cutoff. The voltage range is adjustable via a PCB trimmer, from micro-modulations to full-scale jumps across octaves.

Smooth Random CV: The Hidden Gem

There's also a lesser-known output: smooth random CV. Unlike the stepped S&H output, this is a slow-drifting analog voltage between 0-5V, generated via an infrared-based smoothing circuit. It suits slowly shifting drone tunings, gradual brightness changes, or ambient morphing. Another PCB trimmer adjusts the offset, so you can bias the range higher or lower. You won't use it every day.

Historical Context

The mid-2010s were a golden age for Eurorack minimalism. Skiff culture was in full swing, and builders were squeezing as much functionality as they could into minimum space. The 2HP Zlob arrived in the middle of that movement. It wasn't the first 2HP module, but it was one of the first to prove that such a narrow format could still deliver serious analog performance. Competitors like Intellijel and Doepfer were focusing on larger, more feature-rich modules, while boutique builders like Złob (and later 2HP) carved out a niche for ultra-compact utilities.

It also reflected a shift in modular thinking: randomness and unpredictability were features, not flaws. Digital synths could produce perfectly quantized sequences, and the Zlob offered the opposite, with analog drift, noise, and imperfection. It stood alongside other chaos-bringers like the Mutable Instruments Marbles or the Make Noise Wogglebug, but with a fraction of the footprint and cost. For modular users building their first skiffs, it was an affordable, no-frills way to add life to rigid patches.

2HP acquired it in the late 2010s. 2HP was already known for minimalist designs like the VCA and SINE, so it was a natural home for the Zlob. Production was short-lived, though. The module was discontinued by 2018, likely due to low margins and the niche appeal of such a specialized utility. It showed that you could fit a fully functional analog noise and S&H circuit in 2HP, paving the way for future ultra-compact modules from brands like ALM and Noise Engineering.

Collectibility & Value

Today, the 2HP Zlob is a sought-after oddity, more about utility than raw power. It won't command the prices of rare VCOs or filters, but it isn't common either. On the used market, expect to pay between $100 and $140, depending on condition and whether it's the original Złob-branded version or the later 2HP release. Original DIY kits in good working order tend to be on the lower end. Pre-assembled units with clean panels can fetch closer to $140, especially in rarer panel colors like black or translucent red.

Condition matters. The module uses surface-mount components and a double-sided PCB, so repairs can be tricky. The most common failure points are the power pins and input jacks, which can develop cold solder joints over time. Users have reported occasional ground loop noise when used with certain USB-controlled gear (like the Expressive E Touché), though proper cabling or isolation usually resolves it. The laser-cut acrylic panel is durable but can crack if overtightened or dropped. Replacements are no longer available, so original panels in good condition add value.

For buyers, the biggest red flag is functionality. Test the S&H output with a clock source. The voltage steps should be clean and stable, with no stuck values or drift. The noise output should be consistent across all types, with no hum or oscillation. If the module was built from a kit, check the soldering. Some early build docs had incorrect capacitor values, which leads to instability if not corrected. And while it's labeled 2HP, the PCB slightly overhangs into the third HP, so verify spacing in your case before buying.

Restoration is possible but not trivial. Złob never officially released schematics, so troubleshooting means reverse-engineering or using community-shared diagrams. Recapping is rarely needed unless the module has been stored poorly, but cleaning the jacks and checking power connections is wise for any used unit. With its low current draw and simple circuit, it's not a fire hazard. It is a finicky little thing.