2hp TM (2012–Present)

A tiny brain for your modular that comes up with melodies you'd never think of - sometimes beautifully, sometimes stubbornly.

Overview

You patch in a clock, twist the probability knob, and the synth starts humming a tune that sounds like it came from somewhere else. That's the 2hp TM: a sliver of logic in a 4HP panel that generates evolving sequences. It doesn't play notes directly. It feeds voltages into your oscillators, filters, or envelopes and nudges the patch toward unpredictability. It's a probabilistic step generator. Each step in a sequence (1 to 32) gets a random voltage, and the probability knob decides how random. Turn the probability down, and only a few steps change each cycle. Crank it up, and the whole pattern melts into chaos. It's not a full Turing Machine in the computational sense, but it borrows the spirit - simple rules spawning complex behavior.

It does all this in the width of a credit card. 4HP is absurdly narrow, even by Eurorack standards, which makes the TM a favorite for skiff builders and minimalists who count every millimeter. You set the boundaries - sequence length, voltage range, how often things change - but the actual output is left to chance. Musicians use it for drifting basslines, unpredictable arpeggios, or as a compositional spark when inspiration stalls. It won't replace your sequencer, but it adds subtle mutations that keep a loop from getting stale.

Specifications

Manufacturer	2hp
Production Years	2012–Present
Original Price	$109
Module Width	4HP
Depth	45mm
Current Draw +12V	23 mA
Current Draw -12V	7 mA
Current Draw 5V	0 mA
Polyphony	Monophonic (stepped voltage output)
Sequence Length	1–32 steps
Probability Control	Adjustable from 0% (locked) to 100% (fully random)
Amplitude Control	Adjusts range of random voltage per step
Outputs	1x CV (random stepped voltage)
Inputs	1x Clock, 1x Reset (optional)
MIDI	No
Quantizer Integration	External (output typically patched to quantizer)
Weight	Approx. 50g
Construction	PCB with aluminum front panel
Color Options	Silver, Black

Key Features

The Probability Knob: Your Lever on Chaos

The probability knob is the heart of the TM. At minimum, it locks the sequence. Every step holds its voltage, and the module becomes a static 1-32 step sequencer. As you turn it up, steps begin to refresh randomly with each clock pulse. Even at high settings, some steps may stay the same while others flip, so the pattern evolves partway. Think of a bassline that shifts one note every few bars. It's not generative in the AI sense, but it resists repetition without abandoning structure.

Compact Design, Big Patching Impact

At 4HP, the TM is one of the narrowest modules in Eurorack. It doesn't need a 5V rail, drawing only from ±12V, which helps in power-constrained systems. The front panel has three knobs (probability, length, amplitude) and three jacks (clock, reset, CV out). There's no display, no menu diving, no firmware updates. The trade-off is that you can't see the sequence, only hear it. Debugging a wonky pattern means ear training or patching the CV out to a scope or comparator. Some people like that. Others get a black box that occasionally spits out a -5V spike when they weren't looking.

Deterministic Randomness: The Hidden Limit

Despite its name and conceptual roots in Alan Turing's work, the TM doesn't use true analog noise. It runs on an Atmel microcontroller with a pseudorandom number generator (PRNG). That means the sequence will eventually repeat, though likely after days or weeks of continuous clocking. For live performance or studio use, that isn't an issue, since the cycle is long enough that no human would notice. Purists who want true unpredictability, like those using Make Noise's René or the original Turing Machine by Random*Source, might find this a philosophical flaw. It's not sampling transistor hiss or cosmic noise. It's an algorithm, elegant but finite. For 99% of users, it's random enough, and the predictability of the PRNG can help with repeatability in compositions.

Historical Context

The 2hp TM arrived in 2012, right as Eurorack was shifting from boutique curiosity to widespread adoption. Modules were getting bigger, more complex, and more expensive - multi-function oscillators, digital wavetable beasts, sequencers with OLED screens. The TM went the other way, toward minimalism, inspired by early computer music and algorithmic composition. It drew clear lineage from the Turing Machine concept popularized by electronic musician and engineer Robin Whittle in the 1990s, which used analog shift registers and noise sources to create evolving sequences. The 2hp version was digital, compact, and affordable, and $109 put it within reach of almost any modular user. It wasn't the first random sequencer, but it was the first to fit in 4HP and still offer meaningful control. Competitors like ALM's Pam's New Workout offered more features but took up eight times the space.

Collectibility & Value

The TM has never been rare. 2hp has kept it in steady production since 2012. Used units typically sell for $75-$90, depending on condition and color. Black panels sometimes fetch a slight premium from collectors who like the stealthy look, but silver remains the most common. It's a simple digital module with no moving parts, so failure rates are low. The most common issue is cold solder joints on the power pins, especially in early units, but a reflow fixes them. There are no known firmware bugs that affect operation. Unlike analog modules that drift or need calibration, the TM either works or doesn't. That reliability makes it a favorite for touring musicians who need something that won't fail mid-set. It's not a "grail" module. It won't appreciate in value, and you won't find people scalping it.