x0x-heart Eurorack Module

by Open Music Labs

The heart of a TB303 synth recreated in modular format.

$25,671 raised

of $1,500 goal

1,711% Funded!
Not Available
Jun 27 2016
funded on


Recent Updates

As Featured In

AskAudio Logo


"If you're a fan of acid bass, the original TB-303 and Eurorack synth modules, then this one is for you… With the module being sold for the appropriate sum of $303 it’s easy to see why this has been snapped up so quickly."


"Von den unzähligen Klonen, die den 303-Sound imitieren, gilt die x0xb0x gemeinhin als einer der gelungeneren. In Form des x0x-heart Moduls gibt es ihren Sound nun auch im Eurorack."


"303 Clone For Eurorack Available For $303"

Sonic State

"A TB303 For Your Modular System"

Matrixsynth Logo


"Open Music Labs x0x-heart Eurorack Module Seeks Funding on Crowd Supply"

Beat.de Logo


"x0x-heart fürs Eurorack widmet sich alleine der Erzeugung zwitschernder Acid-Sounds, auf den Sequenzer im 303-Stil wird komplett verzichtet."

The Roland TB303 voice practically defined Acid music, heavily influencing the development of electronic music. Add that voice to your own setup with the x0x-heart Eurorack Module.

The x0x-heart module is the analogue section extracted from the x0xb0x (a TB303 clone) and made small enough to fit the Eurorack format. More nimble as a module, you no longer need to work within the constraints of the original TB303’s sequencer.

Product progression: TB303 -> x0xb0x -> x0x-heart -> xox-heart Module


  • CV control of frequency, gate, accent, slide, env-mod, decay, and cut-off
  • Switches for waveform selection (square and sawtooth), external/internal oscillator mix
  • VCA and VCF outputs
x0x-heart Front and Back


  • Eurorack standard format (3U height)
  • 18hp
  • ~1.75in depth (45mm)
  • +/-12V current draw 10mA
  • 5V current draw: 50mA
x0x-heart Side Angle


  • 10” Euro power cable (16 pin to 10 pin connector)
  • Black anodized aluminum knobs with a diamond knurl pattern and two set screws (with slot heads and flat points)
  • A .063” (1.6mm) highly durable satin aluminum Metalphoto panel with a black print

Stretch goals

If, during the campaign, the funding amount reaches $15,000, the pacemaker circuit board (the one with the knobs) will be re-designed to allow for easier tuning and manufacturing.

If and when the first stretch goal is met, more goals may be announced during the campaign - let us know what you’d like to see as a stretch goal! No promises, of course. Here are some things we’ve been considering to make available - either for additional purchase or as options:

  • Red-anodized aluminum knobs
  • Laser-cut and engraved wood faceplates (which would be more fragile, of course!)

Open source hardware

To help you truly understand and control what you and your module are doing, Open Music Labs makes all schematic and board layout files available for your perusal and use.

Pacemaker (DIY version) source files http://wiki.openmusiclabs.com/wiki/EuroAdapter

Heart source files http://wiki.openmusiclabs.com/wiki/x0x-heart

x0x-heart All Pieces

About Open Music Labs

The goal of Open Music Labs is to create a central web location where people interested in using analog and digital audio equipment can go to find ideas, histories, parts, and like-minded others.

We want to create a resource people can use to share ideas and learn new things about hands-on audio creation, manipulation, and interaction.

Open Music Labs is a subsidiary of Flingco Sound System in Chicago.

2013 flashback: an x0x-heart prototype - slaved to a TB303:

Special thanks

Grayscale: Panel designer/manufacturer and all-around idea factory.

Tyler Thompson - T^2official: Video soundtrack artist and cool dude. His pro tip:

”Well my favorite thing about this module is how close it sounds to the real deal and I can sequence it with a less archaic sequencer. (I personally don’t gel with the x0x style sequencer.)

I recommend people pair it with a sequencer that has adjustable gate length per step like the Audio Damage Sequencer 1 or Industrial Electronics (Harvestman) Stillson Hammer MKII.“


Open Music Lab Logo

Open Music Labs

Analog and digital techniques - tools for musicians, composers, and tinkerers.



Front panel graphical designer

Metalphoto of Cincinnati


Panel manufacturer

RW Technologies US LLC


PCB assembler

See Also

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