Open Music Labs x0x heart (Grayscale)

Open Music Labs x0x heart (Grayscale)

Open Music Labs x0x heart (Grayscale)


The x0x Heart is the core of the famous TB-303, surgically extracted to be transplanted into your designs. The x0x Heart is just the analog section of the TB-303, replicated with SMT components, and made small enough to fit into a Eurorack modular format. It even has a Eurorack power header on it.

This module is designed to be small, inexpensive, and a close replica of the TB-303. It is not a perfect replica – some sacrifices were made to keep costs down – but it’s pretty darn close. It also has no pots or controls, making it great for DIY synth building. All of the useful I/O points are pinned out, and as a special bonus feature, digital control is given for Accent, Slide, Decay, Waveform select, Cutoff, and Env Mod.

The main PCB is a fully assembled and tested SMT board — it’s the analogue heart of the TB-303.

The Pacemaker PCB and DIY Grayscale Eurorack panel can be assembled together with the x0x Heart’s main PCB for a complete DIY Eurorack module!

The full DIY synth kit includes the assembled x0x heart main SMT PCB, the unpopulated Pacemaker through-hole PCB, and all of the Pacemaker PCB and panel parts, including ribbon cable, power cables, mounting hardware and more.

**Based on customer feedback, all newly-built x0x-hearts from synthCube will have a filter cutoff CV modification implemented that improves the response of the Filter Cutoff CV Input at low voltages. This modification may be performed to existing x0x-heart Eurorack modules. The details are here. Also, synthCube can perform this modification to existing modules. Contact us for details.


For more information including videos and links to the manual, please visit the Open Music Labs xOx Heart info page. The link is
Here’s a helpful thread on the muffwiggler forum: x0x Heart Thread


October 2020 Update: New Pacemaker PCB are blue PCB material with gold immersion finish.

NOTE: The unpopulated PCB is a very challenging SMT DIY build. Please do NOT attempt to build an unpopulated PCB unless you are confident and experienced in DIY SMT. 



On Demand Info

These kits and assembled modules are offered on demand, click the link to learn more.



Module Parameters
Panel Size18HP

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  • from $18.00 TO $349.00
  • Ex Tax: $16.00

Available Options

full kit- euro
Out of Stock - $229.00
pacemaker pcb
Out of Stock - $18.00
panel + assembled main pcb + unpopulated pacemaker pcb
Out of Stock - $169.00
panel- euro
In stock / $30.00
Available : 26
pcb, populated w/smt
In stock / $139.00
Available : 58
synthCube assembled, new
Out of Stock - $349.00

Tags: open, music, labs, x0x-heart, pcbs prtolx0xheart00 pcb+panel, bundles, x0xheartmaster diy diy, , grayscale, version (diy, grayscale), synthesizer, kits