Eurorack MIDI DIN5 Thru 1in -> 4out midithru

It has optimized schematics for 5V and 3.3V MIDI sender devices, optimized circuitry for optocoupler to minimize false triggering and improve sensitivity. Finally it uses hex inverter with a Schmitt trigger for driving a stronger output signal. This makes it very reliable device. This is an active circuit, so it does require an external power. That’s the way it should be according to the MIDI specs.

There are several options for providing a power:
  • To be used with Eurorack 16pin power supply and sourcing 5V from eurorack
  • To be used with Eurorack 10pin power supply, sourcing 12V from eurorack and doing onboard 5V conversion
  • To be used with a standard wall adapter 6-12V and 5.5mm*2.1mm connector. The DC barrel socket is available on the back side. This is useful option for eurorack enclosures without built in power supply.

Board size and an enclosure choice: Eurorack size: 6HP, PCB Size: 10.8x4.2cm

Purchasing Options:
  • PCB only - includes the main PCB and the front panel. BOM list and all design specifications are available on Github.
  • Complete kit - includes PCBs and all required components as well as 16-pin eurorack ribbon cable
  • Assembled unit - has all components soldered and comes with a eurorack power cable.

Design notes:
  • This is one of early production batches and I continue improving specifications and product capabilities. Feel free to share your feedback!
  • Beginner soldering skills required. That means you have to understand schematics, not just being able to solder two wires together. There are no high expectations, but being able to read schematics and understand polarity of components are quite important.
  • Populate all passive components first - sockets, capacitors, resistors, etc.
  • Consider proper orientation for Pin1 IC sockets and polarity for capacitors, diode marks.
  • Follow polarity orientation for LEDs. Square pad on PCB is for the negative pin.
  • Please, note, Pin1 of Eurorack power connector(red wire) is faced UP. In future versions it will be down as typically for modules. Set JP2 to use either 5V or 12V rail: (1-2) - 5V, (2-3) - 12V
  • if DC 5.5 barrel jack used for power, JP1 sets external voltage: (1-2) - 5V(also USB cable) or (2-3): 6-12V
  • First prototype boards have an ID label on the front panel, that's expected, later boards will get it removed.
  • Early boards have a front panel mistake the activity LED for power LED labels
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