This Eurorack MIDI Merger is the eurorack re-design of my other MIDI Merger / Splitter with 2 input and 5 output thru box which I made from scratch while not being happy with other options. I actually designed a whole family from the most basic to the complex devices with merging capabilities, please see my store items and review Youtube video.

It has two MIDI input ports which are merged together by a microcontroller and then split to three MIDI outputs. All connectors are DIN5. High quality DIN5 sockets used here with three mounting points on each and sturdy 1.6mm aluminum faceplate. If you're looking for TRS connectors, then I suggest by other product that offers 5x5 TRS and USB functionality. Programmed microcontroller is included with a PCB or Kit purchase.

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 directly
• Alternatively can use +12V Eurorack rail with onboard voltage regulator. JP1 selects the power mode.

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

Purchasing Options:

• PCB only - includes the main PCB, front panel and programmed "merger" chip. 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

• Fully assembled Includes everything

Design notes:

• 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.
• Use 2-pin header to extend leads for D5 LED
• Follow polarity orientation for LEDs. Square pad on PCB is for the negative pin.
• Please, note, Pin1 of Eurorack power connector is faced UP. Set JP1 to use either 5V or 12V power: (1-2) - 5V, (2-3) - 12V
• Connect a power source (center=positive) and meassure +5V rail such as on IC socket for 6N138 between Pin8 and Pin5. Power on board without ICs first to avoid the damage due soldering mistakes.