This Eurorack MIDI TRS Thru box is the eurorack re-design of my other basic 1 input 4 output splitter 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 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.

This TRS version is capable to set a MIDI specification per port for TRS-A or TRS-B by moving jumper settings. This provides the flexibility to interface it with all vendors no matter of the specification used.

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

Board size and an enclosure choice: Eurorack size: 2HP, PCB Size: 10.8x4.3cm

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

• Fully assembled: Includes everything

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. This board is only 2HP, please, consider you have enough room to the next module if it's populated with IC sockets. Discard sockets and shorten jumper pins if required.

• 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.

• Cut pins on the back side of PCB close as possible, so it doesn't short neighbor module.

• 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

• Refer to silkscreen instructions for jumper positions for TRS-A or TRS-B specifications

• Use only TRS 3.5mm cables. Do not use mono eurorack cables.

• First prototype boards have an ID on the front panel, that's expected, later boards will get it removed.