Here is an Eurorack version of the popular Teensy 4.0 controller with 5x5 MIDI interface on TRS-A/B (selectable) ports as well as audio output.

This board is designed for Teensy4.0 and it's not compatible with other Teensy products. If you're looking for a similar board for Teensy4.1 or Teensy3.2, please, check other products in my store.

The board provides 5 input / 5 output functionality. This can be your 5x5 MIDI interface, merger, splitter, filter or whatever else you can imagine. This obviously requires programming the Arduino framework with Teensy extensions. I include basic firmware so, you can get USB MIDI running out of the box without any need to learn Arduino.

This TRS version is capable of setting 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 the specification used.

You also get one Audio output (stereo) from Teensy Lo-Fi MSQ port. By default it's a sine generator programmed onto USB Port 6 and doesn't interfere with other 5x5 MIDI ports. It can be your clock out, trigger out or some advanced synth. Audio programming for Teensy is also straight forward.

All Teensy pins are available on extra pin headers. This allows easy expansion if you're planning to add extra LEDs, buttons, OLED display, in/outs etc... You can do that without soldering.

Package options:

• PCB alone: This includes two PCBs(main and daughter) and aluminum front panel

• Complete Electronics kit: Includes PCBs, front panel and all electronic (but Teensy4.0) - TRS connectors, optocouplers, headers, resistors, diodes. Check BOM list by the link.

• Fully assembled: Includes everything except Teensy microcontroller. Those are always in stock at PJRC.com

Teensy microcontroller is not included with any purchase, you can buy it directly from the manufacturer: https://www.pjrc.com/store/

There are several options for providing a power:

• From Teensy USB port

• To be used with Eurorack 16pin power supply and sourcing 5V from eurorack (JP1 1-2)

• To be used with Eurorack 10pin power supply, sourcing 12V from eurorack and doing onboard 5V conversion (JP1 2-3)

Board size and an enclosure choice: Eurorack size: 6HP, PCB Size: 10.8x5.4cm

Please, consider my page at Github for sample firmware and additional information.

Assembly instructions:

The board is self explanatory but Github link includes schematics, board layout and photos to help if there are any problems. Here are several notes though:

• 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.
• Cut pin headers to appropriate length J14-J16 to fit PCB and Teensy controller
• Populate all passive components first - capacitors, resistors, etc. Consider proper polarity for capacitors, diode marks.
• Follow polarity orientation for LEDs. Square pad on PCB is for the negative pin.
• Populate pin headers except J13.
• Insert long ping header into J17
• Insert main board and daughter board into faceplate, mount TRS sockets, keep J13 not soldered
• Press firmly on the main and daughter boards until they are parallel, so the J13 pins go all the way in female header, while excessive pins go thru J13
• Solder J13, cut extra pins
• Refer to silkscreen instructions for jumper positions for TRS-A or TRS-B specifications
• Please, note, Pin1 of Eurorack power connector is faced down. The arrow indicates a red strip
• Use only TRS 3.5mm cables. Do not use mono eurorack cables for MIDI.
• Audio out is stereo channels