This MIDI Thru box is the special 2 input 10 output splitter which I designed from scratch which is not available in the market. You have the option to buy the PCB only, a Complete Kit with the components (assembly required) or Fully assembled.

With ten MIDI output ports, you set per port which input it comes from. So, effectively it can be two domain independent splitter with any other combination 1x5+1x5 or 1x2+1x8 and so on. This gives lots of flexibility to the routing, as you may have to MIDI input devices such as a keyboard and DAW output that you can map to the required port without messing with cables. This switch doesn't support merging of input 1 and 2, its either of those at a time.

There are two options for switches - micro slide type of the switch or a jumper. Jumpers are for more hardwired environment there you need the robust option that you can't move by a mistake. While slide switch option is for flexibility to choose MIDI input port. For more info refer to the picture.

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 two options for external power:

• To be used with a standard wall adapter 6-12V and 5.5mm*2.1mm connector. In this case a Kit comes with a corresponding socket and 7805 power regulator

• To be powered from USB port. In this case, a Kit includes USB->5.5mm*2.5mm cable, corresponding power socket (so you won't plug wall adapter) and doesn't include 7805. Instead of that you'll solder a jumper Pin 1 and Pin 3. Leave Pin 2 not connected. Please make sure, you use USB port or adapter with 5V output and verify it prior to connecting to the board. There are some QuickCharge USB chargers that can bump a voltage. Please, avoid using them.

Board size and an enclosure choice: Size: 6x27cm

Some of you wondered ideas for enclosure selection. Well, some kits produced here can be installed into cast cases, such as MidiThru-4 or MidiMerge_2in->5out into 1032L enclosure. It requires drilling and some patience. Other boards are just too big to go into a typical aluminum case. I found it much easier to put them in between two acrylic panels cut to the size and connect them with plastic standoffs. I typically use M3 standoff 20mm and 5mm. 20mm goes on top, and has enough room to cover DIN5 sockets, while 5mm goes on the bottom. There is CorelDraw file on Github with precise board dimensions and holes location.