IMG_7166With the recent surge in the availability and popularity of hardware synthesizers, drum machines and other MIDI-based gadgets, there has never been a better time to add a MIDI THRU box to your rig.

Whether it’s to get all your gear synced up to one master MIDI clock, or to distribute MIDI note data from a keyboard or controller, this device with its five active MIDI thru ports will provide all the connections you need (and if it doesn’t – simply chain another one on to add even more outputs).

The single MIDI input is fully optically isolated to protect your devices. Latency is virtually zero.

Power comes from a 2.5mm x 5.5mm DC jack socket, centre-positive, which will accept power from any “wall-wart”-type supply capable of delivering between 9 and 12V DC, to a maximum of 1 amp.

Specifically targeted at entry-level DIY-ers, this project boasts

  • Low part count
  • Clear, simple instructions
  • Complete parts kits, with all parts clearly identified
  • Low tool requirements
  • No setup or calibration
  • Elegantly designed around a widely-available, sturdy enclosure for a great finish

This build is simplicity itself, but the result is a very professionally-finished, robust and hard-wearing device that will deliver great service to your MIDI instrument rig for years to come. In addition, there is flexibility built into the design for those who wish to build their own enclosure, use alternative connectors for MIDI or embed the device into another project (for example, a modular synth case).

Build options & instructions

The PCB for this project supports two types of build:

  • a complete, cased unit, designed to fit in a Hammond 1590B die-cast aluminium enclosure or our NiceBottom kit; you’ll need to order both a PCB and a panel to build this version
  • an “embedded” build, which provides pin connections for power, MIDI in and MIDI thru; build this version if you want to mount your build inside your own enclosure, embed it within a rack or as part of a larger project. This also allows you to use whatever MIDI connectors suit you – lots of synth manufacturers are using 3.5mm jacks for MIDI connections now – with this version of the build, you don’t even have to stick to DIN-format connectors. You’ll only need the PCB to build this version

The ThruBox build instructions provide a clear guide to building either of these options.


The full parts list can also be found in the build instructions. All of the electronic parts for this build can be obtained from Mouser. Mechanical parts (screws, nuts etc) can be obtained easily from a huge range of suppliers (we tend to source ours via eBay).

Our parts kits contain all of the electronic and mechanical parts that you’ll need to do the job; the only things that we don’t supply are:

  • Tools
  • Solder
  • A suitable power adaptor. Unfortunately, it’s just not cost-effective for us to stock the wide range of adaptors we’d need to cover all of the places we ship to – and, to be honest, you can probably source a better one, for less money from a local supplier
  • The Hammond 1590B enclosure; again, it makes better sense for you to source this locally. You’ll get the colour you want, at a better shipping rate than we could manage
  • Feet and any other embellishments for your enclosure

The parts in our kits are sourced from Mouser and are exactly the items listed in the Bill of Materials.



Item Price

PCB only


PCB and panel

Includes 4 x 6-32 UNC x 5/8″ machine screws for attaching the panel to an enclosure.


Full kit, EMBEDDED version

A PCB and all of the additional parts that you need to make the EMBEDDED version of ThruBox.
Power supply not included.


Full kit, CASED version

A PCB, panel and all of the additional parts and fixings that you need to make the CASED version of ThruBox.
Power supply and enclosure not included.


Fully assembled & tested

A fully-assembled ThruBox, mounted in your choice of a black die-cast enclosure or one of our NiceBottom enclosures. Just add a DC adaptor and you’re good to go. Please note that lead times will vary – contact us or see the shop for more details.

£72.80 – £83.60

Prices include packing & standard (untracked) shipping. All prices are given in GBP, your local price after currency conversion may vary.

All of our products are available from our Etsy shop. Although we make efforts to keep our stock levels as constant as possible, demand might occasionally mean that an item is out of stock. Stock replenishment typically takes less than one week.