The perils of cheap MIDI adapters

MIDI

[Arvydas] recently bought a Rock Band 3 Wii keyboard thinking it would be an excellent and very inexpensive (£9.99) MIDI controller. The keyboard has a proper DIN-5 MIDI out port, so theoretically the only thing needed to plug this into a computer is a USB to MIDI adapter. Unlike the keyboard, the MIDI adapter was a cheap piece of Chinese cruft, but given some ingenuity and a handful of components, he was able to get everything working.

The 30-year-old MIDI specification includes a few schematics on how to properly connect MIDI devices together. The most important part of these schematics is an optoisolater on the MIDI in, a valuable addition considering early MIDI keyboards cost thousands of dollars. It seems [Arvydas]‘ MIDI to USB adapter didn’t include this vital component, instead replacing it with a simple resistor. Anything to keep costs down, right?

To get the MIDI adapter working, [Arvydas] headed over to Maplin and bought an optioisolator, With everything wired up on a breadboard, he got it to work and eventually transplanted the circuit to the adapter’s PCB.

It’s a great piece of work to get this MIDI adapter functioning, especially since it’s doubtful the cheap adapter would have worked with any MIDI device.

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