Simple MIDI in Cable




How to make a SUPER simple MIDI cable to send data to your joystick / MIDI port.

I had a M-Audio USB uno, which worked great on my ghetto keyboard, but on my newer setup, it would constantly dump garbage notes. Rather than go spend yet another wad of hard earned money, I realized that I probably had most of the parts at my house already.

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Step 1: Do Your Homework

After googling around for a bit, I came across a few basic schematics. This one was the schematic I was planning on following, but I had to deviate slightly.

My local Fry's Electronics didn't carry a 6N138, but they had the NTE equivalent which I found was a NTE3093. I had resistors at home, but I found I was out of 220 ohm, so I went with 270 ohm, which appear to work just as well.

I didn't care about sending MIDI signals out of my PC, so I left that part out of my design. I wanted all the parts to fit within a DB15 casing.


Step 2: Make It REALLY Small

After verifying that the schematic did in fact work, it was time to start stacking the parts on top of each other. With only 4 components, this was going to be easy. Building projects using this method can be a great space saver, but will make it HELL trying to repair or debug something, so be sure that everything is working as it should first.

To make this go a little easier, I broke off the 3 extra pins from the IC.

Step 3: Hope That Things Still Fit.

Now that all the parts are in a nice little ball, I put some heat shrink over them to protect and insulate them. Since it fits in the DB15 hood with no issue, I do what I do with most of my projects, fill them with hot glue. The glue keeps parts from shaking around, breaking or falling out. Plus, it gives the plug a satisfying weight.

I inject the plug half with glue then smash down the top piece, cutting off the excess with a razor. Then tape around it tightly, and give it 15 minutes to cool down.

I now have a nice MIDI in converter cable with all the parts self contained in the cable. It works much better than my M-Audio USB uno. Hooray for old technology.

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9 Discussions


7 years ago on Introduction

If you don't have the specific optocoupler (I didn't), you can replace the coupler with just about any you can find. I pulled my coupler (SFH617A) out of an old computer powersupply and added a small random transistor because my chip doesn't have a transistor like the 6M138 does between pins 5,6, and 7. It works great.
BTW all the parts you need should be in a computer power supply if you feel like removing parts from the PCB. The coupler will usually be a 4-pin dip.


11 years ago on Introduction

This is cool! I used to use those old XT keyboard extenders for MIDI cables and they worked perfect.

1 reply

Reply 11 years ago on Introduction

Making a USB to MIDI controller would require much more circuitry. The reason this circuit is so simple is because most sound cards and motherboards which have a Joystick port already have MIDI IN and MIDI OUT on pins 15 and 12 respectively.

Actually, I think you could probably wire the instrument directly to these pins, however putting the optocoupler and friends into the design protects both the MIDI device and the PC from destroying each other.

More information about the Joystick/Game port pinout, look here.


11 years ago on Introduction

Only if I had thought of this instead of burning up din-5 and db-15 sockets back in the lat 80's when I was trying to make one when I was much younger.


11 years ago on Introduction

Woah, nice job! Looks neatly done, great Instructable, the pictures are just incredible, nice work!