Art X-15 MIDI controller 7-pin MIDI modification

Here is my version of a converted Art X-15 MIDI controller that I use with my TC Electronic G-Major. The idea here was to get all cabling needs (MIDI in, out, and AC power) to be done with a single connection. Doing this allows me to have very fast setup times without any hassles when gigging.

The parts needed for this are readily available online (which is where I got mine). I bought the 2 MIDI connectors from Allied Electronics. For convenience, I gave links and part numbers for the connectors below. These are high-quality parts made by Amphenol, but pretty much any part or any distributor can be used. There certainly is no "one way" to do this, but I did spend about a week working this out in my head deciding what was best for me. Although this is focused on the Art X-15, these principals can be applied to just about any unit. Tie wraps, shrink tubing, and an ohm meter are things that you would want to have handy for this project. The meter is essential to testing as your progresss with the project.

Controller

I first measured the thickness of the unit before I ordered the parts. The last thing that I wanted was to find out that the parts were not going to fit on the unit. What I found that was in most of the venues that I play, I usually tape the MIDI cables on the floor to my amp. This meant that the cables were plugged in at the front of the pedal, and then wrapped around the side and back to my amp. Rarely (once, actually) did I run the cables straight out of the back of the unit and under the stage. Because of this, I figured that a right angled MIDI plug along with a receptacle out of the side of the unit would be very useful. My idea was to make a long 7-pin MIDI cable with one right angle and one straight. More on the cable later.

I started by picking my placement of the receptacle on the X-15. I chose the right side, towards the front. I ordered the appropriate surface-mount connector from Allied Electronics (type in Allied stock number 246-7232.) To the right is the high-quality receptacle that was sent. This is a locking MIDI connector that can be used with standard cables or locking types. Drilling into the X-15 was probably the most difficult procedure as I did not have the perfect equipment do to so. I carefully covered the unit inside and out (metal fragments would play havoc on the device) and used a drill bit to get me the largest diameter hole possible (5/8 for me). If you have never drilled into metal before, remember that using oil as you drill is critical. Keeping the metal cooler and lubricated will save your bits and keep the metal from overheating. To finish the hole, I used a 1/2" grinding bit in my drill (I would post a pic, but it was a 1-use deal). It only cost me a buck or so at Home Depot.

For both the internal wiring and the "rack adapter" (covered later) I used an old 3-foot MIDI cable that I had lying around. I chose this particular one because all 5 pins of the cable were wired (remember, most MIDI cables are only wired for pins 2, 4, and 5 (the center 3 pins) with pins 1 and 3 (the outer-most pins) not even connected). This can be easily checked with an ohm-meter. 7-pin DIN connectors have a standard wiring pinout, but it is pretty weird. Basically, Pins 1-5 were done first (and are the same for standard 5-pin MIDI) and pins 6-7 were added later. I cut the cable into 3 pieces, with 2 pieces containing the plugs set aside for the rack adapter and the third center piece used for the internal X-15 wiring.

I decided to wire the new plug on the reverse side of the existing PC board (the visible side once the cover is removed). The reason for this was so if I ever had any problems with the new modification, such as my 7-pin MIDI cable getting accidentally sliced, I could still use the stock plugs. This involved using a low-wattage soldering iron (12-15 watts) so as to not damage the existing objects soldered to the PC board. As you see here, I ran the AC separate from the new receptacle to the PC board. Here is the standard that I came up with for wiring my X-15 (keep in mind that this is a closed wiring system with all pinouts being determined at the rack adapter and the internal controller wiring, so you can do it any way that you want).

NOTE: Reverse image on top. Here is the basic routing from the new receptacle to the board. As you can see in my blurry photo (whattaya expect for nuthin'?) the wires are soldered directly to the contact points on the board. Pins 2, 4, and 5 on the MIDI out are wired straight through. Pins 2, 4, and 5 of the existing MIDI in become 2 (shared), 1, and 3 in the new 5-pin configuration. These are shrink wrapped and tied together to add more rigidity. They can even be siliconed down for added strength, but the tie wraps seemed to be enough. I chose to keep the middle 3 (2, 4, and 5) to MIDI pin standard, and added the return (out) MIDI to the corresponding pins above (keep in mind that MIDI IN, OUT, and THROUGH share the same ground in this and most applications, so that does not need to be run again). Pins 6 and 7 were used for power. That means that pin 2 is ground, pin 4 is current source for the MIDI IN, pin 1 is current source for MIDI OUT, pin 5 is current sink for MIDI IN, pin 3 is current sink for MIDI OUT. Knowing what "current source" and "current sink" is for this purpose is not important, it is just mentioned to note a differentiation between the signals. The X-15 can use either an AC power source or a DC power source. Mine is AC, so the wiring of pins 6-7 was not pin-dependant. If you use a DC power supply, then you will need to be sure that you are mapping 6-7 properly. It is, of course, a good idea to map pins 6-7 properly at both ends in case you switch power types.

Make sure to test each contact repeatedly through this process with an ohm meter. You should be able to pass current from the new receptacle through the factory jacks without a problem. This will assure you that you have your pinouts wired correctly as well.

Rack adapter

This little bundle is the matchingconverters for the rack side of things. This also assures that your pre-determined signal paths and pinouts end up where they are supposed to be. You can use the leftover 2 pieces of the MIDI cable that were hacked up earlier or you can make your own. I don't feel that I need to get too into wiring this as it is essentially a process of reverse-engineering what was done at the controller end. I chose to make everything short and to keep it rather permanent in my rack. This way all I have to do is plug in the 7-pin when I am ready to go. The 7-pin female MIDI connector used here is a little different than the one used on the controller because it is meant to be on then end of a cable (as opposed to surface mounted). Punch in Allied Electronics part number 246-7064 for details on this part.

Cable My initial intention was to make a cable with threaded collars for the controller and the rack adaptor. These are fast to screw on and off, but the cost of the shielded wiring and the adapters was pretty expensive, then I found this 25 foot 7-pin MIDI cable for a great price at MIDI Classics (cable pictured right). MIDI standards for cable length have been stated from 30 to 50 feet, but since I am running voltage with the MIDI signal, I did not want to push it. I have found that 25 feet is more than enough for any of the cheesy venues that I play, so I left it at that. Heck, this one even had my straight and angled plugs the way I wanted it. It has worked flawlessly for 6 months now.

I hope that this is enough to get this project done. If you have any questions or comments, please email me at tedtrep@hotmail.com. Peace! -Trip

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