DMC Series Power Over MIDI
Some MIDI devices can get “phantom power” from the MIDI out of the previous device in line. One pin of the MIDI out is at 5VDC, current-limited with a 220 ohm resistor, and the other active pin is connected to ground by the microcontroller or microprocessor in the device. Although it’s not technically part of the specification, it is possible to steal some current from that 5V pin. In order to do that, we need to make ground available to the device that’s stealing power.
On the DMC-3’s, the MIDI jack has pin 1 grounded by design. On pedals with a PCB-mounted jack (DMC-2, -4, -6,) the ground may or may not be connected to pin 1. The first thing to do is plug your other device into the DMC MIDI out and see if it works. If not, here’s how to fix it:
1. Open the DMC pedal case by removing the screws from the bottom.
2. Remove the DMC PCB from the bottom lid of the box by unscrewing the 4-40 screws from the bottom of the lid. Only three of the screws will have nuts on them, the fourth screw can be left in place. If you’re careful, you should be able to remove the board without disconnecting any of the wires.
3. Turn the PCB over and find pin 1 of the MIDI port. It’s right here:
4. Connect pin 1 of the MIDI port to ground by soldering it to any of the shiny area around the pin. All of that area is ground, so just use a bit of component lead or wire (we’ve used some wire here.) Don’t try to just blob solder on there, it probably won’t work. Try to make it look like this:
5. Put the thing back together and test it out. If your connected requires less than 60mA, the DMC should power it OK.
6. If you don’t want to solder this, we can do it for you at no charge – just pay shipping. Contact us for details.