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Midi output from Allen 120-3 expression pedal advice?

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  • Midi output from Allen 120-3 expression pedal advice?

    Having learned a great deal about midifying an Allen 120-3 organ from posts in this forum, which seems to have many helpful people, I am asking for some advice on how to get a midi output from the current expression pedal rather than purchasing an additional dedicated midi expression pedal.

    The organ was originally purchased by me as new in the early 1980's and is in excellent shape, having been used as a home practice organ. In my midification, I am keeping the original organ capability and using Hauptwerk via a Mac Mini. Based upon suggestions in this forum I have installed the Harrison Keyboard/pedal converter with excellent results, perhaps as a result of sending them my Allen board and paying $99 for them to do the soldering rather than trust my limited skills. (service and turnaround great, the instructions are for someone very knowledgeable in electronics, which I am not).

    I wish to y-link the pedal output to either this board, which has three expression input terminals for each division (which I do not know how to wire to use one pedal output to all three devisions, and help here appreciated as well), or to a separate midi board that in the future may support a third manual.

    In researching the pedal, it appears not to be a potentiometer but rather a light chopper array, but am not certain (any information welcome, I do not want to cut into wiring). At the expression input to each of the two amplifiers, there is an rca input from the pedal. With my limited skills with a multimeter, I cannot find a voltage output. I was hoping it would be 0 to 5 volts that could be directed into a midi device with a y connection without removing the existing expression capability in the Allen organ.

    Has anyone tried this and have any advice, suggestions?

    Help appreciated.

  • #2
    Click image for larger version

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    Here's an example of adding linear 10k pots to connect to a MIDI encoder. I used nylon about 3/8" thick, old hinges, shaft collars, eyebolts, and aluminum shafts. All from a local hardware store. The potentiometers are attached with double sided tape. Lots of ways this could be modified -- use your imagination.


    • #3
      Thankyou! I will try this.


      • #4
        A coupe of details. At the bottom of the 12" hollow aluminum shaft there is an eyebolt with a small rubber grommet inserted to make a friction fit with the potentiometer tab. I believe the pot has a 2" range -- it's the longer one from Sparkfun. The shaft collar is at the top of the shaft with the allen screw removed -- replaced by a machine screw.


        • #5
          Thanks again for the clarification.
          Pardon my electronic ignorance, but I purchased such a linear potentiometer and of course they are more complicated for wiring than a normal pot. And I am not finding anything useful on Youtube university or from my purchasing or manufacturing source. Do you have a reference for wiring a linear potentiometer.?


          • #6
            Referencing my photo in an earlier post the bottom terminal would be the +3.3v or +5v connection -- whichever voltage your encoder uses. One top terminal will be ground -- that will be whichever terminal reads the same resistance to the bottom regardless of how the wiper handle is positioned. If those two are right then the remaining terminal is the wiper. Get this wrong and you will short out the encoder's power regulator. Just as an aside, most modern power regulators tolerate a short surprisingly well but we don't want to test that feature.


            • #7
              Thank you for this. I will let you know if I produce smoke.