cv to midi???

The Old Crow oldcrow at oldcrows.net
Mon Nov 8 16:34:37 CET 1999


> > Could you send it in the "Breath control" of a DX7?????  What is the
> > "PINOUT?" =-)  of that jack, anyone know????   And in what form and
> values does the breth controler send it's data in?

  The DX-7 breath controller input jack provides three things: the ground
ring, the "excitation voltage" on the tip, and it picks up the controller
response voltage on the "middle ring".

          ______ middle ring = response voltage
     [] \/
     []     \/-- tip = excitation voltage = ~-10VDC
     []
      |
     _|_
     \_/ (ground ring)

  There are a couple incidental things on the jack as well, such as bypass
caps and a 1K load resistor for when nothing is plugged in.

  The key item to note is that the excitation voltage is *negative*.  This
voltage is fed to one side of a variable resistor.  The other side is
taken to ground, and the response is picked up off the "wiper".

  I've never checked to see what the response voltage range is, but it is
somewhere between a range of -10V to 0V (0V=full scale) and -4V to 1V.
This voltage is taken through an op-amp inverter internally along with a
divider resistor just before input to the inverter.  The inverter is unity
gain, and the output is sent to an A/D channel in the range of 0V to 5V.
(Never checked to see which is the full-scale end, though).

  To send a control voltage into this jack, only the ring=ground and
middle ring=input are needed on a stereo 1/8" phone plug.  For the typical
-5 to +5V control voltage, a -5 to +5 -> -10 to 0 (or whatever the actual
expected range of the BC is) level-shifter is needed.

  The pedal inputs use a positive excitation voltage, incidentally.

  --Crow

/**/




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