How to build a MIDI interface for a Sound Blaster/Sound Blaster Pro:

Probably works with almost any soundcard

      The Sound Blaster MIDI port uses two pins from the 15 pin
      joystick port.  These normally would be redundant +5 volt and
      ground lines.  In the Sound Blaster, there are called MIDI TXD
      (Transmit eXternal Data) and MIDI RXD (Receive eXternal Data).
      The signals to and from the Sound Blaster are TTL logic signals.
      MIDI uses a current loop interface, so the job of the interface
      box is to convert between TTL level signals and the MIDI current
      loop.

      If you want to use the MIDI interface and the Sound Blaster
      joystick interface simultaneously, you can make a simple adapter
      by connecting one male and 2 female 15 pin connectors to a short
      length of ribbon cable.

      SBMIDI1.PCX is a PCX format graphic file of the schematic diagram
      of the MIDI connector circuitry.  You can use Windows Paintbrush
      to view and print the schematic.
Schematic of SBMIDI Interface - you won't get much out of this page if pictures are disabled
      For simplicity, the schematics show the MIDI input and output
      circuits separately, but they share the +5 volt and ground lines.
      (Pins 8 and 5 on the Sound Blaster).  The interface uses 4 wire
      shielded cable to connect the computer to the interface box and
      two 2 wire shielded cables to connect the interface box to the
      input and output ports on the MIDI instrument.

      The MIDI input port only can connect to one instrument, but the
      MIDI Out from the computer could go to up to 5 MIDI instruments.
      The schematic diagram only shows one complete MIDI output line.
      You can connect up to 4 additional MIDI outputs by adding a
      220 resistor (from the +5 volt pin to pin 4 on the MIDI cable)
      and a 220 resistor (from the buffer output to pin 5 of the
      MIDI plug) for each output.  You should also add a 220pf
      capacitor between each additional MIDI line and ground.

Construction:

      Start with using half of a dual 20 pin IC board, using the first
      six pins for the optocoupler and the last fourteen pins for the
      hex buffer.  Then remove portions of some of the copper lines
      on the circuit board with an X-Acto knife, as is shown in the
      schematic below.  Cut each trace on
      both ends first, then remove the copper between the cuts.
Track Cutting Pattern
RED = Remove BLUE = Marked as remove, but doesn't seem to be needed
Now Turn over, left to right...
BLUE = Link wires GREEN = Small components

Component Overlay
Looking at the diagram, I now believe the links from IC2 pin 2 to IC1 pin 3, and IC2 pin 2 to pin 4, to be incorrect. The links IC2 pin 5 to pin 9 and IC2 pin 9 to pin 11 are only required if you intend to use the corresponding outputs - pins 6 and 8. This also explains the additional track cutting
      Now on to component installation!  Be sure to use rosin core
      solder and a low wattage soldering iron.  Solder the 20 pin
      socket to the center of the board, being careful not to bridge
      solder between connections.  Then install the other components
      in the locations shown in the above schematic.  Note that the ringed
      end of diode D1 needs to connect to pin1 of the optocoupler.
      Be sure to run hookup wires from the ground pin on the optocoupler
      (Pin 4) to the ground pin of the hex buffer (Pin 7) and between
      pins 11 and 12 on the hex buffer.  The remaining hookup wires
      are optional for additional MIDI outputs.  Notice that both a
      resistor and a capacitor must be connected in the same hole for
      each MIDI Out.  Then connect the 4 conductor shielded cable to
      pins 5,8,12 and 15 of the 15 pin plug.  Connect the shield to
      the metal case of the plug.  Connect the other end of the 4 wire
      cable to the corresponding locations shown in the above
      schematic.  Tie the cable shield to the large mounting hole in
      the circuit card and connect one end of each of the two connector
      shielded cables to pins 4 and 5 of the MIDI plugs.  Connect the
      shield in the MIDI plugs to pin 2.  Mark one cable "MIDI IN" and
      the other cable "MIDI OUT".  Connect the other end of the cables
      tot he corresponding locations on the circuit card.  Tie the
      shields to mounting holes in the circuit card and connect all
      three shields together with a hookup wire.   Check the card and
      cables to ensure that all connections are correct, file small
      notches in the cover of the aluminum box for the cables, and
      wrap a piece of heavy paper around the circuit card to prevent
      shorting.  Your next step is to plug the 15 pin connector into
      the Sound Blaster and the MIDI In and Out to the MIDI jacks on
      your MIDI instrument.

Testing:

      A MIDI port requires software to function.  You can test the
      input portion of the MIDI interface with the FM Organ program
      bundled with the Sound Blaster.  With "MIDI Mode" selected,
      MIDI Note-On messages will play sounds from the Sound Blaster
      card, but only those notes valid for the musical key you have
      selected.  For example, if you select the key of C, only the
      white keys will sound.  To test the MIDI Out portion of the
      interface, you can use any MIDI sequencer that supports
      Sound Blaster.  All of Voyetra's sequencers, Cakewalk, and
      Trax are examples of some that are available.  When you go
      shopping for a sequencer, make sure you specify that you have
      a Sound Blaster.  The Sound Blaster MIDI interface is NOT
      Roland MPU-401 compatible!  But that's not a major drawback
      anymore - Most companies are now supporting the Sound Blaster,
      but some have separate versions - One for SB, one for Roland.
      There are some ShareWare/DemoWare sequencers available on
      the Creative Labs BBS.  You can reach them by modem at the
      number given at the end of this file.


      Available on the BBS is a library of MIDI files (.MID) as well
      as several ShareWare/DemoWare MIDI applications.

      Note:  Please do NOT call the Technical Support department of
      Creative Labs for help on this - With this file, you have
      just as much information as they do!  If you don't want to
      deal with it, just buy the cable - It costs $24.95 + S&H
      direct from Creative Labs.  The sales number is (408)428-6600.

      Good luck!
Information presented from files obtained via the UK Creative BBS (now defunct), with suitable reformatting into HTML. All information presented is understood to be in the public domain and intended for distribution.
No responsibility accepted for damage or injury resulting from the use of this information - if in doubt, buy it, don't build it! All trademarks acknowledged, particularly CREATIVE, SOUND BLASTER etc. For Creative's web site, go to www.soundblaster.com ... www.creative.com is incorrect, but will offer a courtesy redirection.
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