SUPPLEMENT
 ----------
 I) You can use invertors in place of AND gates. The schematic diagram
    would be the following (for 2 outputs), instead of the old "MIDI
    output part" description.
         !\         !\
 SB      ! \ 2      ! \ 4    +--------+    5  MIDI   4   +--------+      SB
 MIDI ---!  >o--+---!  >o----! R=220  !----[  out    ]---! R=220  !---- +5V
 out    1! /    !  3! /      +--------+      plug 1      +--------+    (pin 
)
  12     !/     !   !/
                !
                !   !\
                !   ! \ 6    +--------+    5  MIDI   4   +--------+       SB
                +---!  >o----! R=220  !----[  out    ]---! R=220  !----- +5V
                !  5! /      +--------+      plug 2      +--------+    (pin 
)
                !   !/
                !
                !
                +--- etc.
 
 Pin 14 of the chip must be connected to +5V, and pin 7 to ground, just like
 with the previous one. Also don't forget to remove the strap between old
 pins 1 and 2! It is no more necessary and would court-circuit the first
 inverter.
 The other inverters in the chip are cabled between pins 13 (input) and
 12 (output), 11 and 10, 9 and 8 (all the inverters point to the right).
 If you try to use CMOS inverters (4... series) instead of TTL ones (74..
 and 74LS... series), please remark that CMOS inverters "point" to the left.
 Tandy references are different for 74.., 74LS.. and 74HC.. circuits.
 II) If you really want to save money, don't put any AND gate. Connect
 together the wires going to pins 1, 2 & 3. Don't short-circuit the power
 supply pins; leave them unconnected.
 III) For the optocoupler, you could also use a 4N26, a 4N27 or a 4N28.
 --
 From: rjf@gdwb.oz.au (Rex Foord)
 Subject: Re: Looking for that Sound-Blaster to MIDI circuit again.
 Date: 6 Dec 92 11:44:14 GMT
 I have just completed a MIDI interface for a soundblaster compatible
 card - Sound Galaxy BX.
 It uses the same pin outs as the soundblaster and it all seems to work.
 Here is a rough diagram of the circuit I used, based on an article in the
 soundblaster newsletter, and some other MIDI interface circuits for other
 systems.
 15 pin D connector             220R
 1 +5v ------------------------/\/\/\---------------\
                                                     \ 4
 5 gnd ---------------------------------------------2      MIDI OUT
                                                     / 5
 12 tx ------------------------/\/\/\---------------/
                                 220R
 1 +5v ---------------
              |      |
              \      |
         220R /      |
          R1  \      |
              /      |
              |      |                  220R
 15 rx --------      |        ---------/\/\/\--------\
              |C     |B       |A     |                \  4
            ---------------------    |                       MIDI IN
            |  6      8       2 |  -----              /  5
            |                   |   / \ IN914      --/
            |      PC900        |   ---            |
            |                   |    |             |
            |  5              3 |    |             |
            ---------------------    |             |
              |E              |K     |             |
              |               |      |             |
 5 gnd --------               ----------------------
 PC900 is a high speed optoisolator
 I built it on a small piece of veroboard in a small plastic box
 with the 2 MIDI 5pin DIN plugs mounted on the lid.
 You may want to check R1 above. In one circuit I saw it was a higher
 value (390R). I used 220R but I haven't looked at the output on a cro
 to check what the signal looks like yet. I tested it using my synth and
 it played ok and I was able to record ok.
... Deep peace and a gentle night to you.
--- PPoint 2.06
---------------