From: rvdm@oce.nl (Ruurd van der Meer)
Subject: A working MIDI connector box for PAS 16 and Soundblaster
Originator: rvdm@st13-sys4
Organization: OCE Nederland B.V.
Date: Tue, 22 Dec 92 08:13:17 GMT

(Re:Re: Looking for that Sound-Blaster to MIDI circuit again.)
The next circuit shows a MIDI connector box for soundcards. Often these use
the game connector for MIDI. Pin 12 and pin 15 are resp. midi transmit and midi
receive. A joystick can still be connected, because these pins do not conflict.
Just put also a 15 pin game connector on your MIDI box if you want. 
A part of this scheme (for the Soundblaster card) I found on the net some weeks ago. This scheme also works for the Pro Audio Spectrum 16. There are two IC's,
some resistors and a 1N914. To test the box: connect midi in with midi out, 
and run "MIDITEST", a program supplied with the PAS 16. If it fails, change 
the resistor 5K6, which value strongly depends on the optocoupler used. 


15 pin D connector             
                                          220R
pin-1 +5v ----+--------------------------/\/\/\---------------\
              |                                                \ 4
              |                                          Gnd--2      MIDI OUT
              |      |\      |\            220R                / 5
pin-12 tr >---|------| o-----| o----------/\/\/\--------------/
              |    14|/ 13 12|/ 10
              |                            220R
              +---------------------------/\/\/\-------------\
              |                                               \ 4
pin-15 rx <---|--------------------+                    Gnd--2      MIDI THRU
              |      |\      |\    |        220R              / 5
              |   +--| o-----| o---+-------/\/\/\------------/
              |   | 1|/ 2   3|/ 4   
              |   |                 
              |   +------+
              |   5K6    |                       220R
              +--/\/\/\--+    +------+----------/\/\/\--------\
              |B         |C   |A     |                         \  4
            +-|----------|----|-+    |                                MIDI IN
            |  8        6     2 |  -----                       /  5 
            |                   |   / \ IN914               +-/
            |      6N135        |   ---                     |
            |                   |    |                      |
            |           5     3 |    |                      |
            +------------|----|-+    |                      |
                         |    |K     |                      |
pin-5 Gnd  --------------+    +------+----------------------+


-+- is a wire connection.
 |

6N135 is a high speed optoisolator, the output current is not so high (6N139
is better). But if you buffer output 6 (with LS7404) it will work. 
Invertors : IC LS7404.
Note: Do not connect MIDI IN pin 2 to Ground 
Good luck !

Ruurd van der Meer (rvdm@oce.nl)

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