SB Midi Cable

Posted on Feb 5, 2014

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 t

SB Midi Cable
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he 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. 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 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. 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...

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