15 PIN D-SUB MALE to the soundcard
5 PIN DIN 180° (DIN41524) MALE to MIDI IN synthesizer port
5 PIN DIN 180° (DIN41524) MALE to MIDI OUT synthesizer port
The Creative Labs Sound Blaster and compatible PC sound cards repurposed the 15-pin DA-15 gameport connector to carry MIDI data, with pin 12 (MIDI TX, computer to keyboard) and pin 15 (MIDI RX, keyboard to computer) handling the serial stream at 31.25 kbaud. Because the gameport pins cannot drive the 5 mA current loop required by the MIDI 1.0 Detailed Specification, the adapter cable contains active electronics — a logic buffer, current-limiting resistors, and an opto-isolator — powered by +5 V tapped from the gameport supply pins. The two DIN-5 sockets on the adapter follow the standard MIDI connector arrangement: pin 2 carries the cable shield/ground, pin 4 is the current source (+5 V through 220 Ω), and pin 5 carries the MIDI signal; pins 1 and 3 are unused. Sound cards of this type emulate Roland MPU-401 UART mode, the de-facto PC MIDI interface standard established in 1985.
Schematic 1
Notes
- MIDI OUT connector must be connected with synthesizer MIDI IN port.
- MIDI IN connector must be connected with synthesizer MIDI OUT port.
- The adapter cable contains active electronics and requires the +5 V supply from the gameport (pin 1 or pin 9) to operate; a passive cable will not work.
- The MIDI IN opto-isolator prevents ground loops between the PC and the synthesizer; the shield on pin 2 must NOT be grounded at the MIDI IN receiver end of the DIN-5 cable.
- Maximum DIN-5 cable length between adapter and synthesizer is 50 ft (15 m) with shielded twisted-pair cable, per the MIDI 1.0 Detailed Specification.
- The 2014 CA-033 update to the MIDI electrical specification permits 3.3 V signalling and adds optional ferrite-bead RF filters on the DIN-5 signal pins; the connector and pin assignments are unchanged.