Interactive Connector Diagram
Click or tap any pin in the diagram below to inspect its signal assignment, electrical specification, and wire colour standard.
Click any pin to view its signal assignment, electrical spec, and wire colour.
Supported Systems / Found On — Retro Machine Hubs
This connector is used on the following retro computer systems. Click any colour-coded badge below to open its full board-level repair, diagnostic, and schematic Machine Hub:
Connector Specifications
Baud Rate
31,250 bps, 8N1 (5 mA Opto-Isolated Current Loop via Sharp PC900V)
Standard MIDI Pins
Pin 4 = +5 V Current Source (via 220 Ω), Pin 5 = Signal Sink, Pin 2 = Shield (MIDI OUT only)
Atari Hidden THRU
On Atari ST MIDI OUT: Pin 1 = +5 V THRU Source (via 220 Ω), Pin 3 = MIDI THRU Sink!
Full Pin Assignment & Wiring Reference
| Pin | Signal Name | Direction | Electrical Spec / Role | Wire Colour / SCART / Adapter Target |
|---|---|---|---|---|
| 1 | ATARI MIDI OUT: THRU +5V Source! | Out | On Atari ST MIDI OUT socket ONLY: +5 V Current Source (via 220 Ω) for MIDI THRU! (NC on MIDI IN) | Splitter Pin 4 (THRU) |
| 2 | SHIELD GND (MIDI OUT ONLY) | GND | Cable Shield Ground on MIDI OUT (Disconnected on MIDI IN to prevent ground loops!) | Bare Shield |
| 3 | ATARI MIDI OUT: THRU Signal Sink! | Out | On Atari ST MIDI OUT socket ONLY: Hardware MIDI THRU Data Sink! (NC on MIDI IN) | Splitter Pin 5 (THRU) |
| 4 | MIDI CURRENT SOURCE (+5V) | I/O | Standard MIDI Current Loop Positive (+5 V via 220 Ω resistor to Optocoupler Anode) | Red / White (Pin 4 -> Pin 4) |
| 5 | MIDI SIGNAL SINK (DATA) | I/O | Standard MIDI Current Loop Data Sink (0 V = Logic 0 Active Current; +5 V = Logic 1 Idle) | Blue / Black (Pin 5 -> Pin 5) |
Building an Atari ST Y-Splitter (MIDI OUT + MIDI THRU) & MIDI-Maze Ring
Driven by a dedicated Motorola MC6850 ACIA at 31,250 baud (500 kHz / 16) with zero timing jitter, the built-in MIDI IN and MIDI OUT ports made the Atari ST the studio standard for Cubase, Notator, and Pro-24. Because the ST case only had room for two 5-pin DIN sockets instead of three, Atari engineered the MIDI OUT socket so that **Pins 4 & 5 carry standard MIDI OUT**, while **Pins 1 & 3 carry hardware MIDI THRU**!
- Atari ST Dual MIDI OUT + MIDI THRU Y-Adapter: Wire a 5-pin DIN Male plug (for the ST's MIDI OUT jack) to two 5-pin DIN Female sockets: Socket 1 (MIDI OUT) connects to Male Pins 4, 5, and 2; Socket 2 (MIDI THRU) connects its Pin 4 to Male Pin 1, its Pin 5 to Male Pin 3, and its Pin 2 to Male Pin 2!
- 16-Player MIDI-Maze Ring Network: Connect MIDI OUT of Atari ST #1 into MIDI IN of Atari ST #2, and MIDI OUT of ST #2 back into MIDI IN of ST #1 (up to 16 machines in a daisy-chain ring!).