TRS MIDI Type A vs Type B: Pinout Differences

This article provides a clear overview of the differences between Type A and Type B TRS MIDI adapters, explaining how traditional 5-pin DIN connections translate to a 3.5mm stereo jack. You will learn the exact pinout configurations of each type, why two competing standards emerged in modern music gear, which brands use which format, and how to connect devices that use different standards together.

The Origin of the TRS MIDI Split

Traditional MIDI hardware relies on bulky 5-pin DIN connectors. As audio gear, synthesizers, and controllers became more compact, manufacturers shifted to using smaller 3.5mm (1/8-inch) or 2.5mm TRS (Tip-Ring-Sleeve) jacks to transmit MIDI data. Because the MIDI specification only requires three conductors (Source, Sink, and Shield), standard stereo audio jacks offered an ideal footprint.

However, before the MIDI Manufacturers Association (MMA) established an official specification in 2018, different hardware companies independently wired their jacks in conflicting ways. This resulted in two primary wiring schemes: Type A and Type B.

The Pinout Differences

Standard 5-pin DIN MIDI uses three active pins:

• Pin 4: Current source (often referred to as MIDI + or pull-up voltage)
• Pin 5: Current sink (the data line carrying the MIDI signal)
• Pin 2: Shield/Ground

Both Type A and Type B assign the Shield (Pin 2) to the Sleeve of the TRS connector. The difference lies strictly in reversing the connections of the Tip and Ring.

Type A (Official MIDI Standard)

Type A was adopted by the MIDI Association as the universal specification (RP-054). Its wiring layout is:

• Tip: 5-pin DIN Pin 5 (Data / Current Sink)
• Ring: 5-pin DIN Pin 4 (Power / Current Source)
• Sleeve: 5-pin DIN Pin 2 (Shield / Ground)

Type B

Type B was developed independently by several prominent synthesizer and controller manufacturers before the official specification was finalized. Its wiring layout is:

• Tip: 5-pin DIN Pin 4 (Power / Current Source)
• Ring: 5-pin DIN Pin 5 (Data / Current Sink)
• Sleeve: 5-pin DIN Pin 2 (Shield / Ground)

Hardware Compatibility

Because the polarities of the Tip and Ring are inverted between the two types, a Type A adapter will not work with a Type B device, and vice versa.

• Common Type A Brands: Korg, Roland, Akai (newer models such as the MPC Live and Force), Make Noise, Dreadbox, and Boss.
• Common Type B Brands: Arturia (e.g., BeatStep, Keystep original), Novation (e.g., Circuit, Launchkey series), 1010music, and older pre-standard hardware.

Connecting Type A to Type B

Plugging a standard 3.5mm stereo cable directly between a Type A device and a Type B device will not transmit data because the data and power pins will not align correctly. However, you will not damage the hardware by doing so; the signal simply fails to pass.

To bridge a connection between a Type A device and a Type B device, you have three options:

1. Cross-over Cable: Use a specialized TRS cable that swaps the Tip and Ring connections from one end to the other while keeping the Sleeve connected straight through.
2. DIN Intermediary: Connect each device to its respective matching adapter (one Type A to DIN, one Type B to DIN) and join them using a standard 5-pin DIN MIDI cable.
3. Switchable Adapters: Use universal TRS MIDI adapters that include a toggle switch to invert Tip and Ring connections on demand.