MM-100 wiring diagram and pin-out

The pin-out for MM-100 cable connector at the headphone side is the following:

TRRS:

Tip - L+

1st Ring - R+

2nd Ring - L-

Sleeve - R-

The wires in the headband are connecting via two TRRS connectors in parallel, so it's not important which side the cable is connected, left or right. Both versions can be used, single ended (TRS) or balanced (TRRS); the left speaker will always take only the left signal and the right speaker will always take the right signal. 

Making this cable balanced will require splitting the L and R channels into appropriate pin-outs for your amplifier.

Here's a diagram for the internal wiring to give a better picture of what's happening:

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