The complete schema is drawn above (click on it for a real size image). I builded and tested it in this form. Some parts are optional or do not apply (it is an adaption of the SCMS-killer circuit).
Part B is the only essential part of the circuit. It adapts the signal to regular S/P-DIF levels. I used 390 and 100 ohm resistors, but the official values are 374 and 90.9 ohm.
Part C is optional, but gives some extra protection. Like providing galvanic isolation. Some implementations omit it. I used a Amidon T-37-0 core, but Digi-Key sells the official part for this: 257-1025-ND (Schott Corp. no. 67129600) for $9.
Below is an impression of how the wire should be wound around the core. There are two wires: one coming from the left, seven times through the core and back to the left. The other wire comes from the right, also seven times through the core and back to the right. I used isolated 0.35mm (0.0137″) wire.
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