Teensy 40 SPDIF in and Audioshield - TeensyUser/doc GitHub Wiki

The Audio Shield Rev D has a capacitor on PIN 15, which is useful if you want to add the potentiometer to the shield. However, it prevents using the S/PDIF-Input which is on the same pin.

So if we do without the potentiometer, we can use the pin for something more useful. To do this, the capacitor must be removed. It is located on the side with the line-in / line-out socket. Since it is the only component on this side, it should be easy to find. Now the "Volume" pin on the other side is free and can be used together with the GND pin next door for a convenient S/PDIF-in connection. The easiest way is to solder a 3-pin header there.