The A1 speaker settings are for the six channel analogue outputs only. Just make sure you have either auto or bitstream selected for SPIDF output on the A1 and let your audio processor deal with the data stream. You should also run analogue cables to your processor from the A1 and give that a try. You will get pure uncompressed PCM sound via analogue and it’s considerably better than SPIDF. If you want to try that, post back and I’ll tell help you set it up.