I have a NUC DN2820FYKH with o/s of windows 8.1 running windows media centre with latest bios update and intel drivers. I am feeding the HDMI output from NUC directly into my TV. I have connected TV's monitor out to the COAX input of my AV receiver (my AV receiver does not support HDMI, only SPDIF Optical/Coax inputs). In this configuration, I am only able to setup stereo speakers under Playback > Devices> Configure. I cannot setup/output 5.1 sound as it is not visible in Audio Channels list (only Stereo is visible). This configuration does provide 5.1 sound when feeding a signal from my set top box (in lieu of the NUC). Any ideas on how I can get 5.1 working from my NUC. Is the issue caused by HDMI handshaking between the NUC and the TV, limiting the available options or is it a driver issue or something else?
Does the coaxial connection support S/PDIF?
Did you try playing surround audio content with a surround sound capable media player? The player should include the necessary codecs.