I was having trouble setting up surround sound on a PC with an integrated Realtek HD Sound Card ALC898. My problem was that although I had a 7.1 soundcard and a 7.1 sound system, not all my speakers where playing.
After checking pulseaudio I noticed that my soundcard was detected only as 5.1 compatible but with two audio inputs, so I was left with the task of turning one of the inputs jacks into an output (preserving one of the inputs for my microphone).