In most cases , you connect them to an A/V or stereo reciever amp that has either connection. This would allow for digital out on the pc to the amp , giving you true 5.1 , 6.1 , 7.1 or 8.1 sound depending on your sound card and amp . Some highend pc speaker systems also have the same option .
This may sound silly but does a sound card need spdif in and spdif out to hook up a mixer to the computer? Or is an spdif connection the same in both directions? Thanks in advance for any help.