When you have a 5.1 or 7.1 surround sound card you can use 3 or 4 stereo output channels for on your mixer!
Use the speaker selection in the settings of Freeplayer for this:
The GREEN output on your soundcard -> Select SPEAKERS FRONT
The BROWN or BLACK output on your soundcard -> Select SPEAKERS REAR
The ORANGE output on your soundcard -> Select SPEAKERS CENTER/LFE
The GRAY (only on 7.1 cards) output on your soundcard – > Select SPEAKERS CENTER REAR

You need to connect the cables to your mixer first before setting the audio settings in Freeplayer!

Always install the correct audio-driver delivered with your sound card. Also check the manufacturer for updates for your sound card.

When using a 5.1 or 7.1 enable the Dolby Surround mode in the driver first to be able to enable the multi speaker selection. See for an example the screenshot below.

Soundcard tip : USB 7.1 card for a good price, working with mutiple channels in Freeplayer : Windows 10 Driver can be downloaded below for these cards.

http://www.bol.com/nl/p/external-sound-card-7-1-usb-2-0/1003004008484665/