I have a 2012 Mac Pro 6-core tower that has a built-in optical audio out jack. I just ordered a Logitech Z906 set of 5.1 Surround Sound THX speakers with controller. I am assuming that I will be able to connect an optical cable directly between the Logitech controller and the Mac Pro, but how "exactly" do I get the Mac to send out true 5.1 signal vs standard stereo? I have searched the Internet an YouTube and everything I find is confusing or contradictory. Anyone have any advice? THANKS!