If they're hooked up with digital connections, direct stereo or pure direct or whatever it's called will not work, as the reciever will be making a digital to analog conversion of some kind. If the player is hooked up with analog connections, the conversion is done in the player itself, and the receiver can be set to direct mode, where it will simply amplify the analog signal sent by the CD player.

I am the Doctor, and THIS... is my SPOON!