As I mentioned in my previous post, the Turtle Beach Audio Advantage Micro uses a USB interface by some company called C-Media Electronics, Inc. A quick Google search finds them in Taiwan. This is the present and future of electronics manufacturing, Taiwanese companies both designing and manufacturing items branded by American companies. It's why PowerBooks ship direct to you from factories on Taipei.
C-Media is quite happy, I'm sure, to sell anyone with enough cash the exact same chip set they sold Turtle Beach, the CM102 USB Audio Controlller. And the provided technical documentation is quite interesting. It looks like almost all the needed functionality you would need to implement a AAM like device is on this single integrated circuit. All that would be needed would be a USB connector, circuit board, a variety of capacitors and resistors and a TOS-Link emitter package; it'd be fun to slap these things together if I did that sort of thing.
But not a lot of help towards knowing what the driver should send the device to get my goal of AC-3 playthrough. It does mention something called "Xear 3DTM Sound Technology," but that is probably something proprietary and useless to me, so I will ignore it for now.
My answers are elsewhere.