So I called allaboutadapters and asked a few questions. Apparently, this adapter will extract surround sound from an LPCM audio format and still send stereo to the TV. Here are the gotcha's:
1. The source (from the Apple or ATT box) must output LPCM audio format. It won't work if the output is any other standard.
2. If using the Toslink output on the adapter box, it will only output Dolby Digital 5.1.
3. Is using the analog outputs on the adapter box (4 mini jacks supporting 7.1), you can get LPCM 8 channel, LPCM 7.1, LPCM 5.1, and LPCM 2 channel.
So, now I need to find out what standard the ATT and Apple boxes output and I need to find out what my Marantz will decode. (I know that it can handle 5.1 with no problem, but I don't know about LPCM surround sound signals.
I wish manufacturers would make things simple and know that not everyone wants to or can fire up their surround sound system when they want to watch a little bit of TV. Designing HDMI devices to talk to each other is all well and good, but not allowing multiple audio formats to run simultaneously is a big mistake. At the very least it should allow 2 channel to coexist with whatever multi channel standard is being used. Grrrrr.....