Of course, I also wanted to have somehow transfer the sound. Therefore I have to transfer even a TOSLINK (optical) cable fetched to the sound via the S / PDIF jack to the AV receiver. After I plugged it all, I was surprised when suddenly standing in the sound output in the system setting "HDMI". I thought I had proposed that the Mini DisplayPort, the sound is often not transmitted, at least it was the MacBook Pro as my father (maybe it was the cord).
So it is me of course prefer the sound through the HDMI cable is transmitted (limited clutter a). It can also be transmitted via a TOSLINK cable maximum 6.1 sound. But my AV receiver supporting up to 7.2 channels.
All in all, I recommend this only!