Thank you for your quick answer. It would be nice if your information would be written somewhere with the unit which I got. It would have saved me money and a lot of time.
I will try with another cable which has the leads according to your drawing and three RCA connectors. Most likely it works fine, the wires are possibly used in a not transparent way (browsing the net I found more than one way the mini jack can be wired). I also will try using the S/PDIF connection.