So my TV was (connected to the same time a PlayStation 3, Sky + HD receiver and a multimedia hard drive is) summarily connected via an optical cable to the converter and this tested in turn with a Coaxial cable to my Dolby system and immediately was everything. Everything worked in Dolby Digital quality up to my receiver, which was transferred to the speaker only on stereo and had a little delay in the lip sync. So in troubleshooting, which was also quickly and unceremoniously dissolved.
If anyone should have the same problem with me I had to stop in the receiver menu that the Dolby Digital signal via the HDMI cable is to be output. Also I have in my TV's menu (Toshiba 40TL838G) adjust the audio delay to 10ms, so that the synchronization is fully prepared.
So the Opto Coax converter is an absolute buy recommendation for those (like me) who have a Dolby system without an optical input but have not want to spend money on a new expensive new equipment.