Only after re-plugging of + 12V ignition permanently Plus useful

The ignition-Plus was not connected to Audi side. That left my new radio without function. I then got an older radio out of the closet and testing purposes connected. Also, this radio was not functioning (although it worked fine in an earlier vehicle). As guilty hence the converter in question.
The radio could reposition the ignition plus a plug on permanent 12V Plus - and lo and behold: The old radio works. A closer look at the Audi connector brings clarity:
The ignition plus, which is used by the converter is on the side of Audi (A6 2003 Audi Original Radio) not connected. In this respect, one should check the connections for 12V and ground using a multimeter and check the wiring -soweit vorhanden- on the radio. As a rule, are so imprinted on the radio. After plugging the cable to the converter (unfortunately very fiddly) it works with two radios.
It would be helpful in the plug would be described a handbook. Also for this typical problem (continuous positive / ignition plus) a chapter in the manual would be helpful. But a manual is missing completely - there is need for action for the not so experienced hobbyists.