Z-Diode D5 muss einfach nur gedreht werden und Kondensator / Widerstand vor "Audio IN" in der Reihenfolge angepasst werden. Niemand hat jemals zuvor so ein Projekt auf die Beine gestellt und es ist absolut unangemessen jetzt hier den "Dicken" zu machen.
Sorry for doing this in English - I can follow the conversation, but I'd probably confuse everyone if I wrote in German...
I've turned around D5, which drops 3V for the SID. Problem is that it drops from 11.6V to 8.6V, which is not enough to even get sound out of the 8580... So I took D5 out all together and tried different Zeners across the jumper. Using a 2.7V one, I got 8.75V on the SID, but it sounded very weak and noisy. With a 2.4V one, the voltage was spot on (9.06V). The sound was still a little weak (compared to using a 6581 at least). Using a 2V Zener, the SID voltage is around 9.4V and the sound is good, only slightly less "full" than using a 6581 (though note that I am not a SID expert, let alone a purist that hears the difference between the two).
I think my preferred option is to use a 6581. I might put D5 back, but a 2V zener would probably give better results if I had to revert to an 8580...