Test results (combsample.d64) for the 6581 in my C64 attached. It has quite lame combined waveforms.
ADSR glitches
Hi Markus, out of interest what hardsid.dll file are you using? I've tried some random ones found online but the sound is a bit off in versions of VICE (<3.3) I've tried.
Attached some other recordings from real SID chips.
6581/8580 filter hard-clipping