OK: https://github.com/hifiberry/hifiberry-dsp/blob/master/sample_files/dspproj/dacdsp-v12-1.dspproj (Had to remove mute, though)
Solution is to open both. Copy graph fullrange-fir into emptied acdsp-v12-1 schematic. Hardware configuration from acdsp-v12-1 must of cource be kept.
Tried for hours to find the difference but gave up.
PP3, HifiBerryOS, Playing music from iphone over AirPlay to RP3, DAC analog out, SigmaStudio