Top panel: the blue line is the scaled extracted echelle order from Keck/HIRES, the black continuous and dashed lines are the FASTWIND profiles for the indicated parameters. Middle panel: blue and red lines are the line profiles normalized using the procedure discussed in the text of Appendix A, while the black lines illustrate the effect of a change of ±0.2 dex in log g at constant T_eff. Bottom panel: here we compare the smoothed, normalized profiles for TNG/HARPS-N, Keck/HIRES and LAMOST, illustrating the good consistency obtained for all three datasets.