Here the other day I updated my Elecraft K3 to MCU 3.11 / DSP 2.15. When testing the NR function I noticed that the sound was very distorted, even on NR setting 1-1. I Googled the problem and found out I'm not the only one experiencing this. I've kept the out of the box ALC settings but will try to find some better settings to solve the problem.
NR distortion with 3.11
Update: I was updating from MCU 02.78 / DSP 01.98 / FPF 00.02
More VLF experiments
10 hours ago