I came across a very interesting video:
Steve Sells presenting the Naim Statement design.
Among many things, he briefly describes Naim’s approach and choices regarding distortion.
Naim could have designed distortion free circuits but chose a different approach:
“simple circuits that have distortion […] pleasant to our ears”
By “pleasant distortion” I guess he means second order harmonic distortion.
NAP500 and NAPS1 having similar designs also have similar approach regarding distortion.
–> https://youtu.be/yqDlAV_tr2s?t=391
Other companies, such as Nagra, CH Precision and Soulution, have different approaches regarding distortion.
Another interesting video presents CH Precision’s head quarter and production facility, and also explains the company’s choices regarding circuits design.
Can be found on YouTube : “AnalogPlanet Visits CH Precision in Switzerland”
It is rather interesting to hear about both Naim and CH Precision approaches.