What?
@tomchr would have something to say about that; and probably all the Topping engineers, too.
Very few I should say. Because if you really think of it. Audio is already a dead horse which has no meaning of improving and technology/knowledge was already proven and set for decades. Surely designing ICs are more extensive. Still it's just something someone loves audio. Like johnc who designed opa1622 opamp.
I will be doing my thesis soon, and including my friends no one is doing audio related topic. The most related is probably neural signal amplifier. Also designing opamp using 32nm process etc. Designing audio is easy. I didn't have the scope for years until I finally realize that audio is just something in your heart. I'll be doing 32nm 1V opamp or 0.2nV/sqrthz 200MHz BW 100dB gain amplifier or something like that. And some others would to tele, control, DSP etc.
And when I say topping I didn't mean in such way. I was talking about making it stable is easy. And making this level of performance is nor hard at all. I didn't mean that topping has all the great engineers or anything.