where/who builds the Borresen / Aviik Denmark gear?

@OP, there are two factory tour articles on Hifiknights.com

Borresen and Aavik/Ansuz do a lot of their "manufacturing" operations in house.

I put manufacturing in quotes because there are very few entirely vertically integrated companies in the modern world, least of all small companies (i.e. most of the hi fi industry). Most manufacturers assemble their products with varying degrees of in house production and sub assemblies sourced from OEMs.

good info yoyoyaya, thank you

I Googled "Borreson Factory Tour" and found a good article on HiFi Knights but @yoyoyaya beat me to it. Here is the link:

Borreson Factory Tour

You're welcome OP. Audio Group Denmark make excellent products with a lot of genuine technical innovation.