Soundcheck is a non profit organization that does double blind tests on RPI DAC hats
In the last soundcheck they used multiple amps and results were judged by a panel of people
They tested Katana , Primo , Boss , Pecan PI and more
On first Ncore amp tested (very good THD+N) Katana and Boss are in the first 3
On second AMP tested (AB class) Katana and Boss placed in the first 3.
More info below.
https://forum.volumio.org/volumio-so...40.html#p64146