Hi to all, during assembly of the amp2 board I observed a difference between the value stamped directly on board and the PDF instruction. This difference regards the R210 resistor stamped in the bottom side of the board, that appears to be R211 in the PDF layout. The result of consulting the electric circuit is that it must be R211, it's quite simple to verify, because it has a pin in common with the C203 capacitor.
I haven't find this argument treated by anyone else in the forum, maybe I haven't searched enough... excuse me
So, the right value is 20K, corresponding to R211 as you can easily verify in the schematic circuit.
Good work to all audiophile friends.