@clustrocasual amazing thanks for the detailed reply. I will try and learn some from Skunkie’s work on the Sun Audio.
There seems to be more awareness about the Sun Audio amp I guess maybe because it’s been around for longer in its current form.
I get the feeling the Sun Valley may not have had the Hashimoto as standard for as long.
Out of curiosity what is wrong with GNF?. Is it considered a less pure design as in if it was a better circuit it shouldn’t need it ?