Simple two stage CFA , has anyone seen such topology? I used low cost version of 240/9240 biasing 1A 24w but it gives very low distortion at 30W/20khz. This is just a "prova" design.
N.pass/Nakamichi has with k170/J74 if someone can remind me the reference.
You are welcome.
I suppose you are referring to the USSA5 amp. For the distortion- if that really matters - see below real measurements at 1W and 6Wrms for 1KHz. Note that with H2 possible cancellation (not the goal here) THD would be about 0.002% of only H3 at 1Wrms. The CFA topology has a poor PSRR so you need a very good PSU.
I have USSA3 with jfet input and USSA5 with bjt inputs. Both amps have their own different sound signatures, you choose which one you prefer.
One thing though is that jfet provides less gain than bjt as input stage so USSA3 has a lower damping factor than USSA5.