This is a superb preamp which I originally breadboarded and sounded so nice that never moved it to a proper chassis. The 01a exceeded my expectations. It’s running with a MOSFET gyrator with mu-follower output. Operating point can’t be definitively be improved as filament bias resistor at hand dictated the bias point. Anyway, sound is clear, very warm and with great tone. Better than 26 in my opinion, but have to do side by side testing to make final call.
I think I posted circuit before, if not let me know if your are interested in it
Thoriated tungsten filament have something special indeed
