During development of cheap Stax amplifier, got a idea about hi-end symmetrical model.
Sort of cheaper version of WooAudio WES (5000$)
The components selected to best linearity and low distortion.
Endstage can give ~325Vrms, choke max 390Vrms. That's enough to damage ears, and maybe destroy the headphones.
Input full sensitivity is <1Vrms; for 100dB out it should be ~0,2Vrms.
For example to decrease input sensitivity, different input transformer should be used (LL1922 8:1+1 or 4:1+1)
Therefore very small distortion is made, also no feedback used here. (bonus)
Second harmonic is canceled due to PP mode, the 3rd is about 0.05%, the 4th is ~0,003%.
Inductors with a mid tap, is good way to improve symmetry of PP stages and distortion.
800H is a huge number, about XL = 5megohms @ 1kHz .. (This gives horizontal loadline => very low distortion)
Next upgrade would be amorphous core or even a silver windings model (~2000€/choke)..
Lundahl does not make PP chokes, therefore a 5 mA model used.