Preamp difference : if it's not the frequency, not the slew rate, and not the harmonics, what is it ?

[RoadrunnerOZ]

I built a V76 with transformers from Ollie and NOS EF 804's, exact same circuit,

A friend bright over a real one and boy was I disappointed , they did not sound the same at all. His was better. What was the difference? I have no idea.

You could try swapping his tubes for yours see if that changes anything

 

[gyraf]

Those "replica" transformers were most hot air, perhaps?

 

[RoadrunnerOZ]

Sounds like it would be the transformers……