Where's the shunt resistor for the attenuator? Without that, you're not driving the transformer with the correct source impedance. Nor attenuating properly.
The phono preamp have 60pF to 70pF range at our about 85x gain including strays, have I to subtract this value of the 100-220pF that I have loaded the secondary, for example use 40-150pF in place of 100-220pF?
edit: That may have been a different thread. In any case, do not forget to take into account the probe's capacitance. From your Post 11:
4) Connect an oscilloscope across the secondary of the input transformer
using a x10 low capacitance oscilloscope probe. You MUST use a x10 probe in
order to prevent adding SIGNIFICANT capacitance across the secondary of the
transformer. Make sure that you have "calibrated" the oscilloscope probe
trimmer capacitor before starting this procedure.
