Hi
Thanks for this, but in SPICE the input impedance of the probe should not matter. Essentially what I have done is disconnect the amplifier from the source signal and all I am doing is measuring the source FFT.
This should be a perfect sinewave - it is SPICE.
To answer your questions, my input is 0dB (obviously), my second harmonic is -70dB, my 3rd harmonic is -40dB.
Picture is attached.
Again, I would expect, in a theoretically perfect system (which SPICE is meant to replicate) that a sinewave just gives a spur at the fundamental.
I cannot measure the distortion of an amplifier if my 'perfect' sinewave input has got harmonics.....
Any further comments would be greatly welcomed