This. I read between the lines the spectrum plots are taken from speaker terminals of a 1W amplifier. That's a complete system where several different variables could affect the test results and setup.
For example, the loading characteristics most likely are not purely resistive and may change at different frequencies. Within tube parameter spread one tube might handle it differently than another. This would undoubtedly create a different spectra.
I dont think the driver tube sees the speaker load....
It wasnt a 1w amplifier, just measurements
I couldnt find my 8 ohm dummyload, and 1w 1 kHz was all I could bear. Also I wanted to see if the speakers uneven impedance curve had any influence on the frequency band.
It is a 15 w triode push pull el34 amplifier.
