Hi Dbphd, the way that tubes operate closer to the rules of human hearing is through the lack of odd-ordered harmonics, which comes from greater linearity and less need for feedback. Feedback runs counter to the rules of human hearing (i.e. adds high order odd harmonics).
Human hearing uses high-order odd harmonics as a way to measure loudness. Our ears are so sensitive to these harmonics that fractions of a percent is easily audible. We hear them as a 'sheen', 'hardness', 'clinical', 'brittle' or 'chalky' quality in the reproduction.
Human hearing uses high-order odd harmonics as a way to measure loudness. Our ears are so sensitive to these harmonics that fractions of a percent is easily audible. We hear them as a 'sheen', 'hardness', 'clinical', 'brittle' or 'chalky' quality in the reproduction.