Modern class D amps are terrific, but it's annoying to see THD brought up as a measure of audio quality. THD is terrible measurement - its value is not that it'

Modern class D amps are terrific, but it's annoying to see THD brought up as a measure of audio quality. THD is terrible measurement - its value is not that it's relevant (except to demonstrate things aren't actually broken), but rather that it's easy to measure. An amplifier's ability to reproduce a 1khz sine wave into a resistive load tells us nothing about how it behaves in the face of 8-10 octaves of frequency range and the real dynamic range and harmonic complexity of actual musical content, when hooked up to the absurdly complex and nonmusical behavior of real speakers. The 5% THD of single-ended tube amps that people who've never heard one tell us proves how "inaccurate" they are is inaudible, but the grimy, dull sound of cheap amps that have excellent THD specs is plain to hear. It's frustrating, in part because this stuff is, so far, mostly impossible to measure. It's hard to get a sense of how an amplifier will sound from specs.