A good Total Harmonic Distortion (THD) percentage for a high-fidelity audio amplifier is generally considered to be below 0.1%, with many premium audiophile solid-state amplifiers achieving ultra-low distortion figures under 0.001%. At these exceptionally low levels, the harmonic distortion introduced by the amplifier circuitry is completely imperceptible to the human ear, ensuring pristine, transparent sound reproduction that stays faithful to the original recording source. While tube amplifiers traditionally exhibit higher THD figures—often ranging between 0.5% and 1.0% or more—listeners frequently find their specific harmonic distortion profile pleasing due to the addition of warm, musical even-order overtones.