ABSTRACT
This chapter focuses on the visual appearance of the distortion residuals produced by totalharmonic distortion (THD) analysis. The distortion products may be low-order, if they appear alone they are simply second or third harmonic, looking basically sinusoidal. Audio commentators have been rudely dismissive of the simplest and most basic kind of distortion measurement, the totalharmonic distortion test. A Blameless amplifier results when the known distortions in the panel on distortion mechanisms have been either minimised or reduced to below visibility on the THD residual. An amplifier has surprisingly low THD, despite its conventional-looking circuitry, but its greatest advantage is its defined performance. Total harmonic distortion is the r.m.s. sum of all the distortion components generated by the path under test. The r.m.s. calculation, taking the square-root of the sum of the squares of the harmonics, emphasises spiky distortions. Intermodulation tests can often dispense with very-low-THD oscillators.
