A worst-case analysis for analog-quality (alias-free) digital dynamics processing

A fundamental problem of digital dynamics processing is that distortion pro ducts are produced which alias below 20 kHz. An analysis of sine-wave clipp ing shows that a 5-MHz internal sampling rate is required to effectively at tenuate aliasing components. A test signal consisting of a pair of closely spaced sinusoids that are slowly swept in frequency is suggested as a means of revealing aliasing distortion in typical digital audio systems. Many cu rrent digital audio products produce audible aliasing distortion when passi ng this test signal. It is suggested that there is a correlation between th e amount of aliasing distortion produced in digital dynamics processors and their sonic qualities.