This application bulletin will provide the reader with an
understanding of test methods for audio digital-to-analog
converters (DACs). In particular, delta-sigma (?Σ) DACs
require a special understanding due to the nature of their
architecture. The dynamic specifications of interest for an
audio DAC are THD+N (total harmonic distortion + noise),
dynamic range, channel separation, and idle channel noise
(often referred to as SNR, signal-to-noise ratio). There are
many possible digital audio applications, but only CD-DA
(reproduction of digital audio from a compact disc) has a
standard specification defined by EIAJ (Electronic Industry
Association of Japan). Test methods for evaluating DACs
used in other digital audio applications are somewhat am-
biguous. For these applications, evaluating the DAC is
highly dependent upon the experience and knowledge base
of the design engineer. Digital audio reproduction is based
upon sampling and Nyquist theorems. This application bul-
letin will describe the operation theory of ?Σ audio DACs,
and associated test methods for these DACs.