ABSTRACT
Single-stage, 1-bit sigma-delta converters are in principle imperfectible. We prove this fact. The reason, simply
stated, is that, when properly dithered, they are in constant overload. Prevention of overload allows only partial
dithering to be performed. The consequence is that distortion, limit cycles, instability, and noise modulation can
never be totally avoided. We demonstrate these effects, and using coherent averaging techniques, are able to display
the consequent profusion of nonlinear artefacts which are usually hidden in the noise floor. Recording, editing,
storage, or conversion systems using single-stage, 1-bit sigma-delta modulators, are thus inimical to audio of the
highest quality. In contrast, multi-bit sigma-delta converters, which output linear PCM code, are in principle
infinitely perfectible. (Here, multi-bit refers to at least two bits in the converter.) They can be properly dithered so
as to guarantee the absence of all distortion, limit cycles, and noise modulation. The audio industry is misguided if
it adopts 1-bit sigma-delta conversion as the basis for any high-quality processing, archiving, or distribution format
to replace multi-bit, linear PCM