Meeting Topic: 32-bit Digital Analogue Converters: Audio Alchemy or Real Engineering?
Moderator Name: Neil Johnson
Speaker Name: Jamie Angus-Whiteoak, Salford University, UK
Meeting Location: Zoom
Recently Digital to Analogue Converters (DACs) that claim to have resolutions of up to 32 bits have become available. How do they possibly achieve such exalted levels of performance? Almost all modern DACs use oversampled multi-bit converters with noise-shaping to achieve their high performance. Oversampling and noise-shaping permits the use of a DAC with a small number of quantising levels, which is easier to manufacture. Unfortunately, traditional noise-shaping does nothing to reduce the effect of component tolerances in the DAC, because the analogue output cannot be fed back to the input.
However, modern DACs do manage to noise-shape the output from the DAC without any feedback. This piece of audio alchemy is critical to the exceptional performance of modern Digital to Analogue converters. The talk will explain how this alchemy is achieved. It will review the problems of component tolerance in DACs and show how these compromise performance. Then noise-shaping, and how it can be applied to a practical DAC — without magic or or knowing the actual converted output -- will be explained. This talk will conclude by discussing how system aspects can limit converter performance, and how you might prepare audio signals to optimise for such limitations.