The vast majority of modern audio DACs use a Delta-Sigma DAC chip because such chips are now tiny, manufactured by companies that sell them in mass relatively cheaply, and have become outstanding in quality. Examples of such chips include the California USA Company’s ESS Technology 9038PRO SABRE chip used in many of the highest-end DACs. Even their slightly lesser chip, the ESS Technology 9028PRO SABRE has been used impressively in some high-end DACs with which I am familiar such as the Mytek Brooklyn DAC + at only $2195.
There are, however, a few companies that use other methods. One novel alternative is illustrated by PS Audio’s DirectStream (DSD) DAC at $6000 that stands out because of its use of a Field Programmable Gate Array (FPGA) which is a circuit board that is programmed with software (that can be upgraded on a regular basis) to perform the essential conversion, and does so using DSD. This FPGA method for use in Hi-Fi audio, however, requires sophisticated software to run which most audio designers do not have the knowledge to assure (PS Audio, for example, leads their effort with one incredibly talented man: Ted Smith). The DirectStream DAC has been my reference for a number of years now.