DSD is the abbreviation of Direct Stream Digital, which stands for direct bit stream digital coding, and it is the coding mode of SACD(Super Audio CD). It is a high-resolution digital audio specification jointly formulated by Sony and Philips in 1996.
The difference between DSD and linear PCM
PCM (Pulse Code Modulation) is the most common audio coding format, almost all common audio such as wav, ape, flac, mp3, etc. Both are pulse code modulation formats.
The principle is simple: first, prepare a set of specified level values (for the concept of level, it can be simply equivalent to voltage), such as -3, -2,-1, 0, 1, 2, 3, etc. And give each value a number, just like ABCD, but we use binary numbers (that is, 0000) for these level values.
Then find the value closest to the sampling level from the previous set of specified levels by rounding, then record the number closest to the value, and then conduct the next sampling ... So repeatedly, the original analog signal from the microphone can be recorded with a set of binary numbers (that is, digital signals), and the recorded digital signal is PCM.