What is DSD, the Premium Quality Audio Format?

The acronyms PCM and DSD represent the two most common ways of digitally storing music. This involves the conversion from the analog to a digital state, in order to then burn the file to a CD or make it available for download or streaming. PCM and DSD are raw, uncompressed formats. You may be more familiar with the more commonly used formats MP3, AAC, and FLAC, where music is compressed (with or without making certain compromises), so that it takes up less space.

DSD stands for Direct Stream Digital, whereas PCM stands for Pulse Code Modulation. The idea behind both technologies is the same: to digitize analog audio signals as precisely as possible. In order to do so, the signal is “sampled,” that is, transformed into 0′s and 1′s, creating a digital file that can be manipulated, recorded, and distributed in different ways.

What are the differences between DSD and PCM?

PCM is foundational to the audio CD: it’s how the music is stored to the disc. A PCM file’s resolution is determined by its level of granularity as well as its sampling rate, the former measured in bits, and the latter in Hertz. On a CD, files are stored at 16 bits and 44.1 kHz. If you increase the resolution in order to digitize the music with even greater precision, you can reach up to 24 bits and 192 kHz, the equivalent of Hi-Res in the PCM format.

DSD has been available to the public since 1999 and the emergence of the Super Audio CD (SACD), the high resolution version of a CD. What remained after this evolution wasn’t PCM Hi-Res, but rather an entirely new format whose objective was to provide even higher quality audio. Instead of 16 or 24 bits, DSD used one single bit, with a sample rate of 2.8 MHz per second.

One bit at 2.8 MHz is technically equivalent to a resolution that’s four times higher than that of the CD. In short, instead of taking 16 samples (consisting of 0′s and 1′s) 44,100 times per second, one single sample is taken (still in the form of a 0 or a 1) at a rate of 2.8 million times per second.

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Studio-grade formats

Just as there are different levels of high resolution for PCM, DSD can also reach very high levels. One bit and 2.8 MHz correspond to what is called DSD64. Why 64? It’s the multiple that turns 44.1 kHz PCM into 2.8MHz DSD. In order to get even more precise files, DSD128 or DSD256 are also options. Naturally, the one bit remains, but the frequency is increased in order to reach 5.6 MHz and 11.2 MHz respectively, and the precision of the digitization increases accordingly. DSD512 and DSD1024 also exist, but not all digital players are capable of supporting them.

DXD is linked to both DSD and PCM. This intermediate format allows for DSD to be turned into PCM at 24 bits and 384 kHz, resulting in a .dxd file intended for treatment and mastering in-studio. As far as DSF and DFF are concerned, these are simply the file extension names for DSD files. The extension .dsf comprises the music and its related metadata, whereas .dff solely contains the music. As a reminder, the extensions for raw PCM files are .wav and .aiff (with metadata).

The advantages and disadvantages of DSD

The main advantage of DSD is that it provides the highest possible definitions for storing and listening to music digitally. It’s therefore most often associated with the commercialization of the highest quality music recordings in existence. However, it does indeed take up more storage space than PCM, although this isn’t much of an issue nowadays, with hard drives that have increasingly more storage space. The only real flaw of DSD is that it isn’t widely recognized by those who aren’t Hi-Fi enthusiasts.

What devices can play DSD files?

Currently, most wireless players accept DSD files, usually up to DSD256. More high-end products are capable of playing DSD512, although files in this format are rather uncommon. As far as DACs go, some accept native DSD files, as long as it’s via a USB port. Others can receive DSD through a form known as DoP, or DSD-over-PCM, which requires either a coaxial or optical SPDIF port, or an AES (XLR) port. In this case, the DSD is first transmitted from the digital player in the PCM format, then reassembled into DSD within the DAC before being converted into analog form. This means that there is a wide variety of ways to listen to DSD quality audio.