What to know Direct Stream Digital (DSD)

Computer Audio has been a hot topic in recent years. Digital music files with sampling frequencies from 76.4kHz to 192kHz/24-bit are increasingly popular and are considered mainstream sources for audiophiles besides Redbook CDs and LPs. However, it seems that hi-res files will soon become obsolete when digital equipment manufacturers and audiophiles have paid the DSD (Direct Stream Digital) format with outstanding sound quality great attention.

Currently, a DAC with a resolution of 192kHz/24bit is very common; besides, some decoders have integrated the ability to support files with higher sampling frequencies up to 384kHz/32Bit. Since the beginning of this year, with CES 2014, the hi-end audio industry has witnessed a big change when audio companies introduced much hardware that supports direct playback of DSD (Direct Stream Digital) format without converting to PCM as before. In addition, the increasing sales of DSD music sources have helped this format develop extremely quickly and attract significant attention from audio players around the world. Let’s take a look at the basics related to the DSD format.

What is DSD?

DSD is a recording system used on the previous SACD (Super audio CD) disc standard. There are many objective and subjective reasons, SACD disc format has not achieved the expected success. However, many recording engineers have chosen and applied the DSD recording technique in their work. DSD streaming is not easy unless you have professional equipment. Sony has come up with a way to play DSD files from VAIO computers and SACD players. SACD discs are encrypted with copy protection so that even DSD-capable readers can directly play files stored on SACD-formatted discs.

PCM (Pulse Code Modulation)

The PCM (Pulse-code Modulation) standard can be seen as an uncompressed digital format standard. This system encodes a sensitive digital signal according to the SIN waveform of an analog signal. The higher the sampling frequency and the number of bits, the more accurately the analog signal will be simulated. Currently, the sampling frequency of PCM format files can be up to 352.8kHz or more; however, DACs are usually limited to 192kHz. PCM can usually be viewed in WAV, FLAC, AIFF, and M4A formats on a computer.

The DSD standard has a very high sampling capacity of 2.8224MHz (2,822,400 samples/sec). The sampling capacity of DSD is 64 times faster than that of CD, but the sample length is only 1 bit. If that bit is one, then signal amplitude increases, bit is 0, then signal amplitude decreases. All music waves are encoded into 0 and 1 pulses of different densities to simulate the generation of analog SIN waves. When stored on a computer, the DSD has the file format of *.DFF or *.DSF. In addition to the previous 2.8224Mhz sampling rate, DSD allows sampling more than two times higher with the current computing power, meaning the sampling rate will be 5.6448 Mhz, and some recordings have been made at the frequency of that sample number. You can sometimes see DSD recorded as DSD64 or DSD128 (aka Double DSD); the numbers 64 and 128 are considered multiples of the CD sample rate (44.1khz).

Today, some DACs can even play DSD files sampled at 12.288Mhz equivalent to DSD256, such as around Audio e20 Mk III or Antelope Audio Platinum DSD recordings recorded at the above sampling frequency can be said very rarely. However, with continuous technological changes in recent years, it is very close to the recording technology approaching the DSD256 standard.

Advantages of DSD format

Record labels have come up with PCM recording and playback solutions at very high resolution, and their sound is already very good. So, why do they need another format standard called DSD? The only reasonable answer is that DSD is of better quality than PCM. So why can DSD give better performance than PCM? The answer is not in the encoding problem when recording but in the audio decoder when playing. From a technical perspective, the PCM format needs a complex filter to reproduce the sound wave better; the higher the sampling frequency, the “lighter” the filter will be. For DSD, due to its very high sampling frequency nature, it is only necessary to use simple filters at low frequencies, similar to those in the loudspeaker crossovers. Reducing the level of filtering will make the sound less different from the original.

Standard DoP (DSD-Over-PCM)

The Microsoft Windows and Apple MAC OS operating systems can only playback audio through the PCM format. So, playing back a DSD file without converting it to PCM is a problem that needs to be solved. A team of experts has devised a way to trick computer systems into playing DSD in its original format without converting. This solution is called DoP(DSD-Over-PCM). To play DSD (without converting to PCM), you need a DAC and a suitable computer. The computer software needs to read the DSD files as data, convert them to DoP and send them to the DAC. The DAC must take the DoP signal, convert it to an analog audio signal, and output it to your audio system.

DSD Transmitter

Like the chicken and the egg question, do the DSD software files (music) come first or the DSD hardware decoders first? In essence, the hardware developed first, the websites offering commercial DSD music files followed.

Hardware for DSD processing has a separate decoder with music data stored inside the hard drive located at the player or externally through a NAS data sharing system. There are many configuration methods for DSD playback systems. For example, the LUMIN Audiophile Network Music player, designed with a DSD converter and DAC in a single block, loads software. Music data is stored on a shared NAS drive via a network connection.

Some other music players like Wyred4Sound MS-1, MS-2 store music data inside the player’s hard drive and use an external DAC; with this form, you can understand like a CD engine. There is an HDD inside. Another form, like the Auraliti PK100 and PK 90, uses the internal DAC and receives data from the HDD through the USB port.

For a system using a computer in combination with a USB DAC, the user needs to be equipped with software to play music with the function of converting DSD data (to DoP). We have Audivana Plus, Channel D Pure Music, HQPlayer, and JRiver Media Center on the Macintosh platform to play DSD in native format. For Windows, there are Foobar2000, JRiver Media Center, JPLAY, the Teac HR Audio Player, and HQPlayer.

Conclude

– Although commercialization has been started, there are not many sources of DSD music, mainly classical music. Sony Music, Universal, Warner are introducing more DSD music sources.

– Although there is a lot of hardware that can play DSD, it requires users to have skills and understanding in the setup process.

– The most common format for DSD is still the DFF file. The DSF file format is very scalable, but DFF is still a safe solution if you buy DSD files.

– Similar to SACD discs, DSD files always have a higher selling price than hi-res PCM files.

– DSD does not determine all the quality of a recording; a good recording depends a lot and mainly on the technique of the recording engineer.

In short, if you’re willing to pay big and don’t have a hard time setting up the hardware, then the DSD will give you the standard and best sound to date.