What is DSD? [Audio Quality, DSD vs PCM]

Probably, you already read articles, that explain DSD audio (Direct Stream Digital). But it may not easy still understand why 1-bit-only DSD may successfully compete with multibit PCM.
Read simple explanation what is DSD exactly and how it works, its sound quality, DSD vs PCM, myths debunking and other essential issues by audio software developer Yuri Korzunov.

What is DSD

DSD (Direct Stream Digital) is an audiophile high-resolution audio format. It is a method of a coding analog signal to digital form.

Digital form is number sequence. Each number is level altering measurement. As rule, DSD is explained as a saw (level grow or fall) between samples. But it did not give easy understanding of basical DSD principles. Read how DSD works...

Read about sound quality comparison with PCM and DSD and PCM DAC. Look for more details in the big educational article "What is DSD music file format?"

DSD history

Audio CD optical disk (PCM modulation / PCM format) was one of first digital formats. It was a source with low distortion and noise level comparing analog ones. I think, now many people forgot what is "real analog noise".

From CD (PCM) to SACD (DSD)

After CD, demands to sound quality improvements could be implemented by increasing sample rate or bit depth.

However, Sony and Phillips decided to use another kind of modulation - 1-bit sigma-delta modulation. At first glance, using 1-bit is impossible, because such bit resolution (bit depth) cause huge noise level. But, if high sample rates are used, noise energy may be pushed out of audible frequency range (to ultrasound). That action is called "noise shaping".

Practically, 1-bit conception may be easier, than multi-bit, in a DAC implementation (read below).

When DSD music is converted to analog, ultrasound noise is filtered.

Medium, that contains 1-bit DSD audio stream was called SACD (Super Audio CD).

Look at DSD file infographic >

How DSD works?

As rule, DSD has explained in the time domain: positive samples increase level, but negative decrease and analog filter smooth "saw" form of signal.

Instead, in the author opinion, the easiest way to explain DSD is looking to spectrum. To estimate DSD sound quality, the quantization noise level is main criteria.

There is an explanation, that DSD has super high sample rate and super low bit depth 1-bit is not matter for noise.

But for DSD 64 it is not enough to be better CD audio.

To decrease noise level, noise shaping is used. Read details here >

DSD myths

Myth 1. DSD is better PCM and vice versa

No. Both format quality is defined by implementation in a device and software.

Also played back record is matter.

Myth 2. DSD has low noise level due to high sample rate

DSD's low noise level is a result of noise shaping.

Myth 3. Multi-bit DSD may be edited natively

DSD bit depth define noise level abilities. After DSD editing sigma-delta remodulation is need.

Myth 4. DSD editing with decimation dramatically degrade sound

The editing with decimation is implemented with low-frequency filter. The filter cause ringing audio.

However, no serious researches, that author know, studied the real impact of ringing to ears.

Also, the ringing depends on filter implementation.

So, currently, we don't know the exact answer to the question.

DSD and Nyquist Theorem

For Nyquist theorem no difference between DSD and PCM: spectrum above [sample rate]/2 is the same to the spectrum below [sample rate]/2 and flipped by frequency axis.

DSD vs FLAC, WAV, PCM comparison

What is DSD? Quick explanation

Bit depth define audible noise. More bit depth is lesser noise.

At the picture, we can see that bit depth decreasing achieved through using only part of the full signal frequency band. Other words, if we want to reduce bit depth, we must increase the sample rate to keep the audible noise level.

Read details of the format comparison in the table: DSD vs WAV vs PCM vs FLAC vs DXD

Note: WAV and FLAC are PCM implementations.

Read which is better DSD or FLAC (Infographic) >

Read more about audio file formats >

PCM versus DSD ADC

PCM vs DSD analog-to-digital converter

Both kinds of DAC contains sigma-delta modulator. It converts the analog voltage to digital samples in a format like to DSD.

Before modulator analog filter ["DSD" sample rate]/2 is applied. Looks details here >

PCM ADC is more sophisticated and contains multibit modulator.

To reduce sample rate "multibit-DSD" signal should be filtered (low-frequency filter) and decimated (removing part of samples). The filter also eliminates shaped noise of "DSD signal".

Read more about PCM and DSD difference >

PCM versus DSD DAC

PCM vs DSD digital-to-analog converter

To easier providing of PCM DAC precision/linearity into this kind of DAC, a digital sigma-delta modulator is used. After it, sigma-delta de-modulator convert digital "DSD" to an analog signal.

In the general case, DSD DAC is simpler. It contains sigma-delta de-modulator only.

It is technically impossible to compare PCM and DSD DACs, because they use different processing / electrical circuits.

Read more what is DSD and PCM DACs and their comparison >

DSD vs PCM sound quality

There is no univocal answer. There is several reasons:

• Quality of a record
• Mixing/re-mixing of the record (including quality of the processing)
• Playback software/hardware implementation
• DAC implementation.

These reasons trigger infinite discussions "what is better PCM or DSD".

Technically, DSD and PCM are incomparable. Even as single DSD/PCM compatible DAC is used for the test, the difference may be caused by different mixing/post-production of records, and the DAC uses the different circuits (see here).

General answer: "Each case is individual and depend on playback system implementation and listened to record".

DSD sound quality and other [Brief F.A.Q.]

• Are DSD downloads worth it? Are DSD files better?
      There is no unambiguous answer to the question. It depends on record quality, your software and equipment.
   
• How big are dsd files?
      1 minute of DSD64 stereo is about 40 Mbytes.
   
• Are all SACD DSD?
      Yes. Hybrid SACD also may contain CD layer compatible with usual CD player.
   
• What are DSD music files?
      .dsf, .dff, .iso (sacd iso), flac/wav (DoP). Read details >
   
• Why is DSD sounds better than PCM?
      Sound is defined by record quality, your playback program and apparatus.
   
• Why upsample to DSD?
      Upsampling can optimize audio file resolution to optimal (minimal playback distortions) for your equipment. Read details >
   
• Where to buy dsd music downloads?
      Read DSD store site list here >
   
• Where to download dsd music free?
      Look at free DSD music download links >

Also read: DSD player F.A.Q., DSD converter F.A.Q., Myths

Is native DSD editing possible?

DSD editing is cutting, merging, gain altering, equalizing, etc. of file(s).

"Native editing" (without conversion to multibit and DSD re-modulation) is possible for cutting and merging DSD records only.

All other kinds of editing demand conversion to multi-bit values and re-modulation. In this case, loses of the editing in itself, comparable with PCM resampling.

Read details here >

How to play DSD?

DSD may be played at a mobile phone, portable players, music servers, SACD-players and other devices.

Some device can support native DSD feed of DSD DACs. Other ones demand pre-conversion to PCM or make conversion "on fly".

Sound quality is a complex matter. Read details about the resolution of audio files and sound quality.

Read details how to open, play DSD on Mac, Windows, iOS, Android, Linux: player list >

Read how to download DSD music and how to get free DSD files here >

DSD player brief F.A.Q.

• Can iTunes play DSD files?
      Yes with additional software. Read details here
   
• Can foobar2000 play DSD?
      Yes. Read details here
   
• Can VLC play DSD files?
      As the author know, not. Details
   
• Can Jriver play DSD files?
      Yes. Look at the player list
   
• Can Vox play DSD?
      As the author know, Vox convert .dsf and .dff files to PCM on fly without native DSD playback.
   
• Can Plex play DSD?
•     As author know, Plex can playback DSF. Details
   
• Can Musicbee play DSD?
      As the author know, yes. Details
   
• Can Amarra play DSD?
      Yes
   
• Can Audirvana play DSD?
      Yes
   
• Can iPhone play DSD files?
      Yes. Look at the player list
   
• Can iPod play DSD?
      As the author knows, there is conversion to PCM files is necessary.
   
• Can Mac play DSD?
      Yes

Also read: DSD converter F.A.Q., DSD F.A.Q., Myths

How to convert DSD?

Read details how to convert DSD on Mac, Windows and other platforms: converter list >

How to create, edit DSD files read here >

How to rip DSD from SACD (to SACD ISO) read here

DSD converter brief F.A.Q.

• How to convert to playback at iTunes?
      Convert DSF/DFF/SACD ISO to *m4a (ALAC, Apple Lossless). Read also (conversion DSF/DFF/SACD ISO to ALAC(m4a) is same) DSF to FLAC, DFF to FLAC, ISO to FLAC.
   
• Conversion DSD to PCM degrade sound?
      Conversion with processing audio (including DSD to PCM) adds distortions. But final distortions is a matter of used playback distortions. Read details here
   
• Conversion DSF to DFF and back is lossless?
      It may be lossless when audio converter doesn't process audio stuff (resampling and other) in conversion.
   
• Do various DSD converters have different sound quality?
      Yes. There is noise level, frequency/phase distortions and tolerance to overload are estimated. Read details here.

Also read: DSD player F.A.Q., DSD F.A.Q., Myths

What is DoP (DSD over PCM)?

DoP (DSD over PCM) is format to provide compatibility with some DSD hardware (USB DAC, for example). The format allows coding 1-bit DSD in usual multibit words (like PCM).

These multi-bit words are transferred as usual PCM. Upper bits of the multi-bit word contains special "DSD over PCM" marker code.

DoP receiver should recognize the marker code and interpret lower part of the multi-bit word as raw DSD bits.

DoP format may be stored into usual lossless PCM file: WAV, FLAC, AIFF.

DoP coding may be chosen in audio player settings.

DoP specification

Conclusions

1. DSD (SACD) appear as improvement of CD-audio.
2. Sound quality is not DSD/PCM format matter, but depend on implementation and quality of a musical record.
3. "Native" DSD editing is possible for limited cases. For other cases, the own editing loses is comparable with PCM resampling.

Read the detailed article about DSD >

Author: Yuri Korzunov,
Audiophile Inventory's developer

DSD High-Resolution Music Downloads [Check Free Files]

What is DSD Audio? Read About 10 Things You Want to Know [ Article ]

DSD vs DSF vs DFF Files Audio. What is the difference [Article]

Where are Free Hi-Res Downloads?

How to play DSD | Player Software List | Read Quick Guide

How to Open DSF Audio Files [Converters, Players]