What Is DSD Audio? [Quick Explanation]

Audio Basis - educational articles

DSD is abbreviation of Direct Stream Digital. It is audiophile high resolution music format. Probably you already read about it. However, this article may open new unclear details for you. Read below essential points, that allow to explain DSD audio format principles, what is DoP, what inside DSD and PCM DAC and why it is impossibly to compare DSD and PCM. If you want more details, also read the educational article "What is DSD?"

DSD history >  DSD vs FLAC, WAV, PCM >  PCM versus DSD DAC >  DSD vs PCM sound quality >  Is native DSD editing possible? >  DSD audio players, converters >  What is DoP (DSD over PCM)? >  Conclusions >

Audio CD optical disk (PCM modulation / PCM format) was one of first digital formats. It was 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 improving could be implemented by increasing sample rate or bit depth.

However, Sony and Phillips desided to use other 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 multibit, in a DAC implementation (read below).

When DSD 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 >

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 full signal frequency band. Other words, if we want to reduce bit depth, we must increase sample rate to keep audible noise level.

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

Note: WAV and FLAC are PCM implementations.

Read about DSD vs FLAC (Infographic) >

PCM vs DSD DAC

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

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

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

Read more about DSD and PCM DAC comparison >

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 an infinite discussions "what is better PCM or DSD".

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

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

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 the editing demands conversion to multibit values and re-modulation. In this case, loses of the editing in itself, comparable with PCM resampling.

Read details here >

Read details about DSD players > and converters >

Read DSD music site list (including free downloads) >

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

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

DoP receiver should recognize the marker code and interprete lower part of the multibit word as raw DSD bits.

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

DoP coding may be chosen in an audio player settings.

DoP specification

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 musical record.
3. "Native" DSD editing is possible for limited cases. For other cases, the own editing loses is comparable with PCM resampling.

Read detailed article about DSD >

Author: Yuri Korzunov, Google+,
Audiophile Inventory's developer

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