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What Is DSD Audio? [Quick Explanation]

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Audio Basis - educational articles

Probably you already heard about DSD. However, this article may open new unclear details for you. Read below essential points, that allow to explain DSD audio format principles, 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

 

On of first digital formats was Audio CD optical disk (PCM modulation / PCM format). 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)

From CD (PCM) to SACD (DSD)

 

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

 

Audio quality is level of noise and distortions, that cause format/software/equipment. The level may be normalized by psychoacoustic criteria.

 

However, Sony and Phillips deside 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).

 

 

DSD vs FLAC, WAV and PCM comparison

 

What is DSD? Quick explanation

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:

Feature DSD FLAC WAV PCM
Coding sigma delta modulation pulse code modulation pulse code modulation pulse code modulation
Sample rate 44100 x 64 x N up to 384 000 Hz up to 2 147 483 648 Hz no limit
Bit depth

1 bit,
sometimes multibit

16 ... 24 bit,
32 bit some applications
integer only

16 ... 64 bit integer,
32/64 float point

multibit
Band for audio signal Low part of the band Full band Full band Full band
Medium file, optical disk: SACD file file file, digital tape, optical disk: CD, DVD

Note: WAV and FLAC are PCM implementations.

 

 

PCM versus DSD DAC

 

PCM vs DSD DAC

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.

 

 

Is DSD sound quality better than PCM?

 

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.

There 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".

 

 

Is native DSD audio 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 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 >

 

 

DSD Audio Players, Converters

 

Read details about DSD players and converters.

 

 

Conclusions

 

  1. DSD (SACD) appear as improvement to 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.

 


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