Editing Direct Stream Digital (section)

==DSD signal format==
[[File:PCM-vs-DSD.svg|thumb|Comparison with [[zero-order hold]] [[Pulse-code modulation|PCM]] ]]

DSD differs from the PCM format used by [[compact disc]] or typical computer audio systems: while PCM uses a multi-bit value (representing a large range of amplitudes) at a low sample rate, DSD instead uses a single-bit value (representing an increase or decrease in amplitude) at a sample rate much higher than the signal's [[Bandwidth (signal processing)|bandwidth]].

The process of creating a DSD signal is the same as the front-end modulator and noise-shaper portion of a [[Audio bit depth|1-bit]] [[delta-sigma modulation|delta-sigma]] [[analog-to-digital converter]] (ADC), without the back end [[Decimation (signal processing)|decimator]] (which would typically convert the 1-bit bitstream into multi-bit PCM). The short-term average of the 1-bit DSD [[bitstream]] signal is proportional to the original signal amplitude. Because of the higher sample rate, an SACD player can use a one-bit DAC with a low-order analog filter to [[Signal reconstruction|reconstruct]] and produce the analog output.

DSD uses [[noise shaping]] techniques to push [[quantization noise]] up to inaudible ultrasonic frequencies. Because of this, single rate DSD64 can deliver a [[dynamic range]] of 120&nbsp;[[decibel|dB]] from 20&nbsp;Hz to 20&nbsp;kHz and<!--Should this be ''or''? Opening the reconstruction filter and measurement bandwidth will bring in additional noise potentially lowering the dynamic range.--> an extended [[frequency response]] up to 100&nbsp;kHz (most recent SACD players specify an upper limit of 80 to 90&nbsp;kHz).{{citation needed|date=September 2023|reason=Many numbers of unknown origin in this paragraph}}

The various DSD formats use sampling rates well into the [[megahertz]] (MHz) range, typically with an ''oversampling ratio'' that is a [[power of two]] relative to the 44.1&nbsp;kHz rate used for CD audio:
{| class="wikitable"
|+
!Name
!Abbreviation
!Sample rate
!Oversampling ratio relative to 44.1&nbsp;kHz
!Notes
|-
|Single-rate DSD
|DSD64
|2.8224&nbsp;MHz
|64x
|The format used for SACD media.
|-
|Double-rate DSD
|DSD128
|5.6448&nbsp;MHz
|128x
|Since its establishment, content creators have made DSD128 recordings available, such as the audiophile label Opus3.<ref>{{cite web |author=Hiro |date=April 7, 2013 |title=Audiophile label Opus3 starts offering 5.6448MHz DSD downloads |url=https://puresuperaudio.blogspot.com/2013/04/audiophile-label-opus3-starts-offering.html |access-date=October 27, 2018 |work=Pure Super Audio}}</ref>
|-
|Quad-rate DSD
|DSD256
|11.2896&nbsp;MHz
|256x
|
|-
|Octuple-rate DSD
|DSD512
|22.5792&nbsp;MHz
|512x
|
|-
|Sexdecuple-rate DSD
|DSD1024
|45.1584&nbsp;MHz
|1024x
|
|}

See {{Slink|delta-sigma modulation|Theoretical effective number of bits}} for analysis of the [[effective number of bits]] that can be achieved by oversampling, especially when using a higher [[Order (differential equation)|order]] modulator.