DSD Explained by Andreas Koch

What is DSD?


PCM Chain


DSD Chain


Delta-Sigma Modulation


Spectrum DSD vs. PCM


DSD as Encoding Format


DSD As Encoding Format


DSD As Encoding Format


Output of 1FS PCM Encoder


Output of 2FS PCM Encoder


Output of  DSD Encoder


DSD Recordings

  • Many recordings exist that were converted from original PCM recordings.
  • Audiophile labels have large libraries of DSD recordings as used for SACD.
  • DSD recordings increasingly available via download.


The Download Bottleneck

  • File sizes for a 3 minute song and download times (assuming 5Mb/sec internet connection):
Redbook (16/44.1kHz) 32MB 1 min.
24/88.2kHz 95MB 2.6 min.
24/96kHz 103MB 2.8 min.
24/176.4kHz 190MB 5 min.
DXD (24/352.8kHz) 380MB 10 min.
DSD 127MB 3.4 min.


DSD Playback Equipment

•Many DACs exist that use standard off the shelf chips that either do not accept DSD or convert DSD inputs to PCM before converting to analog.

•Playback Designs and few other manufacturers offer DACs that truly convert DSD to analog without any detours.

•Variety of playback software exists for Mac and PC that support DSD and PCM file formats.


DSD-over-PCM (DoP) open Standard

•Allows sending of DSD data over standard PCM interfaces (i.e. AES/EBU, SPDIF, USB etc.)

•No conversion to PCM!

•Supported by most DAC and playback software manufacturers


Link to external DAC

Thanks to DoP (DSD over PCM) any standard existing PCM interface can be used for DSD as well:

–Plus: cable length, synchronous
–Minus: limited sample rate, requires 2nd link for master clock
–Plus: synchronous
–Minus: shorter cable length, limited sample rate, requires 2nd link for master clock
–Plus: synchronous, DSD
–Minus: limited sample rate, limited cable length, expensive, no clock master setup
–Plus: standard on all computers, some support by standard operating systems, open ended (can support DSD or any future format), not limited by sample rate, no additional link for master clock necessary
–Minus: limited cable length, non-synchronous
•Firewire – very similar to USB, but less and less popular with computer manufacturers

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