- AccurateRip
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- Bits: 16 or 24
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- Bitrate
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DSD
Direct-Stream Digital (DSD) is the trademark name used by Sony and Philips for their system of recreating audible signals which uses pulse-density modulation encoding.
SACD audio is stored in a format called Direct Stream Digital (DSD), which differs from the conventional PCM used by the compact disc or conventional computer audio systems.
DSD is 1-bit, has a sampling rate of 2.8224 MHz, and makes use of noise shaping quantization techniques in order to push 1-bit quantization noise up to inaudible ultrasonic frequencies. This gives the format a greater dynamic range and wider frequency response than the CD. The SACD format is capable of delivering a dynamic range of 120 dB from 20 Hz to 20 kHz and an extended frequency response up to 100 kHz, although most currently available players list an upper limit of 80–90 kHz and 20 kHz is the upper limit of human hearing.
Source: Wikipedia
The obvious benefit is the wide frequency range allowing you to record without a filter.
If one record using PCM, the input signal should be band limited (low pass filter).
Record e.g. at 48 kHz then the Nyquist is theoretically 24. Any signal > 24 in the input will not be captured properly and hence generates an erroneous value.
The downside is that the noise shaping generates a strong amount of high frequency noise.
This is one of the DSD paradoxes, the bandwidth is tremendous but above 20 kHz the music signal will start to be drowning in the noise.
Accuphase DP-85, 1/3-octave spectrum of dithered 1kHz tone at -150dBFS, with noise and spuriae (from top to bottom): DSD data, 24-bit PCM data (right channel dashed).
Source: Stereophile
DSD quantisation noise with a sampling rate of 64 times 44.06 kHz.
Malcolm Hawksford, Essex University, UK
Source: HDTracks
To play SACD a low pass filter is recommended.
All these strong high frequency content might fry your tweeters!
There are 2 good reasons to convert DSD to PCM
- It is very difficult to process single bit. Almost all studio software uses PCM
- Your PC won’t play SACD so it must be converted to a PCM format like WAV, FLAC, etc.
Again when converting you need a low pass filter.
Bruce Brown converted DSD to PCM using Weiss Saracon software.
Much to his surprise the conversion to 88.2 and 176.4 yielded the same frequency content.
Obvious the (needed) filter applied by Saracon doesn’t allow for anything > 40 kHz.
An 88.2 kHz transfer will need a brickwall filter by 40 or 44 kHz, so most of the noise is filtered out anyway. A 176.4 transfer has more flexibility. They have to decide how much noise they want to let through, but they have the advantage of not requiring such a sharp filter. This results in better sound quality.
Source: Charles Hansen
References
- Direct Stream Digital - Wikipedia
- Accuphase DP-85 SACD player - Michael Fremer - Stereophile Sep 22, 2002
- Converting DSD to LPCM - HDTracks.com
- Weiss Saracon - Bruce Brown on What's Best Forum
- Computer Audio Asylum - Charles Hansen
- Why 1-Bit Sigma-Delta Conversion is Unsuitable for High-Quality Applications
by Stanley P. Lipshitz and John Vanderkooy - Audio Research Group, University of Waterloo - Waterloo, Ontario N2L 3G1, Canada - Audibility of a CD-Standard A/D/A Loop Inserted into High-Resolution Audio Playback - E. Brad Meyer and David R. Moran - J. Audio Eng. Soc., Vol. 55, No. 9, 2007 September