Posted on Wednesday, 16th January 2008 by Auw Jimmy
I read somewhere around people are talking about SACD (Super Audio Compact Disc) and I read many misunderstanding about SACD. I will write short explanation about it.
First, SACD is not a CD (there is SACD Hybrid, we will discuss it later). It’s different with CD standard. CD Audio will use PCM standard at 16 bit 44.1 kHz (this is the only standard for CD Audio). There’s no CD Audio with 24 bit 192 kHz (it’s a marketing gimmick to trick you).
On the other side, SACD will use what we call as DSD (Direct Stream Digital). It uses 1 bit delta-sigma modulation at very high sampling rate (2.8224 MHz) or over 64 times compared to CD Audio which runs at 44.1 kHz.
So it’s totally different architecture with CD Audio. So never expect about 16 bit or 192 kHz for SACD. It’s not using PCM, so forget about it. Also never compare the 1 bit (DSD) vs 16 bit (PCM) or 44.1 kHz (PCM) vs 2.8224 MHz (DSD). It’s totally in different league!
Despite of its controversy, DSD claims to have wider bandwidth up to 100 kHz and high dynamic range up to 120dB.
If we want to “look inside”, the PCM actually could support up to 100 kHz resolution (as DSD) at 192 kHz sampling rate (Nyquist theorem). While the 120db Dynamic Range claimed in DSD also could be provided with 20-24 bit PCM bit depth.
Most audio editing tools right now only support PCM (though later may support DSD-wide at 8 bit or PCM-narrow). So any DSD source should be converted to PCM domain before later converted to DSD again for SACD mastering.
Some people also say that with noise shaping technique used in SACD (it pushes the noise out of audio band), the SACD dynamic range may decrease quickly at frequencies beyond 20 kHz and also the raising noise floor effect. Some low pass filters may be added at the player side to compensate this problem.
There are few types of SACD:
- SACD Hybrid: This SACD is compatible with standard CD Audio player because it uses 2 layers. The first layer contains the data in PCM/CD Audio format. While the second layer contains the DSD/SACD.
- SACD Only: This CD is only compatible with SACD Player. Some SACD will have single layer (4.7 GB of data), some SACD will have double layer (8.4 GB of data). SACD also can provide multichannel 5.1 track, just like your DVD. So you can enjoy surround sound format from SACD.
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