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bit perfect DSD

"I'm not at all clear on what it means to have (or not have) bit-perfect SACD. I certainly understand "bit perfect" -- just not in an SACD context."

I should think that bit perfect SACD would mean that the DSD bits on the disk are transferred to the DAC unchanged. Specifically, the bits going to the DAC would correspond to the DSD master file produced during the mastering process. (The actual pits on the disk would be the result of losslessly compressing the bit stream, encrypting with a DRM key, and then encoding with the optical disk format coding. All of these operations, undone correctly, should produce the original bit stream.)

What the DAC does with these bits are something else. If the bit stream is sent to a flip flop and this is clocked and low pass filtered then the DAC itself is a pure DSD implementation. If the DAC upsamples the DSD to even higher sampling rates then I would say this is still a pure DSD implementation. (Example, the ESS SABRE chips.) However, if the DAC downsamples to a lower sample rate then this would not constitute pure DSD, wherever done. Among other reasons, transients would be smeared due to the necessary filtering.

There is no fundamental difference between PCM and DSD once one considers the application of dither and noise shaping in the PCM environment, as is common today. DSD64 is nothing but noise shaped PCM with a sample rate of 2,822,400 Hz and a word length of 1 bit.

Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar

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  • bit perfect DSD - Tony Lauck 11:34:17 02/29/12 (0)


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