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In Reply to: Now, if we understood the relationship between bit "density" and perceived sound quality. nt posted by G Squared on September 10, 2020 at 11:45:11:
Without understanding the information value conveyed per bit, "Bit density" is a meaningless metric to use in comparing PCM to PDM ("DSD").
What matters is the level of information that is conveyed per unit time. "Resolution" relates the accuracy of the decoded information per unit to represent the original signal. Since a 1 bit converter only has two states compared to a given N-level multi-bit converter, the DSD format needs far more symbols to be transmitted per unit time to convey the same information as a multi-bit converter. DSD is therefore the least efficient way to convey information and why coding in DSD results in larger file sizes. The problem to solve is to recover the encoded signal with the least error.
Back in the 80s and 90s due to the manufacturing challenges in achieving perfect trimming of the resistors down to the LSB, multi-bit converters suffered from poor linearity which is where the shift to PDM gave a theoretical advantage. However, the code/decode accuracy is highly dependent on the level of jitter on the reference clock signals. Additionally, coding a signal with a 1 bit converter results in residual quantisation noise due to the fundamental inability to adequately dither the signal compared to a multi-bit converter - 3 to 4 bits is required for perfect dither.
Therefore any claim of the superiority of DSD to PCM is pointless - the question should be which method gives the smallest error signal between the recovered signal and the original signal. Unfortunately that comes down to the equipment used.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
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- RE: Now, if we understood the relationship between bit "density" and perceived sound quality. nt - flood2 17:42:45 09/10/20 (0)
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