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In Reply to: you missed out on my last paragraph posted by Christine Tham on November 24, 2005 at 20:21:53:
When you mentioned "ultrasonic noise present in DSD", I thought you were talking about the rise in HF noise that results from the 1 bit noise shaping, the noise that players have filters designed to cut to prevent downstream components having problems, not converter noise.Every comparison I read between DVDA and SACD talks of the ultrasonic noise of DSD as against the linear response of PCM, is this not the case, or are you talking about something different?
Follow Ups:
*** When you mentioned "ultrasonic noise present in DSD", I thought you were talking about the rise in HF noise that results from the 1 bit noise shaping, the noise that players have filters designed to cut to prevent downstream components having problems, not converter noise. ***It's actually the same thing. Again, read the application notes from BB and CL. A typical PCM sigma delta ADC does noise shaping on the 1 bit modulated signal, resulting in an ultrasonic noise curve very similar to DSD (I think the latest BB app note even have figures of theoretical curve vs actual measured curve).
*** Every comparison I read between DVDA and SACD talks of the ultrasonic noise of DSD as against the linear response of PCM, is this not the case, or are you talking about something different? ***
PCM derived from a sigma delta ADC does NOT have a linear response. Check actual response curves of real world ADCs, they are NOT flat, because the ultrasonic noise have been filtered away. And if the ultrasonic noise is NOT filtered, then PCM will also have the same noise characteristics as DSD.
PS - Ultrasonic noise is also generated by delta sigma DACs. Again, check real world response curves of actual DVD-Audio players - typically they are NOT flat above 20kHz. For example, on my panasonic DVD-S97, the response is down -0.5dB at 20kHz and rapidly declines after that - again, this is to offset out of band noise generated by the DAC. Hopefully you'll see the actual curve once I publish the review of that player (along with a review of a modded Marantz DV-6500 - that one has an even steeper curve)
The 'very similar ultrasonic noise curve' might look very similar but you fail to mention that the curve rises higher up in the frequency range. A simple analog filter after the dac output easily takes care of this.Note also that this isn't a fault in the pcm storage format. This adc noise floor is generated after the recording and has nothing to do with pcm.
In stark contrast is that with dsd it is a drawback because the generated noise is captured in the recording.
You are dissing up certian player related implementation issues to wrongfully 'prove' imaginary flaws in the pcm storage format.By your logic that would make an additional dsd flaw because some players convert dsd to pcm before the dac.
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and bent theories about digital technologies.Your 'expertise' is coming from a Sony Philips marketing blog and misinterpreted datasheets.
... it is you who is spreading "wrong assumptions" and "bent theories"?I could refute your points, but "frankly", why bother? It's the greater fool who tries to argue with one.
But let me ask a simple question: who is more likely to be right? My statements are backed by application notes and data sheets from multiple manufacturers, and supported by cold, hard, measured data (which anyone can replicate). So far, you haven't provided any substantiation for any of your tortured rationalizations and assertions.
It's just you misinterpreting them.You fail to mention that the 1 bit adc technologie used for many PCM recordings could have the rising noise floor due to noise shaping well beyond the upper frequency limit of let's say a 24/96 recording.
You keep pointing out outdated technolgies like brickwall filters and imply that these are PCM drawbacks.Your "cold, hard, measured data" should clearly show you the disadvantage of DSD.
*You* want to make this into a PCM vs DSD discussion, but I don't.PCM derived from sigma delta (which by the way is 99% of PCM recordings these days) and DSD share many characteristics - good and bad - because fundamentally they are based on the same underlying technology and principles. That's all I'm trying to say.
If you want to turn this into a discussion about a value judgement about the two, then i hope you'll excuse me if I don't join in.
This is link to the BB paper describing out of band noise for PCM delta sigma DACS:http://focus.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=slea048&fileType=pdf
Notice how similar the noise curve is compared to DSD. It's because they are both based on the same underlying converter technology.
As for the noise curve and application of noise shaping on a sigma delta ADC, refer to this oldie but goodie from Analog Devices:
http://www.analog.com/UploadedFiles/Application_Notes/432842357460935458165408691AN388.pdf
I think Cirrus Logic has written a really good paper too, but I'll leave it to you to search for it.
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