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#1
Posted to rec.audio.high-end
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LP inferior?
"Steven Sullivan" wrote in message
... Sonnova wrote: On Fri, 21 Nov 2008 06:15:19 -0800, Steven Sullivan wrote (in article ): Kalman Rubinson wrote: photograph. If it takes up 3/4 of a spectrum, then that only means that the scale of the 'spectrum' has been absurdly expanded to ~100kHz. Well, of course. Koschnike's point was that 192 KHz sampling has response out to 96KHz (half the sampling frequency). so, obviously, the DC-22KHz would be roughly 1/4 of a spectrum that goes to 100KHz. Sorry, but what is the 'point' of making a point like that? All it is, is an entirely predictable confirmation of Shannon/Nyquist: your 'response' will extend out to just less than half of whatever your sample rate is. No one with a clue would ever *expect* to see anything in spectral view beyond what the Nyquist limit of 'response' dictates. So OF COURSE any spectral content visible beyond 22 in 192 kHz-sampled audio, will be absent in a 44kHz sampled version. This shows that the LP faithfully preserves the HF content of the master, while the CD does not. snip------- sounds like someone has a fundamental misunderstanding of sampled data theory if you are sampling a sine wave (or square wave) at a single frequency, so long as your sample rate is 2X or greater than the fundamental, you will not get ALIASING of the fundamental. This says nothing about distortion of phase or waveform. If phase information is important, a significantly higher sampling rate is needed - 10X is much more typical. A control system for a large airplane, for example, had a roll off at 4 Hz - we found it necessary to sample the input data at 60 hz to prevent phase induced instability. That's 15X the maximum passband frequency. I see no reason why this kind of effect does not apply at audio frequencies as well. |
#2
Posted to rec.audio.high-end
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LP inferior?
Bill Noble wrote:
if you are sampling a sine wave (or square wave) at a single frequency, so long as your sample rate is 2X or greater than the fundamental, you will not get ALIASING of the fundamental. This says nothing about distortion of phase or waveform. If phase information is important, a significantly higher sampling rate is needed - 10X is much more typical. A control system for a large airplane, for example, had a roll off at 4 Hz - we found it necessary to sample the input data at 60 hz to prevent phase induced instability. That's 15X the maximum passband frequency. I see no reason why this kind of effect does not apply at audio frequencies as well. Because the ear is insensitive to phase info at the relevant frequencies. Graham |
#3
Posted to rec.audio.high-end
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LP inferior?
Bill Noble wrote:
"Steven Sullivan" wrote in message ... Sonnova wrote: On Fri, 21 Nov 2008 06:15:19 -0800, Steven Sullivan wrote (in article ): Kalman Rubinson wrote: photograph. If it takes up 3/4 of a spectrum, then that only means that the scale of the 'spectrum' has been absurdly expanded to ~100kHz. Well, of course. Koschnike's point was that 192 KHz sampling has response out to 96KHz (half the sampling frequency). so, obviously, the DC-22KHz would be roughly 1/4 of a spectrum that goes to 100KHz. Sorry, but what is the 'point' of making a point like that? All it is, is an entirely predictable confirmation of Shannon/Nyquist: your 'response' will extend out to just less than half of whatever your sample rate is. No one with a clue would ever *expect* to see anything in spectral view beyond what the Nyquist limit of 'response' dictates. So OF COURSE any spectral content visible beyond 22 in 192 kHz-sampled audio, will be absent in a 44kHz sampled version. This shows that the LP faithfully preserves the HF content of the master, while the CD does not. snip------- sounds like someone has a fundamental misunderstanding of sampled data theory if you are sampling a sine wave (or square wave) at a single frequency, so long as your sample rate is 2X or greater than the fundamental, you will not get ALIASING of the fundamental. This says nothing about distortion of phase or waveform. If phase information is important, a significantly higher sampling rate is needed - 10X is much more typical. A control system for a large airplane, for example, had a roll off at 4 Hz - we found it necessary to sample the input data at 60 hz to prevent phase induced instability. That's 15X the maximum passband frequency. I see no reason why this kind of effect does not apply at audio frequencies as well. Sounds like someone wants to challenge Shannon/Nyquist, again.... All you have to do , is show 'this kind of effect' in an audio sample. -- -S I know that most men, including those at ease with problems of the greatest complexity, can seldom accept the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have proudly taught to others, and which they have woven, thread by thread, into the fabrics of their life -- Leo Tolstoy |
#4
Posted to rec.audio.high-end
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LP inferior?
"Bill Noble" wrote in message
if you are sampling a sine wave (or square wave) at a single frequency, so long as your sample rate is 2X or greater than the fundamental, you will not get ALIASING of the fundamental. Sure you will. A square wave will contain significant harmonics of the fundamental. For example, a 22.00 KHz square wave will pass your criteria in a system sampled at the typical 44.1 KHz. The next harmonic will be the third harmonic at 66.00 Hz. Since aliasing repeats itself in successive mirror images as frequency increases, 66 KHz will be aliased to some frequency above 20 KHz. It is therefore an absolute requirement that any broadband input signal be low-pass filtered so that it does not have significant content Nyquist. This says nothing about distortion of phase or waveform. If phase information is important, a significantly higher sampling rate is needed - 10X is much more typical. Ironically, a 10x safety margin is not a requirement for a digital system. While a digital system cannot do *anything* useful with a frequency at or above the Nyquist frequency, there is nothing inherent that says that frequencies just below the Nyquist frequency must have phase distortion. It's all about the anti-aliasing filter, and if that filter is a oversampled digital filter, all sorts of counter-intuitive things can be done. A control system for a large airplane, for example, had a roll off at 4 Hz - we found it necessary to sample the input data at 60 Hz to prevent phase induced instability. That's 15X the maximum passband frequency. I'm somewhat familiar with control systems - I did post-graduate work on them. There are too many missing pieces in this anecdote to diagnose the problem, but there is no need to sample at 15x in order to have minimal phase error. I see no reason why this kind of effect does not apply at audio frequencies as well. http://www.pcavtech.com/soundcards/L...644-xfus10.gif shows the phase response of a high quality audio interface operating at a 44.1 kHz sample rate. The phase error was less than 5 degrees at 20 KHz. A 3 KHz it was something like a degree and a half. I would not consider a control system with a 2 degrees or even 5 degree stability margin to be suitable for use in an airplane. |
#5
Posted to rec.audio.high-end
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LP inferior?
On Sun, 23 Nov 2008 20:23:45 -0800, Bill Noble wrote
(in article ): "Steven Sullivan" wrote in message ... Sonnova wrote: On Fri, 21 Nov 2008 06:15:19 -0800, Steven Sullivan wrote (in article ): Kalman Rubinson wrote: photograph. If it takes up 3/4 of a spectrum, then that only means that the scale of the 'spectrum' has been absurdly expanded to ~100kHz. Well, of course. Koschnike's point was that 192 KHz sampling has response out to 96KHz (half the sampling frequency). so, obviously, the DC-22KHz would be roughly 1/4 of a spectrum that goes to 100KHz. Sorry, but what is the 'point' of making a point like that? All it is, is an entirely predictable confirmation of Shannon/Nyquist: your 'response' will extend out to just less than half of whatever your sample rate is. No one with a clue would ever *expect* to see anything in spectral view beyond what the Nyquist limit of 'response' dictates. So OF COURSE any spectral content visible beyond 22 in 192 kHz-sampled audio, will be absent in a 44kHz sampled version. This shows that the LP faithfully preserves the HF content of the master, while the CD does not. snip------- sounds like someone has a fundamental misunderstanding of sampled data theory if you are sampling a sine wave (or square wave) at a single frequency, so long as your sample rate is 2X or greater than the fundamental, you will not get ALIASING of the fundamental. This says nothing about distortion of phase or waveform. If phase information is important, a significantly higher sampling rate is needed - 10X is much more typical. A control system for a large airplane, for example, had a roll off at 4 Hz - we found it necessary to sample the input data at 60 hz to prevent phase induced instability. That's 15X the maximum passband frequency. I see no reason why this kind of effect does not apply at audio frequencies as well. Well, it MAY. But at this point it is an unknown because we are dealing with a human sensory perception that's difficult, if not impossible, to measure or even easily observe (unlike the the control system of an aircraft). Many people contend that CD contains all of the information necessary for the perfect human perception of music. Others say that CD hasn't the resolving power and that higher bit-rates and more bits are necessary, or that a different encoding scheme (such as DSD) are needed in order to capture the important essence of music digitally. |
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