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MQA 6 months later- have thoughts evolved?

I wouldn't know about JA, but Adamdea has called you a 'real expert' in his reaction to Jim Austin's first instalment of S'phile's new MQA propaganda series.

That just shows I used to be a real spurt. 8-]

I've now been told the reference is a passing mention of me on

https://www.stereophile.com/content/mqa-some-claims-examined

but I've not read the following comments as yet. Been too busy worrying about slightly higher frequencies.

http://jcgl.orpheusweb.co.uk/history/jcmt2/BetterByDesign.html

;->
 

I'm slightly puzzled by the footnote 2 saying the test waveform is 'illegal'.

Any sequences of samples only has their meaning defined when you know the impulse response of what generated them. Its an axiom of Information Theory that you need to know how data was generated to make sense of the data.

Using a single non-zero value in a series would then mean 'the result of whatever you'd need to input into the ADC to get that series of values. For systems obeying Nyquist, etc, that will generally be something like the time-inverse of the ADC's impulse function.

So in principle real ADCs *can* generate a single non-zero sample in a series of otherwise zero samples. The challenge is to perfectly inject the inverse function defined by that ADC's impulse pattern. Which can obey Nyquist in general.

As has been pointed out before. The result is the 'convolution' of all the impulse functions applied at each stage of a data chain.

The useful feature of the single value impulse in a sequence is that it shows you the DAC's impulse function. But that *alone* won't define what was poked into the ADC, or tell you if that's what you get when you play some music.
 


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