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In Reply to: RE: Hey JimiAustin: MQA Enabled ADCs posted by 13th Duke of Wymbourne on October 31, 2016 at 18:09:21
>An ADC is still an ADC. The answer in the linked interview does not state
>there is anything special about the ADC function for MQA except 'low
>modulation noise', i.e. it should be a good ADC.
There are 2 strategies for designing an ADC with a very short impulse
response of the type desired by the MQA system. One is to use a true DSD
converter running at 128Fs or higher with a first-order low-pass
antialiasing filter set well above the desired passband. The other is to do
what Ayre has done in its QA-9 converter at 192kHz, where it uses a
moving-average low-pass filter, of the type described by Keith Howard at
the article linked below.
John Atkinson
Editor, Stereophile
Follow Ups:
Hi John,
I'll stick with my broad-brush 'an ADC is still an ADC' if only to back-up Jim's original statements and not to suggest that Isaac is in any way correct. Now, pretty much all (or just plain all?) ADCs are over-sampled types and the modulators are essentially similar, at least in my way of thinking. All highly-oversampled with a few bits of resolution. How those bit-streams are later decimated, with whatever resulting temporal response, is, to me, secondary.
As you mention DSD, I find it ironic that a recording format was developed to support 1-bit converters only for the converter industry to move away from 1-bit designs because they don't work that well.
When I see some of the arguments that have spun out of MQA related posts I am reminded of the New Yorker cartoon you told me about at the Newport Beach show in June!
Regards
13DoW
I thought this thing could raise the dead, or at least make a Toscanini / NBC Symphony Orchestra recording sound half decent ... now it's just these two things that put out what is desired by the MQA system ???
Better get those MQA samples examined for something else hiding in the origami ... seems to be scrambling the minds of the audio press.
;)
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