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In Reply to: RE: There's no free lunch posted by Charles Hansen on May 22, 2017 at 16:57:53
Thanks for your clear explanation. I understand that the folding of high bit-rate files into lower bit-rate files is but one aspect of MQA- and it is not the one that interests me that much, because, at best, you preserve the quality of the high bit rate.
There is also, as I understand, a claim of improving the quality through the use of processing the audio file to correct for time domain problems in the original recording. This seems as though it could be useful without any sort of new DAC purchase. Do you have any information or thoughts about that aspect of MQA? Thank you.
> > improving the quality through the use of processing the audio file to correct for time domain problems in the original recording < <
To the best of my knowledge the only way to do this is to insert a digital filter into the chain, typically an "apodizing" filter that has a lower cutoff-frequency than the anti-aliasing filter used in the original A/D converter. This will filter out any "ringing" on the recording - but the problem is that the new digital filter will impose its own ringing. The idea of the apodizing filter is that by using a minimum-phase filter, all of the pre- and post-ringing imparted by the A/D converter will be replaced with only post-ringing - thought to be less intrusive sonically.
There are at least two issues with this approach:
1) There are only a minority of recordings where this can be applied. Most early CD releases were transferred from analog tapes using a single stereo A/D converter. While it is conceivable that a digital filter could improve the sound of these recordings, that digital filter can be anywhere in the playback chain. Why insert a special one upstream before the point the file is distributed? It makes more sense to put a filter of this type into the playback DAC so that *all* recordings will benefit rather than a few that have been given a "special proprietary process". Then the end user would not be forced to purchase new hardware to play back these "new" specially encoded files.
2) For the last two decades (at least), most recording start in the digital domain. A modern recording may have several dozens of different A/Ds used to create the final product, each operating at different sample rates, often in from different manufacturers, and even in different studios. There is absolutely no way to "compensate" for all of these different A/D converter "signatures" at once with a single filter.
All postings are my own personal opinions and do not necessarily reflect those of my employer or the local dog-catcher.
The points you made above I raised months ago. And you are spot on.
"There is absolutely no way to "compensate" for all of these different A/D converter "signatures" at once with a single filter."
But there are some who would convince you otherwise.
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