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RE: MQA Loses Part of Spectrum on Some Tracks?

Posted by Charles Hansen on May 31, 2017 at 18:50:48:
>> Perhaps one of the most differentiating features of a DAC is the filter and some companies have developed their own, with Ayre being at the forefront. MQA turns that filter into commodity, all adopting DACS will have the same filter and that unique selling point is lost. <<

Thanks for the clarification. Regarding custom filters, Ayre is actually fairly far from "the forefront". Together Wadia and Theta were the first with custom filters in the late 1980s. In the 1990s dCS joined and those three have perhaps been the most prominent companies with custom filters. Ayre did not join the fun until January 2009 and today there are perhaps a dozen different companies around the world that "roll their own", including Playback Design (Andreas Koch), EMM Labs (Ed Meitner), PS Audio (Ted Smith), Chord (Rob Watts), and many more - most recently Auralic. Unsurprisingly, different custom filter designers have different theories about what constitutes a "better" digital filter.

In my experience, digital filters are one of about a half-dozen major design aspects that will significantly affect the sound of a digital product. Also important are the analog circuitry, the power supplies, the clock implementation, the DAC chip itself, and the presence or absence of any DSP algorithms (such as Asynchronous Sample Rate Conversion - ASRC - and many others). I would be loathe to rank the importance of them, but would agree that the digital filter (or lack thereof, in the case of "non-oversampling") plays an important factor in the overall sound quality.

Any DAC manufacturer can license MQA's technology, and that apparently includes using MQA's filter (or having them customize their filter to "compensate" for the "deficiencies" in whatever digital filter is in the product - be it custom or off-the-shelf). As far as I can tell it turns out that the MQA filter is much closer to what Ayre has developed than anything else of which I am aware. In contrast, the Watts Transient Aligned (WTA) digital filter used in Chord products takes an almost diametrically opposed approach (as noted in the "Conclusion" of JA's recent Stereophile review, linked below). However in either case there is nothing that precludes any company from licensing MQA's technology and using the MQA filter for MQA files and the custom filter for all other files. Schiit Audio (which sells products both with custom digital filters and stock ones built into the DAC chips) is one of the manufacturers choosing not to support MQA for the time being. Their press release of a year ago is available here:

http://schiit.com/news/news/why-we-wont-be-supporting-mqa

"Asked if there was any chance Schiit Audio might support MQA if it became the dominant format in the market, Moffat answered, 'If it becomes the dominant audio technology, or even a very popular second-place format, we would have to evaluate it in the same way we evaluate other lossy compression standards, such as home theater surround formats, Bluetooth codecs, and MP3 variants.'"

There seems to be something of a general trend - manufacturers that have developed their own digital filters tend to be less enthusiastic about MQA than those who strictly use off-the-shelf filters. There are at least two inferences that could be made from this. The first is that companies with custom filters would not want to give up a potential competitive advantage by having the entire industry converge to one single digital filter. The other is that they have a deeper understanding of how digital filters actually work, and therefore have more insight into the advantages and disadvantages of MQA's encode/decode process.

Every audiophile is free to form their own opinions on everything. Just as with the "upsampling" craze of 15 years ago, one can attempt to evaluate MQA by understand the technical underpinnings, or simply listening to it. Similarly they may attach whatever motives they wish to any manufacturer. In my experience one of the best rules comes from the Watergate inquiry - "Follow the money".

As always my posts are strictly my own opinions, and not necessarily those of my employer or mailperson.