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I don't think I've ever seen an audio debate as nasty as the one over Master Quality Authenticated (MQA), the audio-encoding/decoding technology from industry veterans Bob Stuart, formerly of Meridian and now CEO of MQA Ltd., and Peter Craven. Stuart is the company's public face, and that face has been the target of many a mud pie thrown since the technology went public two years ago. Some of MQA's critics are courteous—a few are even well-informed—but the nastiness on-line is unprecedented, in my experience.

It's day five of our planned month-long stay à Paris, late April through most of May. My wife is here for work—for me, it's strictly for pleasure—and we're enjoying Paris's rich, sensual goodness: food, museums, architecture, coffee, people, food. And yet, earlier today, when we were out for a walk—we've been walking close to 10 miles each day, exploring the city—I realized that my life here has been missing something important.

The New Analog: Listening and Reconnecting in a Digital World, by Damon Krukowski. The New Press, 2017. Hardcover, 240 pp., $24.95. Also available as an e-book.

Defining noise is tricky business.

In high-end audio, noise is often defined as the enemy—of music, beauty, truth. Engineers and enthusiasts alike spend significant amounts of time, energy, and money attempting to minimize or control noise so that it has the least possible impact on the source signal: music. In this way—if we are intelligent, careful, and fortunate—we can extract from our stereos cleaner, clearer, more naturally beautiful sound for listening experiences that are enriching, emotionally compelling, and, above all, fun. On the other hand, when noise is allowed to excessively modulate the signal, music can sound relatively abrasive, more mechanical, and, ultimately, less engaging.

I figured it was coming, but it wasn't until just after I'd returned from the Audio Engineering Society's 2016 International Conference on Headphone Technology—held last August in Aalborg, Denmark—and was writing up my report and summary on the event for InnerFidelity.com (footnote 1) that I knew for sure: Headphones are about to change . . . a lot.

Author's Note: We are grateful to Stereophile for the opportunity to address some frequently repeated technical questions appearing in comments to articles. Recently this has included misunderstandings about noise calculation, dynamic range, resolution, definition, music spectra, channel capacity, lossless processing and temporal aspects of digital channels.

To simplify this document we have grouped the topics and set them as questions and answers either as response, tutorial or axiom. Some months ago we published a comprehensive Q&A for an online forum and to avoid repetition we occasionally refer to topics already discussed there (see [37] in the "References" sidebar).—J. Robert Stuart

Jim Austin briefly discusses MQA in his review of the Explorer² in this issue, but a more complete description of MQA can be found in an article posted on Stereophile's website at the end of 2014.

MQA involves two fundamental concepts, discussed in a paper presented to the Audio Engineering Society in October 2014, the first responsible for a potential improvement in sound quality, the second responsible for a large reduction in the bandwidth required for storage and streaming of high-resolution files...