MQA

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.

In an article published in the March 2018 Stereophile, I wrote that critics have been attacking MQA, the audio codec developed by J. Robert Stuart and Peter Craven, by accusing it of being lossy. The critics are right: MQA is, in fact, a lossy codec—that is, not all of the data in the original recording are recovered when played back via MQA—though in a clever and innocuous way. For MQA's critics, though, that's not the point: They use lossy mainly for its negative emotional associations: When audiophiles hear lossy, they think MP3.

The right thing at the wrong time is the wrong thing.—Joshua Harris

The sampling theory formulated by Claude Shannon in the late 1940s had a key requirement: The signal to be sampled must be band-limited—that is, it must have an absolute upper-frequency limit. With that single constraint, Shannon's work yields a remarkable result: If you sample at twice that rate—two samples per period for the highest frequency the signal contains—you can reproduce that signal perfectly. Perfectly. That result set the foundation for digital audio, right up to the present. Cue the music.

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

"The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point."—Claude Shannon

Since its announcement at the end of 2014, Master Quality Authenticated, the MQA encoding/decoding system, has spawned outspoken criticism. Some of the more thoughtful negative reactions have come from engineers such as Dan Lavry, Bruno Putzeys, and Daniel Weiss. Others have been expressed by manufacturers of digital products: the late Charley Hansen at Ayre Acoustics, for example, along with Jason Stoddard and Mike Moffat at Schiit Audio, John Siau at Benchmark Media Systems, and Jim Collinson at Linn Products. Some have been audio writers: Doug Schneider, at SoundStage!, and Paul Miller and Jim Lesurf, at Hi-Fi News. Most vociferous have been anonymous website posters. As Jim Austin remarks in his examination of MQA's decoding of impulse-response data elsewhere in this issue, "the nastiness online is unprecedented."

CES 2016 marked the first time that three writers for Stereophile—Editor-in-Chief, John Atkinson; AnalogPlanet analog guru, Michael Fremer; and this Contributing Editor—could sit down in the same room with Bob Stuart of MQA/Meridian and spend a concentrated amount of time comparing before- and after-MQA encoded (Master Quality Authenticated) tracks.

Radka Toneff & Steve Dobrogosz: Fairytales: Original Master Edition (MQA)
Odin LP03 (original LP, 1982); Odin CD9561 (24-bit/48kHz MQA-encoded FLAC file; Tidal Masters stream; hybrid MQA-CD; original sample rate 192kHz; 2017). Arild Andersen, prod. (1982, 2017); Andreas Risanger Meland, exec. prod. (2017); Tore Skille, Tom Sætre, original engs.; Svein Vatshaug, Rune Sund Nordmark, recorder restoration; Thomas Baårdsen, Geir Iversen, digital transfer of original tapes; Morten Lindberg, Peter Craven, Bob Stuart, digital restoration; Erik Gard Amundsen, technical advisor. DAA (original LP); DDD (MQA). Except: "My Funny Valentine," ADA (LP), ADD (MQA). TT: 40:11
Performance ******
Sonics ******

"See her how she flies . . ." When I first heard that lyric, from Jim Webb's "The Moon Is a Harsh Mistress," sung by a hauntingly fragile woman's voice and supported by a sparse yet lyrical piano accompaniment, at an audio show in 1983, I got chills. Who was this empathetic singer? Back in my cabaret-musician days, more than four decades ago, I backed so many singers with beautiful-sounding pipes but who didn't seem to comprehend the meaning of the words—yet this unknown woman directly communicated the song's emotion.