Master Quality Authenticated (MQA): The View From 30,000 Feet

Disc players,
Digital-to-analog converters
Master Quality Authenticated (MQA): The View From 30,000 Feet

[Editor's Note: The May/June issue of The Absolute Sound, which mails to subscribers on March 30, includes a comprehensive evaluation of Master Quality Authenticated (MQA), a new digital technology that delivers better-than-high-resolution sound quality at a bit rate comparable to that of CD. My evaluation was informed by listening to hundreds of MQA-encoded tracks, decoded by the Meridian 808v6 CD player/DAC, over several weeks in my own reference system.

As part of that package of MQA coverage, which includes an explanation of the technology, FAQ about MQA, an examination of the claim that MQA can sound better than the original master, and reviews of the first MQA-capable decoders (the Meridian 808v6 CD player/DAC and Meridian Explorer2 DAC), I included the following editorial, entitled "MQA: The View From 30,000 Feet."]

In this issue’s cover story I explain some of the technology behind Master Quality Authenticated (MQA) and describe how it sounds. But I’d like to use this space to step back and take a larger view of the history of digitally recorded music, audio technology, and how MQA fits into that historical context.

To recap, MQA is a technology that simultaneously improves digital sound quality while dramatically lowering the bit-rate. It’s an encode-decode system, meaning that for maximum fidelity the music must be encoded with MQA, and played back through a device with MQA decoding. MQA is, however, backward compatible with all existing distribution channels and playback hardware. If you don’t have an MQA decoder, you get slightly-better-than-CD sound. If you have an MQA DAC, the file “unfolds” into the high-resolution signal.

It’s not quite accurate to call MQA a “technology” because it’s more than just a set of hardware and software techniques. Rather, MQA is a nearly-ground-up rethinking of how to best deliver to the listener as close a facsimile as possible of the original musical event. MQA starts with the analog signal in the studio and ends with the analog signal on playback. It ties together every element in that chain into essentially a single analog-to-analog system.

Let’s look at a brief history of digital audio and how that development path led us to the current state of affairs. In the late 1970s, the first digital recorders were commercially introduced, and became ubiquitous a decade later. These machines, based on pulse-code modulation and operating at 44.1kHz or 48kHz sampling and 16-bit quantization, were quite crude by today’s standards. Nonetheless, digital recorders quickly replaced analog tape machines in the studio. The compact disc, with its 44.1kHz sample rate and 16-bit word length, became the standard for distributing digital audio to consumers. As we all know, the CD took over the world beginning in the mid-1980s.

This switch from purely analog technology to digital had its advantages, but also some significant drawbacks. Once the signal was in the digital domain it could be copied, transmitted, and manipulated with no loss of sound quality. But the penalty for that convenience and power was paid at the interfaces between the analog and digital worlds, specifically the analog-to-digital converter used to make the recording and the digital-to-analog converter that transformed a series of numbers back into music. These two ends of the chain exacted a significant sonic penalty, in part because of the steep low-pass filters required to make digital audio work. The design of these filters came out of the sampling theory first developed in 1927 by Harry Nyquist and advanced in the 1940s by Claude Shannon.

Working within the constraints of the so-called “Nyquist-Shannon” sampling criterion, digital audio improved over the past 30 years with higher sampling rates, greater bit depth, lower jitter, and myriad other techniques that realized significantly better sound. In the mid-1990s, recording professionals began using 96kHz/24-bit recorders, which allowed them to make better sounding 44.1kHz/16-bit compact discs. Nonetheless, the consumer experience was limited to 44.1kHz/16-bit quality. In the late-1990s, two attempts to move beyond the CD, Super Audio Compact Disc (SACD) and DVD-Audio, essentially failed in the wider marketplace (DVD-Audio spectacularly so). More recently, the music-only version of Blu-ray Disc has been met with a tepid response.

And then came the Internet, and with it the ability to distribute digitally encoded music without the need for physical formats. It’s impossible to overstate the significance of this development. Physical formats are massively difficult to develop and launch, technically, politically, and commercially. But the Internet allowed music labels (the “content providers” in industry parlance) to distribute high-bit- rate music to consumers in the form of downloads without the constraints imposed by a new physical format.

That development was both a blessing and a curse. The blessing was that here was a cheap and easy way to deliver to consumers the best-available representation of a recording. The curse was that the record companies were delivering to consumers the best-available representation of a recording—a recording that could easily be copied, shared, and even pirated for profit. The record labels’ opening of their vaults by selling high-bit-rate downloads would be tantamount to throwing open the doors to an unguarded shopping mall. Once their catalogs were out in the world, the record companies would have nothing left to sell.