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FeaturesMQAReference
Listening to MQA
John Atkinson  |  Aug 18, 2016  |  67 comments
Last June, Jim Austin briefly discussed the operation of MQA in his review of the Meridian Explorer2 USB DAC, but you can find a more detailed explanation on Stereophile's website here and here. MQA involves two fundamental concepts, discussed in a paper presented to the Audio Engineering Society in October 2014. The first is responsible for a large reduction in the bandwidth required to store and stream high-resolution files, the second for a potential improvement in sound quality. . .
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FeaturesMQAReference
MQA: Questions and Answers
J. Robert Stuart  |  Aug 11, 2016  |  117 comments
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

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HistoricalReference
PASC & Philips' DCC
Peter W. Mitchell, Barry Fox, Peter van Willenswaard  |  Jul 05, 2016  |  First Published: Apr 01, 1991  |  2 comments
Editor's Note: In the 21st Century, lossy audio data compression, in the form of MP3 and AAC files, Dolby Digital and DTS-encoded soundtracks, and YouTube and Spotify streaming, is ubiquitous. But audiophiles were first exposed to the subject a quarter-century ago, when Philips launched its ill-fated DCC cassette format. What follows is Stereophile's complete coverage on both DCC and its PASC lossy-compression encoding from our April 1991 issue.—John Atkinson
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HistoricalReference
PDM, PWM, Delta-Sigma, 1-Bit DACs
Peter van Willenswaard, John Atkinson, Peter W. Mitchell  |  Jun 28, 2016  |  First Published: May 01, 1989  |  3 comments
Editor's Note: One-bit DAC chips in the 21st century, where the analog output signal is reconstructed from a very high-rate stream of pulses, are ubiquitous. But a quarter-century ago, those chips were only just beginning to stream from the chip foundries. In this feature, we aggregate Stereophile's 1989 coverage of the then-new technology, starting with Peter van Willenswaard on the basics.—John Atkinson.

1989 may well become the year of the D/A converter (DAC). CD-player manufacturers have, almost without exception, launched research projects focusing on this problem area of digital audio; many of these projects are already a year old. This is, however, by no means the only imperfection keeping us away from the high-quality sound we have come to suspect is possible with digital audio media, and maybe not even the most important.

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Computer Audio ReviewsFeaturesMQAReference
Inside MQA
John Atkinson  |  May 19, 2016  |  41 comments
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...

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J. Gordon HoltReference
Absolute Phase: Fact or Fallacy?
J. Gordon Holt  |  Nov 19, 2014  |  First Published: Oct 01, 1980  |  9 comments
Natural sounds produce different waveshapes during their positive and negative phases, and playback-system polarity reversal often changes the reproduced sound. Does this mean our ears are phase-responsive, or is there something else here we've been overlooking?

There has been much discussion recently among perfectionists about the importance of what is called "absolute phase" in sound reproduction. Basically, the contention has been that, since many musical sounds are asymmetrical (having different waveforms during positive and negative phases), it is important that a system make the proper distinctions between positive (compression) and negative (rarefaction) phases in playback.

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ReferenceFeatures
Audio Engineering: the Next 40 Years
John La Grou  |  Mar 13, 2014  |  9 comments
By 2035, the way we produce and consume media will be entirely different from how we experience it now. Today there is still a "fourth wall" between us and the media we consume: within three decades, that line between reality and its recreation will all but disappear. Our media experiences will become fully immersive—from spherical audio and video that tracks with our body's movements, to gestural computing, to physical-feedback devices, and more. Using tomorrow's technology, our children and grandchildren may find it difficult to distinguish the real thing from reproduced.
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Reference
Lossy Compression: the Sonic Dangers
Peter W. Mitchell, Robert Harley  |  Dec 10, 2013  |  First Published: Dec 01, 1991  |  13 comments
Editor's Introduction: In 2013, lossy compression is everywhere—without lossy codecs like MP3, Dolby Digital, DTS, A2DP, AAC, apt-X, and Ogg Vorbis, there would be no Web audio services like Spotify or Pandora, no multichannel soundtracks on DVD, no Bluetooth audio, no DAB and HDradio, no Sirius/XM, and no iTunes, to quote the commercial successes and no Napster, MiniDisc, or DCC, to quote the failures. Despite their potential for damage to the music, the convenience and sometimes drastic reduction in audio file size have made lossy codecs ubiquitous in the 21st century. Stereophile covered the development of lossy compression; following is an article from more than two decades ago warning of the sonic dangers.—Editor
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ReferenceFeaturesAudiophile Essentials
The 2011 Richard C. Heyser Memorial Lecture: "Where Did the Negative Frequencies Go?"
John Atkinson  |  Dec 19, 2012  |  First Published: Oct 21, 2011  |  144 comments
In the summer of 2011, Stereophile's long-time editor in chief, John Atkinson, was invited by the Technical Council of the Audio Engineering Society to give the Richard C. Heyser Memorial Lecture at the 131st Audio Engineering Society Convention in New York, October 21, 2011.
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ReferenceFeaturesTonearm Reviews
Arc Angles: Optimizing Tonearm Geometry
Keith Howard  |  Apr 08, 2010  |  First Published: Mar 08, 2010  |  1 comments
As Chester Rice, co-inventor of the moving-coil loudspeaker, once ruefully observed: "The ancients have stolen our inventions." So often, what is painted as new and innovative turns out to be something someone thought of long before. We have a habit of forgetting, and that applies not only to inventions, but to knowledge of other kinds as well.
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Reference
Book Review: Get Better Sound
Art Dudley  |  Jul 14, 2009  |  0 comments
Get Better Sound
By Jim Smith. Quarter Note Press (Cumming, GA), 2008. Paperback, 293 pages. ISBN 978-0-9820807-0-2. $44.50.
Web: www.getbettersound.com.
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Reference
It's a Vinyl World After All
Stephen Mejias  |  Jun 26, 2009  |  First Published: Jan 26, 2009  |  0 comments
It's a Vinyl World, After All: Michael Fremer's Guide to Record Cleaning, Storage, Handling, Collecting, & Manufacturing in the 21st Century
MF Productions mxangle3 (DVD). 2008. Michael Fremer, prod.; Joe Shelesky, Andre Kruger, Jeff Wilerth, dirs.; Joe Shelesky, editor. $30; available from Stereophile's secure e-commerce page.
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Reference
Book Review: Sound Reproduction: Loudspeakers and Rooms
Kalman Rubinson  |  Jun 25, 2009  |  0 comments
Sound Reproduction: Loudspeakers and Rooms
By Floyd E. Toole. Focal Press (Oxford, England, UK, www.elsevier.com, footnote 1), 2008. Paperback, 550 pages, ISBN 978-0240520094. $49.95.
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FeaturesReference
Cut and Thrust: RIAA LP Equalization
Keith Howard  |  Apr 02, 2009  |  First Published: Mar 02, 2009  |  0 comments
Until the Recording Industry Association of America hit the headlines in recent years with its antipiracy campaign, the initials RIAA meant one thing to seasoned audiophiles: the vinyl-disc equalization characteristic introduced in the 1950s to standardize what had previously been an anarchy of different EQs. Three decades later, as CD gained ascendance, a large proportion of audiophiles still knew what RIAA equalization was, and a good number of them had some idea or better of what the RIAA EQ curve looked like, and why it was applied.
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ReferenceFeaturesSubwoofer Reviews
The Science of Subwoofing
Dick Olsher  |  Oct 29, 2008  |  First Published: Jan 29, 1989  |  0 comments
There was a time, as recently as 40 years ago, when frequencies below 100Hz were considered extreme lows, and reproduction below 50Hz was about as common as the unicorn. From our present technological perch, it's too easy to smirk condescendingly at such primitive conditions. But just so you're able to sympathize with the plight of these disadvantaged audiophiles, I should tell you that there were two perfectly good reasons for this parlous state of affairs. First of all, program material at that time was devoid of deep bass; not because it was removed during disc mastering but simply because there wasn't any to begin with. The professional tape recorders of the day featured a frequency response of 50–15kHz, ±2dB—just about on a par with the frequency performance capability of a cheap 1988 cassette tape deck.
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