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Ben Duncan  |  Sep 09, 2020  |  First Published: Jun 01, 2001  |  28 comments
In high-end circles, the sonic repute of integrated-circuit op-amps (from "operational amplifier") is, at best, checkered. Of course, the expertise with which they are used and the parts they're used with can make all the difference. For example, my DIY preamplifier design, "AMP-02," published in Hi-Fi News & Record Review in 1989–90, and my earlier (1983–84) AMP-01 (footnote 1), I used the better IC op-amps of the time throughout. Both units were thought to outperform cost-no-object commercial units of the time that employed discrete transistors and even tubes, and only indicate what's possible.
Peter W. Mitchell  |  Aug 03, 2020  |  First Published: Feb 01, 1991  |  9 comments
I want to talk about the acoustics of live music and recordings. As I write this I'm back in Boston for a week, re-calibrating my ears with (excuse the expression) the "absolute sound" of live music in various concert halls. On Friday the Boston Symphony played symphonies by Mozart and Shostakovich, producing (as always) magnificent sound with the aid of Symphony Hall's near-legendary acoustics.
Ben Duncan  |  Jun 12, 2020  |  First Published: Dec 01, 1995  |  68 comments
Testing the RF transmission of Kimber Kable, up to 3GHz, at Ben Duncan Research Labs, in 2008. The resulting proof of RF rejection was published on-line by Russ Andrews Accessories in England. (Photo: Naomi Swain).

Editor's Preface: In an article in the October 1995 issue of Stereophile, Professor Malcolm Omar Hawksford used Maxwell's Equations to develop a mathematical model describing the behavior of cables at audio frequencies. Among the predictions of this model were that for good conductors there exists an optimum size of wire for audio signal transmission, and that for a wire larger than this size an energy storage mechanism would exist. In his article Malcolm described a simple experiment, the results of which appeared to confirm his hypothesis.

Then serendipity struck. English engineer Ben Duncan, whose writings have occasionally appeared in Stereophile, sent me an article he had written for the pro-audio magazine Studio Sound. The results of a series of cable measurements he had performed seemed to confirm the Hawksford Hypothesis. We offer them here for your delight and delectation.—John Atkinson

John Atkinson  |  May 27, 2020  |  10 comments
Designing Audio Power Amplifiers, Second Edition, by Bob Cordell, Routledge/Focal Press, 2019. 776pp. $160.00, hard cover; $97.95, paperback.

I first met Bob Cordell at clinics he gave at the last audio show Stereophile organized, Home Entertainment 2007, in Manhattan. At those clinics, Bob shared his views on why amplifier measurements are not always good at predicting differences in sound quality. So when I was scheduled to host a seminar—"Amplifiers: Do Measurements Matter?"—at this year's now-canceled AXPONA, Cordell was on the short list of designers I felt would offer valuable insight.

John Atkinson  |  Apr 10, 2020  |  66 comments
In his review of the three-way, active Dutch & Dutch 8c loudspeaker in the August 2019 issue of Stereophile, Kalman Rubinson concluded that "The D&D 8c demonstrates that active, DSP-empowered speakers are the future." I was equally impressed by the 8c's measured performance—a superbly flat on-axis response and an unmatched control of dispersion over the entire audioband—and asked to borrow a pair so I could experience the speakers in my own listening room.
Ben Duncan  |  Feb 12, 2020  |  First Published: Jul 01, 1995  |  7 comments
Have you ever suspected that the component you bought after diligent research is somehow not "typical"? That its sound seems to bear little resemblance to the descriptions in the reviews you read? Sure, you listened to the unit before purchase, but the one you took out of the box at home—was that the same unit? And if you suspect your new unit's sonic quality is below par, just how do you or your dealer go about proving it?
John Atkinson  |  Feb 11, 2020  |  First Published: Oct 01, 1991  |  7 comments
Author's Note: Although I started accompanying Stereophile's loudspeaker reviews with measurements soon after I joined the magazine in 1986, it wasn't until 1989, when we acquired an Audio Precision System One electronics analyzer and the then-new MLSSA speaker measurement system from DRA Labs, that I developed the standardized data presentation that is still featured in our reviews more than three decades later. In this article from October 1991, I summarize the results from the first two years of using MLSSA to test 69 loudspeakers.—John Atkinson
Ben Duncan  |  Oct 10, 2019  |  First Published: Jan 01, 1992  |  10 comments
Power amplifiers fascinate me. In the past 15 years I've helped design and build over a dozen advanced models, with output powers ranging from 50 to 2500W, for a number of the UK's professional equipment manufacturers. To learn from others' ideas and mistakes, I've also repaired, measured, used, and reviewed hundreds of makes of amplifier. My experiences have led me to regard the power amplifier as one of the messiest, most imperfect pieces of electronic equipment in the record/replay path.
J. Gordon Holt  |  Aug 08, 2019  |  First Published: Sep 01, 1966  |  30 comments
One of the most firmly-established audio platitudes is the one which says "The specs don't tell the whole story." One reason for this, of course, is the fact that most manufacturers, preferring to sell their products on the basis of emotional appeals in ads rather than on hard, cold performance claims, do not attempt to make their specs tell the whole story.
Irving M. Fried  |  Jun 06, 2019  |  First Published: Sep 01, 1962  |  16 comments
Ever since the first electrical loudspeaker—a glorified headphone with a horn on it—was outmoded by the balanced-armature cone speaker, paper has been the standard diaphragm material for speakers reproducing low frequencies. The Rice-Kellogg moving-coil transducer replaced the balanced-armature driving system in 1925, but the paper cone remained. And although many improvements have since been made, were no more major changes in loudspeaker design for over 30 years!
Robert Harley  |  May 28, 2019  |  First Published: Nov 01, 1994  |  7 comments
If there's one buzzword in high-end audio for the 1990s, it's undoubtedly jitter. "Jitter" describes timing variations in the clock controlling the ones and zeros that represent the analog audio signal. If that clock isn't stable to an extraordinarily precise degree, the sound quality of the digital processor will be degraded.

A CD transport/digital processor combination introduces jitter in three ways: 1) the transport puts out a jittered signal; 2) the S/PDIF or AES/EBU interface between the transport and processor creates jitter; and 3) the digital processor adds its own jitter to the clock. These additive factors are largely responsible for the great range in sound quality we hear from different transports and interfaces.

John Atkinson  |  Mar 19, 2019  |  9 comments
High Performance Loudspeakers: Optimising High Fidelity Loudspeaker Systems, Seventh Edition, by Martin Colloms. John Wiley & Sons, Inc., 2018. Paperback, 696 pp., $95. Available as an eBook, $79.99.

"Listen to that—that's what I mean by 'cone cry!'"

It was 1979. I'd been taking part in a blind listening test of loudspeakers organized by Martin Colloms (footnote 1) for the British magazine Hi-Fi Choice and, after the formal sessions had ended, had asked Martin to explain something I'd heard. A drive-unit's diaphragm produces cone cry when it resonates at a frequency unconnected with the musical signal it is being asked to produce; we had been using an anechoic recording of a xylophone, and one of the loudspeakers we'd been listening to was blurring the pitches of some of the instrument's notes.

Jay Clawson, Chuck Zeilig  |  Mar 07, 2019  |  First Published: Jun 01, 1986  |  39 comments
Publisher's note: The following article, from the early days of Compact Disc, is presented with no claim for absoluteness. (In fact, just as we go to press in the spring of 1986, we received a manuscript from Philip Greenspun, Product Review Editor of Computer Music Journal (Cambridge, MA), who had precisely the opposite result when comparing CD to analog versions of the same recording, though it was unclear that his test procedures were as thorough as in the tests by these authors.) The tests described are neither single- nor double-blind, and the author's decision to forego conversation while listening to the same products does not by any means guarantee lack of mutual influence—especially because their musical tastes are so well known to each other. Moreover, repeating the test with different phono equipment, a different CD player, and a different replica of the master tape would likely yield somewhat different results.

Nevertheless, I think the basic conclusion is sound: good CD reproduction is remarkably close to a fairly good version of master tape sound; there's a good chance that it's more accurate than what you'll get from the average cartridge, tonearm, and turntable.

J. Gordon Holt  |  Feb 07, 2019  |  First Published: Jul 01, 1985  |  8 comments
The main inherent advantage of the full-range electrostatic loud speaker system is that it allows a single diaphragm to embody the conflicting attributes needed for optimal performance at both extremes of the audio range. Its thin-membrane diaphragm can be made exceedingly light, for superb transient response and extended HF response, yet it can be about as large in area as desired, for extended LF response.
Kalman Rubinson  |  Jan 22, 2019  |  64 comments
Revel began demonstrating prototypes of the Performa F228Be, reviewed elsewhere in this issue, at the Consumer Electronics Show and other audio events in 2015, though they had yet to settle on the model name. The most salient feature that distinguished the F228Be-to-be from the established Performa3 F208 was the new beryllium tweeter, and while it sounded more than okay under show conditions, I always heard a bit of brightness and harshness. I knew it was still a work in progress, but I wasn't very eager to want to take it home.