Fashions, Fads, & Single-Ended Amplifiers
Still other tweaks do seem to have a real effect on sound quality, but one too small or inconsistent to justify the work involved, even if the cost is small. Does anyone other than Clark Johnsen still routinely check their discs for Absolute Polarity? More importantly, does anyone still cryogenically freeze their CDs, or apply CD Stoplight—the infamous "green ink"—to the edges of their CDs? In each of the two latter cases, the effect on sound quality was positive. However, as the underlying technical problem of datastream jitter became more fully understood, and as low-jitter CD transports, D/A processors, third-box re-clocking devices, and electrical datalinks and connectors with matched impedance characteristics became available, the need for the tweak solution faded away.
Where does that leave the current fashion for low-powered, single-ended amplifiers driving high-sensitivity loudspeakers? I just don't know. Certainly, this is no flash-in-the-pan fad—I first heard such a system in Japan in 1978. And the Franco-Japanese philosopher/audio engineer Jean Hiraga has promoted the benefits of simple amplifier design—the simpler the better—since the mid-'70s. But only in the last two years has the single-ended craze really caught fire—driven in the UK by Peter Qvortrup's Audio Note company, and in the US by Joe Roberts' Sound Practices magazine, by Cary Audio Designs, and by commercial and DIY amplifier designs from high-end founding engineer Nelson Pass.
A single-ended power amplifier—tube or transistor—represents a radical departure from the philosophy that has fueled the development of audio equipment since the start: that to make a component "better," you try to make it more "accurate"—trying to prevent it from imposing its own character on the signal. Whereas for decades amplifier designers have striven to make their designs, in effect, "straight wires with gain," a single-ended power amplifier is a bent wire without much gain. True, the best-measuring SE amplifiers, such as Nelson Pass's solid-state designs, or the Bel Canto Orfeo that Dick Olsher reviewed a few issues back, have astonishingly low distortion for such simple circuits. But it's still a high enough level of distortion that there can be no doubt about its audibility.
With their high output impedances, too, SE amplifiers introduce very audible changes to the sounds of almost every loudspeaker they're used to drive—as explained by Robert Grost in this month's "Letters" section. Also in "Letters," Dick Olsher, an enthusiastic proponent of SE designs, argues that a typical response change is only 2dB. But don't forget—if a 0.1dB change in response over, say, a couple of octaves can be heard, 20 times that change over the same bandwidth is, in high-end audio terms, a gross difference, not a subtle one. Heck, my mother could hear that kind of difference.
"Ah, but you have to listen through the errors SE amplifiers make to hear the magic they produce, particularly in the midrange," argue the SE proponents. But with such audible changes, I have a hard time believing that to be possible.
Where do I stand? I don't yet know. Color me skeptical—the only SE amplifier I've heard at any length left me distinctly under-impressed. Yes, the midrange textures were gloriously liquid, but the bass was anemic, the dynamics limited, and the highs both rolled-off and grainy. Yet, as one of the ideas Stereophile was founded on was for its readers to listen for themselves, I have to admit that my opinion of SE sound is not fully formed. What I intend to do early in the New Year, therefore, is to get myself a couple of SE monoblocks—from Cary or Bel Canto, say, or from Gordon Rankin's Wavelength Audio—and have some fun listening. For the one thing that SE amplifier owners seem to be having is fun.
Cyberspace is full of their buzzing. Whether they're enjoying fooling around with homemade horn speakers, mostly based on Dr. Bruce Edgar's Tractrix enclosures, or just grooving on the unique thrill that comes from listening to something you've built yourself, the SE crowd seems to be the furthest thing around from the traditional image of the pursed-lipped, politically correct audiophile sitting in his solitary chair listening to endlessly different LP pressings of the Casino Royale soundtrack. And that can't be all bad.—John Atkinson