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With the Cary's control set to its maximum of "10dB feedback"---when measured, this in fact turned out to be 6dB, a factor of 2x for the 8 ohm output and with the 8 ohm feedback switch position---you could certainly hear a more accurate frequency response, the benefits of a greater damping factor, tighter bass, and a midband more like that of the familiar Wilson WITT. However, much of the magic was lost. That particular degree of perfectly timed involvement, of convincing transient edges, of natural tonality and expression, was lost. Now what we had was just another very good tube amplifier…
Consider the proposition that a pure input signal is subjected to the usual nonlinear amplification and is then applied with all the subsequent errors back to the input to be amplified again. In theory, the errors are subtracted at the feedback connection, but there is inevitably some error in this subtraction. No problem, says the textbook: the wide bandwidth of the closed-loop amplifier will ensure that the signal and errors, and their errors, will go many times 'round the loop, reducing the distortion to below audible levels.
Or will it? Audiophile pundits know only too well that…
Many letters in response appeared in the March, April, and May 1998 issues of Stereophile
Thanks, Martin
Editor:
Many thanks to Martin Colloms for his most interesting article on negative feedback and amplifier design in the January '98 issue (Vol.21 No.1, p.87). Stereophile readers, I am confident, will be interested in reading a similar article by Jan Didden that was published in the Six:1997 issue of Audio Electronics (published by Audio Amateur Publications).
---Ray Segura, New Orleans, LA, Segurar@nctamslantdet.nola.navy.mil
Mr. Didden's article mentioned…
Feedback & Transient Response
Editor:
I read with interest Martin Colloms' discussion of negative feedback in the January Stereophile, and something occurred to me as I digested the article. I was wondering if there has been much thought given to the differences between steady-state vs transient response. It is relatively easy to think about the positive effects of negative feedback---sorry---during steady-state conditions, such as reproducing a sinusoidal waveform. The distortion components are somewhat static, and can be canceled out in real time.
Editor:
I read with interest Martin Colloms' discussion of negative feedback in the January Stereophile, and something occurred to me as I digested the article. I was wondering if there has been much thought given to the differences between steady-state vs transient response. It is relatively easy to think about the positive effects of negative feedback---sorry---during steady-state conditions, such as reproducing a sinusoidal waveform. The distortion components are somewhat static, and can be canceled out in real time.
However, during transient…
Voigt, Not Black
Editor:
I was surprised to find Martin Colloms---and John Atkinson in his footnote---perpetuating the notion that Harold Black "invented" feedback (January '98, p.87). As I recently pointed out elsewhere (Hi-Fi World, April 1997), that honor belongs to the British engineer Paul Voigt, a pioneer of high fidelity, who had incorporated it in his Motional Feedback Patent 231,972, dated January 29, 1924. Over 70 years later, motional feedback as applied to loudspeakers has made little further progress, and Voigt's use therein of selective negative feedback, which he…
Editor:
I was surprised to find Martin Colloms---and John Atkinson in his footnote---perpetuating the notion that Harold Black "invented" feedback (January '98, p.87). As I recently pointed out elsewhere (Hi-Fi World, April 1997), that honor belongs to the British engineer Paul Voigt, a pioneer of high fidelity, who had incorporated it in his Motional Feedback Patent 231,972, dated January 29, 1924. Over 70 years later, motional feedback as applied to loudspeakers has made little further progress, and Voigt's use therein of selective negative feedback, which he…
TIGER OKOSHI: Two Sides to Every Story
Tiger Okoshi, trumpet; Mike Stern, electric guitar; Gil Goldstein, acoustic piano; Dave Holland, acoustic bass; Jack DeJohnette, drums
JVC JVC-2039-2 (CD only). Jim Anderson, eng.; Akira Taguchi, prod. DDD? TT: 65:20
Tiger Okoshi, trumpet; Mike Stern, electric guitar; Gil Goldstein, acoustic piano; Dave Holland, acoustic bass; Jack DeJohnette, drums
JVC JVC-2039-2 (CD only). Jim Anderson, eng.; Akira Taguchi, prod. DDD? TT: 65:20
In recorded music, the artistic merit of the music is not entirely separable from the sonic quality of the recording. It requires an act of the imagination, a leap of faith, and considerable historical curiosity to enjoy old Charlie Parker records. In the case of Two Sides to Every Story, you ask yourself: Does Tiger Okoshi…
"One of the worst-kept secrets in audio engineering is that what we hear does not always correlate with what we measure." So wrote the late Richard Heyser 30 years ago, as quoted in Time Delay Spectrometry, a 1987 anthology of his writings (footnote 1). What do we hear? Music heard live consists of a sound pressure that changes according to the logical demands of two things that have no physical reality: the way in which music is structured in time and pitch, and how that structure is ordered by the composer/musician. Heyser, one of the most perceptive audio engineers I've had the privilege…
I suspect that the faces of many of the readers who thumb through the pages of Stereophile must resemble those peering out of some Norman Rockwell representation of Americana: little children, their noses pressed hard against the display window of an urban department store in the weeks preceding Christmas, eyes aglow at the sight of some epic model train or exquisitely detailed dollhouse. So near, yet so far.
Discussions of the relative merits of SACD and DVD-Audio, or of upsampling and various forms of filtering, must seem every bit as remote to the average audiophile. Still,…
Let 'er rip
With its front-loading disc drawer, illuminated display, and straightforward remote, operating the SACD1000 was self-explanatory, so I just plugged in to the right and left front speaker outs and let 'er rip.
With its front-loading disc drawer, illuminated display, and straightforward remote, operating the SACD1000 was self-explanatory, so I just plugged in to the right and left front speaker outs and let 'er rip.
Having auditioned a number of tubed integrated amps in the months leading up to this evaluation, I decided to remain in that mode for a little while longer. My reference system included a Mesa Baron power amp (mainly in the 90W 1/3 pentode-2/3 triode mode), the single-ended triode Blue Circle Galatea preamp, and a pair of Joseph Audio's two-way RM7si Signature…
Before moving on to SACDs, I dug out my most trusty reference disc, Ralph Towner's A Closer View (ECM 1602), and cued up "Opalesque." The Sony's kaleidoscopic quality of inner detail killed me as usual, but there was something alluring and intimate about the Philips' velvety resolution, and the way it conveyed the physical immediacy of Gary Peacock's bass without shortchanging me in terms of instrumental detail...although, for CD playback, I think I liked the CL-20's balance of euphony, body, resolution, and dimensionality a touch more than the Sony's airy ultraprecision. But now I'm…