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In retrospect (what a clear view you get through the retrospectoscope!), the drum track on the HFN/RR Test CD was a definite non-starter. Among the 4 available amp comparisons, there were 14 sets of comparisons with this selection in the 8 sessions. Table 5 shows that in only 1 of the 14 was the correctness of the responses any better than by chance alone. As can be seen from Table 4, the other six selections were all equally highly effective in demonstrating the overall ability to distinguish difference rather well but to determine sameness rather poorly.
John Atkinson scratches his head
I hope that you will agree from Will's analysis that there did seem to be a slight audible difference between the two power amplifiers. With so many trials, the statistics give a high degree of confidence in the results. Are there obvious measured differences that would explain the blind identification?
I hope that you will agree from Will's analysis that there did seem to be a slight audible difference between the two power amplifiers. With so many trials, the statistics give a high degree of confidence in the results. Are there obvious measured differences that would explain the blind identification?
Absolute phase differences, though often audible under blind conditions, were not a factor here as both amplifiers are non-inverting. Level differences also did not contribute. However, there were slight frequency-response differences between the two…
Many relevant letters in response appeared in the July and October 1989 issues of Stereophile:
A "Golden Ear" or a "Lucky Coin"?
Editor: I've been called many things in my job as an equipment and music reviewer, but "lucky coin" ("Letters," May 1989) is by far the most aggravating. I confronted David "all amplifiers sound the same" Clark at the June 1988 CES and told him that I could hear differences among amplifiers and, furthermore, that anyone who couldn't ought not be reviewing them. He countered that unless I could demonstrate my ability in a double-blind test, my assertion was…
Thanks for the Show
Editor: Just a note to express our gratitude for the High End Show just past. It reaffirmed my belief that your reporting of the changing states of the art is both timely and tuneful. Although we were unable to listen to those few big demonstrations—Thiel, Martin-Logan, Threshold, Audio Research—due to time restrictions, we were able to hear some reasonable demos of their lesser models.
Editor: Just a note to express our gratitude for the High End Show just past. It reaffirmed my belief that your reporting of the changing states of the art is both timely and tuneful. Although we were unable to listen to those few big demonstrations—Thiel, Martin-Logan, Threshold, Audio Research—due to time restrictions, we were able to hear some reasonable demos of their lesser models.
Juli and I both enjoyed the two fringe events we attended most of all—the "Hearing Amplifier Differences" test had the best-quality sound we heard at the show. Hearing the…
Listening tests & discerning listeners
Editor: I think JA has shed some useful light on the continuing and vexing blind test debate, but I don't quite accept his hypothesis, as stated, that a blind listening test can conceal subjective differences. How then to explain the ability of participants with golden ears to hear those differences with very few errors, even in such tests?
Editor: I think JA has shed some useful light on the continuing and vexing blind test debate, but I don't quite accept his hypothesis, as stated, that a blind listening test can conceal subjective differences. How then to explain the ability of participants with golden ears to hear those differences with very few errors, even in such tests?
Two things seem clear: that the ability to discern these differences is a learned skill, and that blind testing, as described, impedes that skill. Those of us whose work demands the evaluation of high-end…
Listening tests & statistics
Editor: As an experimental psychologist, I was glad to see an attempt to apply some of the methods of my science to the issue of audible differences among amplifiers ("As We See It," Vol.12 No.7). While you did a great many things right in setting up this experiment, there are some serious flaws in your statistical analysis which have important implications for interpreting your results.
Editor: As an experimental psychologist, I was glad to see an attempt to apply some of the methods of my science to the issue of audible differences among amplifiers ("As We See It," Vol.12 No.7). While you did a great many things right in setting up this experiment, there are some serious flaws in your statistical analysis which have important implications for interpreting your results.
The basic problem is that your respondents were (as you sort of acknowledge in your footnote on p.17) biased to respond "different"—ie, that they could hear a…
Listening tests: a thorough analysis
Editor: I have read with great interest your article, "Blind Listening," in the July 1989 Stereophile. In view of the importance of the subject, please allow me extended comments on methodology and analysis. Hopefully I am beating the drums neither for subjectivists nor objectivists, but for understanding of the data you present.
Editor: I have read with great interest your article, "Blind Listening," in the July 1989 Stereophile. In view of the importance of the subject, please allow me extended comments on methodology and analysis. Hopefully I am beating the drums neither for subjectivists nor objectivists, but for understanding of the data you present.
For brevity, let D represent "different," and S, "same." D trials refer to trials where the amps were different; D responses, to "different" answers. Similarly for S trials and S responses.
1) Your tests biased…
For me, the iconic Adcom power amplifier was the GFA-555. As an aspiring audiophile, I was deeply impressed with Tony Cordesman's review in Stereophile in 1985 (Vol.8 No.4). That did it! After years of kit-building and doing it myself, the '555 was the first factory-built amp that I wanted and could afford. Over the years, I changed speakers several times, and even added a fully regulated power supply to the '555, but it never balked. At the end of its tenure at my house, it had been demoted to my third-string backup; today it's making someone else tap his toes.
That typifies my…
Sidebar 1: Specifications
Description: Five-channel solid-state power amplifier. Inputs: 1 line-level (RCA & XLR) per channel, switch-selectable; 12V signal input for remote power control. Binding posts: 1 pair multiway per channel. Continuous power: 300Wx5 into 8 ohms (24.8dBW), 450Wx5 into 4 ohms (23.5dBW); both at <1% THD, 20Hz-20kHz. Input sensitivity for full output: 1.61V RMS. Voltage gain: 29.67dB. Input impedance: 500k ohms (RCA), 10k ohms (XLR). THD+noise (typical): <0.135% (8 ohms), <0.3% (4 ohms). Frequency response: 10Hz-20kHz, +0/-0.25dB at 1W, 8 ohms. Power…
Sidebar 2: Cable Issues
The kindly delivery guy hefted the original review sample of the Adcom GFA-7805 (serial no. FCS0044) out of its crate and placed it gently on the floor in front of my equipment rack—it was too tall and deep for the slot available. He left with my gracious thanks for having saved my back. I then transferred the RS Audio Solution multichannel interconnects and the five Goertz speaker cables from my Bel Canto eVo6 amp to the GFA-7805, plugged in the power cord, and fired it up. After a few tense seconds as the front-panel LEDs flickered (as is normal for the power-up…