John Curl's Blowtorch preamplifier part II - Page 1845 - diyAudio
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Old 28th November 2011, 02:35 AM   #18441
Pano is offline Pano  United States
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About 1/3 the price of gold, on the current market.
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Old 28th November 2011, 09:25 AM   #18442
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Originally Posted by SY View Post
It's unremarkable that some people catch differences in sound more easily than other; no-one has ever claimed otherwise.
That is a given, but independent from the ABX case.

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For example, Lipshitz heard differences in his test that Tiefenbrun didn't.
They all missed a difference during the "official" listening trials.

Afterwards Lipshitz realized that difference in relais sound was detectable, afair Vanderkooy detected an additional difference in the noise floor.

Something very similiar happended in the detmold DSD/PCM listening tests and in the swedish radio tests of audio codecs as well.

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One notes that Tiefenbrun agreed before the blind portion that the differences were audible and that the test conditions were satisfactory. Once it was ears-only... errr....
As no positive control under ABX conditions was presented we still donīt know if it was "ears-only" or more lower sensitivity under ABX conditions.

A hint might be the fact, that there were audible differences that remain undetected by Tiefenbrunn.

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It's also unremarkable that people can design a bad test; no-one has ever claimed otherwise. They can also design a good test. With my points attended to, no-one to date has demonstrated audibility of different boxes of gain.
In the quoted sentence you mentioned that a "careful listener.......", but obviously it not only depends on "careful listening" to detect a difference.

And tests without training time for the participants and proper implemented positive/negative controls belong simply not to the category "good test" .

I think Michael Fremer demonstrated that he was capable to detect differences between amplifiers in his double blind test attempt at the AES convention back in ?1989?
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Old 28th November 2011, 09:48 AM   #18443
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Nobody ever claimed controlled tests are perfect and ideal.
Not explicitely but implicitely, otherwise it would not make any sense to mention questionable test results in which listerners failed to detect something.

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But look at the alternative and there's really no competition.<snip>
Of course and there will never be something like a perfect test.
But only _good_ tests lead to useful results.

And most bias effects donīt vanish in a controlled listening test unless the control addresses these effects carefully.

Safeguards in the case of overlooked effects are positive and negative controls.
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Old 28th November 2011, 10:22 AM   #18444
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Double blind ABX tests inhibit hearing ANY subtle differences, except for the few that have been shown to be detectable. Yet, there are many more differences that the ear can detect, especially over a longer period of time.
The proof of this is our listening experience over the decades. IF only the limited criteria of frequency response, reasonably low distortion, level, and absolute polarity were the ONLY subjective differences between amplifiers, or preamplifiers, then EVERYTHING that I have designed in the last 30 years sounds exactly the same. This is because I have taken all of those factors into account for the last 30 years, and more. I told Dr. Lipshitz that in a LTE to TAA back in 1979.
ANY engineer can meet those criteria, so we might as well give up trying to make something 'better'. And you know, many have!
I beg to differ, because I can hear and remember differences in each and every one of the products that I have personally used, and I have a tendency to 'edge out' a great many competing products, without unnecessary advertising and salesmanship. How is this possible? Just about anyone here should be able to make a preamp with some of the cheapest IC's now available that is equal to the Blowtorch. I invite you to do it. Why not?
Of course there might be something wrong with ABX testing, and I think that there is. Then, each and every one of my designs might have a unique signature. That has been my experience.
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Old 28th November 2011, 11:26 AM   #18445
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Originally Posted by Jakob2 View Post

I think Michael Fremer demonstrated that he was capable to detect differences between amplifiers in his double blind test attempt at the AES convention back in ?1989?
No, he didn't. Audiophile lore pumped up by Fremer. When you have 5 trials, 100 participants, and someone doesn't turn in his score sheet, what you have is hype, not results.

As for the rest of what you wrote about Tiefenbrun's demonstration that, by ear alone, he could not detect a 16 bit ADC/DAC inserted into an analog feed, it does not accord with the published account of the test nor the recollections of at least one observer who was there.
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Old 28th November 2011, 11:28 AM   #18446
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Originally Posted by john curl View Post
Double blind ABX tests inhibit hearing ANY subtle differences, except for the few that have been shown to be detectable.
Circular logic. And patently untrue. But hey, if you can't hear differences, you can't hear differences. Nothing wrong with that, it doesn't diminish the quality of your designs.
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Old 28th November 2011, 12:27 PM   #18447
Jakob2 is offline Jakob2  Germany
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No, he didn't. Audiophile lore pumped up by Fremer. When you have 5 trials, 100 participants, and someone doesn't turn in his score sheet, what you have is hype, not results.
Might be, but it was 5 trial dbt, Fremer did turn in his score sheet (John Atkinson did as well), and Fremer correctly identified the amplifier playing 4 times out of 5. So you got Fremer correct 5 times out of 5 on the same/difference question, correct 4 times out of 5 for the question which amplifier (out of 3 possible) was playing. Atkinson and Fremer as a tag team were correct 9 times out of 10 for the same/difference question.

I donīt know if there were 100 participants overall, but it was reported that no other attendee of the AES-convention, who took the test reached a significant result.
Care to calculate the probabilities that Fremer was just guessing and that Fremer and Atkinson as a tag team were just guessing?

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As for the rest of what you wrote about Tiefenbrun's demonstration that, by ear alone, he could not detect a 16 bit ADC/DAC inserted into an analog feed, it does not accord with the published account of the test nor the recollections of at least one observer who was there.
Yeah, it was Lipshitz (and not Vanderkooy) who after Tiefenbrunnīs test realized that the noise level could be detectable; both Lipshitz and Vanderkooy knew already in front of the test, that the relay switching noice could be detectable.

Does this really make an important difference to my description wrt to the sensitivity of that test?
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Old 28th November 2011, 12:33 PM   #18448
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Does this really make an important difference to my description wrt to the sensitivity of that test?
No, it's still incorrect. As is your recounting of the Fremer incident.
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Old 28th November 2011, 12:45 PM   #18449
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Originally Posted by SY View Post
No, it's still incorrect. As is your recounting of the Fremer incident.
Sorry for the inconvenience, but i am not able to see my incorrectness:

Boston Audio Society - ABX Testing article

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.....Tiefenbrun's score for the series was 11 correct decisions out of 20, a result which shows no statistically significant ability to discriminate between "A" and "B" any more accurately than would be expected on the basis of random guessing.

At this point I thought that I could reliably distinguish between the "A" and "B" paths on the basis of the slight noise level increase which occurred when the PCM-F1 was inserted into the chain,.....
(written by Stanley P. Lipshitz)

The "Fremer incident" seems to be what i wrote, due to the description of Michael Fremer; afaik no one, not Clark, not Lipshitz expressed that Fremers description of his results was wrong.
Could you please quote the source, which tells other numbers or another story?
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Old 28th November 2011, 12:56 PM   #18450
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After an acclimatization period, a set of 10 trials was conducted in an unhurried fashion before breaking for lunch, after which a further set of 10 trials was conducted. Tiefenbrun's score for the series was 11 correct decisions out of 20, a result which shows no statistically significant ability to discriminate between "A" and "B" any more accurately than would be expected on the basis of random guessing.

At this point I thought that I could reliably distinguish between the "A" and "B" paths on the basis of the slight noise level increase which occurred when the PCM-F1 was inserted into the chain, and which was marginally audible due to the high gain of the Naim MAP 250 power amplifier combined with the low peak signal levels through the F1, which the peak-hold meters showed to have risen no higher than -20 dB...

I replied that I was going to listen to the difference in background hiss, and the subsequent series of blind trials showed conclusively that the two signal paths could be reliably distinguished on this basis alone.

What conclusion can we draw from this? Tiefenbrun's random results show that he had not been aware of either the background noise difference...
(Boldin is mine- SY) That does seem to be detection during the "formal" trials, right?
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