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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 21st November 2018, 10:29 AM   #10001
mmerrill99 is offline mmerrill99
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Originally Posted by PMA View Post
Thank you for posting your analysis, George. I will post mine as well, but it is good to have yours as an independent one.

However, I do not think it is a technical point or real test parameters that are attacked. It is the ABX itself, by those who do not like the protocol. I understand it, but if I have a choice between technically well performed ABX and a sighted test, I would vote for the ABX. Further, where is the proof that the parameters like level equalization within 0.2dB were fulfilled in the sighted test? That would be my question to the oponnents.
Sure all questions about sighted listening can & are usually asked without the push back seen when questions are asked about ABX testing.

Sorry but I disagree with your categorization of your ABX tests as "technically well performed" for the reasons already stated
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Old 21st November 2018, 10:30 AM   #10002
mmerrill99 is offline mmerrill99
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Originally Posted by PMA View Post
As you know well, level difference is not only a result of "volume control setting", but it is however a quite complex result of frequency response and non-linearities as well. As a non-linearity in my DUT goes up to 1%, it affects the "level" as well, should it be a peak level, peak rms, avg rms and min/max rms. Please check the file stats I have shown in my previous post.

However, we still have a "null" ABX result, so we should not blame the result to a "poor" 0.2dB level matching.
You miss the point completely.
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Old 21st November 2018, 10:58 AM   #10003
gpapag is offline gpapag  Greece
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John Curl's Blowtorch preamplifier part III
Quote:
Originally Posted by PMA View Post
Thank you for posting your analysis, George. I will post mine as well, but it is good to have yours as an independent one.
You are welcome Pavel.
Note: Some differences in min, max RMS Power btn mine and Pavels statistics is due to a different setting of analysis settings. Pavels is at 50ms (Window Width), mine is at 1ms (Resolution). If I set mine to 50ms too, differences are at the second decimal point.

Ive already said that the amp Pavel used does not change the dynamic range of the signal.
I have asked myself a relevant question though on this point.
When I am to arrange such a comparative test: In case one of the DUTs changes the dynamic range appreciably (>1-2dB), either due to increased noise floor or due to smooth compression of the high level peaks or both, what instrument reading should I use for to level equalize the two files (target is equal perceived level of loudness)?
Peak hold, VU peak, average RMS power?


George
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Old 21st November 2018, 11:02 AM   #10004
Jakob2 is offline Jakob2  Germany
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Originally Posted by PMA View Post
Oh, I see. In a test setup itself, the level difference is verified to be in order of 0.01dB. Less than 0.1dB. Now, please tell me why you ask, if there has been no positive ABX protocol yet?.
Im not sure to which event you are referring to?! In which context did i ask "why there has been no positive ABX protocol yet?" (you surely meant ABX result, dont you?).

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In case there are positive results, I understand there is a reason of being suspicious to the level difference only. I still have a strong feeling there is a reluctance to the ABX method itself, rather than to real technical issues. Seems to me as a substitute issue.
Ive presented the results from various studies where different "blind test" protocols were compared. Did you miss these?
Results of these comparison (comparison means to present the same sensory difference to the test subjects and to look for differences in the results/correct answers) were always that the proportion of correct answers in the ABX tests was significantly lower than in the other tests (like A/ or 3AFC) .
That was already noted shortyl after the invention of the original ABX protocol in the 1950s. Tests by other experimenters found that (when testing pitch difference) the DL found was always lower in A/B tests than in ABX tests, which means that the sensitivity of the detectors (aka participants) was higher in A/B than in ABX.
In addition the test participants reported their subjective feeling of beeing more uncomfortable in the ABX tests.

So there exist hard scientific evidence for the fact that the ABX protocol indeed makes it more difficult for participants not only in listening test but in food tests as well.
That holds true for simple directional tests - like the pitch example ive mentioned - and it gets surely even more difficult in the case of multidimensional tests (aka listening for any difference/preference with music as stimulus).

Your next point needs a extra post....
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Old 21st November 2018, 11:08 AM   #10005
PMA is offline PMA  Europe
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Originally Posted by Jakob2 View Post
A positive control is a difference (known to be detectable) presented within a test setup to check if everything works as intended.

So, the answer to your question is simple, use material where such difficulties does not exist; for example take the "wire sample" and use it to present the mentioned level difference as a positive control.
Hello Jakob, once again to this. I made a "wire test" against a "rip" (same music sample, but a little bit different length for the obvious reason - totally same sample would disclose which is which in my hybrid amp listening test). Please see that I was not kidding when speaking about level matching within 0.01dB order.
Attached Images
File Type: png origclapt.png (86.7 KB, 269 views)
File Type: png wireclapt.png (86.8 KB, 270 views)
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Old 21st November 2018, 11:13 AM   #10006
mmerrill99 is offline mmerrill99
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Originally Posted by PMA View Post
Hello Jakob, once again to this. I made a "wire test" against a "rip" (same music sample, but a little bit different length for the obvious reason - totally same sample would disclose which is which in my hybrid amp listening test). Please see that I was not kidding when speaking about level matching within 0.01dB order.
Again, you are completely blind (bias?) to what I & Jakob are saying.
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Old 21st November 2018, 11:17 AM   #10007
PMA is offline PMA  Europe
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Originally Posted by Jakob2 View Post
Im not sure to which event you are referring to?! In which context did i ask "why there has been no positive ABX protocol yet?" (you surely meant ABX result, dont you?).

This one
Can you tell original file from tube amp record? - test
The test is described in the 1st post of the thread.

As a "protocol" I mean a protocol that is provided by an ABX Foobar plug-in (foo_abx 2.0.2 report). This protocol my be checked for validity here
foobar2000 ABX Log Signature Tool

An example of such protocol/report is my result
Can you tell original file from tube amp record? - test

Such report and the signature check makes at least some proof that the test was not cheated by file modification etc., as it is a long-distance test.
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Old 21st November 2018, 11:26 AM   #10008
DF96 is offline DF96  England
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Originally Posted by mmerrill99
Semantics, semantics - you know what I mean but choose to take a different meaning - I wonder should you be accused of "putting words in my mouth"?
So you accept that what you claimed has not not been said 'on here' has been said 'on here'? Even if it had not been said before (which I doubt) it has now been said by you, and you were 'on here' when you said it.

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Try me with some evidence rather than some spurious argument.
Hhoyt has given you some evidence.

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Of course there can be false positives in sighted listening, I stated that many times already but you fail to admit that ABX testing is prone to false negatives despite evidence & many here still use ABX test results (of any quality) to try to claim that a sighted listening report is a false positive. Fact of the matter is you are trying to elevate some unknown quality listening 'test' to a status that is unwarranted & unscientific & trying to use it to negate sighted listening
My bias is that I would take any reasonable unsighted test over any sighted test. There: my bias is out in the open for all to see. It seems to me that this is a common-sense position to take, given all the false positives which can easily be introduced into sighted tests.

My bias is that a genuinely obvious difference will be heard in an ABX test; not necessarily by everyone, and not necessarily every time, but often enough (as shown by the statistics). Whether some other blind test will be better or worse at doing this is a separate issue. I make no claims about how 'scientific' ABX is; I merely believe that all sighted tests are 'unscientific' and some are merely marketing.
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Old 21st November 2018, 11:43 AM   #10009
PMA is offline PMA  Europe
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Originally Posted by DF96 View Post
I make no claims about how 'scientific' ABX is; I merely believe that all sighted tests are 'unscientific' and some are merely marketing.
On this I agree completely, though it took my years (unfortunately) to come to the same conclusion.
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Old 21st November 2018, 11:50 AM   #10010
scottjoplin is offline scottjoplin  Wales
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