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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 13th March 2018, 08:12 AM   #1101
Tournesol is offline Tournesol  Belgium
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Quote:
Originally Posted by hitsware View Post
May I respectfully remind you that calculating the value of a link capacitor for a cut-off frequency of 20 or 20,000Hz at -3dB is a bit far from what one can expect from a "High Fidelity" system.
The phase linearity is something that makes a difference.
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Old 13th March 2018, 08:31 AM   #1102
Joe Rasmussen is offline Joe Rasmussen  Australia
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Originally Posted by scott wurcer View Post
A priori which one is faster or slower? I would think the FM and surface noise would invalidate any concept of blindness. You also imply ABX by stating this, I would be fine with extended listening in comfort as long as there is the "I don't know" factor.
Much to agree with you there.
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Old 13th March 2018, 11:09 AM   #1103
Jakob2 is offline Jakob2  Germany
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Originally Posted by scottjoplin View Post
What would the question be? It's going to have to be subjective. For instance, which is the "better" sounding, that's good enough!
As for the test protocol, forgive me I've no experience and not sure what it means. However, let us assume that everyone involved genuinely wants to find out what it is that makes one piece of equipment sound "better" than another, what would be a way to proceed?
Some people are interested to find out if a difference exists between two DUTs, other people are interested to find out if they prefer one DUT over the other (or are interested to find out if other people do prefer one of the..).

Sometimes they want to know if a specific difference can be detected.
Sometimes experimenters are interested what the population hears (or what subgroups hear).
And further it depends if they are exploring certain properties of the hearing sense (often related to the physiology reasons) and are therefore in most case unidimensional tests.
Otoh we are usually discussing multidimensional experiences and that is in reality a bit more complicated.

After settling the research question the experimenter has to design an experiment to approach that question in the best possible way.
If interested in population parameters he has to draw a sample from that population in the most random way possible.
If interested if a difference between two DUTs exists in principle it might be sufficient to find a single human that can differentiate between the DUTs.

If interested in the abilites of a specific person he would only test that person.

Furthermore it depends if he is searching for universial effects (under every condition in every reproduction system with every piece of music) or for subsets.

And within he choose one of the available test protocols; ABX is one of these and it means that the test participants listens to "A" then listens to "B" and finally listens to "X" (which can be either "A" or "B") and has to correctly identify it as "A" and "B" .
In the original version of this test there was no chance to repeatedly listen to the three options while it is at the discretion of the test participant how often he wants to listen to them.
But it is important to remember that it is only an ABX test if he listen first to "A" then to "B" and then finally to "X" to decide.

Another test protocol is the A/B test - often named as paired comparison - where only two items were presented. An A/B test can be a "same/different" test - when all four possible combinations "AB" "AA" BB" and "BA" are presented - and the participant has to answer if "same" or "different".

It can be a preference test - only "A" and "B" are presented in a random order" - and the participant has to express his preference.
It can be a discrimination test - again only "A" and "B" are presented in a random order - and the participant has either to identify "A" or "B" for a correct response or has to detect a certain difference like "more treble" or "more bass" .

There a several more (like ABC/HR often used in the assessment of lossy compression codecs) and all have specific advantages or drawbacks.
Beside the general interestests and quality criteria that should be met, there are several others that might be of interest, like efficiency for example, that could matter.

And the experimenter has to consider that every test situation and even specific test protocols can have an influence on the results.
Wrt the ABX test protocol it is known (since the ~1950s) that participants function within the ABX worse than in an A/B test.

In food tests there were some comparison done between different test protocols in the 1990s and the proportion of correct responses were higher in A/B tests as in ABX tests. (in short, links to the various publications i´ve posted in a "DAC listening test" thread).

Reasons could be (in our models of the internal judgement processes) that the ABX method is mentally more involving/stressing and that it triggers a different internal decision process than an A/B .
In any case an experimenter should not expect that every particpant in a controlled listening test will be function at his best and should therefore provide countermeasures like accomodation time, training and (mandatory) use positive controls and negative as well.

I hope that helps a bit.


Quote:
Originally Posted by scottjoplin View Post
Then Jakob2 is right (I expect) ABX probably isn't an appropriate test.
Assuming that Jakob2 is right is a good choice as he most likely is....
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Old 13th March 2018, 11:26 AM   #1104
TNT is offline TNT  Sweden
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Gold.

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Old 13th March 2018, 11:57 AM   #1105
scottjoplin is offline scottjoplin  Wales
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Originally Posted by Jakob2 View Post
Assuming that Jakob2 is right is a good choice as he most likely is....
I tend to agree, but what do I know? A lot more now thanks to a clear explanation
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Old 13th March 2018, 12:58 PM   #1106
Jakob2 is offline Jakob2  Germany
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Originally Posted by scottjoplin View Post
I tend to agree, but what do I know? A lot more now thanks to a clear explanation
You´re welcome.

Sorry for the numerous typos and a sentence needs clarification as the important part is missing:

"In the original version of this test there was no chance to repeatedly listen to the three options while it is at the discretion of the test participant how often he wants to listen to them."

It should be:

In the original version - invented around 1950 - there was no chance to repeatedly listen to the three options while in the modern/todays variant it is at the discretion of the test participant how often he want to listen repeatedly.
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Old 13th March 2018, 03:31 PM   #1107
Tournesol is offline Tournesol  Belgium
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Originally Posted by john curl View Post
It's a TUNER DPH! The 2.2uF cap IS the output. By the way, it is a potentially GREAT TUNER.
Did you mean a FM tuner ?
This thing with a 19kHz carrier that carry the stereo signal ?
It is nice to get some background music, or in a car stereo, but, in a hifi system ?
Who cares about ceramic caps distortions in a FM tuner ?
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Old 13th March 2018, 03:33 PM   #1108
billshurv is offline billshurv  United Kingdom
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John Curl's Blowtorch preamplifier part III
its FM HD. So does digital AAC as well as old fashioned FM.
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Old 13th March 2018, 03:50 PM   #1109
Tournesol is offline Tournesol  Belgium
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Originally Posted by billshurv View Post
its FM HD. So does digital AAC as well as old fashioned FM.
Ah, Ok, in europa, we call this DAB+, not FM. And it is quite new: very little coverage.
But tell-me, John would listen to a digital signal? ;-)
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Old 13th March 2018, 03:52 PM   #1110
DPH is online now DPH  United States
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And likely used a software defined radio borrowed from a different product. This isn't a high budget product that worthy is drawing ire over suboptimal output coupling, just replace them and move on. It's more a seemingly great product out punching it's weight, which makes the rant even more confusing.
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