John Curl's Blowtorch preamplifier part II

[Waly]

Originally Posted by Joshua_G

1. I didn't say I don't hear differences in blind test – I do hear differences, at least in some of them.
2. I didn't say that if I don't hear differences, the test must be faulty.

What I said is that in order for such a test to be valid, first it have to show that it can produce also positive results.

Hi Joshua:

Assume we would both agree to DBT the following statement:

"Joshua can hear differences between A and B", where A and B are, for example, two power cords.

What would be an example of "positive results", as you mentioned above?

[Tom Danley]

What is not obvious is that our “hearing” is an adapted skill which because it is learned, also includes what you already know and even less obviously includes what you see. In hearing acuity tests, the object is to evaluate your hearing alone and so there are NO visual clues and an effort made to exclude any external sounds.

A fun demonstration of that “invisible to us” link between what we see and “hear” is the McGurke effect.
Try this and ponder why we only hear sonic reality when we don’t see anything related to the source AND how a blind test (conducted w/o visual stimulus like a hearing acuity test) can give a very different impression of “hearing” than a sighted one.

Try The McGurk Effect! - Horizon: Is Seeing Believing? - BBC Two - YouTube

Best,
Tom Danley
Danley Sound Labs

[Pano]

Originally Posted by SY

At the speaker terminals; same with level adjustment. Just about any amp is flat into a resistor, but if the source impedance is high, it won't be into a speaker load.

Cool, that makes sense. I think many people take FR to be into a pure resistive load, which may not be fair.

For the case of a line amp (which is what I thought we were talking about), at the power amp input- but I haven't seen a non-flat one in decades, it's trivially easy to do.

Right. I'd still be interested to blind test circuits with different harmonic content or output impedance.

[SY]

Originally Posted by Pano

Right. I'd still be interested to blind test circuits with different harmonic content or output impedance.

Well, you have some experience with DBTs. The issue with output impedance is avoiding the unintended effects on level and frequency response (I know you know that, I'm jes' sayin' for completeness).

[Joshua_G]

Originally Posted by Waly

Hi Joshua:

Assume we would both agree to DBT the following statement:

"Joshua can hear differences between A and B", where A and B are, for example, two power cords.

What would be an example of "positive results", as you mentioned above?

Yes, it will (for that particular test). Not all DBT are the same.

[coluke]

Originally Posted by SY

Well, you have to explain why that doesn't happen for frequency response, level, data compression, phase, and other phenomena that are routinely detected in a DBT. Also, why that doesn't happen for other sensory DBTs (e.g., organoleptic, haptic).

No explanation at all - was only speculating on my experience when switching between CD and SACD versions of the same program; it sometimes happened that after discovering in the SACD some details I had never heard before, I noticed I was able to hear the very same details when reverting back to the CD version. Bias power...?

L.

[Waly]

Originally Posted by Joshua_G

Yes, it will (for that particular test). Not all DBT are the same.

Huh? It will what? I asked for an example of "positive result" in this particular DBT.

[Jakob2]

@ zinsula,

thanks for the reminder.


@ SY,

Originally Posted by SY

Since we beat the Fremer deal to death months ago, why do you want to beat it around more?

Seems that requesting some data to back up your assertions beats something to death, mhm?

Is it total ignorance of statistics?

Could you please present an argument containing some statistics (or data) to shed a light on this?
Which obvious statistical result was ignored by me?

Or an insistence on accepting post hoc reframing when it suits your desires?

What was the "post hoc reframing" in the Fremer case??

Or a desire to accept poorly controlled results when that suits your desires?

Do you have any evidence that the results were "poorly controlled" in the Fremer DBT at the AES-Convention?

People can either hear these things with ears-only or they can't.

It is my experience that people indeed can hear such things if the tests don´t include additional confounders they are not used to.
And yes (that is pretty basic stuff in psychology/sensory testing as well) a controlled listening experiment is a confounder by itself.

I´ve cited ITU-R BS.1116 and the other recommendations for subjective evaluation quite often; please reread the parts which describe the efforts to let the (even the expert panel) listeners accustom to the materials and test protocols.

No-one claiming "magic" differences has offered up any reliable evidence. Period. Trying to kick up unrelated dust to confuse the issue doesn't change it, nor does constant moving of the goal posts.

If bringing scientific requirements back to memory is "to kick up unrelated dust to confuse ...." i am guilty.

[Jakob2]

Originally Posted by SY

<snip>Problem is, there's no reliable DBT data showing that, for boxes of gain, anything other than frequency response (assuming no clipping) and level are audible....

No problem at all; zinsulas proposal is reasonable- a positive control is an effect that must be detected under test conditions and of course it should be comparable up to a certain degree.

If the experimenter doesn´t really know what to search for that presents a difficulty, but it is no excuse for violating the scientific rules.

An experimenter has to show that the experiment is objective, valid and reliable.

Nope, all it takes is good data.

Of course.

Well, you have to explain why that doesn't happen for frequency response, level, data compression, phase, and other phenomena that are routinely detected in a DBT. Also, why that doesn't happen for other sensory DBTs (e.g., organoleptic, haptic).

Who says it does not happen??
In fact it does happen all the time in controlled listening experiments; please reread the documentation of public tests with quite big sample sizes, for example the stereophile test on amplifiers.

[Joshua_G]

Originally Posted by Waly

Huh? It will what? I asked for an example of "positive result" in this particular DBT.

When in a certain blind test I hear differences between say power cables, that certain test is capable of giving positive results. Else, I don't understand your question.