John Curl's Blowtorch preamplifier part III

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The Clark tests were numerous and are a matter of public record, and I experienced many of them firsthand, having been the engineer setting them up. I have also conducted tests involving hundreds of recording engineers at AES and ITA conventions, some being well-known engineers who possibly made the material you use for references. Have you any actual experience which is the equal? These tests were conducted some 15-20 years ago and I do not have the test records, perhaps Richard Clark does but he is not in the audio industry anymore.
Thanks, Howie - great experience - thanks for outlining it

I know the Clark tests are public record but I couldn't find any test resembled your description?

I have voiced my objections to aspects of AB and ABX testing, and agree it can deliver a preponderance of negative results if not conducted correctly, however my actual experience (not conjecture) says when there is indeed a difference between A and B these tests do deliver positives.
Ok then we agree about neg results from blind testing if not conducted properly & that's what I'm talking about happens on forums. The real problem is that we don't know if any ABX forum run test has been conducted correctly as there is no control used in Foobar ABX testing which could give us some indication of level of false negatives.

On the wider front, Jakob2 has presented evidence/research showing ABX is less sensitive than other blind listening methods

You can conjecture that the A and B sources must have to be very different for a well-conducted ABX to show positives, but you would be wrong. When levels are matched yet the sources not identical in some respect and a broad range of material is presented over time, a trained listener will indeed be able to render a positive result, I have seen it happen many times. Some people are so good at critical listening they achieve near perfect scores repeatedly while 99% of others do not. As a result of my involvement I have a few conclusions of my own:

1) For an ABX test to give more than null results, the listener must be trained, rested and relaxed and have time to audition as they see fit.

2) Other than for research purposes there is zero reason for a bias to be intentionally introduced such as the ability so see what one is listening to. This type of test is then a control for evaluating factors affecting the test, not a valid test of listener sensitivity.

3) Many adults have damaged or degraded hearing so the sensory apparatus is poor, yet they have not had it evaluated and believe their hearing is as good as anyone else.

4) Many audiophiles and recording engineers have a greatly inflated idea of their own critical listening abilities. Additionally most of the most consistent positive results we saw were by recording engineers who master highly regarded recordings...If these tests were so biased for null results, how did they do that? Perhaps it was the training and years of experience?

We concluded that being trained to listen for specific problems was the #1 factor affecting test results. For example, a Dolby engineer was perfect at picking out slight Dolby mistracking, a vinyl mastering engineer easily picked out slight inter-groove crosstalk the rest of us did not, etc... Once again, when pointed out the issue was easier for the rest of us to notice. I am sure you amp designers have developed the ability to hear minute amounts of crossover distortion which most of us would miss.
I don't disagree with any of this but it is a different world that you are talking about Vs forum based ABX testing. One thing I would add is that "degraded hearing" does not just involve audiometric testing - a lot of degradation is often to do with auditory processing such as inability to decipher speech in a noisy background - often associated with aging

If one of you thinks there has to be a better way to conduct testing, please propose, conduct and report a new type of test, we would then have actual data to discuss. It is easy to sit back and critique the results of others tests, but it would be much more helpful to do tests yourself and let us know how they come out...like PMA is doing.

Cheers!
Howie
PMA's ABX test fall into the category of ABX testing that I am talking about - I already suggested how he might improve it
 
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Telemetry is such a huge thing in F1, but historically (and depending on the race series, now), driver feedback has been critical to suspension setup/etc. And there are some drivers (can't remember names, sorry) that were/are famous for their ability to enumerate the feel of the car and translate that into setup changes that corroborated extremely well with what the telemetry told them as well.

O.T.
I hearty remember characters like Jackie Stewart and the mechanics developing those F1s.
I don’t want to go to pre WWII era car racing (or the old 6 Day Trial for enduro motos)
Telemetry ts, ts ... :D

George
 
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As an audio manufacturer, my 'bias' should be obvious. However, I want to thank 99 and Jakob for putting straight facts about ABX testing forward here in a learned and thoughtful way. Of course, it should be obvious that ABX testing gives false negatives, and we have stated that for the last 40 years, but some people are 'biased' toward wanting audio products to all sound the same, and they will promote ABX even when it gets in the way of progress.

Yes your bias is obvious. What's progress? For someone who makes money from selling audio gear progress is selling more product. And marketing and all the BS they spew is whar matters, not the truth. So why would these people want ABX testing to show there full of BS. And JC has figured this out. If people really new that good amps are indistinguishable ( as Pavel is proving with his tests) why would anyone buy his over priced amps? So he has a vested interest in promoting audiofoolery like the bybee crap.
 
I suppose in a way, mildly curious about how it's going
Wow, I didn't expect an interest (even mild) in the working of auditory perception & the latest research from you!

Here's the intro to that paper - tell me if anything in it sparks your interest
"We perceive the world as stable and composed of discrete objects even though
auditory and visual inputs are often ambiguous owing to spatial and temporal
occluders and changes in the conditions of observation. This raises important
questions regarding where and how ‘scene analysis’ is performed in the brain.
Recent advances from both auditory and visual research suggest that the brain
does not simply process the incoming scene properties. Rather, top-down
processes such as attention, expectations and prior knowledge facilitate
scene perception. Thus, scene analysis is linked not only with the extraction
of stimulus features and formation and selection of perceptual objects, but
also with selective attention, perceptual binding and awareness"

Just in case people think this has nothing to do with listening to our playback systems, an auditory scene is exactly what is the intended illusion meant to be created by the playback system.
 
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Some of what is stated here is not new, I would like to see jn chime in on the apparatus shown (fairly sketchy description).
Their apparatus is changing the coupling by the use of eddy current dragging. The conductor spins, the magnetic field is dragged in the direction of rotation. I didn't really like their use of sqr(x+y) for their magnetic field drawing, as north and south are not shown, just an absolute quantity.

Here however, is the crux:

From their paper: page 213903-4 bottom right:

Quote:""
The use of a moving conductive material to break
magnetic reciprocity boils down to the Lorentz force that
the free electrons of the conductor experience as they move
through the magnetic field. In principle, one could replace
the mechanical movement of the whole material by an
externally applied electric field, which would force the
electrons to move with a constant mean velocity in the
conductor according to Ohm’s law.""end of quote

The first part, that is the eddy current dragging. It is a consequence of a conductive surface being dragged through a magnetic field, the conductor is generating eddy currents.

The second statement, they are saying that in principle, it is possible to replace a moving conductive surface that has eddy currents within by a non moving conductive surface that has current flowing .

Hmmm. I suspect that pair of sentences is where they may be mistaken..

edit: as the copper enters the field location, the eddy currents are circular, the electrons are moving in circular vortices. In a still conductor with current, the conductor will have forces. In their design, it will try to rotate as the outer side will be forced up, the inner down. Nothing in their writeup indicates that the magnetic fields will warp as they show in the rotational simulation with current in place of moving copper. And, they need electron velocities of what??

As to it being a magnetic diode, well, I'm more than a tad skeptical. How they got from this writeup to "one magnet pushes the other, but the other doesn't push back" is pure fiction.. They have a name for that in science fiction, it's called a reactionless drive. I believe Larry Niven used it a lot.

jn
 
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