John Curl's Blowtorch preamplifier part II - Page 3455 - diyAudio
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Old 9th February 2013, 02:05 AM   #34541
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Quote:
Originally Posted by Kindhornman View Post
Have you seen a schematic for the Blowtorch. ... Why don't you try and get your hands on some of the lessor JC products such .... I don't think that we could fault the build quality
JC was kind enough to post circuits for Blowtorch and JC2 Mk1 (which was panned by the reviewers).

I've had extensive hands on experience with a JC design which was only marginally stable on real speaker loads but JC immediately disowned it.

I'm fully appreciative of JC's obsession with build quality but I note he now disclaims responsibility for build quality and only takes responsibility for 'design'.

However, enclosures hand carved from solid BS/Unobtainium by virgins does not preclude the need for competent circuit design, decoupling, PCB layout, and following simple but important recommendations from manufacturers datasheets.

It is the lack of these basic but vital factors that are responsible for JC2 Mk1's poor performance and the likely failure of Blowtorch in Double Blind Listening Tests against a properly implemented 4558 design.

I accept the possibility that some of JC's designs might be OK and be indistinguishable from evil 4558 designs in DBLT bla bla. But not the above 2.
_____________

There has been much talk lately about Bybee's 'smoke screens' but please acknowledge the greatest BS / smoke screen merchant of all.

From a technical critique of Blowtorch, the discussion has shifted to esoteric discussions of a Quantum nature.

I note a determined attempt to provoke criticism of Hawkesford too.

While I have played a small part in 'peer review' of some of Malcolm's papers, I hardly see the relevance of this to Blowtorch.
_____________

Previously, I had thought JC's reluctance to test stuff ... and even greater reluctance to release results, was due to marketing reasons. You don't really want 'stinkin' measurements of your designs to sully your august reputation.

But I now get the impression the real reason for this is that JC doesn't really know how to use new fangled (and even Jurassic) gear. This would explain why he's always on the lookout for new measurements and his vast collection of esoteric measuring gear eg Hirata box, is hardly used.

Perhaps he's hoping for some new gear, based on principles no one else (except he) pretends to understand, will give his most expensive designs the thumbs up ... and damn evil 4558, AD797 etc.

Unfortunately, so far, these promising avenues, eg Quan, have done the opposite.
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Old 9th February 2013, 02:31 AM   #34542
SY is offline SY  United States
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Quote:
Originally Posted by Max Headroom View Post
Ok, so did you try repeated (sighted) A/B testing and glean any sound differences ?.
It made no difference whatever. I didn't bother repeating the exercise blind since no difference was heard sighted. This isn't a surprise since 30 milliohms is not much resistance.

But I'm deaf and have crappy equipment and lousy source material- or so John tells me, so don't take any of this seriously. Storytelling is far more entertaining than reality- and more profitable. Scams work because people like stories.
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Old 9th February 2013, 02:52 AM   #34543
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What on Earth is a JC-2 mk1?
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Old 9th February 2013, 03:26 AM   #34544
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Quote:
Originally Posted by SY View Post
I didn't bother repeating the exercise blind since no difference was heard sighted.
Nice one.
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Old 9th February 2013, 03:30 AM   #34545
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by kgrlee View Post
JC was kind enough to post circuits for Blowtorch and JC2 Mk1 (which was panned by the reviewers).

I've had extensive hands on experience with a JC design which was only marginally stable on real speaker loads but JC immediately disowned it.

I'm fully appreciative of JC's obsession with build quality but I note he now disclaims responsibility for build quality and only takes responsibility for 'design'.

However, enclosures hand carved from solid BS/Unobtainium by virgins does not preclude the need for competent circuit design, decoupling, PCB layout, and following simple but important recommendations from manufacturers datasheets.

It is the lack of these basic but vital factors that are responsible for JC2 Mk1's poor performance and the likely failure of Blowtorch in Double Blind Listening Tests against a properly implemented 4558 design.

I accept the possibility that some of JC's designs might be OK and be indistinguishable from evil 4558 designs in DBLT bla bla. But not the above 2.
_____________

There has been much talk lately about Bybee's 'smoke screens' but please acknowledge the greatest BS / smoke screen merchant of all.

From a technical critique of Blowtorch, the discussion has shifted to esoteric discussions of a Quantum nature.

I note a determined attempt to provoke criticism of Hawkesford too.

While I have played a small part in 'peer review' of some of Malcolm's papers, I hardly see the relevance of this to Blowtorch.
_____________

Previously, I had thought JC's reluctance to test stuff ... and even greater reluctance to release results, was due to marketing reasons. You don't really want 'stinkin' measurements of your designs to sully your august reputation.

But I now get the impression the real reason for this is that JC doesn't really know how to use new fangled (and even Jurassic) gear. This would explain why he's always on the lookout for new measurements and his vast collection of esoteric measuring gear eg Hirata box, is hardly used.

Perhaps he's hoping for some new gear, based on principles no one else (except he) pretends to understand, will give his most expensive designs the thumbs up ... and damn evil 4558, AD797 etc.

Unfortunately, so far, these promising avenues, eg Quan, have done the opposite.
Here yah go ...


Parasound Halo JC 1 monoblock power amplifier Measurements | Stereophile.com
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Old 9th February 2013, 04:54 AM   #34546
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Quote:
Originally Posted by john curl View Post
What on Earth is a JC-2 mk1?
JC, you posted it as phono.pdf and told us it was caned by the reviewers.

You used it as an example to diss AD797 but its obvious you neglected to do any noise 'calculations', check if it was appropriate for the 2 operating conditions .. or even read the datasheet.

At least 10dB of unnecessary noise introduced by your poor circuit and poor understanding of low noise requirements.

Just go back and read the posts. Or even the AD797 datasheet. You might learn something.
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Old 9th February 2013, 05:09 AM   #34547
KBK is offline KBK  Canada
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Something to pick up and beat naysayers with:

Human hearing beats the Fourier uncertainty principle

For the first time, physicists have found that humans can discriminate a sound's frequency (related to a note's pitch) and timing (whether a note comes before or after another note) more than 10 times better than the limit imposed by the Fourier uncertainty principle.

Not surprisingly, some of the subjects with the best listening precision were musicians, but even non-musicians could exceed the uncertainty limit. The results rule out the majority of auditory processing brain algorithms that have been proposed, since only a few models can match this impressive human performance.

The researchers, Jacob Oppenheim and Marcelo Magnasco at Rockefeller University in New York, have published their study on the first direct test of the Fourier uncertainty principle in human hearing in a recent issue of Physical Review Letters. The Fourier uncertainty principle states that a time-frequency tradeoff exists for sound signals, so that the shorter the duration of a sound, the larger the spread of different types of frequencies is required to represent the sound.

Conversely, sounds with tight clusters of frequencies must have longer durations. The uncertainty principle limits the precision of the simultaneous measurement of the duration and frequency of a sound. To investigate human hearing in this context, the researchers turned to psychophysics, an area of study that uses various techniques to reveal how physical stimuli affect human sensation. Using physics, these techniques can establish tight bounds on the performance of the senses.

Read more at: Human hearing beats the Fourier uncertainty principle

Understand that these where discrimination tests performed on people, and their hearing.

That a few musicians turned out to be 'good', ie, 10x better than theory.

Now, imagine the golden eared audiophile. Some that are at the peak of the trade and group?

12x better than theory?

15x better than theory?

Where's the naysayers when the chips are down? they're off hiding. readying to attack again, no doubt.

Last edited by KBK; 9th February 2013 at 05:13 AM.
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Old 9th February 2013, 05:19 AM   #34548
KBK is offline KBK  Canada
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Quote:
Originally Posted by SY View Post
It made no difference whatever. I didn't bother repeating the exercise blind since no difference was heard sighted. This isn't a surprise since 30 milliohms is not much resistance.

But I'm deaf and have crappy equipment and lousy source material- or so John tells me, so don't take any of this seriously. Storytelling is far more entertaining than reality- and more profitable. Scams work because people like stories.
Sure thing, Sy. Sure thing. Yes, I believe you. Yes. I believe you allow yourself, and others to attack on your terms... and other terms ...are deleted. This I have seen. Repeatedly.
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Old 9th February 2013, 05:44 AM   #34549
jcx is offline jcx  United States
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Default Typical sensational science journalism/strawman version Psycoacoustics, Signal Theory

Quote:
Since researchers have known for a long time about the cochlea's nonlinearities, the current results are not quite as surprising as they would otherwise be. "It is and it is not [surprising]," Magnasco told Phys.org. "We were surprised, yet we expected this to happen. The thing is, mathematically the possibility existed all along. There's a theorem that asserts uncertainty is only obeyed by linear operators (like the linear operators of quantum mechanics). Now there's five decades of careful documentation of just how nastily nonlinear the cochlea is, but it is not evident how any of the cochlea's nonlinearities contributes to enhancing time-frequency acuity. We now know our results imply that some of those nonlinearities have the purpose of sharpening acuity beyond the naïve linear limits.

Read more at: Human hearing beats the Fourier uncertainty principle

when they show the Cramer-Rao boundary for the stimulus on the same plot we get excited

Last edited by jcx; 9th February 2013 at 05:55 AM.
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Old 9th February 2013, 07:21 AM   #34550
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Kgrlee, you have it all wrong! The title 'JC-2 mk1' was a working title for the JC-3, that when ultimately finished got 'preamp of the year' in several publications. Please get your facts straight before confronting me with your comments.
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