Lectura interesante

[Raul_77]

Obligatorio para cualquier usuario del vinilo:

http://www.stereophile.com/reference/arc_angles_optimizing_tonearm_geometry/index.html

     

Saludos, Raúl

[feraldi]

Obligatorio para cualquier usuario del vinilo:

http://www.stereophile.com/reference/arc_angles_optimizing_tonearm_geometry/index.html

     

Saludos, Raúl

Je Raúl, me has cogido leyendo sobre protractors...

Me lo apunto a la lista de lecturas pendientes.

Saludos.

[rocoa]

http://www.ciencia-explicada.com/2013/02/no-linealidades-del-oido-permiten-al.html?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+CienciaExplicada+%28Ciencia+explicada%29

[Raul_77]

Muy interesante el tema que trata el artículo, pero también lo que se dice al principio: 'es un concepto puramente matemático, no físico'.

A menudo se plantean argumentos como que no hay que tener miedo de las matemáticas, o que las matemáticas no fallan.

Ante este tipo de argumentos ya he planteado en alguna ocasión que vivimos en un mundo físico, no matemático. Las teorías matemáticas son validadas cuando las confirman experimentos físicos, la física es la realidad y no puede ser negada, la matemática es un sistema de lógica que sigue las reglas de la lógica, si emplea premisas equivocadas llega necesariamente a conclusiones falsas: falla.

Es algo que tengo pendiente, explicar como las matemáticas fallan estrepitosamente en describir la realidad del audio, sobre todo en el tema de las medidas. En algún momento lo abordaré.

Saludos, Raúl

[abroba]

Suena a tema muy interesante y más si viene de alguien con tus conocimientos y con tu buena expresión.

Nada, nada, Raúl, no hay prisa, podemos esperar...



Salu2!

Abel

[Raul_77]

http://www.auriculares.org/foro/index.php/topic,3251.msg122397.html#msg122397

Parece que había Ingenieros que ya lo sabían:

""Mathematician Jean Baptiste Joseph Fourier invented simple way of representing the diverse nature of the batch process through the expression of the process as a sum of sines and cosines of multiple frequencies. Only for periodic processes. Not for any other. One should be aware that the process is 100% periodic. Later mathematicians managed to stick this way for non-periodic processes, more precisely, for pieces of non-periodic processes. The sum of sines and cosines necessarily becomes infinite and therefore has a way only of theoretical significance.

What did from this electronics engineers? Correctly, they just started using it everywhere.

The funny thing is that none of them asked each other: guys, maybe we do with your non-periodic signal? For mathematicians there would be no doubt: once the baseline method are not met - method does not apply. Radio technicians, with their "accelerated courses" of higher mathematics that did not stop. Thus was born the famous "theorem" of readings in 1933 comrade Vladimir Aleksandrovich Kotelnikov. He was then 25 years, he lived in Kazan, his dad was a teacher of higher mathematics at the University, and, apparently, no pope has not done it because "theorem" report implicitly offered much earlier in the form of a numerical method to interpolate functions given in tabular form.

The first mistake was
that the "theorem", "range" of the signal was understood as the result of processing of the signal Fourier transform. That is understood that sampled and restored signals - periodic and bounded in amplitude. Therefore the proof of "Theorem" has been reduced to a tautology: the condition of the limited range of signal (Fourier) representation of the signal above is equivalent to a countable number of sinusoids of multiple frequencies. That is was: a periodic signal, which can be represented by Fourier series as a finite sum of multiple frequencies, we can recover the points by interpolating the finite Fourier sum. Radioengineering interpret it this way: any signal, which succeeded with the help of passive filter to suppress the higher frequencies well, you can just restore the individual (not very accurate) readings with the same linear passive low pass filtering.

The second mistake was
that Kotel'nikov drew a graph of the spectrum to restore the signal not correctly. The fallacy of the graph of the signal by Kotelnikov is that the spectrum is limited to the left by zero. That is, consists of an infinite number of spectral components of low frequency. But this can not be due to the fact that the signal is then not limited in amplitude, that is not the conditions of the limited amplitude of the signal, as well as the convergence of the Fourier integral at infinity - a necessary condition for the existence of the Fourier spectrum. Signal, even periodic, - for the restoration of Kotelnikov should be limited in range and below. And no worse than the top. You know what's funny? The thing is that almost all modern mixing consoles for digital audio include very steep high frequencies filters, which greatly weaken the signal frequency components. Not only that, the latest models also contain a studio microphones with high pass filter.

The third mistake,
"theorem" of readings is that it "proved" to signal to the spectrum of a rectangular shape. At the same time restoring (interpolating digital readout point) has the form sin (x) / x. In the "theorem" says nothing about what should be restoring function for a signal with non- rectangular spectrum. And it must have a very different kind. I personally find ridiculous, that it was much later Kotelnikov his "theorem" counts laid the foundations of the theory of optimal filtering, which asserts that for signals with different spectra of the different needs different restoring function (read - different filters). That is, a change of the signal leads to change of the output filter and digital to analog converter!

Mates! You over there in Moscow, go to the Academician Vladimir Aleksandrovich Kotelnikov - he is now 91, he is still alive and edits the magazine "Radio" - and ask him what he thinks about the inadequacy of digital sound.

Americans are even now take very serious about sampling theorem, which now is in the basis of all communication theory and analysis of radio circuits. They do not even whisper about it wrong! America's "theorem" Shannon sampling invented in 1949. One to one, as by Kotelnikov!

Where the exit from a digital dead end? Ask Sony!

Stop, you can not ask - president of Sony, said the editor of the Journal of Mass audiophile in the world "Stereophile", that Sony does not see the need for a new digital audio format.

How many giga-baks cut down Sony from digital audio? A lot. Megabucks how Sony has spent only on advertising promotion silly (the sound) mini-disk? About three hundred million dollars according to official data very Sony. How much she spent on serious scientific research in the field of sound? Zero? Slightly greater than zero.
Sony bought the entire archive of good analog record company RCA, and it's going to do with it? That's right, to digitize "for better persistence." "

Saludos, Raúl

[Raul_77]

http://www.theabsolutesound.com/buyers_guides/17/download/pdf/



Saludos, Raúl

[Raul_77]

En ON Magazine hay unas cuantas Guías sobre Auriculares:

http://www.on-mag.fr/index.php/guides-d-achat

         

http://issuu.com/pierre-stemmelin/docs/guide-casques-2013?mode=window&backgroundColor=%23222222

http://issuu.com/pierre-stemmelin/docs/on-magazine-guide-casques-2012-1?mode=window&viewMode=doublePage

http://issuu.com/pierre-stemmelin/docs/guide-casques-onmag-2010-vol1?mode=window&viewMode=doublePage

Saludos, Raúl

[Sir_Diego]

Ponen algunos precios bastante desmedidos, y creo que sufren de alguna marquitis...
El ejemplo máximo quizás sea los Q701.

[Raul_77]

No todo va a versar sobre Audio:

http://mamaenalemania.blogspot.com.es/

Saludos, Raúl

[Raul_77]

Lo de asequible es relativo, que diría Einstein, pero por leerla no cobran:

http://www.theabsolutesound.com/buyers_guides/18/download/pdf/



Saludos, Raúl

[victor_cc]

Buena explicación de por qué la señal digital no es simplemente ceros y unos (como ya ha comentado bastante gente en este foro con anterioridad): http://www.audiostream.com/content/qa-john-swenson-part-1-what-digital


Saludos

[Torpedo]

Este artículo no es sobre audio, pero me parece interesante. Creo que tiene mucha relación con la dinámica que se puede establecer en los foros o cualquier entorno donde se intercambien opiniones.

[Raul_77]

Lo es por los consejos que se dan en el texto, pero quizá la parte más notable es que admite que, en ocasiones, un equipo de alto precio puede sonar peor que una radio normal:

http://www.hifiplus.com/articles/why-do-bad-things-happen-to-good-systems/?utm_campaign=Hi-Fi%2B+Weekly+Emails&utm_medium=email&utm_source=email-272

Saludos, Raúl

[Raul_77]

...sobre vinilo:

http://pitchfork.com/features/articles/9467-wax-and-wane-the-tough-realities-behind-vinyls-comeback/



Saludos, Raúl