The Physics of Electricity

For the record, I disagree with just about everything in Geoff's recent posts in this thread.  However I have no interest in engaging in further discussion of these matters, as I would rather focus on threads and discussions that have the potential to be constructive.

Before taking my leave of this thread, though, I'll quote a statement by a world renowned author, consultant, lecturer, and expert on numerous branches of electrical engineering, Ralph Morrison.  This was quoted by member Jea48 in another recent thread, entitled "directional-cables-what-does-that-really-mean?"  Geoff participated extensively in that thread.

Ralph Morrison

"The laws I want to talk about are the basic laws of electricity. I’m not referring to circuit theory laws as described by Kirchhoff or Ohm but the laws governing the electric and magnetic fields. These fields are fundamental to all electrical activity whether the phenomenon is lightning, electrostatic display, radar, antennas, sunlight, and power generation, analog or digital circuitry.

These laws are often called Maxwell’s equations. Light energy can be directed by lenses, radar energy can be directed by waveguides and the energy and power frequencies can be direct conductors. Thus we direct energy flow at different frequencies by using different material.

For utility power the energy travels in the space between the conductors not in the conductors. In digital circuits the signal and energy travel in the spaces between the traces or between the traces and the conducting surfaces.  Buildings have halls and walls. People move in the halls not the walls.  Circuits have traces and spaces, signals and energy moves in the spaces not the traces."

Sound System Engineering 4e

And this from Wikipedia, which Jea48 also quoted in the thread I referred to:

"In physics, the Poynting vector represents the directional energy flux (the energy transfer per unit area per unit time) of an electromagnetic field. The SI unit of the Poynting vector is the watt per square metre (W/m2). It is named after its discoverer John Henry Poynting who first derived it in 1884. Oliver Heaviside and Nokolay Umov also independently discovered the Poynting vector. 

... For example, the Poynting vector within the dielectric insulator of a coaxial cable is nearly parallel to the wire axis (assuming no fields outside the cable and a wavelength longer than the diameter of the cable, including DC). Electrical energy delivered to the load is flowing entirely through the dielectric between the conductors. Very little energy flows in the conductors themselves, since the electric field strength is nearly zero. The energy flowing in the conductors flows radially into the conductors and accounts for energy lost to resistive heating of the conductor. No energy flows outside the cable, either, since there the magnetic fields of inner and outer conductors cancel to zero."

Poynting vector - Wikipedia

I will have no further comments in this thread.

Regards,
-- Al

Gentlemen, note that this is an eight year old thread, that was resurrected earlier today by a newly registered member. Judging by his post, his sole purpose in doing so was to publicize a particular course, most likely for SEO (search engine optimization) purposes (i.e., to elevate the position of the site he linked to in search engine results).

Regards,
-- Al

06-22-11: Lloydc
Unfortunately, no one can predict whether a particular cable will improve your system.

A good example of this would be a comparison between two interconnect cables, one having high capacitance, and the other having low capacitance.

If these cables were used as line-level interconnects, and driven by a component having high output impedance, the low capacitance cable will have GREATER bandwidth/faster risetime/faster transient response than the higher capacitance cable, as a result of its interaction with the output impedance of the component that is driving it.

That same low capacitance cable, if used as a phono cable in conjunction with a moving magnet cartridge, will tend to have LOWER bandwidth/slower risetime/more sluggish transient response than the higher capacitance cable, as a result of its interaction with the inductance of the cartridge.

Same cables, exactly opposite effects depending on what is being connected. And if those cables were compared while being driven by a line-level component having low output impedance, those particular effects would disappear. Is it any wonder that cable threads are so contentious?

Regards,
-- Al

06-24-11: Johnnyb53
Ideally they must convey all the various signals (which are minute voltage fluctuations) in time with one another (with the challenge that signal speed varies with frequency), keep the amplitude of each accurate, minimize (ideally prevent) signals from being absorbed by the dielectric to be released back into the signal path later, and have near perfect rise time (which requires frequency response somewhere past 1 GHz).

Johnnyb53, while your well written post is, IMO, completely correct from a qualitative standpoint (i.e., if quantitative considerations are ignored), as I've mentioned in response to similar posts you've made in the past it is incorrect and misleading quantitatively.

Risetime need only be fast enough to not have audible effects within the frequency range of human hearing. As you know, that is nominally considered to be 20kHz, but even if we apply a huge margin to that figure, 1GHz is still thousands of times faster than necessary.

Furthermore, it is thousands of times faster than the bandwidths of the speakers, the source material, the source component, most electronic components, as well as our ears, so even if cable bandwidth were vastly lower than 1GHz, and cable risetime correspondingly slower, it would not affect overall system bandwidth and risetime to more than an infinitesimal degree.

Finally, I would maintain that for reasonable cable lengths the claimed need for time alignment is speculative at best, as even the audible frequency having the slowest propagation speed (20Hz) still propagates through wires at approximately 5 million meters per second (with the propagation speed of higher frequencies approaching the speed of light). See Figure 2 of this reference.

Regards,
-- Al

06-24-11: Johnnyb53
Some very bright lights in audio base their designs on ultrawide bandwidth ...

In the case of electronic components having ultrawide bandwidth, such as the Spectral products, that means a few MHz, not anything remotely approaching 1GHz. And the basic rationale for that wide bandwidth is, presumably, to avoid undesirable sonic effects that are within the bandwidth of our hearing, which is far less than 1MHz.

If a cable having a bandwidth in the GHz range sounds different than a cable having a lower bandwidth, then given the bandwidth limitations of the speakers, the source material, the source component, the other electronics in the system, and our hearing, the reason for that sonic difference is not the cable's GHz bandwidth.

Test reports that chart frequency response and square wave response show that risetime is visibly slower on amps that start rolling off at about 20KHz.

Yes, of course. I never said anything to the contrary. As I know you realize, bandwidth and risetime have an inverse relationship. Therefore a frequency rolloff that begins too close to the audible frequency range will result in risetimes that are visibly slow when viewed on a time scale that is meaningful with respect to the bandwidth and risetime of our hearing mechanisms.

Regards,
-- Al

06-24-11: Johnnyb53
You may decide that 1 GHz is overkill, but it shouldn't hurt, and the cables (Kimber Hero and Zu Wylde) are pretty affordable. The Kimber Heroes are rated out to 8 GHz and I got them at a pawn shop for $50/pair.

Actually, that would be 8 MHz for the Kimber Hero, not 8 GHz, 8 MHz being a much more reasonable number.

In any event, I have no issues with the approach you've taken. The reason I took exception to some of the statements in your initial post is that IMO mis-identification of the technical reasons for sonic differences between cables, whether by consumers or manufacturers or writers of marketing literature, can result in needless overkill of certain parameters, or focus on the wrong parameters, which in turn may dramatically increase cost without providing any sonic benefit. Although of course it may sometimes provide a marketability benefit, and a profitability benefit. :-)

I consider that some cable effects are simply unexplainable, and that having no explanation is much better than having one that is speculative (at least without it being qualified as such) or misleading or incorrect.

Regards,
-- Al