It seems to me that there is too little scientific, objective evidence for why cables sound the way they do. When I see discussions on cables, physical attributes are discussed; things like shielding, gauge, material, geometry, etc. and rarely are things like resistance, impedance, inductance, capacitance, etc. Why is this? Why aren’t cables discussed in terms of physical measurements very often?
Seems to me like that would increase the customer base. I know several “objectivist” that won’t accept any of your claims unless you have measurements and blind tests. If there were measurements that correlated to what you hear, I think more people would be interested in cables.
I know cables are often system dependent but there are still many generalizations that can be made.
Outrageous claims by high end cable makers? Outrageous or simply the usual audiophile technical verbiage? Let’s take a look, shall we? Here’s an excerpt of the Valhalla 2 cable description from Nordost’s web site. Nordost is one of prof’s examples of “outrageous claims.” Now, I ask you, are these claims outrageous?
“Over the years we have been able to develop cutting edge production techniques and technological innovations that both improve the quality and precision of our manufacturing process and propel the capabilities of our products to previously unattainable levels. The Valhalla 2 range benefits from the gains of those years of research and development in every aspect of its construction.
While V2 cables remain true to the Nordost design philosophy, using silver-plated, OFC solid core conductors, extruded FEP insulation, a mechanically tuned construction, and asymmetrical grounding, the advances made from that jumping-point are astounding.
V2 cables use Dual Mono-Filament technology, along with an innovative, proprietary connector called the HOLO:PLUG®, designed to be the best possible interface between the cable and component. The combination of these two ground-breaking technologies allows Nordost products to perfectly match our philosophy of low mass design, optimal signal transfer and perfect impedance matching.”
And speaking of the One and Only True LCR, that trudgeon that the fundamentalists love to use to beat the non-believers about the head and shoulders so they will hopefully see reason, or at the very least just be quiet in the face of overwhelmingly superior knowledge. Well on the plus side of the ledger its really simple, its really easy to understand and thus allow the faithful adherents to appear intelligence when using it in an argument ( read, all the elements required for truthiness ). The problem with this is that LCR is very much more suited to dealing with DC, whereas audio signals are AC, and there is world of difference in terms of complexity between the two, the former is basically simple, the latter not so much.
Find below a fairly good overview that will hopefully give some insight into the problems of applying something simple like LCR onto something like an audio signal which, as mentioned above, is an AC phenomenon. See this as an expansion of a Roger Skoff line from a quote introduced earlier. Though it doesn’t include the more complex and equally important issues mentioned earlier ....a short snippet of which is immediately below....then followed by the overview...
I would argue that on a slightly handwaving way, you can study "electricity" using classical physics. After all, much of it can be understood through Maxwell's equations. However, if you do this, you simply have to consider the charge densities, dielectric constant, magnetic permeabilities, et cetera as black boxes.
Quantum mechanics kicks in if you want to understand why a material is a conductor or an insulator
What is the difference between resistance and impedance?Asked by: Venudhar
AnswerResistance is a concept used for DC (direct currents) whereas impedance is the AC (alternating current) equivalent.
Resistance is due to electrons in a conductor colliding with the ionic lattice of the conductor meaning that electrical energy is converted into heat. Different materials have different resistivities (a property defining how resistive a material of given dimensions will be).
However, when considering AC you must remember that it oscillates as a sine wave so the sign is always changing. This means that other effects need to be considered - namely inductance and capacitance.
Inductance is most obvious in coiled wire. When a current flows through a wire a circular magnetic field is created around it. If you coil the wire into a solenoid the fields around the wire sum up and you get a magnetic field similar to that of a bar magnet on the outside but you get a uniform magnetic field on the inside. With AC since the sign is always changing the direction of the field in the wires is always changing - so the magnetic field of the solenoid is also changing all the time. Now when field lines cut across a conductor an emf is generated in such a way to reduce the effects that created it (this is a combination of Lenz’s and Faraday’s laws which state mathematically that E=N*d(thi)/dt , where thi is the magnetic flux linkage). This means that when an AC current flows through a conductor a small back emf or back current is induced reducing the overall current.
Capacitance is a property best illustrated by two metal plates separated by an insulator (which we call a capacitor). When current flows electrons build up on the negative plate. An electric field propagates and repels electrons on the opposite plate making it positively charged. Due to the build up of electrons on the negative plate incoming electrons are also repelled so the total current eventually falls to zero in an exponential decay. The capacitance is defined as the charge stored/displaced across a capacitor divided by the potential difference across it and can also be calculated by the size of the plates and the primitivity of the insulator.
So simply resistance and impedance have different fundamental origins even though the calculation for their value is the same:
R=V/I Answered by: Martin Archer, Physics Student, Imperial College London, UK
Impedance is a more general term for resistance that also includes reactance.
In other words, resistance is the opposition to a steady electric current. Pure resistance does not change with frequency, and typically the only time only resistance is considered is with DC (direct current -- not changing) electricity.
Reactance, however, is a measure of the type of opposition to AC electricity due to capacitance or inductance. This opposition varies with frequency. For example, a capacitor only allows DC current to flow for a short while until it is charged; at that point, current will stop flowing and it will look like an open. However, if a very high frequency is put across that capacitor (a signal that has a voltage which is changing very quickly back and forth), the capacitor will look like a short circuit. The capacitor has a reactance which is inversely proportional to frequency. An inductor has a reactance which is directly proportional to frequency -- DC flows through easily while high-frequency AC is stopped.
Impedance is the total contribution of both -- resistance and reactance. This is important for AC analysis and design. At DC, reactive elements can be replaced with their steady-state model (capacitor->open,inductor->short) and resistance can be considered. (this isn’t true for transient analysis)
It is important to mention that while energy goes into both, it is only ’burned off’ through resistance. Power has to be given in terms of resistive power and reactive power. Resistive power actually burns off energy into heat while reactive power simply stores energy in E-fields and B-fields.
Often you’ll hear about the ’impedance’ of transmission lines, like the cables which run between components of your stereo system, and impedance of things like speakers. You’ll also hear that it is important to match these or else you’ll get reflection.
This is a much more complicated subject, which a few answers have commented on in recent questions about light and its speed.
However, what I want to mention is that when you hear about the impedance of a transmission line, like speaker cable or an antenna or coaxial cable or anything else, this does not represent energy which is "burned off" in the cable. This has to do with how energy is stored in the cable as it propagates down it. The cable does not (well, in reality it does, but assume the lossless case for simplicity) get hotter as a signal travels down it. It is not proper to think of a ’75-ohm cable’ as a 75-ohm ’resistor.’ That 75-ohms is purely reactance (ideally, though there really is attenuation in real cables).
Note that impedance and reactance are both given in units of ’ohms’ just like resistance. Capacitance is measured in Farads and inductance in Henries, and these relate to impedance, but they are not measures of impedance. As I said, the impedance of a capacitor is inversely proportional to its capacitance and the impedance of an inductor directly proportional to its inductance.
This may sound a little abstract. Impedance really is an abstraction of things that are far more complicated (things like time constants and rise times) that electrical engineers have to constantly consider. The idea of ’impedance’ allows for many of these things to be wrapped up into one subject so that they are easier to communicate.
The short answer is -- impedance includes reactance, and reactance includes effects which vary with frequency due to inductance and capacitance. Answered by: Ted Pavlic, Electrical Engineering Undergrad Student, Ohio St.
In many ways our wee hobby is a "its just not good enough" thang. We have over the years been told, either individually, or as a group that our hobby and/or our particular way of undertaking it is foolish , silly, stupid, idiotic, don’t know the science, can’t understand the engineering etc etc but we have persevered and despite all the negative vibes we have, often inch by inch, moved the pile forward. In fact it could be that we have become so inured to this that it may well be now part of our culture’s DNA, or at least the minimum requirement for inclusion.
So where was I going with this ?....oh yeah.
OK, was once having lunch with one of the top noise/vibration control guys in North America who worked for the the largest noise/vibration control company in the world ( at the time ). He was still basking in the afterglow of just having received an Technical Achievement Oscar for an rather innovative use of one of their products ( it made film cameras much quieter and allowed for better recording ). So during the lunch I brought up the possibility of using said technique to modify stereo components. Well the rest of the lunch was dedicated to proving beyond a shadow of a doubt how that idea made absolutely no scientific sense. Formulas were throw out, scientific fact was cited etc etc. For some reason I didn’t back off and continued to pursue that avenue and eventually moved the pile forward enough that the gentlemen saw/heard my point of view and apologized for his earlier lambasting and then we laughed and had another beer. Read, stereo component noise/vibration control is now an accepted part of our hobby, despite all that day’s respectable evidence to the contrary.
So here we are again, different song but the tune is very very familiar.
And btw that product that won the Oscar, in base function it is not much unlike our very own GeoffKait’s Brilliant Pebbles concept....but that is another story for another time in a thread far far away.
And here is the mornings entertainment.....and prof et al is the guy on the throne....and Mr Columbus is the everyman stereo dude...hope you like it, I do and it pops into my head every-time I come across a "cable" food fight, errr, discussion or something similar.
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