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Matched Propagation Conductors
Cardas' patented, Matched Propagation cables (US Patent 7,674,973) address a core problem that is intrinsic to all cables (audio, telephone, data, etc.), matching the signal propagation velocity of the conductor to that of the dielectric quite clearly improves the sound of audio transmission.
The Trouble is Dielectrics
The best solid insulating materials transfer charge 22% slower than standard conductors. This is a mismatch that can be corrected in only one way; you must match the velocity of the conductor to that of the dielectric in the cable itself. Networks, working after the fact, cannot restore lost low level information or the lost time integrity of the music.
The Matched Propagation Solution
Cardas' ingenious, patented solution uses a precisely controlled coated strand geometry to mitigate the effects of cable capacitance continuously in the cable. This technique eliminates the low level smearing and preserves musical integrity and dynamic range by correcting an imbalance in the basic velocity relationship of the cable's conductors and dielectric.
Huge Dynamic Range of Resolution
Matched propagation cables preserve phase, dramatically lower resonance effects, have a huge dynamic range and amazing resolution. They preserve low level detail, leading edge integrity and accurately preserve the heart, soul and emotion in the music. Matched Propagation technology brings unprecedented clarity and realism to your listening experience. Matched Propagation technology can be found in all cables in our Clear product line, and in our Parsec Interconnect.
This video shows part of the process of constructing a Cardas Pure Copper Litz Conductor.
A Short History Of Audio Cable
A signal cable's quality is primarily determined by the relationship of its conductors and dielectrics. In thelate 1800's, signal cables were created to replace telephone, open wire, transmission lines.
In the 1800's, telegraph signals used a single open wire lead and the ground for the return. Transmission distance and dynamic range were determined by voltage and repeater sensitivity. It was a simple rising impedance system that could deliver a finger tapped, digital signal 200 miles on an 8 gauge wire!
By 1870, the “open wire, ground return” systems hit their limit. With the advent of the Telephone millions of quiet, low distortion lines would be needed. The existing cables were unusable because of a basic miss match in the way conductors and dielectrics transfered signal.
By 1873, James Maxwell had deduced four basic laws that explained known electric and magnetic phenomenon, but it was two more decades before they found a workable solution cable problem.
By 1890, shielded, dry paper insulated cables evolved. The better dielectric constant and the velocity of propagation of dry paper improved sound quality and transmission distance, but after this, the quality of telephone cables has changed very little. Compared to "open wire", cables were still inefficient, signal quality was poor and transmission distance was very limited. The cable problems were and always will be, rooted in the difference between conductor and dielectric time constants. Signal travels at light speed on open wire, but must slow considerably in cables, as conductors are forced to track the slower dielectric velocity of propagation (VoP). At audio frequencies the trauma of this transition obliterated the signal in short order, rendering cables unusable except for short distances.
As a note, dry paper insulated, twist pair cables of the time were probably superior to what we have today. Technically dry paper is a better dielectric than PFA. As used by the telephone company, the cables were pressurized with dry nitrogen to assure the paper maintained its dielectric constant of 2.0 or less.
By 1900 the country was in crisis and ATT (Bell) offered a huge reward to any one that could resolve the problem.
In 1904, Michael Pupin came forward with the solution. By placing coils of wire in series with the conductor, at intervals in the cable, you could match the conductor propagation velocity (and subsequent cable loading) to that of the dielectric. They were called load coils (or Pupin coils or inductors). They did not really fix the cable problem, but combined with a plethora of networks, EQ and amplification, they did make cable usable. In effect they traded bandwidth and dynamic range for a fairly dramatic increase in the distance over which an intelligible signal could be transmitted. A patent was issued to Michael Pupin in 1904 and AT&T paid him generously for its use.
The basic flaw in load coils is that they make the correction at intervals rather than continuously in the cable. Essentially they match conductor velocity to that of the dielectric with a series of chokes.
Cable itself has changed little since the 1890's. The focus is on compensating for its problems or bypassing it all together. A true solution to telephone audio frequency cable problems was not found. Radio and Digital Carrier Systems simply bypassed the audio cable problem by converting the signal to easily repeated pulses. These systems made the first transatlantic telephone cable possible.
In 1956, using a pair of huge, unidirectional coaxial cables with polymer dielectric in ridged copper tubes, they could carry 48 lines, with a bandwidth of 3 kilohertz, over 1500 miles between Scotland and Nova Scotia, using nearly 100 repeaters. Local telephone service still uses coil loaded balanced lines (3.2 kilohertz Bandwidth). With equalization and amplification, a directional pair of these cables can cover small distances. For longer runs load coils are removed and digital carrier is used.
In the 1960s, audio began to establish its own standards. The lossy “600 ohm balanced lines” were abandoned before stereo arrived and solid state components in the 1970's drove originating impedances even lower, making the “rising impedance system” universal. This "system” is very efficient, but provides little or no cable damping and cable resonance was back! Signal quality was lost and at first, "solid state" took the blame. But in reality solid state was only one part of a complex chain reaction. A cable resonance control system had been unceremoniously dropped in the pursuit of simplicity, component compatibility, larger dynamic ranges and the economy of construction. The origin of bright fatiguing sound, was a ghost from days gone by, because we forgot the cable!
In the 1970's, the realization that cable was indeed part of the equation spawned a era of experimentation. Soon cable alternatives became available, along with the screams of nay sayers. It is amazing how fast we lose the lessons that were learned by our ancestors. In the 1980’s, signal cable reasearch resumed with a vengeance in audio industry. It was soon apparent that loss was not the issue, and it was also apparent that conductors made a noticeable change in cable resonance and glare. Tiny bronze strands, individually insulated, in different lays (litz wire), concentric's, weaves and braids, different shaped large solid conductors, and different metals were tried. Eventually dielectric involvement was minimized and a conductor geometry evolved!
In the 1990's, resonance associated with metals and dielectrics, microphonics, eddy currents and many other issues that contribute, in part, to a complex picture were and continue to be addressed. To achieve a dynamic range of true resolution, over a 100db range, requires attention to many details in the cable and connections. In the end the main problem will be the same: dielectrics can't transfer charge as fast as conductors can propagate and “rising impedance systems” can't shunt the resultant electrical turbulence.
By 2000 most of the cards were on the table, face up, if you chose to look. The main players were busy making cable and gave little time to those who wished the cable problems were not true. The overall depth of knowledge is now at a new level. I for one am enjoying watching it sink in.
2009 The impact of conductor/dielectric transition time differentials runs deep. Asymmetrical dielectric charge and decay causes subtle waveform distortions, floating DC offsets, inter transient noise, and veiling of low level information. It is responsible for Inter Symbol Interference (ISI) and jitter. It is why the dielectric constant seems to vary with frequency. It is the most fundamental issue that must be resolved in cable design.
The speed (Vop) of Solid and bare stranded conductors is about 127% of the best solid dielectric. How you balance this difference is key to cable quality. Simply reducing dielectric involvement or placing coils on the ends of the cable is not the answer. By Matching conductor velocity to dielectric constant, resonance and waveform distortion can be eliminated, without the bandwidth and dynamic range limitations of periodically loaded cables or the glare and distortion of unloaded cables.
Signal in a cable can be envisioned as a boat entering a canal at high speed. Initially, the boat breaks the surface of the water with much turbulence. As the boat begins to decelerate it generates a smooth wave (charge builds in the dielectric) and as the boat speed approaches wave speed (VOP) turbulence subsides. The boat can now travel at wave speed without creating any turbulence. This speed is the VOP of the boat in water.
Matching conductor propagation to dielectric constant, rather that allowing the change to take place as cable length accrues, quiets transient turbulence and makes it possible to produce a silent cable that sounds the same at every length and maintains the clean, natural harmonic halo found in the original signal. It is curious how the human focus works. Seemingly gross flaws in low frequency reproduction and crossovers are largely ignored as we try to view tiny details through windows of clarity in the system. Details at -60 db from the fundamental signal are still relevant and those details are strongly influenced by the quality of the cables.
Cardas’ cable design incorporates, Golden Ratio, Constant Q, Cross-Field, pure copper Litz, conductor technology. Why should I use it? What will it do for my system?
It is said, wire is just wire. In reality, a high-end audio cable must balance resistance, capacitance, inductance, conductance, velocity of propagation, RF radiation and absorption, mechanical resonance, strand interaction, high filtering, reflections, electrical resonance, dissipation factors, envelope delay, phase distortion, harmonic distortion, structural return loss, corrosion, cross-talk, bridge-tap and the interaction of these and a hundred other things. As a high-end cable manufacturer, Cardas Audio strives to address every detail of cable and conductor construction, no matter how small.
An elegant solution deals with quality, not quantity. Cable geometry problems are resolved in the cable’s design, not after the fact with filters. George introduced the concept of Golden Section Constant "Q" Stranding to high-end audio, but Golden Ratio, 1.6180339887... : 1 is as old as nature itself. Golden Ratio is the mathematical proportion of life itself, the heart of musical scales and chords. "Discovered" by the Greeks, but used by the Egyptians in the Great Pyramid centuries before, man has employed Golden Ratio to create his most beautiful and naturally pleasing works of art and architecture.
The signal used by your system, be it digital or analog, through tube or solid state, is always alternating current. The cyclic effect of alternating current vibrates the wire in your system like the strumming of a guitar string. The beating of the capacitive, inductive and mechanical elements in audio cable is set in motion by the transient energy of the audio signal, just as the guitar string is set into motion by the strike of a pick. This form of vibration or resonance distorts the audio signal and produces many sound anomalies, from colored bass to glare. Every interconnect, every speaker cable, every chassis and speaker wire has its own resonant signature. Like the mass, tension and hardness of the guitar string, the mass, tension and hardness of the conductor, coupled with its inductance and resistance, and the capacitance of the cable, determine what sound is made. Each strand in a cable has its own note or beat. Conductor strands interact with other same sized, near unison, and multiplistic sized strands creating beats the same way a cube listening room would, or one with multiplistic dimensions like 8’ x 16’ x 32.
Stereo systems depend on the purity of the audio signal. When the cable linking all components together imparts its own sound, the audio signal is corrupted. Cardas created a conductor that absorbs or cancels the noise released by the current fluxuation, by progressively layering strands that share no common resonant multiple. This conductor uses the same mathematical proportioning seen in the worlds greatest concert halls for essentially the same reasons. The infinite indivisibility of the Fibonacci Sequence or Golden Section is a key to controlling resonance. The ratio of ø (Phi), or 1 to 1.6180339887... to (infinity), is the Golden Mean, called Golden Ratio or Golden Proportion.
In Golden Section Stranding, individual strands are arranged so each strand is coupled to another, whose note or beat is irrational with its own, thus nulling interstrand resonance. This is the famous "Silent Conductor". It is the silence of Cardas conductors that allows them to be so uniquely musical and pure.
At the heart of cable oscillation is delayed or stored energy. This energy results from the lowered internal "Q", or resonant point, of conventional conductors. Cardas cables employ a unique stranding method where strands diminish in size towards the interior of the conductor. This design is called Constant Q Stranding and it allows each strand of the cable to share the load equally. It is a very effective method of reducing the Non-linearity seen in conventional conductors, without compromising the symmetry of the conductor or the capacitance of the cable.
Ordinary Cables are di-pole antennas, both radiating and absorbing RFI/EMI, which sustains system resonance. George’s cable design incorporates Crossfield Construction in its manufacture, which reverses every other stranding layer to defuse the di-pole effect and match conductor propagation to that of surrounding dielectric materials.
Cable resonance is further reduced through the use of ultra pure copper, air dielectrics and state of the art connection techniques. Our ultra pure and homogeneous metals have proven to be the best conductors for audio signals. Cardas uses diamond dies exclusively, drawing the strands in a hydrogen reduction atmosphere. This process reduces the amount of impurities and eliminates the surface contamination that occurs when standard metal dies are used. As each strand is drawn, the resultant ultra pure surface is immediately given a urethane enamel "Litz" coating. This is a continuous process that results in a perfectly insulated strand and ultimate longevity of the conductors. Ordinary uncoated copper stranding corrodes in a relatively short time. Cardas meticulously maintains the purity of the conductor strands until they are sealed at termination.
Golden Ratio, Constant Q Stranding
Golden Section Stranding mathematically eliminates resonant multiples in conductors by sequencing strand masses and their associated inductive effects in an irrational progression.
A great cable has the best dielectrics and conductors, and the geometry to match one to the other. Golden ratio constant "Q" conductors (GRCQ) correct conductor problems and match dielectric propagation velocity. Interior propagation of solid strands slows in proportion to strand size and signal change, resulting in eddy currents, skin effect, "Q" fluctuations and conductor resonance. Cardas individually insulates strands and proportions their size to depth in conductor, eliminating eddy currents, "Q" fluctuations and resonance. Strands are precisely layered to match dielectric materials and cable type. Golden Ratio keys into the proportioning of conductors and dielectric as elegantly as it does into music and nature itself.
Golden Section Stereo Magic
Alternating current can shake a wire like a guitar string. The audio signal in a stereo system is seen as alternating current. The audio signal, be it digital or analog, through tube or solid state, is always alternating current.
The signal's cyclic effect, causes all the wire in the system to vibrate and ring. This ring becomes a song sung to the resonance of the electrical and mechanical components of the cable.
Every interconnect, every speaker cable, every chassis and speaker wire has its own song. The stored mechanical and electrical tension and time delay characteristics of the cable determine what song is sung.
Each and every strand in a cable has its own note or beat. Two or more wires of the same mass and tension have common mechanical resonating points and share the same note. Two or more wires or bundles of wires, differing in size, each have their own resonant points. When combined, wires find new points of interaction, creating yet another note.
The sound produced by any stereo system depends on the purity of the audio signal. When the cable that links all the components together imparts its own sound the audio signal is corrupted.
There is a unique way to eliminate the harmonic or resonant effect produced by the conductor itself. Create a multiple strand conductor, where the individual strands share no common mathematical node or resonant point and layer them to cancel the noise they each create.
An infinitely indivisible progression known as the Fibonacci sequence or Golden Section is the key to resonance control. The ratio of Phi, or 1 to 1.6180339887...to infinity, is the Golden Mean, called Golden Ratio or Golden Proportion.
In Golden Section Stranding, strands are arranged so that every strand is coupled to another, whose note is irrational with its own, to dissipate conductor resonance. This creates a silenced conductor, allowing Cardas cable to produce the purest possible audio signal. No other cable geometry, no other conductor design, can create the listening magic of Golden Section Stranding.
The root or power plant of conductor oscillation is stored and reflected energy. The progressively layered constant Q conductors effectively attenuate this energy.
Cardas cables employ a unique stranding method where the smaller strands are placed towards the interior of the conductor in Golden Proportion. This is called constant "Q" stranding. It is a very effective method for reducing the inductively stored and reflected energy that fuels cable resonance.
Cardas uses pure copper, Litz wire, pure PFA and air dielectrics, ultra pure eutectic solders, custom made rhodium plated connectors and each cable is terminated by hand. It is this meticulous attention to the details of design and care in construction that have made Cardas the heart of the most uniquely musical systems in the world.
There are many factors that make cable break-in necessary and many reasons why the results vary. If you measure a new cable with a voltmeter you will see a standing voltage because good dielectrics make poor conductors. They hold a charge much like a rubbed cat’s fur on a dry day. It takes a while for this charge to equalize in the cable. Better cables often take longer to break-in. The best "air dielectric" techniques, such as PFA tube construction, have large non-conductive surfaces to hold charge, much like the cat on a dry day.
Cables that do not have time to settle, such as musical instrument and microphone cables, often use conductive dielectrics like rubber or carbonized cotton to get around the problem. This dramatically reduces microphonics and settling time, but the other dielectric characteristics of these insulators are poor and they do not qualify sonically for high-end cables. Developing non-destructive techniques for reducing and equalizing the charge in excellent dielectric is a challenge in high end cables.
The high input impedance necessary in audio equipment makes uneven dielectric charge a factor. One reason settling time takes so long is we are linking the charge with mechanical stress/strain relationships. The physical make up of a cable is changed slightly by the charge and visa versa. It is like electrically charging the cat. The physical make up of the cat is changed by the charge. It is "frizzed" and the charge makes it's hair stand on end. "PFA Cats", cables and their dielectric, take longer to loose this charge and reach physical homeostasis.
The better the dielectric's insulation, the longer it takes to settle. A charge can come from simply moving the cable (Piezoelectric effect and simple friction), high voltage testing during manufacture, etc. Cable that has a standing charge is measurably more microphonic and an uneven distribution of the charge causes something akin to structural return loss in a rising impedance system. When I took steps to eliminate these problems, break-in time was reduced and the cable sounded generally better. I know Bill Low at Audioquest has also taken steps to minimize this problem.
Mechanical stress is the root of a lot of the break-in phenomenon and it is not just a factor with cables. As a rule, companies set up audition rooms at high end audio shows a couple of days ahead of time to let them break in. The first day the sound is usually bad and it is very stressful. The last day sounds great. Mechanical stress in speaker cables, speaker cabinets, even the walls of the room, must be relaxed in order for the system to sound its best. This is the same phenomenon we experience in musical instruments. They sound much better after they have been played. Many musicians leave their instruments in front of a stereo that is playing to get them to warm up. This is very effective with a new guitar. Pianos are a stress and strain nightmare. Any change, even in temperature or humidity, will degrade their sound. A precisely tuned stereo system is similar.
You never really get all the way there, you sort of keep halving the distance to zero. Some charge is always retained. It is generally in the MV range in a well settled cable. Triboelectric noise in a cable is a function of stress and retained charge, which a good cable will release with both time and use. How much time and use is dependent on the design of the cable, materials used, treatment of the conductors during manufacture, etc.
There are many small tricks and ways of dealing with the problem. Years ago, I began using PFA tube "air dielectric" construction and the charge on the surface of the tubes became a real issue. I developed a fluid that adds a very slight conductivity to the surface of the dielectric. Treated cables actually have a better measured dissipation factor and the sound of the cables improved substantially. It had been observed in mid eighties that many cables could be improved by wiping them with a anti-static cloth. Getting something to stick to PFA was the real challenge. We now use an anti-static fluid in all our cables and anti-static additives in the final jacketing material. This attention to charge has reduced break-in time and in general made the cable sound substantially better. This is due to the reduction of overall charge in the cable and the equalization of the distributed charge on the surface of conductor jacket.
It seems there are many infinitesimal factors that add up. Overtime you find one leads down a path to another. In short, if a dielectric surface in a cable has a high or uneven charge which dissipates with time or use, triboelectric and other noise in the cable will also reduce with time and use. This is the essence of break-in
A note of caution. Moving a cable will, to some degree, traumatize it. The amount of disturbance is relative to the materials used, the cable's design and the amount of disturbance. Keeping a very low level signal in the cable at all times helps. At a show, where time is short, you never turn the system off. I also believe the use of degaussing sweeps, such as on the Cardas Frequency Sweep and Burn-In Record (side 1, cut 2a) helps.
A small amount of energy is retained in the stored mechanical stress of the cable. As the cable relaxes, a certain amount of the charge is released, like in an electroscope. This is the electromechanical connection.
Many factors relating to a cable's break-in are found in the sonic character or signature of a cable. If we look closely at dielectrics we find a similar situation. The dielectric actually changes slightly as it charges and its dissipation factor is linked to its hardness. In part these changes are evidenced in the standing charge of the cable. A new cable, out of the bag, will have a standing charge when uncoiled. It can have as much as several hundred millivolts. If the cable is left at rest it will soon drop to under one hundred, but it will takes days of use in the system to fall to the teens and it never quite reaches zero. These standing charges appear particularly significant in low level interconnects to preamps with high impedance inputs.
The interaction of mechanical and electrical stress/strain variables in a cable are integral with the break-in, as well as the resonance of the cable. Many of the variables are lumped into a general category called triboelectric noise. Noise is generated in a cable as a function of the variations between the components of the cable. If a cable is flexed, moved, charged, or changed in any way, it will be a while before it is relaxed again. The symmetry of the cable's construction is a big factor here. Very careful design and execution by the manufacturer helps a lot. Very straight forward designs can be greatly improved with the careful choice of materials and symmetrical construction. Audioquest has built a large and successful high-end cable company around these principals.
The basic rules for the interaction of mechanical and electrical stress/strain variables holds true, regardless of scale or medium. Cables, cats, pianos and rooms all need to relax in order to be at their best. Constant attention to physical and environmental conditions, frequent use and the degaussing of a system help it achieve and maintain a relaxed state.
A note on breaking in box speakers, a process which seems to take forever. When I want to speed up the break-in process, I place the speakers face to face, with one speaker wired out of phase and play a surf CD through them. After about a week, I place them in their normal listening position and continue the process for three more days. After that, I play a degaussing sweep a few times. Then it is just a matter of playing music and giving them time.