Archived from Audio Direction Ltd (ADL)
This article will cover some of the theories concerning cable design and manufacture. It will include a brief discussion and hopefully will provide some enlightenment for our readers.
Cables were a simple thing in the 40’s and 50’s. Basically everything was either lamp cord (twin lead, , say 14 to 16 gauge) or coaxial RG 59 types. In the 70’s and perhaps a bit earlier, things started to change, with various designers coming up with interesting concepts.
One of the earliest was Robert Fulton. He utilized fairly large gauge wire for speakers but argued that since every cable acted as an antenna (just look at the typical 300 ohm FM radio antennas or the external antenna used on older automobiles). Fulton claimed that the standard 3 foot/1 meter lengths made ideal antennas and so he offered his cabling in “off” lengths , so that they were not so susceptible to picking up RF.
Along comes Noel Lee, a former physicist with Lawrence Livermore Laboratories and starts Monster Cable. Initial offering consisted of that clear insulated 10 gauge wire and has rapidly expanded since.
The initial design wire use a large aggregate gauge in order to get good bass, but the individually insulated strands was composed of finely stranded copper wire, in order to propagate more highs.
Lawrence Livermore was to produce many audio designers and another designer was Bruce Brisson. Allied with Noel Lee, he conceived the concept of using three gauges. One center wire was fairly large gauge, and around that was wound a medium sized gauge. Over all, he then has a finer wire in order to get more highs.larger gauges does tend to favor the bass or lower frequencies.
Brisson’s first designs were sponsored by Monster and the identical cables ( different jacketing) were available under the Monster, Spectral and MIT ( Brisson’s Company).
Brisson’s research lead to increasing sophisticated evolutionary features.
While the three different gauges did work, there were gaps between the “sweet” spots of each gauge, particularly at different overall lengths. I believe the boxes and their circuit are designed to iron out those spots.
At about the same time Stan Warren of PS audio was also experimenting with cables and gauges. Warren came up with a cable using seven common wire gauges, with a braided configuration of the insulated strands. The three wire braid was offered by PS Audio as their Reference B interconnect. Making cables was deemed impractical for PS Audio, so Ray Kimber enters the picture and starts up Kimber Kable and extends the braided design to speaker cables also.
The multiple gauge design enters a another phase With George Cardas. Cardas patents an idea which places multiple gauges set at the golden ratio to each other ( 1 to 1.6188…) This juxtaposition is supposed to reduce resonances in the wire bundle. Rowland Research electronics uses this ratio when drawing out parallel circuit board traces.
Then there was an unusual cable espoused by International Audio Review’s Peter Moncrief, the founder of the wonder line ( Wonder caps, Wonder Wire, etc). He advocated a combination of Polk Speaker wire. and household Romex. The Polk wire was a complex braid interweaving the positive and negative leads over a soft core. It had extended highs but a tad soft on the bass which the large gauge Romex provided. On its own the Polk cable, with its ultra extended top end, could drive wide bandwidth solid state amps into oscillation, which made it a rather “twitchy” cable.
The endorsement of large gauge Romex started a trend perhaps most personified by The Australian Tara Labs designs. If you want really large gauge stranded wire, a good source is welding cables.
From there cable design began a drift towards wave guide theory, using a rectangular core wire ( ribbon) as a wave guide. Such wave guides generally focus on one or perhaps two frequencies, but can exhibit very low loss signal transfer. Nordost, Tara, Omega Micro and others use such cables based on wave guide design. Kimber manufactures a very unusual design but rather than using a rectangular cross section, their SF series uses an oval design with a 2 to 1 ratio of height vs width. It is an very even sounding cable frequency response wise, and is used in their Select copper interconnects.
There are many other wire design theories. Purist Audio uses a fluid filled jacket on their conductors. They have an very smooth even sound. When held up to the light, you can see particulates in the liquid jacket. I can see a coppery colored particuleta and some darker material which I suspect to be ferrite material.
There was a cable called Lindsey Geyer made from parallel strands of mu metal tubing.
exceedingly stiff it claimed to address the magnetic aspect of the EMF field an AC conductor generates.
Many designs use a form of circular or oval configurations. Analysis Plus uses an oval cross section braid to simulate two parallel tubes, claiming that it reduces cable interaction. Straightwire and Wire world use concentric braided conductors, positive inboard and negative outboard. They are trying to simulate two concentric conductors and the parallel surfaces make for a more even but higher capacitance.
The three primary conductor materials are silver, copper, and gold, and, increasingly of interest in the modern world, carbon, particularly graphene. Graphene, once production can fabricate usable dimensional material ( big enough), has the lowest resistance of any material yet known , at least in non cryogenic conditions.
The material with the greatest conductivity is silver with about 8% better conductivity over copper, the most common metal used. Annealed copper is better than non annealed copper by a factor of 2 to 4%. Gold is actually a distant 30 % more resistant, surprisingly. Brass, the material often used for base metal of ends is an even more distant 70%.
Brass is used often because it machines easily and produces very dimensionally accurate end product. It is also similar in color to gold so it enables the more “shady” manufacturers to use extremely thin gold plating, which if scraped off is not very visible.
Gold is used because as a “noble” metal, as it does not tarnish and can preserve the contact cleanliness. Gold prices have sky rocketed in recent years, an thus old plating is getting thinner and thinner and there is a movement to other metals.
George Cardas feels that the use of silver and gold for contact surfaces is a bad one because these metals are extremely soft. When used for mechanical contact surfaces, the metals will gall, that is, literally ball up from the friction created between the mating surfaces and actually spread them apart.
Cardas prefers the use of rhodium, tough and non corrosive. It is expensive and resistance is high ( 60% greater than copper). However, George feels that because the metal is so tough and smooth, the reduced galling actually increases the contact patch and actually increases conductivity that way.
Conductivity is not the entire issue though. Silver, in order to maintain the highs, needs to have an extremely smooth surface. When Monster made their top line video cables they polished the positive silver conductor. Kimber latest silver cable has a shine which looks like chrome: brilliant and bright. I thought they were plating the cable but I was informed that the shine was due their use of diamond dies laser etched and polished. Those custom dies impart an extremely smooth surface.
An imperative factor is to avoid cross contamination of the various wires. Most wire manufacturers use one set of dies for all their metal pulling (check out the MWS website). This practice, though, will leave traces of the metal previously pulled on the new batch. Very few manufacturers actually are raw wire manufacturers. Kimber moved into a position where he actually owns a wire pulling company (50%) and can actually specify separate and custom dies for his various audio wires.
Contamination is a a large issue rarely addressed by wire companies. Most do not know that wire is literally pulled through a series of increasingly smaller dies and it is mechanically pulled into the desired size. The metal must be annealed ( softened through heat) and then pulled though. Usually a lubricating fluid is used, again adding an issue of possible contamination. Very few companies use diamond dies, which need little, if any lubrication, with the majority using hardened steel dies, which again can add to the contamination issue.
Advertising 6N copper ( 99.99995% purity) is probably fiction by the time the wire actually
reaches the consumer. Even Acrotec, one of the initial manufacturers of 6N copper, would not guarantee their 6N copper purity once the plastic vacuum seals were broken. Apparently simple exposure to air would already would contaminate the copper.
The Kimber SF oval wire can not be pulled through dies, BTW. The wire must be passed through custom rollers otherwise the wire will come out very kinky.
Cryogenic treatment is another word often bandied about these days. The effects on ferrous material is well known and documented. Its effects on non ferrous material is less known.
I was informed by Jack Bybee that Kimber has some of the finest cryogenic equipment currently available but again does not advertise it. Curious I asked Ray about that. He does not cryogenically treat all his wire because he is not so sure how long the effect will last. He has recently started to treat his Wattgate ends however (along with his motorcycle parts)
He did point out that cryoing copper literally shrinks the metal even to the molecular level and thus it can literally “squeeze” out dissolved molecular gas in the base metal, gaining a tenth of percentage in purity. Early offerings of 6N wire (usually Japanese manufacturers), carried with them a warning to avoid repeated flexing of the cables. The ultra high purity copper will generate very long crystalline structures and with repeated and sharp bending will fracture those crystals, allowing molecular gas to enter the base metal.
Insulation of wires also plays a critical part of the sound. Normally comprised of varius plastic, they have electrical properties of their own, which will affect sound.
Teflon, a Dupont invention ( an accidental discovery), was originally commissioned for the US atomic bomb progam in WWII for its extreme resistace to corrosion. Teflon has very hgh heat resistance and is popular for use in avionics.
There are many variant sof teflon however. The type normally seen is PTFE, and is used for insulation as well as more mundane things like frying pans. PTFE has the best heat resistance and thus requires a high working temperature. This causes a bare copper wire to “burn” , oxidize and turn black. Ths most PTFE teflon has to be applied on copper wire which has been either nickel or silver plated as both metals can withstand much higher heat.
There is one teflon group which has much lower het resistance and thus much lower working temperatures: FEP. FEP teflon can be applied directly over copper without the black tarnish occuring.
Some manufacturers like polystyrene, because of all the plastics it has the lowest dielectric “memory”. Most plastics will absorb a signal in the wire they coat and then release it at a slightly later time. Polystyrene has the lowest memory.
Unfortunately polystyrene has dioxin,a noxious toxin, as a byproduct of its manufacture. ts manufacture has basically been banned in Europe and the US, and thus polystryrene has become relatively scarce, althought I understand manufacture has resumed in mainland China.