July 2014

Oxygen Free Copper Wire
Worthy of the hype?
Article By A. Colin Flood

  This month Enjoy the Music.com has two review articles. One is the Onyx interconnect patch cord from DanaCable (sold by Gingko Audio) with Oxygen Free Copper (OFC). The other is a loudspeaker cable that goes even further and uses Pure Copper Ohno Continuous Cast (PCOCC). The expensive, but good-looking and sounding, Clarus Crimson line relies on PCOCC technology.

Copper is lot cheaper than silver, which is a lot cheaper than gold. So of course, copper is the meat of most cables and cords. To improve audio performance, many companies use, and charge, extra for OFC wire in home theater music and movie reproduction connections. OFC wire is supposedly advantageous for cables and cords. The slinky, woven black DanaCable loudspeaker cable by Gingko Audio for example, scored an amazing four Blue Notes across the board for above average performance with OFC!

In fact, search the halls of Enjoy the Music.com for OFC and pages of popular brand names appear! Art Audio, Nordost, Final Labs, Dynamic Design, Silent Source, Calyx, Shanling, Acoustic Arts, Coincident, AKG, Audiomagis, Response, Singlepower, Yamamoto, Dynaudio, Kharma, Telos, Music Culture, Acoustic Preference, Cable Research, MIT Cables, Earthworks; just to name a few from the first few Enjoy the Music.com pages that all use OFC.

But Google "OFC" and Wikipedia comes up. The publicly edited online encyclopedia cites Roger Russell (see Speaker Wire, A History), who says conductivity for common copper and OFC wires are identical! Russell is no "stumbling-in off-the-street" slouch. He was Director of Acoustic Research at the famous McIntosh Laboratory and the originator of their loudspeakers. He graduated from Rensselaer Polytechnic Institute in Troy, NY, with a degree in Electrical Engineering.

Russell says even expensive, "highly refined copper with silver impurities removed, and oxygen reduced to 0.0005%, has only one percent higher conductivity." He says this improved conductivity however is "INSIGNIFICANT in audio applications."

So is OFC really just expensive audiophile snake oil or can golden ears of tweaking audiophiles actually hear the difference?

Impact In The Real World
"Most likely hype." My friend Joel Scilley seems to agree with Russell. Scilley crafts gorgeous slabs of sumptuous wood into beautiful turntables that win awards from art and home designer magazines (see Audiowood). "Although I suspect that most OFC cables are also more highly purified."

"An important question," he says, "is whether this purity has any impact in the real world. In an average audiophile system, the 'magic' loudspeaker cable is connected to high-brass-content (less conductive) binding posts and mystery metal spades or bananas. Then the cable is connected to more mystery metal connectors on the loudspeaker side. Once inside the loudspeaker, the wire type usually changes entirely and goes on to (presumably) brass driver tabs, and another small run of usually unspecified wire." Scilley suspects all these low-quality connections degrade the benefit of OFC.

"Real wire science would involve blind, or (preferably) double-blind testing of wire by independent observers," he says. But, another question Scilley has is whether the oxygen content in copper wire has any impact on oxidation over time, as he has "cut into older cables that were totally oxidized in the center of a run." So not just sound quality, but also age might be an important consideration with OFC. Scilley suggests a double-blind test of the two versions by same manufacturer with no terminations at the next tweaking audiophiles' club Meetup.

Hear Things Normal Human Can't
"My intuition tells me that it is a marketing ploy. Just like $80 HDMI cables." Iain Galloway, Technology Strategist at a semiconductor company said. He has B.Eng., Electrical Engineering with Computer Science from University of New Brunswick. Yet he cautions that he has "to be careful what I say here!"

"Audiophiles seem to have an X-men like ability to hear all kinds of things that normal humans can't discern," Galloway says. "For example, physics can tell us that standard gauge lamp cord is the same resistance as a nice blue or red translucent cable of the same wire gauge, but somehow audiophiles hear the difference." Yet others in the business of selling high-end, expensive cords and cables are quite sure there is a beneficial and valuable difference. They blasted Russell...

Really Minute Changes
While Galloway concurs with Russell, he still suggests double-checking Russell's 1% number – he doubts it is even that large a difference in conductivity. Galloway referred to a "Conductivity and Resistivity Values for Copper & Alloys" table complied for the Collaboration for Nondestructive Testing web site PDF:

Galloway says the table shows something called %IACS, or the percentage of the International Annealed Copper Standard. %IAC is a unit of electrical conductivity for metals and alloys relative to a standard annealed copper conductor. An IACS percentage of 100% refers to a conductivity value of 5.80 × 107 Siemens per meter (58.0 MS/m) at 20 °C.

However, Galloway says, "the actual resistivity (inverse of conductivity) shows really minute changes." These numbers are 1.724E-08 versus 1.740E-08 Ohms-m (note the expontential-08!) or 0.0000001724 ohms! Therefore, actual resistivity is infinitesimal. Compare minute fraction of an ohm that with an 8, 4 or 2-ohm speaker resistance. The actual resistivity is so small, the number could barely appear on the same chart as normal loudspeaker resistance. The chart would not be large enough to show both on the same relative scale. Galloway said there is need for more investigation as to what the actual resistance in a wire is for a specific wire gauge.

"Someone might argue something about capacitive effects and frequency roll off. I don't believe any of this could be effected by the speaker wire in the [20 Hz to] 20 kHz-ish frequency range that humans can actually hear."

Far More than Resistance
"If 'conductivity' is all this Russell knows, then he should get out of the business of commenting on what he has too little understanding of," Igor Kuznetsoff of K Works Audio quickly wrote back.

Kuznetsoff supplies loudspeaker, interconnect and headphone cables and cords, line conditioners, headphone amplifiers and vibration isolation feet. He uses OFC wire (see Brilliant Zen Audio). I reviewed his $350 silver-colored Empowered Cord (version one). I hated his power cord on two systems but loved it on a third one. Kuznetsoff is never short on words. His response?

"Every time I read about some Flat Earther's comments, I see this sort of thing" Kuznetsoff said. There is discussion of ("more like pontification on") only resistance or conductivity, which are obvious relatives. Yet, there is "no understanding of phase-linear transmission," he says, "and what it takes to get the signal there without mangling it, all parts of it in time and original relation.

"Every time I read about some Flat Earther's comments, I see this sort of thing" Kuznetsoff said. There is discussion of ("more like pontification on") only resistance or conductivity, which are obvious relatives. Yet, there is "no understanding of phase-linear transmission," he says, "and what it takes to get the signal there without mangling it, all parts of it in time and original relation.

"OFC is not related to home theater or movie reproduction or music reproduction," Kuznetsoff continued. "It is related to all signal transmission if copper is being used - the fine points that count to listeners with good ears and equipment beyond Stereo Barn results, not what an Ohmmeter can measure.

"Resistance in interconnects, for instance," Kuznetsoff went on, "is INCONSEQUENTIAL over a far larger range by orders of magnitude compared to changes due to temperature given they terminate into input impedances of at least 10K typically, and running into 250K, if not mega-ohms occasionally - for just one example. Resistance is more important in speaker cables because the terminating impedance is low at only 2 to 32-Ohms, typically so the ratio of cable to termination is closer - but even there it is but one factor among many, and hardly the only thing to consider.

Fewer Boundary Crossings, Less Disturbance
"You hit a raw nerve with that one." Kuznetsoff admitted. "I run across this sort of "very short (of) real science" attitude from Stereo Barn types and egocentric sorts who feel that if they can't hear it, or they can't measure it - whatever the subject is can't exist and has to be bunk and all audiophiles must be deluded fools - because they don't understand it and can't prove it to themselves, all too often. I normally avoid wasting time on arguing with people, who feel that I should wear their blinders. Their ability to hear is limited, so I/you must be deluded and imagining things... in concert with many others who can also hear the differences, and must be part of the mass hysteria...

"No idea who this Russell is, nor will I waste time trying to learn from him what he obviously doesn't know," Kuznetsoff was adamant. "Copper purity affects its crystal structure and the accuracy of phase transmission, which is not dependent on tiny differences in conductivity, meaning resistance.

"The casting, drawing and tempering techniques used in forming the raw conductor affect the formation of crystal boundaries in the copper (re: PCOCC casting and other techniques)," he said, "which affects the signal transmission in tiny ways that add up after millions of crystal boundary crossings by the signal that are more subtle than the relatively crude measurement techniques used to "prove", or disprove, what our ears, evolved over the lifetime of the human race to keep us alive certainly can hear."

The ability to hear those differences varies, but the logic of OFC is simple, "fewer boundary crossings, less disturbance," Kuznetsoff says. "It is sad that Darwinism does not extend to the dissemination of faulty knowledge, so his quote appears in Wikipedia."

Kuznetsoff easily explains what Scilley is seeing inside old oxidized cables. He thinks the cables in question had PVC insulation. The PVC reacts chemically with copper over time and the copper turns an ugly black-green and gets seriously oxidized.

Beach Of Sand
He thinks the problem inside old cables is the PVC. This type of insulation is "terrible sounding," but Kuznetsoff says it is a "ubiquitously common dielectric with a very poor Dielectric Factor of around 3.4-3.5 where something like solid form Teflon is generally 2.0, Polypropylene 2.1-2.3, Polyethylene around 2.2, and none of these will react directly with copper. PVC is commonly used because it is cheap, and entrenched in common low-grade wire production. The original early Monster cable that kicked off the thick speaker cable popularity was exactly that and all of it and its knockoffs turned green-black with time." (As did my Monster cables.) Editor's note, that is because Noel Lee seemed to use inexpensive plastic surrounding the wire. i had the same problems back then, too. Bruce Bisson of the company MIT designed those early Monster Cables, so if you want true quality seek out MIT cables and not Monster Cable.

For example, Kuznetsoff emailed me, "the Dielectric Factor (DF) number is only a start in assessing dielectric performance. There is much more to that electro-chemistry, like polar covalence behavior. Ever heard of that? Or that a dielectric can "ghost" the signal in a tiny distorted echo after it passes via absorption/release of it, which is also more significant than the tiny effect of the resistance." But wait, there's more!

"That is only a beginning consideration in this area," Kuznetsoff says. "There are more advantageous material forms like the foamed versions that reduce the DF number." This is a very complex subject and he is appalled by how many consider themselves "expert" enough to offer opinions while knowing next to nothing about the complexities of signal transmission and the huge number of subtle chemical and electrical factors, such as field-effects, that affects it. "To focus on just resistance," Kuznetsoff says, "is like judging the beach by one grain of sand on it."

Nelson Pass On OFC
"Objectively speaking there is not much difference between OFC and regular copper," says Nelson Pass. He is the designer of high-end home audio amplifiers. He received his B.S. in physics from the University of California-Davis. Pass co-founded Threshold Electronics, famous for their monster amplifiers in 1974. He founded Pass Labs in 1991. I reviewed and loved his Pass Labs X-250. Pass then founded low-power First Watt amplifiers. His SIT amplifiers are the first of a new generation of audio amplifiers using Static Induction Transistors in a single-stage, single-ended, Class A circuit without feedback or degeneration (see "SET And SIT Amplifiers). I loved his 10-watt SIT-2 on Big Ole Horn loudspeakers. Over the past decade, Pass amplifiers are always among the very best amplifiers I have ever heard on any type of loudspeaker with any type of source.

Pass says the OFC issues aren't about "resistance as such. He says, "oxides are routinely the source of distortion on contact surfaces (true) and somehow could might be concern inside the conductor itself. The extra cost of OFC is marginal in the scheme of things."

"Most audiophiles want a reasonable level of perfection and some peace of mind in their enjoyment of the music and the system. This is not unlike the car that somehow drives better after a nice wash and polish. Someone could argue to the car owner that the car drives only 1% better. This person is doing no one a favor."

"This is the entertainment business," Pass says, "not dialysis. And yet, if you look at dialysis equipment I bet you will find very high quality parts, including wire."

Not Really Oxygen Free
The next grade above normal high purity electrical-grade copper is OFC (Oxygen-Free Copper), or sometimes Oxygen-Free High-Conductivity (OFHC) copper. Jay Victor is the designer of the high-end Clarus line of cables and cords.

Victor is a Mechanical Design Engineer who worked at Monster Cable Products. He founded Orbital Development. Victor is the holder of approximately 50 patents for cable geometry and connector design. He  developed and successfully introduced into the market for such brands as PS Audio, Belkin , Ethereal Home Theater, StreetWires, Esoteric Audio, Phoenix Gold, Fender, Vox, Savant, Tributaries, Horizon/Rapco, Core One, Clarus, Ultralink, XLO, and other well-known brands.

Victor thinks the OFC term is quite misleading, because OFC is not really oxygen free. True, OFC is cast and drawn in a process where oxygen content is limited, thus reducing the formation of copper oxides, which lead to a larger number of crystals. The oxygen content for OFC is typically in the range of 40 parts per million (PPM), while normal grade copper is approximately 235 PPM, about six times less. The result is that OFC has approximately 400 grains or crystals per foot, as opposed to 1500, or about four times less.

Less grain means "there are significantly less boundaries for the signal to cross," in OFC, Victor says, "thus the signal is degraded far less." He admits OFC is a substantial improvement over normal high-purity electrical wire. But he cautions that OFC and OFHC materials are not all the same however, and these are much-abused terms.

"The oxygen content does vary," he says, "it is a range, rather than a finite definition. Performance levels do vary with the quality level of the material, and not all 'OFC' sounds or performs at the same level. The best level of copper for audio and video applications would obviously be totally free of crystal boundaries."

Homogenous Inside The Copper
"It is audible electrons," Vinh Vu of Gingko Audio, also disagrees with Russell. Sound with OFC, he says, "flows much more unimpeded. If you take a picture of copper [molecule] at a minute level, it's not like it is homogenous inside the copper. Extruding [the copper] pulls it a certain way" Vinh Vu of Gingko Audio is the exclusive distributor of the Dana Cable product line. Vu has 23 years at Bell Labs and Lucent Technologies in electronics. He has a Masters of Engineering in Industrial and Systems Engineering from Virginia Tech. Gingko Audio makes amazingly effective Vibration Isolation Platforms (VIP). I have and enjoy their Cloud 10 isolation platform.

Dana Robbins, cable designer for Gingko Audio, sent the YouTube video seen below titled "Why Should I Buy Oxygen Free Copper (OFC) Cable?" from Sonic Electronix.com.

Knot Inside The Wire
"OFC copper has fewer impurities and therefore fewer internal phase shifts, period." My friend, Phil Rastocny, is a retired Bell Labs science writer and Macintosh amplifier user. He is also author of the $2.99 "Extreme Audio" series on Amazon. His fourth eBook is on interconnects and ground loops. Rastocny says, "people who listen with their eyes lean toward accepted published specs of THD/IM and do not consider phase."

"Ever tie a knot and the pull on it hard?" He uses a rope analogy to explain what happens inside a wire. "What happens to the knot? It changes its shape, right? This is 'sort of' what happens inside of a loudspeaker cable or interconnect patch cord."

"Electricity does not move in a straight line down a wire," he says. "You have to look at what's going on at the subatomic level and understand what happens at a boundary layer between impurities. Electricity ALWAYS wants to take the path of least resistance – although some will flow in the path of greater resistance. When this occurs, guess what happens to the phase relationship of the signal? Answer: a minor vectored velocity change of the speed of electricity within a non-pure conductor.

"When only one frequency is present, say 60 Hz or DC, this phase shift is not that big of an issue. But when trying to keep phase and frequency in perfect alignment (zero degrees phase shift), say between 20 Hz and 20 kHz, impure conductors present greater phase degradation than pure conductors. While this issue is miniscule (we're talking fractions of a fraction of a degree in some cases), the fact of the matter is that phase still changes."

Universal Agreement
"Yes, I can hear the difference." Victor says. "One of the first tests I participated in at Monster Cable was a comparison between common bare copper and OFC. The panel consisted of me and a number of audiophiles and non-audiophiles, many of whom had no previous critical listening experience. The result was that everyone, regardless of experience, heard definite differences and preferred the sound of the OFC."

If you study Russell's web site, Victor advises, "you will quickly see that he is clearly in the 'anti-audiophile, and measurements tell you everything' camp. There are no references whatsoever to any listening tests he has personally performed. His references to "Stereo Review," a long out-of-print audio magazine are a testament to an outmoded mind set. All of these ideas have long been abandoned by the audio world for good reasons. Nearly everyone has heard an amplifier with exemplary measurements that sounded terrible. Today, the audiophile press universally recognizes that cables make a difference, and that some are better than others. Nobody really debates this any longer.

"A discussion of conductivity is necessary," Victor says. "It is interesting to note that Russell mentions two different grades of OFC. In fact, OFC is a range of materials, and there is not one single specific, universally agreed upon set of manufacturing specs and processes to make OFC. So, OFC is not a clearly defined or absolutely quantified material, especially if it was made specifically for audio applications.

Where Is The Proof?
"Every manufacturer is free to use their own specific recipes and processes to make their copper, and there can be a lot of variation in material properties," Victor says. "So, if you are going to compare OFC and common bare copper, what OFC are you comparing? Unless you got it directly from a copper manufacturer, you really do not know specifically what you are comparing. To make matters worse, there are some unscrupulous brands that use bare copper, but claim to be using OFC.

So, how do you conduct a proper comparison? What test methods did Russell use to obtain his conductivity measurements? Not specified, so if this came from a manufacturer, how reliable is the information, and exactly what quality OFC are we talking about? He states that there is a 1% difference in conductivity between the common electrical copper and OFC, and that nobody can hear the difference. What test instrument can tell you the smallest difference in conductivity that the human ear can detect? There is none, so where is the proof that nobody can hear this difference?"

Russell's arguments seem to be based on the assumption that conductivity is the only relevant measurement that is related to audio quality. But Victor says, "where is the proof of this? My experience as a cable designer, and having designed hundreds of audio cables, and having compared every available type of conductor material tells me that the hierarchy goes like this:  Common electrical grade copper is the worst, and coincidentally has the most copper crystals per foot. Copper has a crystalline structure, and each crystal represents a boundary that the signal needs to cross.

Fewer Crystals Per Foot
Next comes OFC copper, which represents a big improvement, and it has far fewer crystals per foot than the common electrical grade copper. Victor says the best copper he has tried is PCOCC. "This has almost no crystal structure, and is a huge improvement over every copper I've tried. So, the conclusion seems to be that crystal structure is far more important than conductivity."

If you look at the typical conductor materials available, he says, typical high purity electrical-grade copper has approximately 1500 grains (or crystals) per foot. The boundaries of all these crystals must be crossed by the signal in the process of being transmitted across the cable.

"It is not hard to imagine that crossing all of these boundaries must cause some sort of loss and/or distortion of the signal," he said. "This may be similar to the effects of stranded wire, and it does seem to cause the same sort of audible distortion."

Lower Room Temperature
The Russell site also site adds "the resistance of most metallic conductors increases by about 1% for every 3°C (5°F) increase in temperature, which means a small temperature rise would negate any benefit of having better conductors."

So maybe tweaking audiophiles should simply listen at 5°F lower room temperatures rather than invest in OFC cords and cables? Perhaps that is why night time listening seems better? Could everything from street to house to front-end rack to amplifiers to speakers is cooler, with lower resistance?

"Night listening IS better," Kuznetsoff says, however it is "because the power is cleaner with fewer appliances and electrical gear being used all around you. The world is quieter via air transmission. The ground is quieter from traffic rumble (quite important as it affects your equipment - or would Russell deny that, and therefore vibration isolation, too?), and the cooler air makes listeners more comfortable, which works directly on the listener."

"Not in my humble opinion." Dana Robbins also disagrees with lower room temperatures to improve conductivity. He is the designer and maker of these DanaCables by Gingko Audio. Robbins is a degreed Electrical Engineer with 25 years in the aerospace industry. With retirement some 5 years ago, he finally had time to delve deeper into his life-long hobby of audio. Good music reproduction always intrigued him.

Robbins says he is "basically an SET tube amplifier nut who loves to fiddle with all the parameters associated with those glowing bottles." Though he made changes to bias currents, plate resistor values, and was getting better and better measurements in the lab, it wasn't transferring to what he was hearing in his system.

"That's when I rolled up by sleeves and began measuring everything, he says, "I mean everything!" Robbins discovered that his cables were holding his system back. The result is his cable designs. DanaCable was born.

"I lived in Phoenix AZ for 25 years; I was also running those hot 845 tube amps, so a five to 10 degree decrease in temperature for the whole house would have cost me plenty! Cheaper to buy good cables (haha!) But seriously, that is why our speaker cables are the lowest, or among the lowest, in the industry. Even our Onyx [cables] with only four 8-AWG wires manages to come in at 0.006 Ohms. That's only 6 milliOhms; even with a 50-degree temp increase, we are only talking an increase to 6.6 milliohms. I say that DanaCables can take the heat and then some, bring it on!"

PCOCC
The Clarus line uses Pure Copper Ohno Continuous Cast (PCOCC) devised by Professor Ohno at Chiba Institute of Technology. Under a microscope, PCOCC clearly looks smooth and uniform compared to regular copper. Think flat plains compared to craggy mountains.

Professor AtsumiOhno began the study of the solidification of metals in the mid 1960's, and published his landmark book, "Solidification; The Separation Theory and its Practical Applications," in 1984. In this book, Dr. Ohno describes his many theories and concepts regarding the processing and solidification of molten metals, and the resulting crystal structures. He goes on to describe his unique process for casting metals with virtually no crystal structure, the O.C.C. process. This concept was first conceived of in 1978, and utilizes heated molds in a continuous casting process. Eventually, international patents were granted for O.C.C. (Ohno Continuous Casting). The copper produced by this method is small rods of O.C.C. pure copper, from which wire can be drawn and which can have copper grains of over 700 feet in length. Unfortunately, the primary manufacturer of this material has now stopped production.

Second To Gold
Asked to comment on the responses above, Russell simply added, "I am a life member in the Audio Engineering Society and prior to McIntosh, I was a Senior Engineer at the Sonotone Corporation."

The Dual Connects was three delicately braided plastic threads, glimmering with gold, with gold plating on solid silver contacts. Gold is considerably less conductive than copper (compared to the tiny differences Russell mentions). DACT said though copper is a better conductor than gold, gold has one free electron that is two orbits further out than copper. They said this means there is no direct relation between this and pure resistive conductivity.

The Onyx loudspeaker cables from DanaCable with OFC sounded great. So did their Onyx patch cords with OFC. So it will be very interesting to see how the Clarus Crimson cables with PCOCC compares to the DanaCables! See this month's Clarus Crimson Cable review.

Special thanks to Igor Kuznetsoff for his contribution.