Conductor types and purity have often been a topic of hot debate where on side endorses use of exotic materials and another snubs up their noses at any audible benefit. To set the historical record straight, below are some notes that should help you understand why this topic seems to rear its head so frequently.
Back in the early 1970s, someone questioned one of the most
overlooked and common components in every audio system: the material used for
wire or conductors. Since once cannot escape wires in interconnects, speaker
cables, speaker voice coils, phonograph cartridges, internal chassis wiring,
and circuit boards, this seemed to be a logical area for investigation. If
there were an advantage to moving to a different material, there were a diverse
number of places it could be implemented. A few companies introduced speaker
wires and interconnect cables in response to this curious question touting this
or that advantage because of this or that feature. In reality, most claims were
fruitless and sheer marketing hype.
This doesn’t mean that there were not differences between conducting
materials – there are drastic measurable differences – but when marketing spun
the assets of these features they turned out to sound more like snake oil than
science. After a prolonged learning curve, these marketing goons learned what
did and did not work when pumping up the benefits of their products and today
buzz words associate fair, good, better, and best conductors. (BTW, I love
these goons since they are the people responsible for advancing sales and
therefore the advancement of the high-end itself, but often question their
choices of words or stand on reasoning.) Before jumping into the fray of these
buzz words, let’s review a bit of historic around conductor materials.
When wires were first needed, scientists analyzed which pure
materials (not alloys or processed metals) had the least opposition to
electrical flow and in the order of their “conductivity” (electrical resistance
per unit length) are from best to worst are: silver, copper, gold, aluminum, zinc, and
nickel. So the best conductor was silver with copper a very close second. Two
characteristics of silver eliminated it from the desirable material list since
it was expensive and it easily oxidized. Copper was therefore the number one
choice (see a highly descriptive resistivity table for all electrically
conductive elements in the periodic table at http://hyperphysics.phy-astr.gsu.edu/hbase/tables/elecon.html#c1).
With the introduction of computers and high-speed electrical
signal technologies, coated copper materials were developed to improve
high-frequency characteristics. Called “wire-wrap wire” this coated copper also
came in a new manufacturing process introduced in 1975 called OFHC (oxygen free
high conductivity). Here, oxygen normally encountered in is production is
eliminated from the extrusion process thereby improving its conductivity. Another
refinement also improved conductivity by eliminating normally-encountered
impurities (called high-purity or HP). Again, audio manufacturers swarmed
behind this new process and introduced a variety of cables featuring this new
type of copper.
Recently, a further copper refinement process was patented
by Professor Ohno of the Chiba Institute of Technology in Japan that reduces
the number of fractionated crystal structures and other impurities. Termed the
Ohno Continuous Cast (OCC) copper, this metallurgical process uses a heated
mold for casting and extruding, with cooling taking place in a separate
process. The result is ultra-high purity copper with a larger crystal size.
Copper
Type
|
Oxygen
Impurities (PPM)
|
Hydrogen
Impurities (PPM)
|
Traditional (TCP)
|
200-500
|
|
OFC
|
10
|
0.5
|
LC-OFC
|
||
OCC
|
5
|
0.25
|
With these results, the OCC process creates
"ultra-pure" (UP), also known as “ultra-high purity” (UHP), copper
and the abbreviation for this material is UP-OCC. (See http://www.copper.org/publications/newsletters/innovations/1997/12/wiremetallurgy.html
for more information on current high-technology metallurgical manufacturing
processes for copper.)
Oxygen Free Copper (OFC): Oxygen free copper was developed
in Japan around 1975 as it became increasingly apparent that sound quality was
related to the quality of copper and the processing used during cable
manufacture. OFC is produced is a carefully controlled oxygen free environment
resulting in a significant reduction in oxygen content (10 ppm). There are
fewer crystal boundaries in OFC which results in much higher performance than
TPC where the numerous crystal boundaries cause a degradation of the audio
signal.
Linear Crystal Oxygen Free Copper (LC-OFC): In 1975 Hitachi
improved the OFC process to further reduce impurities and crystal boundaries.
The patented LC-OFC process developed by Hitachi re-heats the copper following
extrusion which reduces impurities between the crystal boundaries as the copper
crystal expands. This in turn leads to a longer overall crystal length. A
typical crystal in a 1mm diameter LC-OFC conductor is 130 mm long which can be
compared to typical crystal length of 4mm long in TPC conductors.
Ultra High Purity Oxygen Free Copper (UHP-OFC) is processed
much in the same way as OFC but is also subjected to a further Zone Refining
process (developed by William Gardner Pfann). With Zone Refining the purity of
the copper crystals is increased by drawing a narrow molten region of a
crystal. This molten zone is moved along the crystal (in practice, the crystal
is pulled through the heater). As the molten region melts it leaves a wake of
purer material solidified behind it. The impurities concentrate in the melt,
and are moved to one end of the conductor whilst it is being drawn.
Ohno Continuous Casting (OCC): In 1985 Professor Ohno from
the China Institute of Technology developed his patented method for the
extrusion of a grain free copper wire. When a pure metal solidifies, its
crystals grow in a specific geometrical pattern (typical to that metal)
emanating from a nucleus, rather like the dendritic growth pattern of a tree.
The size of the metal crystals grown can be varied by repeatedly annealing metal
such as is done in the LC-OFC process. The structure of a strand of copper may
be likened to that of a bag of sugar. Every grain of sugar has a crystal
boundary. In a conductor, these crystal boundaries (potential barriers) act as
a non-linear resistance to the flow of electric current. It follows that, the
fewer the boundaries, the less the effect there is on an electric signal as it
propagates from one end of the conductor to the other. The Ohno Continuous
Casting method re-heats the extrusion as the molten copper is forced out of the
mould and very slowly and gradually draws the grain or crystal down the
conductor's length, creating a 'single crystal structure'. The typical crystal
length of OCC copper is more than 200m.
So what’s the conclusion from this? In 350BCE, Aristotle
wrote that women have fewer teeth than men and everyone did not question Aristotle
because…well he was Aristotle, someone much smarter than most ever would hope
to be just do not question these sort of things. But one day, someone got a
brainiac idea, “Let’s count them!” What a concept. And sure enough, men and
women both had the same number of teeth proving that even the great Aristotle could
make a mistake. WOW! This means that even the brightest minds can learn a few
things since their followers are taught to blindly do what they were told…until
someone doesn’t. This is how advances are made – by questioning authority and
finding out if what was once believed to be true still is - or is not.
Technology advances every day and sometimes several times a
day. Our understanding of the world and how it works constantly evolves and
with it should our reasoning for accepting old facts. What was once understood
by one set of physical laws will always change once our understanding of these
laws advances. It was once believed that the world was flat and the earth was
the center of the universe. Anyone who disagreed was considered at the least
off his/her rocker and at the worst a heretic and put to death. Skeptics have a
purpose in keeping those of us who wish to investigate our changing understanding in one word "honest." Truth must prevail but even skeptics can be biased since they
adhere to what they know – which may be an old understanding to which they unquestioningly now
regurgitate the words of their teachers.
What I am trying to say is this: keep an open mind and even
though the reason someone states that this is why something like wire sounds
better than this other conductor, it is the goons who write the words you read (or
even the idea maker her/him self) that may not be quite right. This does make
the advancement any less justified; it is that we as human beings always struggle
explaining what is going on with a new discovery of change. One day, Einstein, Stephen Hawking, every skeptic, every critic, you, and I will all be
proven wrong. It is inevitable; all we need is more unconstrained time and
open-mindedness for future generations to clearly understand why.
The best position you can take is that of neutral; neither
for nor against but completely open minded. You count the number of teeth, you
listen to the differences, and you make the choice. Don’t let biases influence
your decisions and a better sounding system can result. Give that linear-crystal
wire in our tonearm a shot, give that interconnect cable or power cord a try, and
give that new CD player a go. All you can do is be wrong, and what’s wrong with
that? No one ever advanced anything without making a few mistakes. Go ahead:
fail and learn something new about what does not work. Then, try again.
Yours for higher fidelity,
Philip Rastocny
I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.
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