User Manual

CABLE THEORY

Page 7

tecting more vulnerable materials like copper and brass. The nature of gold’s distortion is mellow and

pleasant, which makes it preferable to the irritating sonic signature of nickel. A bare copper or brass part

will outperform a gold plated part, but only until the metal corrodes. In comparison, high quality thick

silver plating actually improves performance. Silver is not noble like gold, but it does resist corrosion

and it enhances performance.

As for conducting materials, normal, high purity (tough pitch) copper has about 1500 grains in each

foot (5000/m). The signal must cross the junctions between these grains 1500 times in order to travel

through one foot of cable. These grain boundaries cause the same type of irritating distortion as current

crossing from strand to strand.

The rst grade above normal high purity copper is called Oxygen-Free High-Conductivity (OFHC) cop-

per. In fact, this copper is not Oxygen-Free, it should more properly be called Oxygen-Reduced. OFHC

is cast and drawn in a way that minimizes the oxygen content in the copper: approximately 40 PPM

(parts per million) for OFHC compared to 235 PPM for normal copper. This drastically reduces the

formation of copper oxides within the copper, substantially reducing the distortion caused by the grain

boundaries. Additional improvement can be attributed to OFHC copper having longer grains (about 400

per foot), further reducing distortion. The sound of an OFHC copper cable is smoother, cleaner, and

more dynamic than the same design made with standard high purity copper.

Not all OFHC is the same. If the poorest copper were given a value of one, and the best was a ten,

then OFHC ranges from two to four-it is actually a range rather than a single performance level. Since

the most important audible attributes are due to the length of the grains, we use the name LGC (Long

Grain Copper) to describe the very best OFHC.

The next higher grade is an elongated grain copper sometimes

called “linear-crystal” (LC-OFC) or “mono-crystal”. These cop-

pers have been carefully drawn in a process that results in only

about 70 grains per foot. Cables using LC-OFC have an obvi-

ous audible advantage over cables using the same designs with

OFHC or LGC. From 1985 to 1987 several AudioQuest models

benetted from this quality material.

In 1987 AudioQuest introduced FPC (Functionally Perfect Copper) in the higher models. FPC was

manufactured by a process called Ohno Continuous Casting (OCC).Through this process, the metal

is very slowly cast as an almost perfect single crystal small diameter rod. This near-perfect rod is then

carefully drawn to maximize grain length. However, OCC is a process, not a material. The metal (usu-

ally aluminum or copper), the purity, and the size of the cast rod all make a tremedous diference. FPC

copper was drawn from a smaller rod, causing less damage to the near perfect cast state, a single grain

was over 700 feet long. The audible benets were very obvious.

A couple of years later the “nines” race began. This refers to how many times the number “9” can be

repeated when specifying a metal’s purity. In 1989 AudioQuest introduced FPC-6 in the highest models.

FPC-6 had only 1% as many impurities as FPC. The prime contaminants in very high purity (99.997%

pure, four nines) copper, like LGC and FPC, are silver, iron and sulfur, along with smaller amounts of

antimony, aluminum and arsenic. FPC-6 was 99.99997% (six nines) pure with only 19 PPM of oxygen,

0.25 PPM of silver and fewer than 0.05 PPM of the other impurities. The improvement was dramatic.

From 1989 to 1999, many of AudioQuest’s most famous models used FPC-6.