FASHION TRUMPS ENGINEERING
Copper is valued in the electronics industry for its high electrical conductivity and reasonable cost. Only silver has a higher electrical conductivity (though only by about 6%) however its cost is significantly higher, making it limited to special applications.
One area where silver has made a name for itself is in the audiophile cable market where its cost isn’t of such a limiting factor.
And this leads us to ask the question, why would you pay the price for the higher conductivity of silver, only to alloy with an even more expensive metal (gold) which results in an electrical conductivity that’s even lower than that of copper?
One word comes immediately to mind—Fashion.
Like diamonds, gold has a certain allure to it for reasons other than its electrical conductivity.
One company that has been making a name for itself selling this fashion statement to its customers is Toxic Cables, which is based in the UK (though it appears to have got its start back in the ’90s with the Dutch company Siltech). Toxic Cables is of the belief that because silver is so highly conductive, and because gold, though not quite as conductive, is still pretty conductive just the same, that alloying just a small amount of gold with silver will have a negligible effect on the conductivity of the resulting alloy.
To wit, from a HeadFi post by Toxic Cables in 2014:
Silver is more conductive then [sic] copper to start with, gold is also quite conductive, so adding 1% gold in my Poison or a little more in the SW will not make it 50% less conductive then [sic] copper, both the SP and SW are still more conductive then [sic] copper with the gold in it. Adding just 1% gold in the silver barely effects [sic] it’s [sic] conductivity and anyone with a brain will know it won’t make it 50% less conductive.
These statements amply demonstrate that Toxic Cables has absolutely no knowledge or understanding of metallurgy. They are based on the completely naive notion that there is a linear relationship when alloying two or more metals of a given conductivity.
GOLD IS “TOXIC” TO SILVER
We would like to begin this discussion with the following excerpt:
Gold has a conductivity of 78. The alloy of gold and silver calls attention to a remarkable feat. When silver is alloyed with a small percentage of gold, the conductivity immediately diminishes. 2 per cent. of gold is sufficient to reduce the conducting power from 100 to 60. An increase in the proportion of gold, however, is attended with a decrease of conductivity at a less rapid rate, the minimum of 16.12 being the conductivity of an alloy of equal parts of gold and silver.
This excerpt wasn’t from any modern textbook or research paper. It is actually from an issue of Van Norstrand’s Engineering Magazine published in 1885. One hundred and thirty years ago!
What it states is that the addition of even very small amounts of gold to silver results in a very rapid decrease of the conductivity of the resultant alloy. And at a 50/50 mix, the conductivity is lower than gold itself by a very wide margin.
This completely dispels the naive notion that alloying just a small amount of gold with silver will have a negligible effect on conductivity. And reveals the Toxic Cable lie that with just 1% or a little more of gold, the conductivity will still remain higher than that of copper.
The truth is that the addition of just 1% gold will reduce the conductivity to well below that of even bog standard plumbing grade copper, which is less conductive still than electronics grade copper. Yet Toxic Cables claims to use even more than 1% gold in their top of the line Silver Widow cable, making the situation even worse!
This level of ignorance and deceit is unconscionable.
ADVANCED RESEARCH PROJECTS AGENCY
Although the 1885 article really tells us all we need to know in order to put the lie to the claims made by Toxic Cables, some may argue that that was a long time ago, and perhaps their measurements were too crude to determine what the truth is.
Certainly some things have changed since 1885, most notably materials processing. Back in 1885, the conductivities of copper and silver were considered to be the same, and were assigned a reference value of 100. The conductivities of other metals and alloys were compared to this reference and assigned a value which represented the percentage of the reference.
In 1913, this method was adopted and became the International Annealed Copper Standard, or IACS and conductivities of other metals and alloys were expressed as “%IACS.”
But as materials processing advanced, the conductivities of commercial copper and silver began to exceed 100% IACS. Which is why today we have commercially available electronics grade copper in the form of ETP (Electrolytic Tough Pitch) and OFC (Oxygen Free Copper) that is rated at 102% IACS. Silver is now rated at approximately 106% IACS.
Indeed, a side note in the 1885 article makes note of contemporary advances in the processing of copper and its subsequent improvements to conductivity.
But none of this undermines the underlying fact that alloying small amounts of gold with silver drastically reduces conductivity.
In 1966, researchers at the University of Maryland, under contract with the Advanced Research Projects Agency (ARPA, the civilian version of DARPA), revisited this issue, but within a broader range of temperatures. This research was published in the Journal of the Less-Common Metals.
Taking from original work by Augustus Mathiessen in 1860, they produced equations to plot the curve of resistivity (which is simply the reciprocal of conductivity) for silver-gold alloys ranging from 100% silver to 100% gold. They then produced a number of specific alloy samples and compared their resistivities to what was predicted by the curve. All of the samples fit perfectly to the curve (represented by the dots on the curve).
With this information, we can mathematically determine the conductivity for any silver-gold alloy.
Shown below is a graph of the electrical conductivity as %IACS versus the amount of gold alloyed with the silver up to 5%, where electrical conductivity is reduced to a mere 50% IACS. The red point on the graph shows electrical conductivity with just 1% gold. This illustrates quite well that the claim made by Toxic Cables that 1% silver-gold will still be more conductive than copper is not even remotely close to the truth. To remain at or above the conductivity of copper, the amount of gold would have to be kept below about 0.2%.
To put this into perspective, and referring to the historical conductivities of copper wire mentioned above, Toxic Cables’ 1% gold has managed to reduce the conductivity of the world’s most conductive metal to that of the crude copper wire used for the Malta-Alexandria submarine cable in 1861. A giant 154 year step backwards.
And you can pay even more and buy Toxic Cables’ top of the line cable which uses greater than 1% gold to step even further back into time. Such a bargain!
Sadly this is what happens when someone is passing themself off as being authoritative though in reality has no real understanding of what they’re doing, except perhaps from the standpoint of marketing. In other quarters, such showy pretense of knowledge while trying to get people to part with their hard earned money is called charlatanry, if not outright fraud.
REFERENCES
M. L. Weiler, Van Norstrand’s Engineering Magazine, No. CCII, October, 1885, Vol. XXXIII, pp. 288-295
V. K. Iyer and R. M. Asimow, J. Less-Common Metals, 13 (1967), pp. 18-23
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