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Cables 101 #3 - Core Material: Conductivity

What’s a Cable Core?

Right in the middle of all the different layers in your cable lies a wire. This wire has the all-important task of carrying the audio signal from the instrument you’re playing to your next piece of gear, be it a pedal, amp, DI box, sound console, so on and so forth.


What are Cable Cores Made of?

Some of you may know that there are several types of material that can be used for cable cores. Different types of copper, as well as silver, or even silver-coated copper can be used as cable cores. In this article, we’re going to take a brief look at all of these choices and what you should really consider as truly important factors for choosing cable cores.


Copper Cores

Used for more than a century as an electrical conductor, copper is the classic core material for cables.

There are many good reasons for this.

Copper has great electrical conductivity. In fact, it’s so good that electrical conductivity for other metals is measured against that of coppers. In other words, it is the benchmark for electrical conductivity.

In terms of physical qualities, copper has high tensile strength, which means it can be pulled with a lot of force before breaking. It also has high ductility, which means it’s a flexible metal.

Three types of copper are used in the making of cable cores. There’s OFE (Oxygen-Free Electronic) copper, which has the least amount of oxygen in it. There’s also OFC, short for OF (Oxygen-Free) copper. And then there’s ETP (Electrolytic Tough Pitch) copper, which, being 99.9% free of oxygen, has the most amount of oxygen in it.

Manufacturers like to make a big deal about using OFC, Oxygen-Free Copper, which is 99.99% free of oxygen. In fact, the Sommer cables that we use do have OFC in them, but we don’t really talk about it very much

Why ever not?

Well, because for our purposes, it doesn’t actually make a difference.

Where OFC or OFE copper does matter is in applications where chemical purity is really important. Some of these applications include the manufacture of semiconductors and super-conductor components, and the assembly of high-vacuum devices such as particle accelerators. It’s critical to use OFC in these apps because the release of oxygen, among other things, can cause undesirable chemical reactions.

Last we checked, guitars were not particle accelerators…


Silver Cores

Silver is the only metal with higher electrical conductivity than copper.

Why don’t cable manufacturers use silver then?

For one, silver is a precious metal so it’s really expensive - many times more so than copper. Wait, let’s rephrase that - using that much silver in a long, thick instrument cable is PROHIBITIVELY expensive. You wouldn’t want to buy it. We definitely wouldn’t buy it. And manufacturers simply don’t make what we consumers don’t want to buy.

Furthermore, silver oxidises more easily than copper, which means that this high level of conductivity degrades much more quickly than coppers. This is especially so in a high-humidity environment much like… You guessed it, Singapore. Which means that despite being more expensive, you’d need to replace a silver-cored cable more often than copper-cored one.

In any case, silver is also not as strong as copper, which means that if you pull too hard, it breaks more easily than copper. That’s not something you want in a roadworthy cable isn’t it?


Silver-coated Copper

Silver-coated copper has better levels of conductivity, especially for radio frequencies. The only thing is, these frequencies are far above the audible frequency range. Not even bats can hear that!

Also, unless sealed from air and moisture, places where the copper beneath the silver is exposed can corrode very easily, which is known as red plague corrosion. Instrument cables are not air-sealed and are frequently handled in high-humidity environments, so there’s a pretty good chance of this happening.

Furthermore, silver-coating copper wires add processing costs into manufacturing - costs which are then passed on to you, the consumer. While it won’t cost as much as pure silver core wire, it’ll be markedly more expensive than pure copper cores.


So What’s Important?

Despite apparently having so much to consider, much of this amounts to nothing more than pure marketing. In terms of what affects our tone, the single most important factor we need to pay attention to is conductivity. This is followed by secondary factors such as cost, strength, and flexibility.

In the end, the better physical properties and much lower cost of copper cores win over the marginally better conductivity of silver and silver-coated copper cores.

If we look at the bigger picture and include cable construction, capacitance takes far more importance in terms of tone preservation, as we’ve written about in this article.

Keen on further cable knowledge? Feel free to peruse our humble Cable 101 series of articles here:

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