To be honest, I thought for a very long time that cables didn't make a real difference. This was just until I did a fair comparison of 6 different guitar cables. Then, I've understood that they really make a difference in your tone.
- EMI rejection
- Low noise
- Low microphonics
- Frequency range preservation
- Signal level preservation
This is very typical in big Musical Stores, where they buy cheap bulk cables and connectors, creating their cheap line of guitar and patch cables. But there are some brands that buy unlabeled or relabeled cables and connectors to the real makers, making the assembling themselves.
This is very typical in Brands like Monster Cable, Planet Waves, etc. You will see a Rock-Cable, Jazz-Cable, Vintage-Cable, etc. That is, a model that better fits to a certain musical style.
This is the clear example of Evidence Audio or Vovox, by example.
This is the typical design of an standard guitar (audio) cable:
This is more or less what we will see if we cut the cable and face that cut (cable section).
The outsider black circle corresponds to the external isolant layer of the cable, the one that is being trampled under our feet, dragged along the floor and, subject to all kinds of friction.
So, we need a relatively thick layer of isolant here but, not so rigid that it can compromise cable's flexibility.
Also, that isolant layer should isolate the electrical signal in this cable from external electrical and magnetical interferences.
Materials used to build this layer are important in several aspects. In my experience, Vintage alike cables, that wear that fabric jacket are more prone to microphonics issues (whistles and howls). This is what I've experienced when trying several different cables and, specially under high gain situation (with several gain pedals switched on together). The only cable that seems immune to this issue is the Evidence Audio The Lyric II.
Most of the currently produced cables have some kind of plastic polymer for this layer but, not every polymer works equally fine. Some polymers have a very spongy aspect. Those are incredible flexible but, their porosity seems to work against good noise rejection. In my own experiences, I've found this kind of foamed cables to be more prone to microphonics issues, even more than vintage alike cables.
At the end, every cable maker should take some compromised solution to deliver a good isolating level with a reasonable flexibility and good mechanical resistance.
The next layer that we will find, from outside to inside, is the shield layer.
Shield layer is a big surface of some conductive material that completely envelops the signal conductor.
The idea behind all this is to create some kind of Faraday's Cage, to protect the signal conductor from external electrical and magnetical interferences and, to protect the quality of the electrical characteristics of the signal path. This layer is always soldered to the ground path, to throw all that catch noise to ground.
The standard, long time ago, was to use some kind of aluminium folder for this layer. I suppose it is the cheaper solution but, probably not the best one.
Nowadays standard seems to be a twisted thread of copper strands that cover in more or less degree the whole length.
Anyway, a shielding factor of 100% is the real deal here. A shield that doesn't covers the 100% of the inner signal conductor is an open Faraday's Cage and then, it has "holes" that maybe strained by noise and interferences. Please, do not assume that every audio or guitar cable has a shielding factor of 100%; carefully read cable' specifications.
Next layer is the inner isolant layer.
This layer has the goal to separate the signal conductor and the shield (ground).
We know that when we have to conductive surfaces (as two plates) separated by some kind of dielectric, we achieve a Condenser or Capacitor.
That layer is working as the dielectric of the capacitor created by the cable. As you can imagine, the characteristics of this isolant layer is crucial to reduce the capacitance effect of the cable.
The immediate issue related to capacitance is the gradual lost of high-end respect of the original guitar' signal. When we put together an inductance (coil) or resistance (pots) and a capacitor (cable) we have a passive electronic filter, that catches some frequencies band, which cutoff frequency value is being determined by capacitor's capacitancy value and that leads to "throw to the trashcan" that frequencies range.
The highest the capacitancy of the cable is, the higher the loss of high-end respect of the original signal.
Capacitancy of a cable is being expressed related to a length unit, by example 78 pF / meter, because the longer the cable is the higher the capacitancy goes. By example, that value means that a cable of 10 meters with such a value, will have a capacitancy of 780 pF. The capacitancy of a typical guitar cap used for tone control is about 22000 pF so, cable capacitance is affecting to the very high end frequencies, probably beyond the "air" band.
One of the tricks that Modifiers (as mentioned above) use is just to change the capacitanty of cables, to affect the frequencial content of the signal, to achieve a "warmer" cable, etc. While, Developers are trying to minimize that capacitancy, trying to get the most accurate signal, as it was originated.
Last layer corresponds to signal conductor and, this is the core of the cable.
This is the conductor where the real signal, originated in guitar, travels to the pedal board or amp. The shield layer, connected to ground, creates a zero-point reference for voltage. The best the zero-point reference is, the clearer the signal will be.
Definitively, solid signal conductors have the best preservation ratio of the signal so, this is the common tendency when looking to the purest signal representation so, solid cores are being used where their low flexibility doesn't compromise the work, as inside some high-end amps, etc.
Cables like Evidence Audio The Lyric II have a solid core and, they have so low flexibility that make them a bad deal to be hanging from your guitar in a performance, they are not comfortable. But, you can run a length of such a cable from your pedal board to the amp, since this doesn't compromises your movements over the stage.
Vovox goes even worst, since the have signal and ground in two complete separated cables, twisted together, what makes a thicker virtual cable, very rigid.
So, we have a big issue here. Solid core conductors are best to the sound but, worst for ergonomy. That's why the common and traditional solution was to use a thread of cooper strands to carry the signal. That thread gives a nice flexibility to the cable.
But, that approach leads to one more issue. When in our audio path we have signal strands that can freely frictioning with other strands, we have microphonics issues. That's why coils are being wax potted (to avoid the mechanical movement of coil cables) but, is not usual to see waxed signal conductors.
Evidence Audio, by example, in their cable The Forte are isolating every strand of that signal thread with some kind of chemical product, just to avoid microphonics (and it works!).
One of the most usual cooper used here is 99% Oxygen Free. This has become an standard in audio cables but, even that, there are cooper strands plated with some other conductive material, by example, silver or tin platted cooper strands.
In my own experiences, I've found silver plated cooper strands the most hi-fi sounding cables. This is because silver is way more conductive than cooper. Those cables sound more pure but, remember that this can go against musicality. They are awesome for Hi-Fi projects.
I think, Vovox is using silver-plated cooper strands and, Sommer Cable, in their SC The Spirit are using tin platted cooper strands.
Different approaches lead to different cables
We see that there are more issues to handle than seemed to achieve a good guitar cable and, the way as every cable maker deals with every issue ends to several cable models with different compromised solutions. As in many other complex cases, to optimize one characteristic unbalances others.
In Studio environment, the standard is to use balanced cables with jacks type XLR. The signal level on those studio cables is very low but, it is being sent in two different signal cores, with opposite electrical phase (one negative, one positive). When the signal is "re-build" in the other end of the cable, whatever noise get for whichever of the two cores is being eliminated by electrical cancellation (you can read a deeper and accurate description on how it works in some places specialised in audio electronics, do not expect a better explanation from myself, I am sorry).
Some high-end cables for guitars are being developed following same principles (but with instrument level signal and common 1/4" Jacks) and, they provide an outstanding noise an EMI rejection level.
One of the cables very often used in Studio environment are Mogami's. Mogami's instrument cables are very similar to the standard cable described above but, they insert a layer of a carbon composite between the inner isolant layer (that separates the signal from shield). This seems to enhance the noise and EMI rejection and to lower cable's capacitancy. Sommer Cable is using same approach in their high-end cables, as well.
Vovox is using two separated standard cables to drive signal and ground. These two cables are twisted together. They are using cooper silver plated conductors inside, also. To twist cables is a very known method of reduce signal noise and interferences and, it is being in use for a very long time.
If you look to high voltage lines, you will always see that cables are twisted. If memory does not lies me, this is because the magnetic field results twisted also and this, improves the noise and interferences rejection (but, please, read a deeper and accurate description in any electronics specialised page).
Different cables lead to different issues and sound quality
Well, at the end, you can see that even that most of cables are made in a very standard way, the thickness and materials used for every layer can differ in several ways, what ends in different cables, with different characteristics and issues, of different prices. So, does it affects to sound?. Yes, certainly.
When you run short footage of cable, issues are not so apparent. When you play just clean, without gain pedals between your guitar and amp, issues are less apparent. When you start to stack pedal effects and have a long run of cable (virtual), from your guitar to the amp and, when your high-gain pedals are switched on, the most of the issues pop up in your face.
I did an experiment, some time ago, testing 6 different guitar cables and, what was in my aim was to demonstrate that cheap cables can sound as good as expensive cables. Er... well... conclusion was very different and, I was surprised hearing that every cable sounds really different.
This is the video I already did related to this experiment:
So, the truth is that every cables sounds slightly different and that they have different ways to handle the issues that we already discussed. Some are worst for microphonics, some are worst for ergonomy, etc.
What I cannot say is which one is the best cable. Everything in music is a matter of taste and, everything depends on the complete rig and situation.
By example, if we are after a vintage tone, maybe we need a cable that can mime that high-end roll off that cheap vintage cables had. If we are dealing with a very bright amp and we wanted to warm a bit the tone, maybe it's a good idea to use a cable with higher capacitancy (warmer). If we are dealing with a very dark amp, we can have some enhancement by using the most transparent cable, and so on.
At the end, is up to you which cable suits best to your needs but, please, experience the differences.