Brass and especially copper are both appropriate choices of material for the core, however it’s not a simple case of copper/brass verses steel. The quality of the copper and brass should also be considered. It should be realised that as these metals become scarcer, they are being recycled more frequently and as this process is repeated contaminants such as iron and steel are introduced affecting the composition of the brass. More information on issues affecting brass quality can be found in this well written short article ‘Getting Down to Brass Tacks on Quality’ by Jim Burstein. Both Neutrik and Switchcraft utilise single piece tip and rod construction, whereas the G&H rod is bonded to a brass tip. To summarise, the type of metal plating on the jack plug surface is quite literally just the tip of the iceberg. The internal composition of the core has as much bearing on the durability and tone of the jack plug as do the physical differences between gold, nickel or silver plating.
Additionally, there are other internal factors such as the quality of insulation materials. Several different types of material have been and are utilised for the bushings and spacers within jack plugs, including hardened rubber, various types of plastics such as thermoplastic, mica, phenolic, fibreglass and nylon. Each material has its own strengths and weaknesses in terms of insulation resistance and durability and price. Mica is a superb insulator and resistant to high temperatures (again, suitable for use on for Venus) but brittle, nylon has good longevity in comparison to rubber and plastic because it more chemically inert. Many of these materials are excellent insulators and perform more than adequately in normal gigging/studio conditions. Some plastics do not have good long term stability and will consequently limit the life of the jack plug. There are countless types of plastics and it is impossible to know what you’re buying unless you purchase from a reputable manufacturer who specifies the materials they utilise.
One excellent type of plastic that seems to have been overlooked by jack plug manufacturers in the guitar industry is PTFE (polytetrafluoroethylene). This is often used in BNC connectors (for test instrumentation) and in the hi-fi industry for phono (RCA) sockets. It is and excellent dielectric, is immune to most solvents and acids, has a very high melting point (for a plastic), is extremely tough and it also has very low friction – practically perfect in every way for use as an insulator. A silver plated jack plug with PTFE insulators would be this engineer’s dream of something made from the appropriate materials with no corners cut.
From a textbook engineering perspective it could be argued that even the poorest quality metal – steel in this instance – is a more than adequate material for the core and sleeve. Afterall the fraction of an Ohm resistance in a jack plug is vanishingly small in comparison to several thousand Ohms already in series with the signal from, say a passive pickup or a low impedance buffer (which may still be in the order of Ohms or tens of Ohms). So why all the fuss? Does it really matter? Well the issue here is that it’s not just that steel is cheap, it’s the CHEAPEST metal that can possibly used. Iron (Fe) costs less than $0.20/lb. Compare this to Nickel (Ni) at $8.40/lb, Copper (Cu) at $3.00/lb and Zinc (Zn) at $0.94/lb. When a manufacturer specifies steel over, say brass, that’s not an engineering decision, it’s an accountancy decision. There are no physical properties of steel that would encourage an engineer to even consider it in preference to brass, copper or a host of other more suitable metals and alloys. This then also raises further doubts and suspicions. If the cheapest metal is being used then what about the other materials and processes used in manufacture? Could insulation material be a poor quality plastic? Is the plating process well-controlled? Profits are surely the prime motivation here, not the desire for engineering excellence or a love of music. This is something I do not wish to support or be involved in. I want peace of mind that what I’m purchasing is a quality product, that the company who makes it is genuine and takes pride in their workmanship. Now that’s something I do want to be involved in!
How guitar cables and jack plugs affect the tone of the instrument has been known to catalyse heated debates amongst musicians and studio engineers. This isn’t helped by the unlimited ‘factoids’ in circulation on the internet or the ‘creative’ (often scientifically incorrect) marketing ‘flim-flam’ employed by some manufacturers in the relentless, competitve battle to differentiate their product from a competitor. My aim in writing this article has been to research and uncover the real science – the relevant engineering facts – of the materials and construction techniques used in the manufacture of jack plugs. To ascertain what is significant and what’s not so significant for good tone and reliablity. I welcome any comments or additional information that might help improve the content of this article. Thanks for reading.