A bit about Wax Potting

To prevent ingress of moisture, wax has been used for over a century to encapsulate electronic components like transformers, inductors and coils. Wax is still used today in guitar pickup manufacture.

Let’s take a look at what wax does for your guitar tone and address a common myth – “Wax won’t change the tone”.

We see many pickups in for repair that are extensively wax potted. Often the pickup is encased in a block of wax that must be removed before any repairs are carried out. In mass produced pickups internal parts like magnets, slugs and screws can be poorly fitting or loose, coil loops may extend beyond the boundary of a bobbin, fitted covers may ring and squeal, so it makes sense for high volume producers to vacuum wax pot their pickups. This approach can achieve a baseline sound, a consistent product that any worker can make, and help to minimise warranty claims for the manufacturer.

Out in the field repair techs will often advise customers with a squealing pickup to have it wax potted, but this doesn’t always solve the customer's specific problem and wax potting can change the tone of your pickup.

Magnetic Permeability - Wax has a magnetic permeability similar to air, so it’s almost completely inert with regard to magnetic fields. Wax is not contributing to any significant magnetic loss (reluctance) in proximity to stationary, permanent magnets.

Insulators – Wax functions as an electrical insulator between adjacent wires within the guitar pickup coil. Different types of wax have different dielectric properties and give rise to frequency dependent dielectric losses. This is a very small factor in overall guitar pickup design, but it is measurable. In short, it can change your tone, but not by much.

Mechanical and capacitance - When wax is heated it expands and when it cools, it contracts. Different wax types or mixes can expand and contract by different amounts. When cooling, this contraction pulls the coil wires closer together. This in turn alters coil capacitance and can change the sound of a pickup, usually to the detriment of treble response. By this mechanism, wax potting can suck the “airiness” from the treble end of a pickup if not carefully carried out.

Mechanical, acoustical and more electrical – Coil wires are receiving information from both the progress of mechanical vibration through the instrument (strings, guitar body etc) and surrounding air pressure variation (sound waves from amp speakers and P.A).

One of Faraday’s Laws states “When a conductor (coil wire) moves through a magnetic field (Pickup magnets), there will be a generated motional emf (Voltage & Current)

When coil wires inside a guitar pickup move in sympathy with their environment the result we may hear is a range of harmonics. “Even order” are the pleasing musical harmonics that we like to hear; the Major 3rd, 5th and Octaves of the fundamental pitch, but also a range of other audible complexities. This is what folks often refer to as “character” in pickups without wax. How the coil is wound is equally important. We use subtle, specific variations in tension to ensure some parts of the coil, but not all, will move in sympathy with any received information but not give any problematic squealing.

Thorough wax potting almost completely removes this specific type of “character” from a pickup. Using no wax is great if you want vintage tones with rich harmonics and character, but not so great if you play through a high gain, high volume amp. The decision comes down to what the guitarist needs and the experience of the pickup winder to decide how much wax, if any, is appropriate.

We carefully select or make our parts so that they go together well. A well-built pickup with well-fitting parts will not give any problems like squealing, even without wax.

Posted 31 August 2023