Tuesday, September 23, 2008
the wax man cometh (Tim has a melting moment)
Electric guitar pickups can squeal. The approximately 6,000 to 9,000 turns of very fine magnetic wire that make up a pickup coil can start vibrating within itself. As the gain increases so does the vibration and that brings with it the potential for microphonic feedback. Metal pickup covers, pole-piece screws or anything loose can also vibrate annoyingly on a pickup. Squeals are typically quelled by potting (or dipping) the pickup in a thin waxy liquid that permeates the coil and holds it all together. We use hot wax in a vacuum to get as much permeation as possible. Occasionally we may use lacquer or very thin epoxy - whatever is best for the job and will not compromise the pickup. Here Tim is mixing up waxes with different properties. Some experimentation is required to come up with the best formula.