What is microphonic feedback?
Microphonic feedback is similar to having a microphone to close to a speaker and you get uncontrollable feedback or high pitched squeal. In guitar pickups it is caused by loose or vibrating parts such as the various ferrous components and also eddy currents within the coil. Feedback is increased in instruments due to pre-amps, overdrive pedals, louder amplifiers and loose and vibrating parts within the guitar. Make sure the pickup mounting screws are firm in humbucking pickups and that the height adjust screws found in humbuckers and single coil pickups are not loose. I often put a rubberband around the humbucking springs to dampen any unwanted spring vibration that could cause feedback. I would use rubber grommets instead of the steel springs as used in many Fender model guitars.
