Strat Inductance Plates
Adding an inductance plate is a simple modification for any Strat bridge pickup. Essentially, it works just like the base plate on a Telecaster pickup. According to pickup maker Bill Lawrence, Leo Fender used copper-plated steel base plates to stabilise and to increase the magnetic force of the comparatively weak Alnico III slugs available in the early 1950s.
The ferromagnetic steel plate increases the inductance of the coil, much like increasing the number coil windings. A pickup with a base plate should have a slightly higher output.
Steel, copper, brass and aluminium base plates cause eddy current interference, which lowers the resonance frequencies, so the pickup will sound beefier and smoother in the top end. You can achieve this effect without altering the inductance or the magnetic field by using aluminium or brass base plates rather than steel.
Lawrence also notes that if the plate is too thick, you may end up with a muddy pickup: the ideal thickness is between 1/32" and 1/16". You can use Copydex glue to fix the plate to the pickup, and there should be a strip of tape on the plate to prevent the metal making direct contact with polepieces. If you’re interested in trying this mod, plates are available from Fralin or Callaham for a mere £10.
9. Wiring Secrets Pt.9