I'm putting a Baseplate on my Strat's Bridge pickup on Monday and was just curious what a BP would do to the neck and middle pickup tone. Anyone tried this?

What a proper ferromagnetic baseplate does is it increases the inductance of the coil, making it respond like it had more coil windings than it does by strengthening the magnetic pull. The plate also creates eddy currents which shift the frequency response toward the lower ends of the spectrum. Mounted to a metal housing, as the plate itself also radiates, it can also offer a resonant twang of sorts. Of course, too thin, the plate does nothing, too thick it turns the pickup's tonality to mud.

So, in a direct answer to your question, it is a 'passive' pickup booster of sorts where higher frequencies will be shifted down to mids and lows which is where the 'balls' of any pickup comes from.

A word of caution: The baseplate must be firmly attached to the pickup and grounded. There should be no air pockets between the mating side of the plate and the underneath of the pickup or you will get squeal and howl like there's no tomorrow.

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You dig?