As there is now only a single rotor disk, each horseshoe magnet comprises a stack of individual magnets, but acts through a pair of pole pieces.
32.
These pickups have a large, flat coil with adjustable steel screws as pole pieces, and a pair of flat alnico bar magnets lying under the coil bobbin.
33.
The first reason is that the pole pieces had too much magnetism on the strings and could cause some lower notes to go out of pitch in a Doppler effect.
34.
A "'pole piece "'is a structure composed of material of high magnetic permeability that serves to direct the magnetic field produced by a magnet.
35.
The design of the bar magnet gives it a smoother distortion, better sustain through the amplifier, and have less fade onto the strings than the design of pole pieces.
36.
For instance, the shape of the pole piece affects the magnetic interaction between the voice coil and the magnetic field, and is sometimes used to modify a driver's behavior.
37.
The " aperture function " cuts off beams scattered above a certain critical angle ( given by the objective pole piece for ex ), thus effectively limiting the attainable resolution.
38.
Imperfections in the manufacture of the pole piece can induce severe distortions in the magnetic field symmetry, which induce distortions that will ultimately limit the lenses'ability to reproduce the object plane.
39.
The Firebird pickup uses a pair of long'rail'magnets whereas the Les Paul Deluxe mini-humbucker uses a single bar magnet below one ferrous rail and six threaded ferrous pole pieces.
40.
The pole pieces of the magnet are so shaped that there is a region in which the product of the field strength and field gradient in the " z " direction is constant.
