Electrical pickup for a stringed musical instrument

Abstract

An electrical pickup for a stringed musical instrument includes a permanent magnet having one field polarity intersected by the string, a pair of coils, and each coil having a pole piece so arranged that the pole pieces are magnetically neutral and are thus not loaded magnetically but serve merely as inductors.

Description

BACKGROUND OF THE INVENTION

1. field of the Invention

This invention relates to an electrical pickup for converting vibrations of a musical instrument string into corresponding electrical signals, for example, a guitar pickup.

2. Prior Art

The development of guitar pickup art has been such that pickup construction, and hence cost, has progressively increased. Not all such increase in complexity in prior art devices has been accompanied by appropriate or corresponding increase in performance capability.

SUMMARY OF THE INVENTION

In this invention, the pole pieces of the pickup coils are disposed so as to be located in a neutral part of the magnetic field of the permanent magnet so that such pole pieces are not loaded magnetically.

Accordingly, it is an object of the present invention to provide a simplified construction for a good quality guitar pickup.

Another object of the present invention is to provide a guitar pickup that can be produced with virtually no additionally tooling other than that which the manufacturer in this field already has.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheet of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

ON THE DRAWING

FIG. 1 is an enlarged cross-sectional view of an electrical pickup shown adjacent to the string of a musical instrument; and

FIG. 2 is a wiring diagram thereof.

AS SHOWN ON THE DRAWINGS

The principles of the present invention are particularly useful when embodied in an electrical pickup for a stringed musical instrument, such as a guitar, such as shown in FIG. 1, the pickup being generally indicated by the numeral 10. The pickup 10 is shown mounted on a guitar body, schematically shown at 11 in proximity to a steel string 12. The pickup 10 includes a permanent magnet 13 which is so magnetized that one pole face 14 is directed toward the string 12, while the other pole face 15 at the opposite side thereof is directed away from the string 12. The magnet 13 has a magnetic field which, except for the string, is disposed in the ambient, and the string 12 intersects such magnetic field at a portion having a single polarity, for example, north.

The pickup 10 further includes a pair of coils 16, 17. Each of the coils 16, 17 comprises a bobbin or coil form 18 on which there is randomly wound a selected number of turns of a selected wire size. These are normally so constructed that they have the same number of turns and the same wire size in each coil, thus rendering the coils 16, 17 to be interchangeable. In FIG. 2, the left end of each coil represents the end of the wire that is against the center of the bobbin when winding of the coil begins. Although the coils are connected in series as shown, they are in fact connected in out-of-phase relationship to each other so that the one coil bucks or cancels signals in the other coil which are induced by interfering sources nearby, such as an amplifier transformer. Thus, the present pickup is of the hum-bucking type.

Each of the coils 16, 17 has within its bobbin 18 an iron pole piece 19, 20 which are also alike. The pole pieces 19, 20 are so arranged that the end face of each which is directed toward the permanent magnet 13 is so disposed that it is proximate to the permanent magnet 13 at a point intermediate the poles thereof, thus making the pole pieces magnetically neutral, namely neither north nor south.

To assemble the device, each of the coils 16, 17 with its pole piece 19, 20 is disposed against the permanent magnet 13 and placed into a plastic cover 21, and any space left inside the cover is filled with an encapsulation compound 22, such as of the epoxy resin type.

The axes of the coils thus extend coaxially with each other in the direction of the length of the string 12 and parallel thereto.

The pickup 10 is normally constructed to have an extent in a direction transverse to all the strings so as to underlie all the strings 12 of a guitar.

Such assembly is greatly simplified by the fact that there are only four different components that need to be stocked, namely, a number of identical coil assemblies, a number of identical pole pieces, a number of unitary magnets, and a number of covers. The plastic covers can be those that are now in use in production. The molded bobbins 18 are commercially available as are the permanent magnets 13 which are of the ceramic type. The pole pieces are easy to construct without use of specialized tooling. It is thus shown that a particularly simple type of construction is provided wherein labor, materials and tooling for the manufacture thereof are truly minimized.

Notwithstanding such simplification, and for reasons not known, this particular pickup construction works fantastically well. A representative number of turns is 4,250 of No. 42 wire per coil. The number of turns does not particularly affect performance, but it does affect the impedance of the coil, and that number of turns stated for that size of wire produces an impedance which is good or usable for the average present commercial guitar amplifier. For amplifiers having less impedance than is now conventional, the number of turns would be correspondingly reduced as desired. Although it is not understood why this particular pickup construction works fantastically well, it is evident that the iron pole pieces are not loaded magnetically with the field from the permanent magnet, and yet they act as inductors for the coils, being disposed in a magnetically neutral location in the field.

Although various minor modifications may be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon, all such embodiments as reasonably and properly come within the scope of my contribution to the art.

Claims

I claim as my invention:

1. An electrical pickup for a stringed musical instrument having ferromagnetic strings, said pickup comprising:

a. a pair of axially spaced coils arranged to have their axes extend along the length of an instrument string;

b. a permanent magnet disposed between said coils, said magnet having a pole face of one polarity arranged to be directed toward the string, and a second pole face of opposite polarity arranged to be directed away from the string; and

c. a pair of magnetic pole pieces respectively disposed in said coils, each having an end face directed toward a magnetically neutral portion of said permanent magnet.

2. A pickup according to claim 1 in which said coils are connected in series in out-of-phase relationship to each other.

3. A pickup according to claim 1 in which said coils are respectively disposed on a pair of bobbins, said bobbins, said magnet and said pole pieces being held together as a unit by encapsulating material.

4. A pickup according to claim 1 in which said coils, said magnet, and said pole pieces are elongated in a direction transverse to the string length so as to be responsive to a plurality of parallel strings.

5. An electrical pickup for a stringed musical instrument having ferromagnetic strings, said pickup comprising:

a. a permanent magnet arranged to be supported with one pole directed toward an instrument string and the other pole directed away from the string so that only one polarity of its field is intersected by the instrument string;

b. a pair of coils connected in series in out-of-phase relationship; and

c. a pair of pole pieces respectively disposed in said coils and located so that the coils are disposed to be influenced by the magnetic field, each of said pole pieces being disposed against a central portion of said magnet between its poles so that said pole pieces are magnetically neutral.