Natural Performance Extended Range Pick-up Device

Abstract

A pick-up device for electrical guitars and like instruments includes pick-up coil formed by first and second windings wound in parallel on the same coil bobbin one on top of the other. The impedance of first, inner winding is less than that of the second winding, a turns ratio of one to four being typical, and the resultant output characteristic of the composite coil provides high quality reproduction of both treble and bass.

Description

FIELD OF THE INVENTION

The present invention relates to electro-mechanical transducers and, more particularly, to electromagnetic pick-ups for musical instruments such as electrical guitars.

BACKGROUND OF THE INVENTION

Electrical instruments such as electric guitars employ a number of different electromagnetic transducers for converting the vibratory energy of a plucked string into a corresponding electrical output. One such transducer device includes a core assembly comprising a plurality of core members individual to the strings of the instrument, permanent magnets common to the core members, and a coil assembly including a plurality of coils individual to each of the core members or common to predetermined groups of core members. Another such device employs a series of permanent magnets individual to the instrument strings and a common coil wound collectively around the magnets.

In order to increase the fidelity of the output produced by such transducers the trend has been toward the use of finer, higher gauge wire in the coils. However, this approach has not been entirely effective and, in addition, the cost of higher gauge wire is considerably higher than that of the conventional lower gauge wire normally used. Further, the resistance of finer wire is higher.

SUMMARY OF THE INVENTION

In accordance with the invention, a greatly improved electromagnetic pick-up device is provided wherein a coil assembly comprising a coil including first and second windings connected in parallel and wound one of top of the other is utilized. The number of turns of the first winding is less than that of the second winding, and in a presently preferred embodiment the first winding is wound on the coil bobbin and the secondary winding is wound on top thereof.

Although the reason therefor is not completely understood, the multiple-coil pick-up device of the invention provides a substantial improvement in the fidelity of the sound reproduced as compared with single-coil devices or other conventional pick-up devices. In use, the pick-up device of the invention provides high quality reproduction in both the bass and treble ranges and provides a considerably more natural sound than any known pick-up device. It is thought that the relatively low impedance first winding provides reproduction of treble range frequencies and the relatively high impedance secondary winding provides reproduction of the bass range frequencies and that together, through mutual coupling, the two windings provide the extended range response produced.

Other features and advantages of the invention will be set forth in or apparent from the detailed description of a presently preferred embodiment thereof found hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a guitar incorporating two pick-ups in accordance with the invention;

FIG. 2 is a perspective view of a pick-up device in accordance with a presently preferred embodiment of the invention, with the winding assembly shown in phantom lines for illustrative purposes;

FIG. 3 is a section taken along line III--III of FIG. 2 with the windings shown in solid lines;

FIG. 4 is a plan view of the pick-up assembly of FIGS. 2 and 3;

FIG. 5 is an electrical schematic diagram of the composite coil of 2 to 4; and

FIG. 6 is a graphical representation of the response characteristics coil of the invention and of the individual windings acting alone.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a conventional guitar is shown which includes a head 10, a neck 12 including a finger board 12a, and a body 14 having a bridge assembly 16 mounted thereon. A series of six guitar strings 18 are mounted over the upper surface of body 14 and neck 12, strings 18 being individually stretched between corresponding tuning screws 20 and bridge assembly 16. First and second electromagnetic pick-up devices 22 and 24 are shown mounted in spaced relationship beneath strings 18 in inductive relationship thereto although it will be appreciated that different numbers of pick-ups in other arrangements can also be used.

Referring particularly to FIGS. 2 to 4, a pick-up device in accordance with the present invention and corresponding to pick-up devices 22 and 24 of FIG. 1 is shown. The pick-up device, which is denoted 30 in FIGS. 2 to 4, includes a bobbin 32 which is preferably fabricated on acrylic plastic and includes spaced upper and lower plate-like portions 32a and 32b joined by and formed integrally with a central post portion 32c. A series of six core members 34a, 34b, 34c, 34d, 34e and 34f are formed by screws which extend through central bobbin post 32c and serve in securing pick-up device 30 to the guitar body. Core members 34a to 34f are positioned adjacent and associated with corresponding ones of strings secured to lower plate-like portion 32b of bobbin 32. First and second magnets 38 and 40 extend longitudinally of bobbin 32 beneath plate 36 and on opposite sides of core members 34a to 34f, like poles of magnets 38 and 40 (north poles in the embodiment under consideration) facing these core members as illustrated in FIGS. 3 and 4.

In accordance with the invention a dual winding pick-up system is provided wherein the pick-up coil 42 is formed by first and second windings denoted I and II wound onto bobbin 32. Windings I and II are common to core members 34a to 34f, with winding II being wound on top of winding I as shown in FIG. 3. Windings I and II are wound in parallel as is indicated schematically in FIG. 5 and are wound in the same direction.

Also as is indicated schematically in FIG. 5 as well as in FIG. 3, the number of turns making up winding I preferably substantially less than the number of turns making up winding II. In an exemplary embodiment the ratio of the number of turns in winding I to the number of turns in winding II may be one to four although, of course, other ratios such as two to four can also be used. In an exemplary relatively high impedance coil, winding I may contain 2000 turns and winding II may contain 8000 turns with winding I have a d.c. resistance of about 2.2k ohms and winding II having a d.c. resistance of about 10k ohms. In an exemplary low impedance embodiment, winding I may contain 200 turns and winding II may contain 800 turns. The connection of the relatively high impedance winding II in parallel with winding I and the winding of winding II on top of winding I, through means of the mutual inductive coupling therebetween, provides high quality reproduction of bass sounds and virtually eliminates distortion. The relatively low impedance winding I provides high quality reproduction of treble sounds. The response characteristics of the windings I and II, acting alone, are indicated in FIG. 6 by curves 50 and 52 respectively whereas the resultant or composite response produced by composite coil 42 is indicated by curve 54. It will be appreciated that coil 42 produces an extended response and provides a high level response in both the treble and bass ranges. The response in the treble range is considerably improved as compared with prior art pick-ups and the overall sound reproduction is considerably more true and natural than that produced by any available pick-up.

It should be pointed out that conventional amplifiers designed for electrical instruments are generally high impedance devices. Although the multiple coil pick-up of the invention is essentially a low impedance device and hence a mis-match exists over the operating range of the pick-up, the use of multiple coils enables the high quality operation described above despite this apparent mis-match.

Although the recent trend in pick-up design has been toward the use of finer wire in the windings, the pick-up of the present invention permits relatively large size wire to be used. More specifically, in a preferred embodiment 43-gauge wire is used, rather than the 44 and 45- gauge wire now commonly used, although the wire size is a function of the space requirements of the system in which the pick-up is employed. Both of the windings I and II can be formed of the same size although different wire sizes may be used.

Although these dimensions are merely exemplary and a number of different bobbin arrangements can be used, in the embodiment shown in FIGS. 2 to 4 plate-like portions 32a and 32b are 31/4 inches long, 13/8 inches in width and one-eighth inch thick and are separated by approximately seven-eighths inch. Grounding plate 36 is approximately 0.062 inch thick.

Although the invention has been described in detail with particular reference to preferred embodiments thereof, it will be understood that variations and modifications can be effected within the scope and spirit of the invention as described hereinabove and as defined in the appended claims.

Claims

We claim:

1. In a pick-up device for a stringed electrical musical instrument for producing an electrical output in accordance with the movement of the instrument strings and including magnetic core means, the improvement comprising a coil arrangement comprising a first winding wound about said core means and a second, separate winding wound about said first winding and connected in parallel with said first winding.

2. A pick-up device as claimed in claim 1 wherein said second winding is wound in the same direction as the second winding is wound.

3. A pick-up device as claimed in claim 2 wherein the number of turns of said first winding is less than the number of turns of said second winding.

4. A pick-up device as claimed in claim 1 further comprising a support member for supporting said coil arrangement comprising first and second spaced, generally flat, plate-like portions and a central post-like portion located between said plate-like portions and formed integrally therewith about which said first and second windings are wound, first and second spaced permanent magnets extending longitudinally of said support member and a grounding plate secured to said second plate-like portion of said support member, said core means comprising a plurality of screw members extending transversely through said support member and outwardly thereof in the space between said and second permanent magnets, like poles of said magnets lying adjacent said screw members on opposite sides thereof.

5. A pick-up device as claimed in claim 3 wherein the ratio of the number of turns of the first winding to the number of turns of the second winding is one to four.