Abstract:
A bifilar pickup for an electrical stringed musical instrument is provided. The bifilar pickup comprises a dual coil wherein at least one coil is formed with two closely spaced bifilar parallel wound wires. A guitar in combination with the pickup unit is additionally provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This Application claims priority to U.S. Provisional Patent Application Ser. No. 61/407,799, filed Oct. 28, 2010, and PCT Patent Application No. PCT/US2011/058190, filed Oct. 28, 2011, both of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD  
       [0002]    The field of the disclosure relates generally to the construction of transducers for converting the vibration of the strings of electrical musical instruments into a measurable voltage. More particularly, the disclosure relates to the construction of electromagnetic dual coil bifilar pickups. 
       BACKGROUND  
       [0003]    Electromagnetic pickup devices are used in conjunction with stringed musical instruments such as electric guitars and basses to convert the vibrations resulting from the movement or “picking” of the strings into electrical signals, for subsequent transmission to amplification devices to produce a desired sound. The pickup is generally positioned under the strings of the instrument on the base surface and the signal transmitted by an electromagnetic pickup is dependent upon the motions of each string. 
         [0004]    The most essential components of a dual coil pickup are a permanent magnet and two coils of wire. Generally, two oppositely polarized magnets will be used although in some embodiments, only a single bipolar magnet is incorporated into the embodiments. The magnets generate a magnetic field that passes through the pickup coils and also extends into a space occupied by at least one string of the instrument. Vibration of the string changes the reluctance of the magnetic path and creates disturbances in the magnetic field proportional to the string vibration. The changing magnetic field in the pickup coils in turn induces an electrical signal in the coils. From the output of the pickup, a circuit connection is made to an amplifier. 
         [0005]    There are several types of pickups with varying coil configurations known in the art. One type of electromagnetic pickup device is a dual coil pickup or a humbucking pickup. In a humbucking pickup, two coils are associated or connected in a manner so as to reduce hum. 
         [0006]    As a rule, a central design problem of any pickup is that of obtaining both a faithful signal and a good signal to noise ratio. It is well known that the pickup coils, in addition to their desired function of picking up string vibrations, also tend to pick up electrical noise and interference signals from various extraneous sources. Also, because of the impedance associated with common dual coil pickups, frequency response may be limited. Therefore, there is significant value in a pickup that has improved noise rejection of radiated frequencies from extraneous sources and extending the frequency response while still maintaining response to desirable string vibrations. 
       SUMMARY  
       [0007]    In one aspect, the present disclosure is directed toward a dual coil transducer wherein at least one of the coils has two wires wound side by side in the same direction with coaxial turns. In one embodiment, the two coils are additionally electrically connected to each other. 
         [0008]    In addition to the coils, the pickup comprises at least one magnet and potentially bobbins and pole pieces. The coils may be directly wound around the permanent magnets or pole pieces or alternatively may be wound around the bobbin and then the bobbin is placed around the pole pieces. 
         [0009]    Consistent with yet a further aspect of the disclosure, a guitar with a disclosed pickup is claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  depicts a front elevational view of a stringed electrical musical instrument with the pickups of the present disclosure. 
           [0011]      FIG. 2  illustrates the common pieces of a dual coil pickup. 
           [0012]      FIG. 3  demonstrates a close-up view of the bifilar winding of at least one of the coils. 
           [0013]      FIG. 4  is a schematic diagram of the circuitry of the dual coil bifilar pickup wiring. 
           [0014]      FIG. 5  depicts schematic circuit diagrams of common modes of connection of the dual coils; A—In phase, parallel; B—In phase, series; C—Out of phase, parallel; D—Out of phase, series. 
       
    
    
     DETAILED DESCRIPTION  
       [0015]    Before describing the exemplary embodiments in detail, it is to be understood that the embodiments are not limited to particular apparatuses or methods, as the apparatuses and methods can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which an embodiment pertains. Many methods and materials similar, modified, or equivalent to those described herein can be used in the practice of the current embodiments without undue experimentation. 
         [0016]    As used in this specification and the appended claims, the singular forms “a”, “an” and “the” can include plural referents unless the content clearly indicates otherwise. Thus, for example, reference to “a component” can include a combination of two or more components. 
         [0017]    Exemplary embodiments of the dual coil bifilar pickup will now be explained with reference to the figures. This description is provided in order to assist in the understanding of the invention and is not intended to limit the scope of the invention to the embodiments shown in the figures or described below. As used herein, a “coil” is a wound spiral of two or more turns of wire used to conduct current.  FIG. 1  demonstrates a stringed electrical musical instrument. In the embodiment of  FIG. 1 , the stringed instrument is a six stringed guitar. However, the components and advantages currently disclosed are applicable to other types of stringed instruments, such as bass guitars, ukuleles, mandolins, violins or guitars with a different number of strings. Referring now to  FIG. 1 , guitar  100  comprises a neck  101  and a main body  102 . The guitar  100  includes guitar strings  103  that are secured on one end to a tuning head  104  and on the other end to a bridge  105  in a manner well known in the art. 
         [0018]      FIG. 1  further demonstrates a pair of pickup units  106  arrayed beneath the strings  103  and secured onto the face of the main body  102  of the guitar in a conventional manner. In certain aspects, pickup units  106  are fitted into apertures in main body  102 . In order for the disclosed pickups to function as desired, strings  103  must be made from a magnetizable material such that pickup can electromagnetically interact with strings  103 . The pickups may be placed in various positions on the main body  102  of the guitar. Pickups placed near bridge  105  are generally called bridge pickups, whereas pickups placed adjacent to neck  101  are called neck pickups. The embodiments disclosed may be use as both bridge and neck pickups. Furthermore, more than one pickup may be used with a stringed electrical musical instrument. In the event more than one pickup is used, the pickups may be connected via switches such that one, or more than one, may transmit at a time. This type of switching is well known in the art and examples can be found in U.S. Pat. No. 5,780,760, hereby incorporated by reference. The pickups disclosed may also be used with other types of pickups such as traditional single coil or traditional humbucking pickups. 
         [0019]    Pickup units  106  comprise at least one permanent magnet  108  and at least two coils  110 . The embodiment of  FIG. 2  demonstrates a pickup unit with two permanent magnets and two coils. Although the embodiment in  FIG. 2  demonstrates use of the permanent magnets as pole pieces, other exemplary pickup units  106  may also include pole pieces of different types. The particular pole piece is not limiting and any magnetizable material in contact with the permanent magnet  108  to produce an electro-magnetic field is contemplated. For example, in one embodiment, the pole pieces are adjustable threaded steel poles. Nevertheless, certain embodiments will have non-adjustable pole pieces. In yet other embodiments, there may be both adjustable and non-adjustable pole pieces. In addition to embodiments having a pole piece for each string, pole pieces may also be shaped as a blade or as a rail. 
         [0020]    The dual coil type device may include a pickup cover (or cap)  109  as well as spacers  111 , which align and stabilize the coils, bobbins  116 , and base  118 . Although not shown in  FIG. 5 , a pickup trim ring is also contemplated. A pickup cover, spacers, and pickup trim ring may also be used with the single coil pickup shown in  FIG. 2 . As understood by the skilled artisan, different types of covers, spacers, and pickup trim rings may be used without changing the character of the invention. Generally, at least one of the two coil forms has two wires wound in a parallel manner with coaxial turns. The electrical diagram of the dual coil bifilar wiring, without showing the connection between the coils  110 , is demonstrated in  FIG. 4 . In the dual coil pickup of  FIG. 4 , the two coils are substantially identical, with each coil having two wires,  120  and  122 , and two permanent magnets  108  with transverse polarity. 
         [0021]    The magnets used in exemplary embodiments of the pickup units  106  are not meant to be limiting. Several different types of permanent magnets, such as Alnico, ceramic, and samarium-cobalt are contemplated. Depending on the embodiment, the number and shape of the magnets may also vary. In one embodiment, the pickup unit  106  has two permanent magnets  108 . In another embodiment, pickup unit  106  has one permanent magnet  108 . If Alnico permanent magnets are used, they may be either cylindrical or bar-shaped. In embodiments which use Alnico magnets, the grade of the magnet may be Alnico 5, Alnico 2, Alnico 3, Alnico 4, Alnico 7 or Alnico 8. In one embodiment, a bar-shaped Alnico 5 magnet is used. In embodiments with more than a signal magnet, use of different types and/or shapes of magnets within a single pickup are contemplated. 
         [0022]    Examples of specific magnet sizes and shapes that may be used in embodiments of the invention include, but are not limited to, a ceramic 5, ceramic 8, an Alnico 2, or an Alnico 5 magnet that is rectangular with a length of about 2 inches, a width of about 0.5 inch and a depth of about 0.12 inch. While a particular polarity is shown for permanent magnets  108  in  FIG. 4 , the polarity may be reversed without affecting the operation of the pickup. 
         [0023]    Coil  110  is constructed by winding at least two wires in a bifilar manner. In the embodiment of  FIG. 2 , coil  110  is constructed by first winding two wires around bobbin  116 , which is then placed around pole pieces, which concentrate the magnetic field from permanent magnets  108 , which are under the bobbin. In some embodiments the bobbin has a web containing bores adapted for containing the pole pieces. The skilled artisan may directly wind wire around the pole pieces or magnet  108  in some embodiments. Bobbin  116  may be made of any non-conductive material. In some embodiments, bobbin  116  is made from plastic such as nylon. In other embodiments, bobbin  116  is made from wood. In many embodiments, it is preferable to make bobbin  116  from material that is an electrical insulator. 
         [0024]    As is well understood by the skilled artisan, the shape of the coil form may vary depending on the type of pickup sound being sought. In many embodiments, the coil form will be a generally rectangle shape with soft corners, such as the coil form in  FIG. 3 . 
         [0025]      FIG. 3  demonstrates the detail of the winding of coil  110 . In embodiments of the invention, a bifilar coil is created by simultaneously winding two insulated wires  120  and  122  side by side in a parallel direction with coaxial turns. Wire  120  and wire  122  are electrically connected to each other on the ends of the wires but may be isolated from each other in the turns. They may be associated within tubing or bonded together. In exemplary embodiments, the wires from the two coils  110  may be shielded with tubing  113  as the wires leave the pickup for connection to the musical instrument wiring. Winding in a bifilar manner allows for a low impedance coil. 
         [0026]    The first lead assembly  124  of wires  120 / 122  can be connected to a switch, the jack of an amplification device, or a ground through a coil output or can be connected to another coil. Second lead assembly  126  of wires  120 / 122  can also be connected to a switch, the jack of an amplification device, or the ground through a coil output or can be connected to another coil. In some embodiments, when the lead assemblies of different coils are connected to each other, the remaining lead assembly of each coil will be connected to an output, where the output is a switch, a jack, or a ground. 
         [0027]    The wire gauges used for coil  110  can be of any pre-determined gauge. As is well understood by the skilled artisan, the desired tonality and output of the pickup device may be achieved by using a variety of gauges. For example, some embodiments use American Wire Gauge (AWG) 38 or AWG 40 or AWG 42 or AWG 43 or AWG 44. In an exemplary embodiment AWG 42 is used for both wire  120  and wire  122 . 
         [0028]    Generally, the wires  120  and  122  are insulated copper wire. The copper wire may be enameled. Different types of insulation are known in the art and are not limiting when used with exemplary embodiments. For example, in other embodiments wires  120  and  122  may be insulated with polysol or polyurethane. 
         [0029]    Various numbers of turns of wires  120  and  122  can be used in embodiments of the invention. As is well understood in the art, the number of turns of wire on a particular coil  110  contributes to a particular pickup sound. Therefore, the turns of wire  120  and wire  122  can be varied depending on the type of sound desired. In most embodiments, wire  120  and wire  122  will have an equal number of turns. In one embodiment, coil  110  consists of about 4000 turns of both wire  120  and wire  122 . In other embodiments, coil  110  consists of about 5000 turns. In yet another embodiment, wire  120  and wire  122  have less than about 2500 turns, between about 2500 and 3500 turns, or between about 3500 and 4000 turns. 
         [0030]    Although each coil in the dual coil pickup forms an independent low impedance circuit and can function as an independent single coil, such as is well known in the art, in certain embodiments, the two coils  110  will be connected in a manner to form a lower impedance circuit capable of high output. In certain embodiments of the dual coil bifilar pickup, only one coil  110  will be wound with two wires whereas the other coil  110  will only be wound with a single wire. In some embodiments, the two coils  110  will be connected side-by-side. In other embodiments, the two coils  110  will be stacked. Generally, a dual coil pickup is any pickup with two coils having opposing electric and magnetic polarity capable of electrically affecting each other. 
         [0031]    In the embodiment of  FIG. 2  and  FIG. 3 , both coils are wound in the same direction. The two coils in the dual coil pickup unit  106  may be connected in a variety of manners. For example, the two coils may be connected in phase parallel, in phase series, out of phase parallel and out of phase series.  FIG. 5  demonstrates example electrical configurations of the connection between the dual coil pickups. 
         [0032]    Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Exemplary embodiments may be implemented as a method, apparatus, or article of manufacture. The word “exemplary” is used herein to mean serving as an example, instance, or illustration. 
         [0033]    From the above discussion, one skilled in the art can ascertain the essential characteristics of the invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the embodiments to adapt to various uses and conditions. Thus, various modifications of the embodiments, in addition to those shown and described herein, will be apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims.