Patent Publication Number: US-7718886-B1

Title: Sensor assembly for stringed musical instruments

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation-in-part application of U.S. patent application Ser. No. 10/053,440, filed Jan. 18, 2002 now U.S. Pat. No. 6,897,369 and entitled “Sensor Assembly for Stringed Musical Instruments,” and claims the benefit of U.S. Provisional Patent Application Ser. No. 60/488,128, filed Jul. 17, 2003 and entitled “Sensor Assembly for Stringed Musical Instruments.” 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to musical instruments and, more particularly, to a sensor assembly for use with stringed musical instruments. 
   2. Description of the Related Art 
   Generally, stringed musical instruments such as electric guitars have electromagnetic sensors or pick-ups for sensing mechanical vibrations of the strings and converting such into electrical signals. The electrical signals from the electromagnetic sensors are amplified and modified and, ultimately, reconverted into acoustical energy, to produce music and the like. 
   U.S. Pat. Nos. 5,501,900 and 5,438,157, issued to Lace, disclose an acoustic electromagnetic sensor assembly and mounting assembly for a stringed musical instrument. In these patents, the sensor assembly has a mounting assembly that fits in a sound hole of the stringed musical instrument. These electromagnetic sensors have a high visual impact when mounted on a stringed musical instrument such as an acoustic guitar. Further, these electromagnetic sensors typically have a tone and output that has a single value. 
   It is desirable to provide a sensor assembly that has less of a visual impact. It is also desirable to provide a sensor assembly with more variations in tone and output. Therefore, there is a need in the art to provide a sensor assembly, which meets these desires. 
   SUMMARY OF THE INVENTION 
   It is, therefore, one object of the present invention to provide a sensor assembly for a stringed musical instrument. 
   It is another object of the present invention to provide an electromagnetic sensor for an acoustic stringed musical instrument that has a low visual impact. 
   It is a further object of the present invention to provide an electromagnetic sensor for an acoustic stringed musical instrument that provides flexibility in tone and output of the sensor. 
   To achieve the foregoing objects, the present invention is a sensor assembly for a stringed musical instrument having a plurality of movable strings. The sensor assembly includes a primary winding adapted to be disposed at one end of either one of a fingerboard and a neck of the stringed musical instrument. The sensor assembly includes at least one magnet disposed adjacent the primary winding and the movable strings to generate a magnetic field. The primary winding creates a primary current from a disruption in the magnetic field by the movable strings and the primary current creates a primary electromagnetic flux. The sensor assembly further includes at least one secondary being coupled to the primary winding. The at least one secondary winding transforms the primary electromagnetic flux into a secondary current adapted to pass out the stringed musical instrument. 
   One advantage of the present invention is that a new sensor assembly is provided for a stringed musical instrument. Another advantage of the present invention is that a sensor assembly is provided for a stringed musical instrument, which has low impact visually on the instrument or is completely invisible on the instrument. A further advantage of the present invention is that the sensor assembly provides flexibility in the tone and output of the sensor. Yet a further advantage of the present invention is that the sensor assembly is quieter via making a primary winding humbucking. Still a further advantage of the present invention is that the sensor assembly uses neodymium magnets to decrease the packaging size, making the assembly smaller, and more versatile in mounting. Another advantage of the present invention is that the sensor assembly aesthetically blends into the neck or fingerboard of the stringed musical instrument such as a guitar. Yet another advantage of the present invention is that the sensor assembly has full humbucking primary and secondary windings. Still another advantage of the present invention is that the sensor assembly has greater sensitivity with a primary winding at the top of the blade. A further advantage of the present invention is that the sensor assembly is non-visually distracting and blends in with the end of the neck or fingerboard or can be in the neck or fingerboard. 
   Another advantage of the present invention is that the sensor assembly has quiet operation and strong passive output. Yet another advantage of the present invention is that the sensor assembly combines a magnetic pickup with a polymer film/piezo bridge pickup on an acoustic guitar. Still another advantage of the present invention is that the sensor assembly is substantially completely passive and has loud passive more accurate acoustic reproduction. A further advantage of the present invention is that the sensor assembly has high feedback rejection. Yet a further advantage of the present invention is that the sensor assembly has a passive operation. Still a further advantage of the present invention is that the sensor assembly is available as an OEM factory installation or aftermarket installation. 
   Other objects, features, and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a sensor assembly, according to the present invention, illustrated in operational relationship with a stringed musical instrument. 
       FIG. 2  is a side elevational view of the sensor assembly and stringed musical instrument of  FIG. 1 . 
       FIG. 3  is a perspective view of the sensor assembly of  FIG. 1 . 
       FIG. 4  is a side elevational view of the sensor assembly of  FIG. 1 . 
       FIG. 5  is a plan view of the sensor assembly of  FIG. 1 . 
       FIG. 6  is a front view of the sensor assembly of  FIG. 1 . 
       FIG. 7  is a schematic view of a single secondary winding for the sensor assembly of  FIG. 1 . 
       FIG. 8  is a schematic view of a dual secondary winding in parallel for the sensor assembly of  FIG. 1 . 
       FIG. 9  is a schematic view of a dual secondary winding with a potentiometer for the sensor assembly of  FIG. 1 . 
       FIG. 10  is a perspective view of another embodiment, according to the present invention, of the sensor assembly of  FIG. 1  illustrated in operational relationship with a stringed musical instrument. 
       FIG. 11  is a plan view of the sensor assembly of  FIG. 10 . 
       FIG. 12  is a front view of the sensor assembly of  FIG. 10 . 
       FIG. 13  is a plan view of yet another embodiment, according to the present invention, of the sensor assembly of  FIG. 1  illustrated in operational relationship with a stringed musical instrument. 
       FIG. 14  is a partial perspective view of the sensor assembly and stringed musical instrument of  FIG. 13  illustrated with the strings removed. 
       FIG. 15  is a perspective view of the sensor assembly of  FIG. 13  illustrated with the secondary windings removed. 
       FIG. 16  is a plan view of the sensor assembly of  FIG. 13 . 
       FIG. 17  is an exploded perspective view of the sensor assembly of  FIG. 13 . 
       FIG. 18  is a perspective view of still another embodiment, according to the present invention, of the sensor assembly of  FIG. 1  illustrated in operational relationship with a portion of a stringed musical instrument with the strings removed. 
       FIG. 19  is an exploded perspective view of the sensor assembly of  FIG. 18 . 
       FIG. 20  is a schematic view of the sensor assembly of  FIG. 18 . 
       FIG. 21  is a fragmentary elevational view of the sensor assembly and stringed musical instrument of  FIG. 18 . 
       FIG. 22  is a schematic view of the sensor assembly and stringed musical instrument of  FIG. 21 . 
       FIG. 23  is a perspective view of a further embodiment, according to the present invention, of the sensor assembly of  FIG. 1  illustrated in operational relationship with a portion of a stringed musical instrument. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
   Referring to the drawings and, in particular, to  FIGS. 1 and 2 , one embodiment of a sensor assembly  10 , according to the present invention, is illustrated in operational relationship with a stringed musical instrument, such as a guitar, generally indicated at  12 . The guitar  12  is of the acoustical type having a neck portion  14  with a fingerboard  15 , a body portion  16 , and a plurality of strings extending along the neck and body portions  14  and  16 , respectively. The sensor assembly  10  is disposed beneath the strings  18  and mounted to the body portion  16  adjacent to or in the fingerboard  15  in a manner to be described. Although the sensor assembly  10  is illustrated with a guitar  12 , it should be appreciated that any suitable type of stringed musical instrument may be enhanced by the sensor assembly  10 . It should further be appreciated that the sensor assembly  10  may be used with an electric type of stringed musical instrument  12 . 
   The sensor assembly  10  may include a case (not shown) extending longitudinally and having a general “U” shape cross-section. The case has a generally planar base wall and a pair of generally planar side walls substantially parallel to each other and connected by generally arcuate shaped corner walls to the base wall to form a longitudinal channel. Preferably, the longitudinal channel has a lateral width greater than a height thereof. The case is fabricated from a single piece of ferromagnetic material such as an iron-based steel. The case may be secured by suitable means such as fasteners (not shown) to the fingerboard  15  as illustrated in  FIG. 2 . 
   Referring to  FIGS. 2 through 6 , the sensor assembly  10  includes a primary winding  26  made from a conductive material. Preferably, the primary winding  26  is made of a conductive material such as copper. The primary winding  26  is preferably a solid piece of copper made as a single layer stamping or multilaminate construction. It should be appreciated that the primary winding  26  may be made of any suitable conductive material. 
   The primary winding  26  has a configuration that acts as a one-turn receiver. In one embodiment, the primary winding  26  has a generally rectangular shape with a slot  27  extending therethrough. The primary winding  26  has a predetermined length. Preferably, the primary winding  26  extends to encompass all of the moveable strings  18 . It should be appreciated that the primary winding  26  may be configured to have other suitable shapes other than the rectangular shape. It should also be appreciated that the primary winding  26  may be a plurality of windings. 
   The sensor assembly  10  also includes at least one, preferably a plurality of magnets  28  disposed adjacent the primary winding  26  to provide a magnetic flux field to the strings  18 . The magnets  28  are secured to the interior surface of the case by suitable means such as an adhesive bonding agent. The magnets  28  are a permanent magnet strip and is made of a flexible permanent magnet material such as PLASTIFORM° which is commercially available from Arnold Engineering, Marango, Ill. The magnets  28  extend longitudinally and are generally rectangular in shape. It should be appreciated that the magnets  28  are orientated in a manner to be described. 
   The sensor assembly  10  also includes at least one, preferably a plurality of secondary windings  30  adjacent to the primary winding  26 . In one embodiment, the secondary windings  30  extend generally perpendicular to the primary winding  26 . The secondary windings  30  are coils of a conductive wire such as copper wrapped around core elements  32 , 34  to be described. It should be appreciated that the secondary windings  30  can be either single or multiple coils connected in series or parallel. 
   The secondary windings  30  are susceptible to electromagnetic flux transferred by the core elements  32  to be described from the primary winding  26 . The secondary windings.  30  transform the primary electromagnetic flux into a secondary current. More specifically, the primary winding  26  and the secondary windings  30  and the core elements  32 , 34  act together as a transformer which transforms the primary current into the secondary current. The secondary current is passed through an output port (not shown) to electronics subsequent to the sensor assembly  10 . Although the primary winding  26  is shown to be a separate circuit than that of the secondary windings  30 , the secondary windings  30  may in an alternative embodiment (not shown) be connected in series to the primary winding  26  at a common point to create an autotransformer. It should be appreciated that possible electronic components, which may be operatively connected to the output port include receivers, synthesizers, amplifiers, speakers, and the like. 
   The secondary windings  30  are shorter in length than the predetermined length of the primary winding  26 . The secondary windings  30  include a first core element  32 , which extends through one end of the secondary windings  30  and a second core element  34 , which extends through the other end of the secondary windings  30 . In one embodiment, the first and second core elements  32 , 34 , which are “U” shaped in appearance, extend into the secondary windings  30  from each end and telescopingly engage. The core elements  32 , 34  are made from laminations of a high permeable magnetic material such as steel. It should be appreciated that the sensor assembly  10  may have a single secondary winding  30  as illustrated in  FIG. 7  or multiple secondary windings  30  as illustrated in  FIGS. 3 through 6  that can be combined in different ways to create a variety of tones. It should also be appreciated that the multiple secondary windings  30  may be configured in a dual parallel arrangement as illustrated in  FIG. 8  or with a potentiometer  36  as illustrated in  FIG. 9 . It should further be appreciated that the use of multiple secondary windings  30  provides flexibility in the tone and output of the sensor assembly  10 . It should be still further appreciated that the multiple secondary windings  30  can be a variety of values and can be used with an elongated primary winding  26  to allow flexibility in the design and placement of the sensor assembly  10 . 
   The sensor assembly  10  further includes a blade  40  extending through the slot  27  in the primary winding  26 . The blade  40  acts as a core piece to conduct the magnetic field and to provide a flux connection to the strings  18 . The blade  40  is fabricated from a ferromagnetic material such as cold rolled steel. The blade  40  is a thin plate made of steel or other such material that is susceptible to a magnetic field. The blade  40  includes a base end  42  and a distal end  44 . The base end  42  is disposed adjacent the magnets  28  and may be fixedly secured to the magnets  28  via any suitable securing device, such as an adhesive epoxy. The distal end  44  is a sharp edge, which receives the movable strings  18  thereon. The distal end  44  is curvilinear allowing it to blend in with the curvature of the fingerboard  15  and apply equal flux on each of the movable strings  18  so that each of the movable strings  18  affects the magnetic field from the blade  40  equally. It should be appreciated that the curvilinear shape of the distal end  44  might vary depending on the type of stringed musical instrument  12  used. It should also be appreciated by that the distal end  44  may even be straight for such instruments as acoustic violins, banjos, ukuleles, and the like wherein the strings all are set in a single plane. 
   Referring to  FIGS. 10 through 12 , another embodiment, according to the present invention, of the sensor assembly  10  is shown. Like parts of the sensor assembly  10  have like reference numerals increased by one hundred (100). In this embodiment, the sensor assembly  110  includes a case or cover  150  extending longitudinally and having a general “U” shape cross-section. The cover  150  has a generally planar base wall  152  and a pair of generally planar side walls  154  substantially parallel to each other and connected by generally arcuate shaped corner walls  156  to the base wall to form a longitudinal channel  158 . Preferably, the longitudinal channel  158  has a lateral width greater than a height thereof. The cover  150  has a flange  160  extending outwardly at each corner wall  156  and generally perpendicular thereto. The flange  160  has an aperture  162  extending therethrough to allow a fastener (not shown) to extend through the aperture  162  and slot  127  of the primary winding  126  and secure the cover  150  to the body portion  16  of the stringed musical instrument  12 . The cover  150  is fabricated from a single piece of material such as plastic or an iron based steel and forms a cup to contain the magnets  128 , primary winding  126 , and blade  140 . 
   The sensor assembly  110  also has a case  164  for the secondary windings  130 . The case  164  is disposed about the secondary windings  130  and secured thereto by suitable means. The core piece  132  may have a projection  166  to extend through the slot  127  to secure the secondary winding  130  to the primary winding  126 . It should also be appreciated that the primary winding  126  may have a portion disposed below a plane of a remainder thereof to which the secondary windings  130  are attached. 
   Referring to  FIGS. 13 through 17 , yet another embodiment, according to the present invention, of the sensor assembly  10  is shown. Like parts of the sensor assembly  10  have like reference numerals increased by two hundred (200). In this embodiment, the sensor assembly  210  includes a primary winding  226  having a configuration that acts as a one-turn receiver. In this embodiment, the primary winding  226  has a base  226   a  extending transversely to encompass all of the moveable strings  18 . The primary winding  226  also has a first end  226   b  extending generally perpendicular to the base  226   a  and a second end  226   c  extending generally perpendicular to the base  226   a . The second end  226   c  has a generally “J” shape for a function to be described. The primary winding  226  is made from a non-ferrous, conductive material. Preferably, the primary winding  226  is made of a conductive material such as copper. It should be appreciated that the first end  226   b  and second end  226   c  do not contact each other and that the primary winding  226  is not a closed loop, but an open loop. 
   The sensor assembly  210  also includes at least one, preferably a plurality of magnets  228  disposed adjacent the primary winding  226  to provide a magnetic flux field to the strings  18 . The magnets  228  are secured between and to a pair of blades  240  to be described by suitable means such as an adhesive bonding agent. The magnets  228  are made of a permanent magnet material such as Neodymium, which is commercially available. The magnets  228  are spaced longitudinally and are generally circular in shape. It should be appreciated that the magnets  228  are orientated in a manner to be described. It should also be appreciated that the magnets  228  may be made of other types of magnetic material. 
   The sensor assembly  210  also includes at least one, preferably a plurality of secondary windings  230  adjacent to the primary winding  226 . In one embodiment, the secondary windings  230  extend generally perpendicular to the primary winding  226 . The secondary windings  230  are coils of a conductive wire such as copper wrapped around core elements  232 , 234 . 
   The secondary windings  230  are susceptible to electromagnetic flux transferred by the core elements  232  from the primary winding  226 . The secondary windings  230  transform the primary electromagnetic flux into a secondary current. More specifically, the primary winding  226  and the secondary windings  230  and the core elements  232 , 234  act together as a transformer which transforms the primary current into the secondary current. The secondary current is passed through an output port (not shown) to electronics subsequent to the sensor assembly  210 . It should be appreciated that possible electronic components, which may be operatively connected to the output port include receivers, synthesizers, amplifiers, speakers, and the like. 
   The secondary windings  230  are shorter in length than the predetermined length of the primary winding  226 . The secondary windings  230  include a first core element  232 , which extends through one end of the secondary windings  230  and a second core element  234 , which extends through the other end of the secondary windings  230 . In one embodiment, the first and second core elements  232 , 234 , which are “U” shaped in appearance, extend into the secondary windings  230  from each end and telescopingly engage. Each of the core elements  232 , 234  is made from a plurality of laminations, preferably four, of a high permeable magnetic material such as steel. It should be appreciated that the sensor assembly  210  has a pair of secondary windings  230  that act as dual humbucking secondaries. It should also be appreciated that the secondary windings  230  may be spaced farther from the primary winding  226  as illustrated in  FIG. 14 . 
   The sensor assembly  210  further includes a plurality, preferably a pair, of blades  240  disposed on the sides of the primary winding  226  such that the primary winding  226  is disposed therebetween. The blades  240  act as a core piece to conduct the magnetic field and to provide a flux connection to the strings  18 . The blades  240  are fabricated from a ferromagnetic material such as cold rolled steel. The blades  240  are a thin plate made of steel or other such material that is susceptible to a magnetic field. The blade  240  includes at least one, preferably a plurality of apertures  260  extending therethrough for a function to be described. One of the blades  240  is disposed adjacent the magnets  228  and the blade  240  may be fixedly secured to the magnets  228  via any suitable securing device, such as an adhesive epoxy. The other one of the blades  240  has an inner surface  261  that is electrically insulated from the magnets  228 . That blade  240  disposed on one side of the primary winding  226  and the other blade  240  is disposed on the other side of the primary winding  226  and the primary winding  226  and blades  240  are electrically secured together by suitable means such as soldering at a plurality of locations  262 . The blades  240  have a distal end  244  that is curvilinear allowing it to blend in with the curvature of the fingerboard  15  and apply equal flux on each of the movable strings  18  so that each of the movable strings  18  affects the magnetic field from the blades  240  equally. It should be appreciated that the curvilinear shape of the distal end  244  might vary depending on the type of stringed musical instrument  12  used. It should also be appreciated by that the distal end  244  may even be straight for such instruments as acoustic violins, banjos, ukuleles, and the like wherein the strings  18  all are set in a single plane. It should further be appreciated that one of the blades  240  is magnetic north and the other blade  240  is magnetic south. It should still further be appreciated that the sensor assembly  210  may be mounted to the end of the neck  14  by suitable means such as fasteners (not shown) extending through the apertures  260  in the blades  240  and into the neck  14 . 
   Referring to  FIGS. 18 through 20 , still another embodiment, according to the present invention, of the sensor assembly  10  is shown. Like parts of the sensor assembly  10  have like reference numerals increased by three hundred (300). In this embodiment, the sensor assembly  310  is mounted at the end of the fingerboard  15  proximate to the body portion  16 . The sensor assembly  310  can be attached to the fingerboard  15  or body portion  16  by suitable means such as adhesive tape or adjustable screw mounts (not shown). 
   The sensor assembly  310  includes a primary winding  326  having a generally “T” shape. More specifically, the primary winding  326  has a base  326   a  extending laterally to encompass all of the moveable strings  18  and having a function to be described. The base  326   a  has at least one slot  327  extending therethrough and a plurality of generally circular apertures  327   a  spaced substantially equidistantly along the base  326   a  for a function to be described. One slot  327  interconnects one set of three apertures  327   a  and another slot  327  interconnects another set of three apertures  327   a . It should be appreciated that the base  326  is operatively supported by either the fingerboard  15  or body portion  16 . 
   The primary winding  326  also has a stem portion  326   b  extending generally perpendicular from a central portion of the base  326   a . The primary winding  326  also includes at least one preferably both slots  327  extending through and along the stem portion  326   b . The slots  327  are spaced laterally. The primary winding  326  is made from a non-ferrous, conductive material. Preferably, the primary winding  326  is made of a conductive material, such as copper. It should be appreciated that a corner interconnecting the base  326   a  and the stem portion  326   b  can be arcuate. It should also be appreciated that, when the sensor assembly  310  is mounted to the guitar  12  adjacent the fingerboard  15 , the stem  326   b  extends into a sound hole  19  of the guitar  12 . It should further be appreciated that the primary winding  326  acts as a humbucking primary. 
   The sensor assembly  310  also includes at least one magnet  328 , preferably a plurality of magnets  328 , operatively supported by the primary winding  326  to provide a magnetic-flux field to the strings  18 . More specifically, the magnets  328  are generally circular in shape and disposed within the apertures  327   a  of the base  326   a  of the primary winding  326 . The magnets  328  are of various magnetic strengths and made of a permanent-magnet material such as Neodymium, which is commercially available. It should be appreciated that the magnets  328  may be made of other types of magnetic material, such as ceramic. It should also be appreciated that the magnets  328  and, thus, the apertures  327  can be any suitable size and shape. It should further be appreciated that the there is one magnet  328  for each string  18 , which is located below each string  18 . 
   The sensor assembly  310  further includes at least one secondary winding  330 , preferably a plurality of secondary windings  330 , adjacent the primary winding  326 . The secondary windings  330  are generally perpendicular to the stem portion  326   b  such that the secondary windings  330  are generally parallel with both the fingerboard  15  and strings  18 . The secondary windings  330  are coils of a conductive wire, such as copper, wrapped around core elements  332 , 334 . 
   The secondary windings  330  are susceptible to electromagnetic flux transferred by the core elements  332  from the primary winding  326 . The secondary windings  330  transform the primary electromagnetic flux into a secondary current. More specifically, the primary winding  326 , secondary windings  330 , and core elements  332 , 334  act together as a transformer, which transforms the primary current into the secondary current. The secondary current is passed through an output port (not shown) to electronics subsequent to the sensor assembly  310 . It should be appreciated that possible electronic components, which may be operatively connected to the output port, include receivers, synthesizers, amplifiers, speakers, and the like. 
   The secondary windings  330  are shorter in length than the predetermined length of the primary winding  326 . The secondary windings  330  include a first core element  332 , which extends through one end of the secondary windings  330 , and a second core element  334 , which extends through the other end of the secondary windings  330 . The first and second core elements  332 , 334 , which are “U” shaped in appearance, extend into the secondary windings  330  from each end and telescopingly engage. 
   Each of the core elements  332 , 334  is made from a plurality of, preferably four, laminations of a high permeable-magnetic material, such as steel. The sensor assembly  310  is approximately three millimeters tall and five millimeters wide, and weighs approximately eight grams in a fully shielded humbucker configuration. It should be appreciated that the sensor assembly  310  has a pair of secondary windings  330  that act as dual humbucking secondaries. It should also be appreciated that the secondary windings  330  are disposed within the sound hole  19  from the end of the stem portion  326   b  opposite the base  326   a  and radially away from a center of the sound hole  19 . It should further be appreciated that the sensor assembly  310  is humbucking in the primary winding  326  and secondary windings  330  as illustrated by the schematic of  FIG. 20 . 
   Referring to  FIGS. 21 and 22 , a transducer system, generally indicated at  370 , includes the sensor assembly  310  and a bridge pickup or sensor  371 . The bridge pickup  371  is supported on the body portion  16  of the guitar  12  on the other side of the sound hole  19  by the body portion  16  opposite the fingerboard  15  of the guitar  12 . The bridge pickup  371  is of a piezo type. The bridge pickup  371  is generally rectangular and disposed substantially perpendicular to the body portion  16 . It should be appreciated that the bridge pickup  371  is conventional and known in the art. 
   The transducer system  370  may include a polymer film  372  shielding the bridge pickup  371 . The polymer film  372  is made of Kevlar® for dramatically quieter performance. The bridge pickup  371  is operatively connected to the sensor assembly  310  by suitable means such as a wire  374 . 
   The transducer system  370  may include a volume control switch  376  and series/parallel switch  377  located below an edge defining the sound hole  19  and mounted to the body portion  16  by suitable means (not shown). The volume control switch  376  is a potentiometer that is adjustable by a player of the guitar  12  to control the master volume output of the sensor assembly  310  and bridge pickup  371 . The series/parallel switch  377  is a three-position micro switch located at a base edge of the sound hole  15  (or under a pickguard on an archtop). The switch  377  is ergonomically located just below the edge of the sound hole  15  and allows the player of the guitar  12  to combine the signal from the bridge pickup  371  either in series or parallel with the secondary windings  330  of the sensor assembly  310  as illustrated in  FIG. 22 . The volume control switch  376  and series/parallel switch  377  are electrically connected to the sensor assembly  310  and an output jack  378  on the guitar  12  by suitable means such as wires  380 . It should be appreciated that the volume control switch  376 , series/parallel switch  377 , and output jack  378  are conventional and known in the art. 
   In operation of the transducer system  370 , the bridge pickup  371  is of a voltage inducing type and introduces its signal into the secondary windings  330  in between the two humbucking windings  330  so that the signal (voltage) of the bridge pickup  371  combines with the signal (current) of the sensor assembly  310 . The bridge pickup  371  can combine its signal either in series or parallel via the series/parallel switch  377  with the secondary windings  330  of the sensor assembly  310 . 
   It should be appreciated that the sensor assembly  310  amplifies the signal from the bridge pickup  371  and combines its detail with that of the warmth of the magnetic sensor assembly  310  to produce a more accurate acoustic tone. 
   In the transducer system  370 , the signals of the bridge pickup  371  combine with the signal of the sensor assembly  310 . These signals are mixed and matched by the switch  377 , which assigns the two signals in either series, parallel, or true stereo-output modes. 
   In series mode, the signal from the bridge pickup  371  is inserted directly into the secondary windings  330  on the sensor assembly  310 , providing an increase in feedback rejection and volume boost to the mono signal. In parallel mode, the two signals from the sensor assembly  310  and bridge pickup  371  are summed to mono, with the sensor assembly  310  covering most of the bass response and the bridge pickup  371  contributing clarity and attack in the high mids and treble. In the stereo mode, the signal from each of the sensor assembly  310  and bridge pickup  371  comes out independently. 
   The bridge pickup  371  adds articulation, detail, and dynamics to the mix while the sensor assembly  310  amplifies the signals from the bridge pickup  371  to produce a louder and more passive and accurate acoustic tone or reproduction with high feedback rejection during passive operation. Switching between the series and parallel modes via the switch  377  during performance is like throwing a switch between rhythm- and lead-playing modes. 
   Referring to  FIG. 23 , a further embodiment, according to the present invention, of the sensor assembly  10  is shown. Like parts of the sensor assembly  10  have like reference numerals increased by four hundred (400). In this embodiment, the sensor assembly  410  is similar to the sensor assembly  310 . The sensor assembly  410  has a base  426   a  of the primary winding  426  disposed below or built into the fingerboard  15  proximate to the body portion  16 . The base  426   a  of the sensor assembly  410  can be attached to the fingerboard  15  or body portion  16  by suitable means such as adhesive tape or adjustable screw mounts (not shown). The operation of the sensor assembly  410  is similar to the operation of the sensor assembly  310 . It should be appreciated that the base  426   a  of the sensor assembly  410  is submerged below a surface of the fingerboard  15  and is not visible. 
   Accordingly, the transducer system  370  is completely passive and needs no pre-amp to function properly (except for one channel off-board when used in stereo mode. The transducer system  370  is extremely lightweight with non-invasive installation. The transducer system  370  has the highest feedback threshold commercially available and three-way switching between series, parallel, and stereo modes. The transducer system  370  is nearly invisible including the sensor assembly  310 , which does not block the sound hole  15  of the guitar  12 . The transducer system  370  is extremely low noise and relative quick and easy to install. The transducer system  370  is available as a package or as separate components, compatible with nearly all amplifiers, PA, and recording equipment. 
   The present invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. 
   Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.