Stringed musical instrument pickup with two electromagnetic coil assemblies having toothed cores

An electromagnetic pickup for a guitar or similar stringed musical instrument has two coil and core assemblies adapted to extend across the strings of the associated instrument at different points along the length of the strings, the coil and core assemblies being associated with a permanent magnet means creating magnetic flux circuits through the cores and the strings. Each of the cores is in the form of an elongated strip having teeth vertically extending therefrom with the teeth being equal in number to the strings of the instrument and spaced in conformity with the string spacing so that each tooth of each core can underlie a respective one of the strings. The elongated strip of one core is located adjacent to the strings and that of the other core is located remote from the strings so that somewhat different signals are induced by string vibration in the coils associated with the two different cores. Each core carries two separate coils. The coils of the two cores are connected so as to be series aiding with respect to voltages induced by string vibrations and to be series bucking with relation to voltages induced by stray magnetic fields. The coils are connected to a number of output conductors in such a way as to allow a performer to select for feed to an associated utilization system various different ones or combinations of the signals induced in the individual coils received on the two cores.

FIELD OF THE INVENTION 
This invention relates to electromechanical pickups or transducers for use 
on stringed musical instruments such as guitars for producing electrical 
output signals corresponding to the string vibrations which signals may be 
amplified, possibly conditioned and modified in various ways, and used to 
drive speakers to produce a magnified version of the sound generated by 
the strings; and deals more particularly with such pickups of the 
electromagnetic type wherein the string vibrations are detected by way of 
changes in magnetic flux passing through coils which flux changes are 
caused by the string vibrations. 
BACKGROUND OF THE INVENTION 
Electromagnetic pickups for stringed musical instruments such as mentioned 
above are well known in the prior art and have been used for many years 
with guitars and other stringed musical instruments using strings which 
are at least in part made of a ferromagnetic material so as to be capable 
of, when vibrated, generating the magnetic flux changes to which the coil 
means of the pickup is sensitive. 
The general object of this invention is to provide an electromagnetic 
pickup which is improved in comparison to prior ones and which is of a 
simple construction using few parts and produces output signals of 
desirable quality. 
A more specific object of the invention is to provide an electromagnetic 
pickup including a first coil and core section producing electrical 
signals representing a mixture of the separate vibrations of the 
individual strings in which mixture the components originating from the 
individual strings are to a significant degree distinguishable from one 
another and a second coil and core section producing electrical signals 
representing a more melded combination of the vibrations of the individual 
strings with the coil means of the two sections being wound and connected 
to one another and to output conductors in such a way that the outputs of 
the two sections are humbucking relative to one another in regard to stray 
magnetic flux fields and so as to allow a performer to vary the character 
of the reproduced sound by selecting for feed to the associated sound 
system the output signal of the first coil and core section, the output of 
the second coil and core section or an output consisting of a combination 
of the outputs of the two coil and core sections. 
Other objects and advantages of the invention will be apparent from the 
following detailed description of an electromagnetic pickup embodying the 
invention. 
SUMMARY OF THE INVENTION 
The invention resides in an electromagnetic pickup for a guitar or similar 
stringed musical instrument comprising two coil and core sections, the 
cores of which sections in cooperation with a permanent magnet means 
located between the cores form part of a magnetic flux circuit passing 
through the strings of the instrument, the reluctance of which circuit is 
varied by the vibrations of the strings to in turn produce flux changes 
inducing signal voltages in the coil means wound on the two cores, each of 
the cores of the two coil and core sections being an elongate blade of 
ferromagnetic material having a plurality of vertically extending teeth 
horizontally spaced from one another and connected to one another by a 
horizontally extending strip, the teeth being equal in number to the 
number of strings of the instrument and spaced from one another in 
conformity to the spacing of the strings so that the pickup can be located 
on an instrument with each of the teeth of each of the blades underlying a 
respective one of the strings. 
The invention also resides in the two blades of the pickup being arranged 
so that in the case of one of the blades the elongated strip is in the 
upper portion of the blade so as to immediately underlie the strings of 
the instrument, and so that in the case of the other blade the elongated 
strip is located at the bottom of the blade so that the free ends of the 
teeth of that blade are located immediately below the instrument strings. 
The invention also resides in that blade in which the elongated strip is in 
the upper portion of the blade having the upwardly facing surface of the 
elongated strip shaped so that the spacings of the strings of the 
instrument from that upwardly facing surface is non-uniform. 
The invention also resides in the coil of one of the two coil and core 
sections being connected to the coil means of the other coil and core 
sections and to two output conductors in such way that the signals 
generated in said two coil means by string vibration are in series aiding 
relationship in respect to the voltage appearing across the two output 
conductors and so that the voltages induced in said two coil means by 
stray magnetic fields are in series bucking relationship to one another in 
respect to the voltage appearing across two output conductors. 
The invention also resides in the coil means of the two coil and core 
sections being connected to further output conductors such that in 
addition to the combined output of the two coil means which appears across 
another said above-mentioned two conductors, the voltage produced by the 
coils means of the first coil and core section appears across another pair 
of conductors and the voltage produced by the coil of means the other of 
the two coil and core sections appears across yet another pair of 
conductors. 
The invention also resides in other features and advantages of the 
invention defined by the following description and claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The electromagnetic pickup of this invention is one intended for use with 
stringed musical instruments, such as guitars; and, by way of example, 
FIG. 1 illustrates a guitar 10 including an electromagnetic pickup 12 
embodying the invention. Except for the pickup 12 the guitar 10 is an 
otherwise conventional electric guitar having a solid body 14 and six 
strings S.sub.1 to S.sub.6 extending generally parallel to one another 
from a combined bridge and tail piece 16 to a nut 18 and head stock 20, so 
as to pass over the pickup 12. Each of the strings S.sub.1 to S.sub.6 is 
made at least in part of steel or other ferromagnetic material so as to be 
cooperable with the pickup 12 in producing output voltage signals related 
to the vibration of the string. An output cable 22 includes conductors for 
conducting the signal produced by the pickup 12 to an associated 
utilization system such as a sound system including amplifiers for 
amplifying the pickup signals and speakers driven by the amplified 
signals. 
The detailed construction of the pickup 12 is shown in FIGS. 2 to 9. 
Turning to these figures, the pickup 12 includes a first coil and core 
section 24, a second coil and core section 26, a permanent magnet means 
28, a plastic housing 30, and plastic potting material 32, as best seen in 
FIG. 4. 
The first coil and core section 24, as best seen in FIG. 5 includes a core, 
made of steel or other ferromagnetic material, in the form of a blade 34 
having a lower portion consisting of a horizontally extending strip 36 and 
an upper portion consisting of a plurality of teeth 38 extending upwardly 
from the strip 36. The teeth 38 are equal in number to the number of 
strings S.sub.1 to S.sub.6 of the guitar 10 and are spaced in conformity 
with the spacing of those strings so that each tooth 38 underlies a 
respective one of the strings. Each tooth 38 has an upwardly facing upper 
end surface 40, which faces are located in a common horizontal plane so 
that the vertical spacings between the faces 40 and the strings S.sub.1 to 
S.sub.6 are uniform. Wound around the upper portion of the blade 34, that 
is around the teeth 38, are two separate coils C and D, preferably of 
equal numbers of turns, with each coil C and D being carried by a separate 
plastic bobbin 42. 
The second coil and core section 26, as best seen in FIG. 6, includes a 
core, made of steel or other ferromagnetic material, in the form of a 
blade 44 having an upper portion consisting of a horizontally extending 
strip 46 and a lower portion consisting of a plurality of teeth 48 
extending downwardly from the strip 46. The teeth 48, similarly to the 
teeth 38 of the first blade 34, are equal in number to the number of 
strings S.sub.1 to S.sub.6 of the guitar 10 and are spaced in conformity 
with the spacing of those strings so that each tooth 48 underlies a 
respective one of the strings. The horizontally extending strip 46 has an 
upwardly facing upper end surface 50, which surface is of such a shape, as 
viewed in FIG. 6, as to cause the spacing between the surface 50 and the 
strings S.sub.1 to S.sub.6 to be non-uniform. It will be appreciated that 
the spacing between each string and the surface 50 influences the 
character of the signals generated in the coils A and B by the vibration 
of that string and that the shape of the surface 50 may be varied from 
that shown in FIG. 6 to provide for spacings between the strings and the 
surface 50 different from those shown in FIG. 6 to produce output signals 
from the coils A and B differing somewhat from the signals produced with 
the shape of the surface 50 shown in FIG. 6. The shape shown in FIG. 6 is, 
however, the presently preferred shape for the surface 50. 
The permanent magnet means 28 extends between and engages the bottom 
portion of the blade 34 and the bottom portion of the blade 44 and applies 
a south magnetic polarity to one of the blades and a north magnetic 
polarity to the other of the blades. The permanent magnet means 28 
therefore acts as a source of magnetism providing a flux circuit, such as 
shown by the broken line 58 of FIG. 4, for each string passing through the 
permanent magnet means, the associated tooth 38 of the first blade 34, the 
associated string and the associated tooth 48 of the second blade 44, the 
reluctance of which flux circuit is varied by the vibration of the string 
so as to induce voltages in the associated coils A, B, C and D. 
The actual construction of the permanent magnet means 28 may vary, but as 
shown in FIGS. 4, 7 and 9, it includes a permanent magnet 54 in the shape 
of a rectangular bar having side faces of opposite magnetic polarity, and 
an iron bar 56. One side face of the magnet 54 engages the lower portion 
of the second blade 44, the other side face of the magnet engages one side 
face of the iron bar 56 and the other side face of the iron bar 56 engages 
the lower portion of the first blade 34. 
The four coils A, B, C and D are connected to one another and to four 
conductors, 60, 62, 64 and 66, of the output cable 22 in the way shown in 
FIG. 9. In this figure the dots associated with the coils indicate coil 
ends of similar polarity with respect to voltages induced in the coil by 
flux changes arising from string vibration. The coil A has one end 
connected to the output conductor 60 and its other end connected to one 
end of the coil B at a common point 68. The common point 68 is also 
connected to the output conductor 62. The other end of the coil B is 
connected to an intermediate point 70 which intermediate point is also 
connected to the output conductor 64. The intermediate point 70 is also 
connected to one end of the coil D. The other end of the coil D is 
connected to a common point 72 which is also connected to one end of the 
coil C. The other end of the coil C is connected to the output conductor 
66 which is also grounded. 
From FIG. 9 it will be seen that the coils A, B, C and D are connected in 
series with one another across the output conductors 60 and 66 with the 
individual voltages appearing across the individual coils being additive 
to one another when such voltages are produced by string vibration, it 
being noted that the flux circuit established by the permanent magnet 
means 28 moves through the teeth 38 of the first blade 34 in directions 
opposite to its movement through the teeth 48 of the second blade 44. In 
contrast to this, any stray magnetic field which may pass through the 
pickup 12 will essentially pass through the teeth of the two blades in the 
same direction and therefore the voltages induced by such stray magnetic 
field in the coils A and B will be in bucking relationship to the voltages 
induced by that field in the coils B and C so as to cancel one another and 
therefore not be present in the voltage signal appearing across the output 
conductors 60 and 66. 
Also from FIG. 9 it will be observed that the combined output of the two 
coils A and B appears across the conductors 60 and 64, and the combined 
output of the coils C and D appears across the conductors 64 and 66. 
Further, the output voltage of the coil A by itself appears across the 
output conductors 60 and 62, and the output voltage of the coil B by 
itself appears across the conductor 62 and 64. Therefore, a performer, as 
by means of suitable switches (not shown) associated with the output 
conductors can select from a number of different options the particular 
output voltage used as the feed to the associated sound system or other 
utilization system.