U.S. patent number 3,715,446 [Application Number 05/155,528] was granted by the patent office on 1973-02-06 for magnetic pickup for stringed musical instruments.
Invention is credited to Frank Joseph Kosinski.
United States Patent |
3,715,446 |
Kosinski |
February 6, 1973 |
MAGNETIC PICKUP FOR STRINGED MUSICAL INSTRUMENTS
Abstract
A magnetic pickup for stringed musical instruments has a
balanced coil assembly for each string. Each assembly includes a
bar magnet supporting a pair of pole pieces, each pole piece having
a separate coil wound thereon. Each coil assembly is provided with
an adjustment device for individually balancing the output of each
string.
Inventors: |
Kosinski; Frank Joseph
(Hauppauge, NY) |
Family
ID: |
22555818 |
Appl.
No.: |
05/155,528 |
Filed: |
June 22, 1971 |
Current U.S.
Class: |
84/727;
984/369 |
Current CPC
Class: |
G10H
3/182 (20130101) |
Current International
Class: |
G10H
3/00 (20060101); G10H 3/18 (20060101); G10h
003/00 () |
Field of
Search: |
;84/1.01,1.14,1.15,1.16 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Wilkinson; Richard B.
Assistant Examiner: Weldon; U.
Claims
What is claimed is:
1. A magnetic pickup for a stringed musical instrument comprising a
plurality of coil assemblies, each of said coil assemblies
including a magnet, each of said coil assemblies further including
a plurality of pole pieces supported on said magnet, each of said
coil assemblies also including a plurality of induction coils equal
in number to the plurality of pole pieces, each of said plurality
of induction coils being separately wound around one of said pole
pieces with the coils being electrically connected in series, means
for connecting the outputs of said coil assemblies and means for
supporting said plurality of coil assemblies on a stringed musical
instrument with each string of the instrument passing over a
different one of said coil assemblies.
2. A pickup according to claim 1 further including means for
individual adjustment of each of said coil assemblies so that each
of the coil assemblies may be individually raised or lowered to
balance the output of each string.
3. A pickup according to claim 1 wherein said magnetic pickup is
adjustably mounted on said instrument.
4. A pickup according to claim 1 further comprising fiber shims
located between adjacent coil assemblies to align said coil
assemblies so as to provide a self-supporting pickup.
5. A pickup according to claim 2 wherein said adjustment means
includes spring-biasing means in order to separately tension each
of said coil assemblies.
6. A pickup according to claim 1 wherein each of said pole pieces
are formed of magnetizable material and are mounted in holes formed
in said magnets.
7. A pickup according to claim 6 wherein an insulating bobbin is
mounted on each pole piece, with each bobbin supporting one of said
separately wound coils thereon.
8. A pickup according to claim 1 wherein said plurality of pole
pieces includes a first and second pole piece mounted on opposite
ends of said magnet.
Description
This invention relates to an electromagnetic pickup arrangement for
stringed musical instruments, such as electrical guitars, and more
particularly relates to a novel arrangement wherein a balanced coil
assembly is provided for each string in order to more faithfully
reproduce the fine nuances of the vibrating strings.
In electrical stringed instruments, sound is reproduced by
vibrating metallic strings which pass in close proximity to
cylindrical soft iron cores, hereinafter referred to as pole
pieces. Vibration of these strings varies the magnetic field
established by the pole pieces, inducing an electrical current in
coils which surround the pole pieces. This current is then
amplified and reproduced acoustically by the use of a loudspeaker
in a well known manner.
In the past, it has been a general practice for magnetic pickups to
employ one coil structure wound around a plurality of pole pieces,
each of the pole pieces being in proximity to a different string.
In another arrangement, a separate coil is wound around each pole
piece, there being only one pole piece for each string. U.S. Pat.
No. 2,896,491 is an example of a magnetic pickup which utilizes the
former concept. In this arrangement, a large coil is wound around
all the pole pieces on one side of a magnet with a duplicate coil
structure wound around all the pole pieces on the other side of the
magnet. In this manner, each of the strings passes over two pole
pieces. However, there are several shortcomings with this type of
arrangement. First, because of the large coil structure surrounding
the six pole pieces, the capacitance of the winding is very high.
For example, if the six pole pieces are spaced over a two and a
half inch distance, then the coil wound around the six pole pieces
would be approximately five inches long. Since capacitance
increases directly with the length of the winding and since there
are several thousand of such windings for each coil structure, the
capacitance becomes very high and causes a serious reduction in its
capability of reproducing all of the higher order harmonics and
thereby reduces the quality of the sound reproduced by the
instrument. Second, because one coil structure is wound around a
plurality of pole pieces, rather than around each individual pole
piece, the magnetic lines of force produced by the pole pieces will
only cut two sides of the coil structure rather than all four
sides. This results in a decreased induced current and therefor
adversely affects the sound reproduced by the instrument. This loss
is compounded by the fact that the magnetic field is reduced by the
square of the distance between a pole piece and the coil structure.
For example, if the distance from a pole piece to the coil
structure is normally one thirty-second of an inch and because of
the winding configuration, the distance is increased to
one-sixteenth of an inch, or doubled, the magnetic field is reduced
to one-fourth of its original intensity. As a result, the
sensitivity of the magnetic pickup is reduced and, more important,
the low and high level harmonic content of the strings will be lost
entirely. Third, in this prior art structural arrangement, there is
no provision for individually balancing the output current from
each of the strings. More specifically, there is no provision for
individually raising and lowering each pair of pole pieces in order
to balance the output from each string. This type of adjustment is
desirable when a musician is vibrating some of the strings at a
higher amplitude than the others in order to produce varying nodes.
If no adjustment is provided for varying the distance between each
string and pole piece, this will make some strings sound louder or
softer than others when amplified and will result in poor balance
of sound.
As mentioned above, another prior art construction provides only
one coil wound around each pole piece, there being only one pole
piece and coil for each string of the instrument. In this
arrangement, there is also no provision for balancing the output
current of each of the strings individually as each of the pole
pieces is not separately adjustable with respect to each string.
This results in the same problem as above of a poor balance of
sound. Moreover, another disadvantage which arises when there is
only one pole piece provided for each string is that it allows only
fundamental nodes to be reproduced with no capability of
reproducing varying nodes.
The magnetic pickups of the prior art are not capable of
reproducing a high quality of sound including both lower and higher
level harmonics as well as the varying nodes of the vibrating
strings which must be reproduced for a full fidelity of
reproduction.
It is the general object of this invention to provide a magnetic
pickup having an improved mechanical and electrical design in order
to provide a much superior reproduced sound. Another object of this
invention is to provide a magnetic pickup that will produce both
low and high order harmonics and, further, will produce varying
nodes of the vibrating strings as well as the fundamental node.
Briefly, in accordance with the principles of my invention, a
magnetic pickup is constructed having a separately adjustable coil
assembly for each string of the musical instrument in order to
balance the output current of the individual strings. Each coil
assembly includes two pole pieces and individually wound coils
around each pole piece. This arrangement provides several
advantages over the prior art devices. First, having a coil
structure separately wound around each pole piece substantially
reduces the capacitance to a fraction of what it would be when one
large coil structure is wound around a plurality of pole pieces.
This results in low attenuation of all high order frequencies and
thereby results in the most faithful reproduction of all tones and
harmonics heretofore obtained. Second, because a separate coil
structure is wound around each pole piece, current is induced
around all four sides of each of the pole pieces resulting only in
negligible losses. This results in maximum sensitivity during
induction with a high capability of reproducing both low and high
level harmonics. Third, by providing each coil assembly with its
own adjustment device, this allows the distance between each pair
of pole pieces and its respective string to be varied and thereby
balance the output current of the individual string. This avoids
the problem of some strings sounding louder or softer than others
when vibrated at different amplitudes in order to produce varying
nodes.
Further objects, features and advantages of my invention will
become apparent upon a consideration of the following detailed
description of a presently preferred embodiment when taken in
conjunction with the accompanying drawing, wherein:
FIG. 1 is a plan view of a stringed musical instrument having the
magnetic pickup of the present invention mounted thereon;
FIG. 2 is an enlarged fragmentary plan view of the magnetic pickup
shown in FIG. 1 with parts broken away in horizontal
cross-section;
FIG. 3 is an enlarged vertical cross-sectional view of the pickup
taken along line 3--3 in FIG. 2 illustrating a representative coil
assembly;
FIG. 4 is an enlarged vertical cross-sectional view of the pickup
illustrating a coil assembly in a tensioned position; and
FIG. 5 is a schematic view taken along line 5--5 in FIG. 3
illustrating the electrical circuit of the magnetic pickup of the
present invention.
Referring now to the specific drawings, there is shown in FIG. 1 a
stringed musical instrument embodying the features of the present
invention and generally designated by the reference numeral 10.
Instrument 10 is an electric guitar which comprises a solid
non-vibrating body portion 12 and a neck portion 14 provided with a
finger board. The instrument 10 has a plurality of strings 16 that
are of magnetic material, such as steel. (Although the number of
strings may vary, in the preferred embodiment, there are six). The
strings are secured to the body portion 12 by a tail piece 18 and
extend over a portion of the body 12 and along the neck portion 14
to a plurality of tuning keys 20 which adjust the tension in the
strings to obtain the desired pitch. The strings 16 are held in
overlying relation to and are spaced from the body portion 12 by
bridge means 22 mounted on the tail piece 18. The metallic strings
16 are also stretched over a magnetic pickup device generally
indicated at 24.
As is more clearly illustrated in FIG. 5, the preferred embodiment
of the magnetic pickup device 24 comprises six coil assemblies 26,
one assembly 26 being provided for each of the six strings of the
musical instrument. Fiber shims 28 are placed between adjacent
assemblies 26 in order to provide a self-supporting unit when it is
placed in the instrument 10. Each coil assembly 26 includes two
coils which are connected in series adding, as shown by
representative lead 34, and, in addition, all of the coil
assemblies are connected in series. The leads from the outermost
coil assemblies are the output leads and are connected to a jack 36
(FIG. 1) by means of which the pickup 24 can be electrically
connected to an amplifier and loudspeaker in a well-known
manner.
In FIG. 2, there is shown an enlarged plan view of the magnetic
pickup 24 and the manner in which it is mounted on the body 12 of
the instrument 10. The coil assemblies 26 are supported in a case
38 formed of non-magnetic material and having a bottom cover 40
(see FIG. 3). A mounting plate 42 is secured to the body portion 12
of the instrument 10 by screws 44 and case 38 is in turn attached
to mounting plate 42 by means of mounting and adjust screws 46.
Screws 46 are provided so that the entire magnetic pickup 24 may be
adjusted as a unit with respect to the strings 16.
As shown in FIGS. 3 and 4, each of the coil assemblies 26 includes
a single bar magnet 48, a pair of coils 30, 32, a pair of pole
pieces 50, 52 and an adjusting screw 54. The bar magnet 48 is
formed of permanent magnetic material and pairs of holes 56 and 58
are formed in each of the bar magnets so that they may receive pole
pieces 50, 52. Pole pieces 50, 52 are formed of cylindrical soft
iron cores which may be pressed into their respective holes 56 and
58, or otherwise mounted on bar magnets 48, there being a pair of
pole pieces for each of the strings 16 of the instrument 10. Each
of the pole pieces 50, 52 project through respective insulating
bobbins 60, 62, bobbin 60 having a coil 30 wound therearound and
bobbin 62 having a coil 32 wound therearound, each coil being wound
in a plane parallel to the magnet 48 and the surface of the
instrument 10. In addition, each of the bar magnets 48 is provided
with a tapped hole 64 centrally located between each of the pairs
of holes 56, 58. Adjusting screws 54 are threaded into holes 64
with each of the screws 54 having a heavy spring 66 therearound in
order to tension the coil assemblies 26. Adjustment of one of the
screws 54 will permit its corresponding coil assembly 26 to be
raised or lowered in the case 38 in order to balance the output of
the individual strings. As shown in FIG. 4, as screw 54 is threaded
into bar magnet 48, the entire assembly 26, including magnet 48,
pole pieces 50, 52 and coils 30, 32, is brought closer to string
16.
The permanent magnet system created by the permanent magnets 48 and
pole pieces 50 and 52 establish north and south poles at the
exposed ends of each pair of the pole pieces in proximity to the
superimposed metal string 16 of the instrument, and opposite poles
are accordingly induced in the metal string. Vibration of the
string causes it to move over the ends of the pole pieces creating
a variation in the magnetic field through the coils 30, 32 in a
well-known fashion. In the preferred embodiment, each pole piece 50
has a north pole at its upper end and a variation in the strength
of the magnetic field (by plucking of the respective strings) will
tend to create a current in the coil 30 in the direction indicated
by the arrow 68 and a concurrent vibration of a string 16 over the
pole piece 52 will tend to induce a current in the coil 32 in the
same direction, as indicated by the arrow 70. The currents in the
two coils are thus added together and this resultant current is
added to the currents produced in the other coil assemblies 26 to
provide a strong signal in response to vibration of the strings 16.
A maximum number of turns are provided for each of the coils 30, 32
in order to achieve an output equivalent to that which is derived
from a rhythm and blues guitar.
From the foregoing, it will be appreciated that there is provided
in accordance with the present invention, a magnetic pickup for a
stringed musical instrument having an individually adjustable coil
assembly for each string which allows a balanced output current to
be produced for each string. Further, because a coil structure is
separately wound around each pole piece, the capacitance produced
remains low and allows all high order harmonics to be produced.
Also, as a result of providing separately wound coils, the magnetic
lines of force from each of the pole pieces cut through all sides
of the coil structure, resulting in an increased induced current,
thereby increasing the sensitivity of the pickup and, more
important, increasing the capability of reproducing both the low
and high level harmonic content of the strings. Moreover, due to
the fact that there are two pole pieces provided for each string of
the musical instrument, the magnetic pickup is capable of
reproducing varying nodes as well as the fundamental node as the
distance between each pair of pole pieces can encompass the varying
nodes.
A latitude of modification, change and substitution is intended in
the foregoing disclosure and, in some instances, some features of
the invention will be employed without a corresponding use of other
features. Accordingly, it is appropriate that the appended claims
be construed broadly and in a manner consistent with the spirit and
scope of the invention herein.
* * * * *