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Claims  |
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I claim:
1. A stringed musical instrument comprising a plurality of strings, each of
which has a mass and tension different from the others, and a device for
sustaining the vibration of the strings, said device comprising:
pickup means for detecting the vibration of the strings and producing an
electric signal in response to said vibration;
amplifying means for amplifying the electric signal from said pickup means
and producing a driving signal output;
electromagnetic driver means for receiving said driving signal output and
emitting magnetic flux to excite each of said strings; and
excitation balance matching means comprising a phase control circuit in
said amplifying means for providing a total balanced excitation between
said plurality of strings by adjusting the relative quantities of magnetic
flux provided to said strings in correspondence to the mass and tension of
each of said strings.
2. A stringed instrument as set forth in claim 1 wherein said phase control
circuit has a fixed phase characteristic and causes each string to be
excited by a uniform and balanced driving force such that a least
excitable string is provided with an optimum condition of the phase
characteristic to sustain the vibration of the string and other strings
are provided with a progressively mismatched condition to weaken the
vibration of the strings suitably.
3. A stringed instrument as set forth in claim wherein a plurality of said
phase control circuits are provided, each corresponding to one of said
strings, each phase control circuit having a respective fixed phase
characteristic and causing a corresponding string to be excited by a
uniform and balanced driving force such that the least excitable string is
provided with an optimum condition of the phase characteristic of its
corresponding phase control circuit to sustain the vibration of the string
and the other strings are each provided with another predetermined
condition of the phase characteristic of the corresponding phase control
circuit to weaken the vibration of the string.
4. A stringed instrument as set forth in claim 2 or 3 wherein said phase
control circuit enables the excitation of a plurality of the strings
simultaneously by the application to each string of a uniform and balanced
driving force.
5. A stringed instrument as set forth in claim 2 or 3 wherein said least
excitable string is the highest frequency string.
6. A stringed instrument as set forth in claim 1, wherein said phase
control circuit provides a balanced excitation to each of said plurality
of strings, enabling the playing of a chord by said phase control circuit.
7. The stringed instrument as set forth in claim 6, wherein said
electromagnetic driver means comprises a coil and a plurality of pole
pieces each corresponding to one of said strings and shaped so as to emit
a magnetic flux for its corresponding string which provides a balanced
excitation to each of said plurality of strings.
8. An electromagnetic driver used in a device for sustaining the vibration
of the strings of a musical instrument having a plurality of strings, each
of which has a mass and tension different from the others, which driver
comprises means for emitting magnetic flux to excite said plurality of
strings, and means for uniformly providing a total balanced excitation
between each of said plurality of strings by controlling the quantity of
magnetic flux emission provided to each of the strings in correspondence
to the mass and tension of each of said strings, wherein said
electromagnetic driver has a coil and a plurality of pole pieces each
corresponding to one of said strings and shaped so as to emit a magnetic
flux for its corresponding string which provides said balanced excitation
between each of said plurality of strings.
9. The electromagnetic driver of claim 8, wherein the electromagnetic
driver comprises a permanent magnet, a coil and a bar type pole piece
magnetically combined with the permanent magnet, and said means for
providing a balanced excitation and controlling the quantity of magnetic
flux emission is a magnetic flux emission deflecting means formed in the
bar type pole piece for deflecting emitted magnetic flux.
10. The electromagnetic driver of claim 9, wherein said bar type pole piece
has a straight upper end.
11. The electromagnetic driver of claim 9, wherein said bar type pole piece
is a plate formed of a permanent magnet.
12. The electromagnetic driver of claim 9, wherein said bar type pole piece
is a plate formed of a magnetic substance magnetically combined with a
permanent magnet.
13. The electromagnetic driver of claim 9, wherein said magnetic flux
emission deflecting means is a sub-magnet placed at a position in which a
polarity of a magnetic flux emission surface of the sub-magnet is the same
as a magnetic flux emission surface of said bar type pole piece.
14. The electromagnetic driver of claim 13, wherein said sub-magnet is
disposed at least in the neighborhood of the highest frequency string.
15. The electromagnetic driver of claim 9, wherein said magnetic flux
emission deflecting means is a magnetic air gap formed in the bar type
pole piece.
16. The electromagnetic driver of claim 15, wherein said magnetic air-gap
is a slit.
17. The electromagnetic driver of claim 15, wherein said magnetic air-gap
is a small hole.
18. The electromagnetic driver of claim 15, wherein said magnetic air-gap
is a gap.
19. The electromagnetic driver of claim 15, wherein said magnetic air-gap
is at least one of a non-magnetic substance and a weak magnetic substance.
20. An electromagnetic driver for a device for sustaining the vibration of
a string, comprising:
three spaced-apart bar type pole pieces disposed in parallel to each other
at a right angle to the string;
a pair of magnetic flux producing substances, each positioned on a side of
the center pole piece different from the other and between two of said
pole pieces in parallel with the string, magnetically combined with the
bar type pole pieces and having the same polarization in relation to the
center bar type pole piece, and
a coil wound around each magnetic flux producing substance or the center
bar type pole piece.
21. The electromagnetic driver as set forth in claim 20, wherein said
magnetic flux producing substance is a permanent magnet.
22. The electromagnetic driver as set forth in claim 20, wherein said
magnetic flux producing substance comprises a combination of a permanent
magnet and a ferromagnetic substance.
23. The electromagnetic driver as set forth in claim 20, wherein said
magnetic flux producing substance is a weakly polarized ferromagnetic
material.
24. The electromagnetic driver as set forth in claim 20, wherein a
permanent magnet is positioned apart from the center portion of each of
said magnetic flux producing substances in contact with an outer one of
said pole pieces.
25. The electromagnetic driver as set forth in claim 20, wherein said bar
type pole piece has a slit formed under and in the neighborhood of said
magnetic flux producing substance along the length of the bar type piece.
26. An electromagnetic driver used in a device for sustaining the vibration
of the strings of a musical instrument having a plurality of strings, each
of which has a mass and tension different from the others, which driver
comprises means for emitting magnetic flux to excite said plurality of
strings, and means for uniformly providing totally balanced excitation
between said plurality of strings by providing different quantities of
magnetic flux to each of said strings in accordance with the mass and
tension thereof, wherein said means for providing a balanced excitation
comprises a coil and a plurality of pole pieces each corresponding to one
of said strings and shaped so as to emit a magnetic flux for its
corresponding string which provides said balanced excitation between each
of said plurality of strings.
27. The electromagnetic driver of claim 26, wherein said means for
providing a balanced excitation comprises a permanent magnet, a coil and a
bar type pole piece magnetically combined with the permanent magnet, and
magnetic flux emission deflecting means formed in the bar type pole piece
for deflecting emitted magnetic flux.
28. The electromagnetic driver of claim 27, wherein said bar type pole
piece has a straight upper end.
29. The electromagnetic driver of claim 27, wherein said bar type pole
piece is a plate formed of a permanent magnet.
30. The electromagnetic driver of claim 27, wherein said bar type pole
piece is a plate formed of a magnetic substance magnetically combined with
a permanent magnet.
31. The electromagnetic driver of claim 27, wherein said magnetic flux
emission deflecting means is a sub-magnet placed at a position in which a
polarity of a magnetic flux emission surface of the sub-magnet is the same
as a magnetic flux emission surface of said bar type pole piece.
32. The electromagnetic driver of claim 31, wherein said sub-magnet is
disposed at least in the neighborhood of the highest frequency string.
33. The electromagnetic driver of 27, wherein said magnetic flux emission
deflecting means is a magnetic air gap formed in the bar type pole piece.
34. The electromagnetic driver of claim 33, wherein said magnetic air-gap
is a slit.
35. The electromagnetic driver of claim 33, wherein said magnetic air-gap
is a small hole.
36. The electromagnetic driver of claim 33, wherein said magnetic air-gap
is a gap.
37. The electromagnetic driver of claim 33, wherein said magnetic air-gap
is at least one of a non-magnetic substance and a weak magnetic substance.
38. An electromagnetic driver used in a device for sustaining the vibration
of the strings of a musical instrument having a plurality of strings, each
of which has a mass and tension different from the others, which driver
comprises means for emitting magnetic flux to excite said plurality of
strings, and means for controlling the quantity of magnetic flux emission
in the direction of each of the strings so that the quantity of magnetic
flux provided to each string is in correspondence to the mass and tension
thereof, wherein said electromagnetic driver has a coil and a plurality of
pole pieces each corresponding to one of said strings and shaped so as to
emit a controlled quantity of magnetic flux for its corresponding string.
39. The electromagnetic driver of claim 38, wherein the electromagnetic
driver comprises a permanent magnet, a coil and a bar type pole piece
magnetically combined with the permanent magnet, and said means for
controlling the quantity of magnetic flux emission is a magnetic flux
emission deflecting means formed in the bar type pole piece for deflecting
emitted magnetic flux.
40. The electromagnetic driver of claim 39, wherein said bar type pole
piece has a straight upper end.
41. The electromagnetic driver of claim 39, wherein said bar type pole
piece is a plate formed of a permanent magnet.
42. The device for sustaining the vibration of one or more strings as set
forth in claim 39 wherein said bar type pole piece is a plate formed of a
magnetic substance magnetically combined with a permanent magnet.
43. The electromagnetic driver of claim 39, wherein said magnetic flux
emission deflecting means is a sub-magnet placed at a position in which a
polarity of a magnetic flux emission surface of the sub-magnet is the same
as the magnetic flux emission surface of said bar type pole piece.
44. The electromagnetic driver of claim 43, wherein said sub-magnet is
disposed at least in the neighborhood of the highest frequency string.
45. The electromagnetic driver of claim 39, wherein said magnetic flux
emission deflecting means is a magnetic gap formed in the bar type pole
piece.
46. The electromagnetic driver of claim 45, wherein said magnetic air-gap
is a slit.
47. The electromagnetic driver of claim 45, wherein said magnetic air-gap
is a small hole.
48. The electromagnetic driver of claim 45, wherein said magnetic air-gap
is a gap.
49. The electromagnetic driver of claim 45, wherein said magnetic air-gap
is at least one of a non-magnetic substance and a weak magnetic substance. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stringed instrument, e.g., a guitar or a
piano, and more particularly to a stringed instrument having a device that
drives the strings thereof to sustain the vibration of the string and an
electromagnetic driver for the device.
A guitar or a piano differs from a violin in that after the string of a
guitar or a piano is excited, the magnitude of the vibration of the string
will become half within about a half second and die within about 7
seconds. Particularly, for example, in the case of an electric guitar, it
seems that the attenuation speed of the vibration of the string is shorter
than that of an acoustic guitar because of the electric characteristics of
an amplifier. Thus, an effector, which is a device for adding several
sound effects, e.g., Delay, Reverb, Compressor, Overdrive, etc., to the
sound of the guitar is often used to enable more sustained sound to be
heard acoustically.
An effector using Delay or Reverb adds reverberations to a musical sound,
and the sound is produced by recording and playing back the sound on a
magnetic tape or by delaying the tone by a spring arrangement. Recently,
simple electronic devices using BBD (Bucket Brigade Device) have been
utilized for the Delay or the Reverb. An effector using a Compressor
increases the amplitude of a music signal sent to by an amplifier in
reverse proportion to attenuation characteristics of the vibration of the
strings, and an Overdrive amplifies the signal beyond a generally
permissible level so as to obtain a long tone. A longer tone can be
achieved by using these effectors, although the effectors cannot maintain
the tone after the vibration of the string has stopped.
Currently, musicians investigate various sounds and develop the art of
musical performance in order to play said various sounds in response to
their individual performance. For example, a style using a loudspeaker
feedback is one that produces the sound of a guitar at high volume so as
to sustain the vibration of the string on the guitar for a long time
without attenuation by way of sympathetic vibration in cooperation with
air vibration emitted from the loudspeaker. As described above, the
feedback can maintain the vibration of the string for a long time, but in
order to sustain the sound, the player must utilize a skilled and
high-grade technique to overcome several limitations, i.e., sound volume,
location of the amplifier, length of the strings and musical interval,
etc. Further, there is a weak point in that the tone of the first string
on the treble side, which is the most significant for musical expression,
cannot be easily sustained. Therefore, a device that easily sustains the
vibration of the string for an extended period has been in demand for a
long time.
2. Description of the Prior Art
Several devices for sustaining the vibration of strings are disclosed in
relation to an electric guitar. For example, U. S. Pat. No. 4,941,388
(Hoover, et al.) and U. S. Pat. No. 4,907,483 (Rose, et al.) disclose an
arrangement of an electric guitar having such a device, the former is
referred to by the trade name of "Sustaniac" and the latter by the trade
name of "Kramer-Floyd Rose Sustainer" and both has been put into practical
use and are available on the market.
Although an electric guitar having the device that is put into practical
use as described above can excite and sustain the vibration of the strings
quite adequately, there are some problems from the point of view of a
musical instrument.
The first problem is that a stringed instrument, e.g., a guitar and a
piano, has plural strings and the thickness and tension of every string is
different, and so the driving force applied to each of them is also
different. Namely, in a conventional case an electromagnetic driver of a
stringed instrument having a device for sustaining the vibration of the
string, for example an electric guitar, emits a constant driving magnetic
energy against every string uniformly so that the first string that has
the smallest mass and thickness and relatively large tension cannot be
excited, oppositely, the fifth string and the sixth string can be excited
easily because of the large mass and thickness and relatively low tension
of the string.
Therefore, in such a self excitation system there are several defects in
that a player cannot participate in the operation of volume control
between the strings overall and various tones produced by large and small
vibrations of each string give the player an unpleasant feeling
occasionally, and although the first string is the most important for
musical expression, the first string cannot be excited easily in
comparison with the other strings since the first string is the finest out
of the strings and its mass is the lightest.
Furthermore, there is another problem that a string other than the first
string, e.g., the fifth string or the sixth string, experiences sudden
self-excitation when providing the first string with increased driving
force in order to solve the problem as described above.
It is difficult to maintain a balance between the vibration of each string
as described above, and if an optimum magnetic energy output for driving a
string is adjusted to the least excitable string, e.g., a first string,
the optimum magnetic energy output for driving the first string provides a
relatively excitable string, e.g., a fifth string or a sixth string, with
excessive driving energy, and thereby, there is a problem in that a fifth
string or a sixth string experiences sudden self-excitation by the
excessive driving energy described above although the fifth or sixth
string is not used for playing music. To prevent said problem, a musician
must always mute the fifth and sixth string while playing the guitar and
that is a serious problem for the musician.
Also, a method of playing a chord that simultaneously plays plural strings
in such a stringed instrument is very important for musical performance,
however, there is a defect in that only a particular string is excited by
an excitation imbalance between the strings as described above and so it
is impossible to play a chord in the prior art.
Next, the second problem is the emission efficiency of driving magnetic
energy. Namely, for example in the case of an electric guitar, it is most
preferable to mount a device for sustaining the vibration of a string on a
guitar body as a package, and it is clear that an external effector type
guitar is substantially inferior to an internal effector type guitar. Also
in the internal effector type guitar, a power supply unit for a device for
sustaining the vibration of a string must be essentially small, e.g., a
small dry cell battery, to be mounted inside a guitar body. A driving
current used to excite a string in such an excitation system is usually
about 50 mA, and so the emission efficiency of driving magnetic energy is
very important so as to prevent the necessity of frequently changing the
dry cell battery.
As for an electromagnetic driver of a device for sustaining the vibration
of a string mounted on an electric guitar, a bar type pole piece is
generally used to enable the guitar to be played using a method for
changing pitch, e.g., bending, in which a string is drawn on a fret
parallel with the fret by the finger, and thereby, tension of the string
and pitch vary. Conversely, a single type pole piece is scarcely used,
because magnetic energy emitted from each pole piece corresponding to each
string lies in the neighborhood of just above each pole piece so that a
cut tone is generated if a string is out of the magnetic energy area while
playing using the Bending method.
A bar type pole piece has a flat magnetic flux emitting characteristic and
a magnetic field is formed in the up and down direction uniformly.
However, circular magnetic fields are formed in the neighborhood of both
side ends of a bar type pole piece. Therefore, a magnetic field provided
to the strings from a second string to a fifth string is relatively stable
and uniform, but a magnetic field provided to a first string and a sixth
string is curved as described above so that magnetic field density falls
and the driving force for driving a first string and a second string is
smaller rather than that for other strings, and excitation balance between
strings is lost thereby.
Further, magnetic flux emitted from a bar type pole piece in the reverse
direction of the strings is not used to drive a string and so energy is
wasted.
SUMMARY OF THE INVENTION
The purpose of the present invention is to solve the problems described
above. To solve the first problem related to an excitation imbalance
between strings, an excitation balance matching means is provided.
Briefly, the excitation balance matching means is a phase control circuit
provided in an amplifier and/or means for properly setting up magnetic
flux emitted from an electromagnetic driver corresponding to each string.
Also, to solve the second problem related to an emission efficiency of
driving magnetic energy, a magnetic flux emission controlling means for
controlling the relative quantity of magnetic flux emission corresponding
to each string is provided.
Further, the purpose of the present invention is to develop consumption
efficiency by providing a driving proper and sufficient magnetic energy to
each string, using the excitation balance matching means. Furthermore, the
purpose of the present invention is to provide a new designed
electromagnetic driver that significantly develops the magnetic energy
emitting characteristics.
According to the present invention a stringed instrument having a device
for sustaining the vibration of a string; said stringed instrument being a
musical instrument having plural strings with the mass and tension of each
string being different, comprises pickup means for detecting the vibration
of a string, amplifying means for amplifying an electric signal detected
by said pickup means, an electromagnetic driver for emitting magnetic
energy to drive a string by a driving signal output from said amplifying
means, and excitation balance matching means for providing well-balanced
excitation to each of the plural strings and/or magnetic flux emission
controlling means for increasing the quantity of magnetic flux emission in
the direction of a string.
The excitation balance matching means is a phase control circuit provided
in said amplifying means and the phase control circuit has a fixed phase
characteristic and causes each string to be excited by a substantially
uniform and well-balanced driving force such that the least excitable
string is provided with an optimum condition of the phase characteristic
so as to sustain the vibration of the string, and other strings are
provided with a progressively mismatched condition so as to suitably
weaken the vibration of the strings.
Further, according to the present invention, an electromagnetic driver of a
device for sustaining the vibration of a string that is used in a musical
instrument having plural strings, the mass and tension of each string
being different, comprises pickup means for detecting the vibration of a
string, amplifying means for amplifying an electric signal detected by
said pickup means, an electromagnetic driver for emitting magnetic energy
so as to drive a string by an output signal from said amplifying means,
and excitation balance matching means for providing well-balanced
excitation to each of the plural strings and/or magnetic flux emission
controlling means for increasing the quantity of magnetic flux emission in
the direction of a string.
The electromagnetic driver has the arrangement of a coil and plural pole
pieces corresponding to plural strings and said excitation balance
matching means has a constitution for setting up a magnetic flux emitted
from each pole piece properly so as to emit well-suited magnetic flux
corresponding to each string respectively, and the electromagnetic driver
has an arrangement of a permanent magnet, a coil and a bar type pole piece
combined with the permanent magnet magnetically, and the excitation
balance matching means and/or the magnetic flux emission controlling means
are magnetic flux emission deflecting means formed in the bar type pole
piece for deflecting emitted magnetic flux.
Furthermore, according to the present invention a stringed instrument
having a device for sustaining the vibration of a string; the stringed
instrument being a musical instrument having plural strings, the mass and
tension of each string being different, comprises pickup means for
detecting the vibration of a string, amplifying means for amplifying an
electric signal detected by the pickup means, and an electromagnetic
driver for emitting magnetic energy to drive a string by a driving signal
output from the amplifying means, characterized in that the device for
sustaining the vibration of a string sustains the vibration of plural
strings simultaneously thereby enabling the playing of a chord.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more clearly understood from the description
as set forth below with reference to the accompanying drawings.
FIG. 1 is a general schematic arrangement of an electric guitar having a
device for sustaining the vibration of strings.
FIG. 2(a) and FIG. 2(b) are cross sectioned views of two types of
electromagnetic pickups; one is a so-called single coil type pickup in
FIG. 2(a) and the other is a so-called double coil type pickup in FIG.
2(b).
FIG. 3 is a schematic view of a magnetic field emitted from a
electromagnetic pickup.
FIG. 4 is an example of block diagrams of a device for sustaining the
vibration of a string.
FIG. 5 is an example of a phase shift circuit.
FIG. 6 is a schematic view of an example of a device for sustaining the
vibration of a string in which plural phase shift circuits are used
corresponding to each string.
FIG. 7 is a schematic view of the first embodiment of the electromagnetic
driver according to the present invention.
FIG. 8 is a schematic view of the second embodiment of the electromagnetic
driver according to the present invention.
FIG. 9 is a schematic view of the third embodiment of the electromagnetic
driver according to the present invention.
FIG. 10 is a schematic view of the fourth embodiment of the electromagnetic
driver according to the present invention.
FIG. 11 is a schematic view of the fifth embodiment of the electromagnetic
driver according to the present invention.
FIG. 12 is a schematic view of the sixth (1) embodiment of the
electromagnetic driver according to the present invention.
FIG. 13 is a schematic view of the sixth (2) embodiment of the
electromagnetic driver according to the present invention.
FIG. 14 is a schematic view of the seventh (1) embodiment of the
electromagnetic driver according to the present invention.
FIG. 15 is a schematic view of the seventh (2) embodiment of the
electromagnetic driver according to the present invention.
FIG. 16 is a schematic view of the eighth embodiment of the electromagnetic
driver according to the present invention.
FIG. 17 is a schematic view of the ninth (1) embodiment of the
electromagnetic driver according to the present invention.
FIG. 18(a) and FIG. 18(b) are schematic views of the ninth (2) embodiment
of the electromagnetic driver according to the present invention.
FIG. 19 is a schematic view of the tenth (1) embodiment of the
electromagnetic driver according to the present invention.
FIG. 20 is a schematic view of the tenth (2) embodiment of the
electromagnetic driver according to the present invention.
FIG. 21 is a schematic view of the eleventh (1) embodiment of the
electromagnetic driver according to the present invention.
FIG. 22(a) and FIG. 22(b) are schematic views of the eleventh (2)
embodiment of the electromagnetic driver according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before describing the preferred embodiments according to the present
invention, examples of the related art are provided with reference to
accompanying drawings (FIG. 1, FIG. 2(a), (b) and FIG. 3).
FIG. 1 shows an electric guitar that has a so-called "sustainer" 20 for
sustaining the vibration of a string 6. In FIG. 1, an electric guitar 1
has a body 2 and a neck 3 combined with the body 2. Frets 9 are placed
side by side on the surface of the neck 3 and a head 4 is shaped at an
elongated end portion of the neck 3. A plurality of pegs 5 (string
winders) are attached to the head 4 and each peg 5 has a structure for
winding up one end of the string 6 made of a metal conductive wire. The
other end of the string 6 is fixed at a tailpiece attached to the surface
of the body 2 or a Tremolo device 7 for producing a Tremolo effect
characteristic of an electric guitar by a bar that provides pitch change
capability by varying string tension. 8 is an electromagnetic pickup.
There are typically two types of pickups 8 as shown in FIG. 2(a) and FIG.
2(b).
FIG. 2(a) is a so-called single coil type pickup that comprises pole pieces
10 made of a magnetic substance, i.e., a permanent magnet, a coil 11 wound
around the pole pieces 10 and a cover 12. FIG. 2(b) is a so-called double
coil type pickup or a hum-bucking pickup that comprises two pole pieces 13
facing each other and made of magnetic substances, i.e., a ferromagnetic
material (FIG. 2(b) shows an example of a so-called bar type pole-piece.),
coils 14 wound up around each pole piece 13 and a permanent magnet 15
combined magnetically with each pole piece 13. An induced electromotive
force generated at both ends of the coil 11, 14 of the electromagnetic
pickup 8 is produced by a variation of magnetic flux penetrating through
the inside of the circumference of the coil 11, 14. The vibration of the
conductive metal string 6 in the magnetic field causes a change in
magnetic reluctance in the neighborhood of the electromagnetic pickup 8
and thereby the magnetic flux density inside of the circumference of the
coil 11, 14 varies in response to the vibration and an electric signal is
produced by the induced electromotive force.
In such a case of an electric guitar, the sustainer 20 consists
fundamentally of the following elements. There are three elements, those
are, an electromagnetic pickup 8 for detecting the vibration of the string
6, an amplifier 18 for amplifying an electric signal detected by the
electromagnetic pickup 8, and an electromagnetic driver 17 for emitting a
driving magnetic energy converted from the electric signal. The sustainer
20 as described above operates in the following manner.
A signal detected at the electromagnetic pickup 8 is applied to an external
guitar amplifier 21 and the guitar amplifier 21 outputs a loud sound. The
signal of the vibration of the string 6 detected at the electromagnetic
pickup 8 is also applied to the amplifier 18 within the guitar body 2 and
the amplified signal is applied to the electromagnetic driver 17. The
electromagnetic driver 17 basically uses the inverse of the principle of
the electromagnetic pickup 8. The electric signal detected at the
electromagnetic pickup 8 is amplified by the amplifier 18 and provided to
an electromagnetic transducer, i.e., the electromagnetic drive 17. The
electromagnetic driver 17 has the same structure as the electromagnetic
pickup 8 shown in FIG. 2(a) or FIG. 2(b) and causes the string 6 to be
excited by the emitted magnetic flux. However, the coil portion of the
electromagnetic driver 17 is not the same as the electromagnetic pickup 8
because the electromagnetic driver 17 needs a lot of power to obtain
significant flux and thereby to drive the string 6. Accordingly the coil
of the electromagnetic driver 17 uses a copper wire with a diameter of 0.3
mm larger than that of the electromagnetic pickup 8 and about 200 turns of
the wire is wound, therefore the electromagnetic driver 17 has small
electric resistance about 7 ohm and low power-loss characteristics.
As for an electromagnetic driver of a device for sustaining the vibration
of a string mounted on an electric guitar, a bar type pole piece is
generally used to enable the guitar to be played using a method for
changing pitch, e.g., bending, in which a string is drawn on a fret
parallel with the fret by the finger, and thereby, tension of the string
and pitch vary. Conversely, a single type pole piece is scarcely used,
because magnetic energy emitted from each pole piece corresponding to each
string lies in the neighborhood of just above each pole piece so that a
cut tone is generated if a string is out of the magnetic energy area while
playing using the Bending method.
As shown in FIG. 3, a bar type pole piece 13 has a flat magnetic flux
emitting characteristic and a magnetic field is formed in the up and down
direction uniformly. However, a circular magnetic fields is formed in the
neighborhood of both side ends of a bar type pole piece 13. Therefore, a
magnetic field provided to strings 6 from a second string to a fifth
string is relatively stable and uniform, but a magnetic field provided to
a first string and a sixth string is curved as described above so that a
magnetic field density falls and so driving force for driving a first
string and a second string is smaller rather than that for other strings,
and an excitation balance between strings is lost thereby.
Further, magnetic flux emitted from a bar type pole piece 13 in the reverse
direction of strings 6 is not used to drive a string 6 and so it was
wasted as useless energy.
In the following, the preferred embodiments corresponding to respective
means described above according to the present invention are described
briefly with reference to accompanying drawings.
First, an embodiment of means for matching a balance of excitation of
plural strings at an optimum phase, mass and tension of each of which is
different, is explained briefly with reference to FIG. 4-6. The means has
a constitution that suitable adjusting an output phase of magnetic energy
to cause the least excitable string, for example a first string, to be
driven efficiently and shifts the output phase of magnetic energy
intentionally in relation to a fifth string that can be easily excited,
and thereby, matches the excitation balance of the plural strings overall.
FIG. 4 is a block diagram of an embodiment of a device for sustaining the
vibration of strings according to the present invention. These circuit
elements are mounted on a circuit board located inside a guitar body,
except for a string 6, an electromagnetic pick | | |
