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BACKGROUND OF THE INVENTION
The present invention is directed in general to the tuning of musical
instruments and more particularly to a new and improved device which
facilitates the tuning of musical instruments to a predetermined standard
frequency.
As well known, each instrument of a band, orchestra, or the like must be
tuned to a common or related frequency note at frequent intervals to
assure that the tunes played by such groups are pleasing to the ear and
not in discord. It is not unusual, for example, for such groups to tune
their instruments prior to each rehearsal or performance.
At one time the human ear provided the only means by which a note of an
instrument could be compared to the pitch of a frequency standard, such as
another instrument or audio oscillator. However, in practice, this method
was found to be very inaccuracte and unsatisfactory.
Since then, various forms of electronic tuning aids have been proposed. One
such aid converts the audible note of the instrument to pulsations of
light which are then used to illuminate a rotating strobe disc. Deviation
in pitch or frequency of the note from a predetermined standard frequency
results in apparent movement of a pattern of light and dark regions on the
disc.
Another form of tuning aid includes a frequency counter which displays the
frequency of the instrument note. The displayed frequency must be compared
to the standard frequency and the instrument adjusted accordingly.
While these tuning aids and others have improved upon the previous devices
and methods for tuning musical instruments, there remains substantial room
for improvement. For example, prior tuning aids have been very expensive
and generally are not affordable by small music groups or individual
musicians. Also, prior tuning aids have been relatively inflexible in that
they only provide the universal standard frequency of A-4, 440 or a
limited number of standard frequencies and have not enabled tuning to an
external frequency standard. Furthermore, they have been relatively
complicated to use and the indicators which they employ are not always
easily readable by untrained users. Lastly, prior tuning devices have not
provided a means by which an electric guitar or the like which utilizes an
external amplifier may be tuned silently to avoid interruptions of, for
example, a performance or rehearsal.
It is therefore a general object of the present invention to provide a new
and improved device which facilitates the tuning of musical instruments
with speed and accuracy.
It is a further object of the present invention to provide such a device
which is substantially less complicated and thus less expensive than prior
devices of its kind.
It is a still further object of the present invention to provide such a
device which is substantially more flexible to use and which provides
plurality of standard frequencies in the form of a plurality of selectable
tempered chromatic scale octaves based upon a fixed frequency of A-40, 440
or a variable frequency equal to an external standard frequency, and
wherein any one of the individual pitches of the scales may be selected as
a standard frequency.
The invention therefore provides a new and improved tuning device for
assisting in the tuning of a musical instrument to a predetermined
frequency standard. The device includes oscillator means for providing a
signal having a frequency which is harmonically related by a preselected
even numbered factor to the predetermined frequency, amplifier means
adapted to be coupled to the musical instrument and arranged for
converting the waveform of the musical instrument output signal to a
square-wave signal, and indicating means coupled to the oscillator means
and to the amplifier means. The indicating means includes a plurality of
light emitting devices, the number of the devices being equal to the
preselected factor, and wherein the indicating means is arranged for
causing one half of the devices to appear to continuously and
simultaneously emit light when the frequency of the musical instrument
output signal is equal to the predetermined frequency and for causing
different groups of one half of the devices to appear to sequencially and
simultaneously emit light when the frequency of the musical instrument
output signal is less than or greater than the predetermined frequency to
thereby provide a visual indication when the musical instrument is in
tune.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention which are believed to be novel are
set forth with particularity in the appended claims. The invention,
together with further objects and advantages thereof, may best be
understood by making reference to the following description taken in
conjunction with the accompanying drawings, in the several figures of
which like reference numerals indicate indentical elements, and wherein:
FIG. 1 is a schematic circuit diagram of a musical instrument tuning device
embodying the present invention; and
FIG. 2 illustrates graphical representations of waveforms generated within
the device of FIG. 1 and which may be utilized hereinafter for gaining a
better understanding of the operation of the embodiment of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, the musical instrument tuning device 10 there
illustrated generally includes a multiple position switch means comprising
a four pole, three position switch 12, a saturated audio amplifier 14, a
power source 16, an oscillator 18, a frequency or octave divider section
20, an indicating means 22, and a signal deriving means 24.
The switch 12 as previously mentioned is a four pole three position switch
having poles 26, 28, 30, and 32. Each of the poles 26, 28, 30, and 32 are
associated with three contact terminals wherein the individual contact
terminals are indicated by the reference character of their corresponding
pole followed by an appropriate a, b, or c suffix. Additionally, each of
the poles 26, 28, 30 and 32 are associated with respective wiper contacts
26d, 28d, 30d, and 32d respectively.
Pole 26 is coupled to an output terminal 34 which is adapted to be coupled
to an external amplifier (not shown) of the type which is customarily used
in conjunction with an electric guitar or the like for amplifying the
notes produced by the electric guitar to render the produced notes
audible. Pole 28 is coupled to an input terminal 36 which is adapted to be
directly coupled to a musical instrument of the type which utilizes an
external amplifier, such as an electric guitar, or coupled by a microphone
(not shown) to a musical instrument such as a piano which does not utilize
an external amplifier. Pole 30 is coupled to the output of the saturated
audio amplifier 14, and pole 32 is coupled to one side of an AC receptacle
plug 38 which is adapted to be connected to a house current AC receptacle.
The other side of the plug 38 is coupled to the power supply 40 which
forms a part of the power source 16.
With respect to the contacts associated with pole 26, pole 26a is floating,
pole 26b is coupled to ground, and pole 26c is coupled to the output of a
filter 42 which forms a part of the signal deriving means 24. With respect
to the contacts associated with pole 28, contact 28a is coupled to pole
26, contact 28b is coupled to the input of the saturated audio amplifier
14, and pole 28c is coupled to ground. With respect to the contacts
associated with pole 30, contacts 30a and 30c are floating, and contact
30b is coupled to the cathodes of a plurality of light emitting diodes 43
through 52 which form the indicating means 22. With respect to the
contacts associated with pole 32, contact 32a is floating, and contacts
32b and 32c are coupled to the power supply 40. The power supply 40 has an
output terminal 54 which of course is coupled to the various active
elements of the musical instrument tuning device in accordance with
customary practice.
The oscillator 18 includes an RC oscillator circuit 56. The circuit 56 is
of the type which oscillates at a frequency determined by the values of
impedance and capacitance elements coupled thereto. To that end, the
circuit 56 is coupled to a capacitor 58 and to a pair of switches
including a single pole, twelve positioned switch 60 and a double pole;
two position switch 62. The switch 60 includes a plurality of contacts
which are coupled to the power supply terminal 54 by respective impedance
elements or resistors 63 through 74. The other switch 62 has a first pair
of contacts which are coupled to ground by a fixed capacitor 75 or a
variable capacitor 76 depending upon the position of switch 62. Switch 62
has another pair of contacts, one of which is floating corresponding to
the first position of switch 62, and the other one of which is coupled to
ground by a resistor 78 and light emitting diode 80.
The oscillator 18 by virtue of the values of resistors 63 through 74 and
capacitors 58, 75, and 76, cause the oscillator 18 to provide an output
signal having a frequency which is 10 times the frequency of a given
predetermined standard frequency to which an instrument is to be tuned.
More specifically, each of the resistors 63 through 74 corresponds to a
respective note of an equal tempered chromatic scale. When switch 62 is in
its first position as shown, the fixed capacitance element 75 causes the
chromatic scale obtainable upon rotation of switch 60 to be based upon a
fixed frequency corresponding to the A-4, 440 universal standard. When
switch 62 is in its second position, the variable capacitance element 76
will cause the chromatic scale produced by the oscillator as switch 60 is
rotated to be based upon an adjustable frequency. Preferably, the
mid-capacitance value of variable capacitance element 76 is equal to the
capacitance value of capacitor 75 so that the adjustable range of
frequencies is centered on the frequency standard A-4, 440, and adjustable
above and below that frequency. The purpose of the variable capacitance
element 76, as will be more fully described hereinafter, is to enable the
musical instrument tuning device of FIG. 1 to tune an instrument to an
external standard frequency other than the fixed A-4, 440 frequency. When
switch 62 is in its second position, the resistor 78 and light emitting
diode 80 will be connected upon the positive power supply terminal 54 and
ground so that the light emitting diode 80 will be lit to warn the user
that the frequency standard upon which the tuning of the instrument is
based is an adjusted frequency corresponding to an external frequency
standard.
The octave divider section 20 comprises a plurality of frequency dividers
82 through 88. The dividers 82 through 88 are serially connected together.
Switch 90 is a single pole, eight positioned switch which enables the
selection of respective serial groups of the frequency dividers to provide
oscillator frequencies corresponding to eight different octaves. As a
result, by virtue of the octave dividers 82 through 88, the oscillator 18
is enabled to provide an equal tempered chromatic scale for eight
different octaves upon selective positioning of switch 90, and any one of
the notes within the chromatic scales responsive to the selective
positioning of switch 60.
As previously mentioned, the oscillator 18 provides its output frequencies
which are ten times greater in frequency than the selectable standard
frequencies to which the musical instrument may be tuned. Of course, as
will be made clear subsequently, the output frequencies of oscillator 18
may be harmonically related to the corresponding standard frequencies by
any even numbered factor.
The switch 90, and thus the oscillator 18, is coupled to the indicating
means 22 by a decade counter 92 and a four line to ten line decoder 94.
The decade counter 92 has an input 93 which is coupled to the pole of
switch 90 and four outputs 95 through 98 which are coupled to respective
ones of the inputs of decoder 94. The decoder 94 in turn has ten outputs
with respective given ones of the outputs of decoder 94 being coupled to a
respective one of the anodes of light emitting diodes 43 through 52
respectively.
By virtue of this arrangement, each of the light emitting diodes 43 through
52 will have impressed upon their respective anodes a waveform signal as
illustrated by the waveform 120 of FIG. 2. Each of the anodes will receive
such a signal waveform, with the only difference between the waveform
received by the various diodes being that each successive diode will
receive a waveform which is delayed by one pulse of oscillator 18.
Because the oscillator oscillates at a frequency which is ten times greater
in frequency than the given predetermined standard frequency to which the
musical instrument is to be tuned, a signal deriving means 24 is provided
for deriving from the oscillator signal impressed upon the diodes 43
through 52 an output signal which is equal in frequency to the desired
standard frequency to which the musical instrument is to be tuned. To that
end, the signal deriving means 24 includes a flip-flop 99, a pair of
diodes 100 and 102, and the filter 42 which comprises resistors 104 and
106, and capacitor 108 and 110. The input to flip-flop 99 is coupled to
the first output of decoder 94 by diode 100 and to the sixth decoder
output by diode 102. The output of flip-flop 99 is coupled to the contact
26c of switch 12 by the filter 42. As a result of this arrangement of
flip-flop 99 and diodes 100 and 102, the output of flip-flop 99 will be a
square wave having a frequency equal to the predetermined standard which
the instrument is to be tuned. More specifically, because the diodes 100
and 102 are coupled to the first and sixth outputs of decoder 94, the
frequency of the oscillator 18 will be divided by a factor of 10. Since
the oscillator was caused to oscillate at a frequency ten times greater in
frequency than the desired standard frequency, the output of flip-flop 99
will be equal in frequency to the desired standard frequency. The filter
42 serves to round off the square wave produced by the flip-flop 99 to
provide a pleasing tone.
In operation, when the switch 92 is in its first position as shown, the
wiper 26d will be in engagement with contact 28a, and wiper 30d will be in
engagement with contact 30a. In this switch position, the tuning device
will be off. The musical instrument coupled to the input terminal 36 will
be connected to the output terminal 34. Hence, if the instrument coupled
to the tuning device is an electric guitar which normally utilizes an
external amplifier, it will be directly coupled to its external amplifier
through the switch 12. Of course, should the instrument be a piano or some
other instrument of the type which does not utilize an external amplifier,
since this type of instrument would be coupled to terminal 36 by a
microphone or the like, a direct connection to an external amplifier would
be unnecessary. Also in this switch position, it can be noted that the
wiper 32d is in engagement with contact 32a thus disconnecting the power
supply 40 from the AC receptacle plug 38. Hence, no power will be applied
to the tuning device.
When the switch 12 is advanced to its second position, wiper 26d will be in
engagement with contact 26b, wiper 28d will be in engagement with contact
28b, wiper 30d will be in engagement with contact 30b, and wiper 32d will
be in engagement with contact 32b. In this switch position, the terminal
34 coupled to the input to the external amplifier of the musical
instrument is grounded to prevent any signal from reaching the external
amplifier. As a result, tuning of the instrument is permitted during a
performance or a rehearsal without interference. The terminal 36 which is
coupled to the musical instrument is connected to the input of the
saturated audio amplifier 14 and the wiper 30d provides connection between
the output of the saturated audio amplifier 14 and the cathodes of the
light emitting diodes 43 through 52. Lastly, because wiper 32d is in
engagement with contact 32b, the AC receptacle plug 38 will thereby be
connected to the power supply 40 so that the power source 16 provides
activating power to the various active components of the tuning device at
its terminal 54.
As a result, when switch 12 is in this second position, the tuning device
is activated and ready to facilitate the tuning of a musical instrument.
In tuning the musical instrument, the user first selects the given
predetermined frequency to which the musical instrument is to be tuned.
For example, should the user desire to tune the instrument to, for
example, the universal standard frequency A-4, 440, the user merely
positions switch 60 to connect the resistor 72 corresponding to that note
to the RC oscillator circuit 56. Since the standard frequency is to be
internally generated by the tuning device, switch 62 will be set to select
the fixed capacitor 75. Further, the user selects the appropriate octave
by the switch 90, in this case the 3rd octave, the output of divider 85.
As a result of the foregoing, the oscillator 18 will be caused to provide
an output frequency which is ten times greater in frequency than the A-4,
440 frequency. In other words, the oscillator 18 will provide the decade
counter 93 with an output signal having a frequency of 4,400 cycles per
second.
Once the oscillator 18 has been properly conditioned, the user then
produces the corresponding note on the instrument. The waveform of the
note produced by the instrument is converted to a square wave by the
saturated audio amplifier 14 which is then impressed upon the cathodes of
light emitting diodes 43 to 52 through the wiper 30d of switch 12. As a
result, the cathodes of the light emitting diodes will see a waveform as
depicted in FIG. 2 and identified as 122. If the instrument is in tune to
the selected A-4, 440 frequency standard, the relative positions of the
waveforms 120 and 122 as shown in FIG. 2 will ensue.
It will be noted from FIG. 2 that during the time periods between t.sub.2
and t.sub.3, five out of the ten light emitting diodes will be lit, and
during the time period between t.sub.1 and t.sub.2, or t.sub.3 and
t.sub.4, the other five light emitting diodes will be off. Hence, when the
frequency of the instrument to be tuned is exactly one tenth of the
oscillator frequency, five of the light emitting diodes will be lit during
the positive half cycle of the input signal from the instrument and five
will be off. Because the same light emitting diodes are continuously
activated at the frequency of decoder 94, a "picket fence strobe" effect
results with the picket fence being stationary. However, when the incoming
signal from the musical instrument is not exactly one tenth of the
oscillator frequency, the picket fence is caused to appear to move. In
other words, different groups of one half of the light emitting diodes
will appear to sequentially and simultaneously emit light when the
frequency of the musical instrument signal is less than or greater than
the predetermined frequency standard.
Preferably, the light emitting diodes 43 through 52 are arranged linearly
or in line. Hence, when the musical instrument is slightly out of tune,
the movement of the picket fence will be readily apparent. The speed and
direction of movement of the picket fence is in direct relationship to the
number of cycles that the musical instrument signal is off or deviates
from the predetermined standard frequency. The picket fence will appear to
move to the right from light emitting diode 43 to light emitting diode 52
the same number of times in a second that the instrument signal is high in
frequency. When the instrument signal frequency is low in frequency, the
picket fence moves to the left from diode 52 to diode 43 in the same
manner.
If the user desires to check the frequency of some other note of the
instrument, that note may be merely selected by the switch 60. When the
user then produces a corresponding note on the instrument, the tuning of
the instrument to that new note is accomplished in the same manner as
described above.
If it is desired to tune the instrument to an externally produced frequency
standard, the user merely disconnects the instrument from the terminal 36
and connects the external frequency standard producing device to the
terminal 36. The switch 62 is then placed in its second position which
selectively connects the variable capacitance element 76 to the oscillator
circuit 56 and causes the light emitting diode 80 to light thus warning
that the standard frequency to which the instrument will be tuned is based
upon an external standard frequency. The external standard frequency is
then introduced into the saturated audio amplifier 14, and the value of
variable capacitance element 76 is adjusted until the picket fence created
by light emitting diodes 43 through 52 appears to be stationary as
explained above. It is to be noted that in establishing the standard
frequency responsive to an external standard, the values of resistors 63
through 74 were not changed. As a result, the chromatic scales enabled to
be produced by the oscillator 18 will be based upon the adjusted frequency
as determined by capacitator 76 but retains the standard relationship
between each note of the chromatic scale.
When switch 12 is advanced to its third position, wiper 26d will engage
contact 26c, wiper 28b will engage contact 28c, wiper 30d will engage
contact 30c, and wiper 32d will engage contact 32c. In this switch
position, the tuning device power supply is activated to energize the
tuning device, the instrument connected to terminal 36 is grounded to
prevent stray pickup, the output of the saturated audio amplifier 14 is
disconnected from the light emitting diodes 43 through 52 to prevent their
activation and to conserve power should the power source be a battery, and
the signal deriving means 24 is connected to terminal 34 which is in turn
coupled to the input of the external amplifier. Hence, in this switch
position, an audible tone having a frequency equal to the desired
frequency may be produced. The filter 42 comprises an audio filter which
rounds out the square wave signal received from the decoder 94 so that the
audible tone has improved tonal qualities. The filter 42 additionally
reduces the amplitude of the derived signal to approximately the level
produced by a microphone or electric music instrument so that no change in
amplifier gain setting is required when switching to this position.
From the foregoing, it can be appreciated that the present invention
provides a new and improved device which facilitates the tuning of a
musical instrument to a standard frequency with speed and accuracy. The
tuning device is substantially less complicated than those of the prior
art and covers a frequency range of 12 notes of an equal tempered
chromatic scale in eight octaves and is adaptable to operate on
self-contained rechargeable batteries. Either an internal frequency
standard based upon the A-4, 440 universal standard or any external
frequency may be used as a base to tune instruments using the present
invention. Furthermore, as a convenience, when the device is turned off,
an electric music instrument will be directly connected to its associated
external amplifier. This is an important feature when a stringed
instrument becomes detuned or breaks a string during the playing of a
performance. To retune, the tuning device is merely turned on,
disconnecting the instrument from its amplifier, the string is tuned, and
the tuning device is turned off thus reconnecting the instrument with its
amplifier for use.
As a further feature of the present invention, an external frequency
standard may be accommodated. After the variable capacitance element has
been appropriately adjusted, all 96 tones available from the oscillator
will be based upon the one external tone. If a tone which is accurate in
frequency is desired from the external amplifier, the internal frequency
standard may be switched into the amplifier.
Lastly, the tuning device of the present invention provides a display which
is easy to read even from a distance. When the instrument is in tune, it
can be readily discerned that the picket fence created by the indicator is
stationary and when the instrument is slightly out of tune, the direction
and speed of movement of the picket fence facilitates rapid adjustment of
the instrument.
While a particular embodiment of the present invention has been shown and
described, modifications may be made, and it is therefore intended to
cover in the appended claims all such changes and modifications which fall
within the true spirit and scope of the invention.
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