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BACKGROUND OF THE INVENTION
The present invention is directed toward a device for the remote control of
electronic musical instrument equipment and more particularly toward a
device which is primarily intended to remotely control an electronic
tuning circuit.
Numerous electronic tuning devices have been proposed which are intended to
aid a musician in the tuning of a stringed instrument such as a guitar.
Many of these proposed devices include a microphone or pickup for
converting the sound produced by a vibrating string into an electronic
signal. This signal is then compared with a signal from a frequency
generator which is selected to be equal to the frequency of the string
being tuned. These prior devices include numerous different techniques for
indicating when the comparator senses that the frequency of the string is
equal to the frequency of the frequency generator. Examples of this type
of tuning device are shown in U.S. Pat. Nos. 3,766,818; 3,861,266 and
3,901,120. In an effort to improve the accuracy of electronic tuning
devices such as those described above and to simplify the operation
thereof, Applicant has proposed to connect the tuning device directly in
line with the audio cable leading from the guitar pickup to the guitar
amplifier. Thus, rather than requiring a separate microphone for the
tuner, the audio signal representing the frequency of the vibrating string
is taken directly from the audio cable.
This technique, proposed by Applicant, does however create an additional
problem. That is, the amplifier is quite often located at a remote
location from the guitar and accordingly it would be extremely
inconvenient if not impossible for the musician desiring to tune his
guitar to control the tuner. In other words, each time the musician wished
to tune a different string on his guitar he would have to walk some
distance to the tuning device to turn a switch which would control the
output frequency of the frequency generator therein. This, of course,
cannot possibly be done during a performance although it is quite often
necessary to tune or at least check the tuning of a guitar at that time.
SUMMARY OF THE INVENTION
The present invention is designed to overcome the foregoing described
problem. This is accomplished by a manually operated switch located on the
electric guitar which controls a remotely located tuning device through
the existing guitar cable. Preferably, the switch is located in an adaptor
which plugs into the audio output jack of the guitar and into which is
plugged the guitar cable. Circuitry associated with the switch sends a
control signal on the audio cable and circuitry located adjacent the tuner
interprets the control signal for controlling the tuner. It is also
contemplated that the present invention may be utilized with other types
of audio equipment such as a microphone or the like instead of a guitar
and may be used for controlling equipment such as an amplifier or the
like. In this regard, the control circuit may be utilized for remotely
controlling the volume of the amplifier.
BRIEF DESCRIPTION OF THE DRAWINGS
For the purpose of illustrating the invention, there are shown in the
accompanying drawings forms which are presently preferred; it being
understood that the invention is not intended to be limited to the precise
arrangements and instrumentalities shown.
FIG. 1 is a block diagram schematic representation of a remote control
circuit for electronic musical instrument equipment constructed in
accordance with the principles of the present invention;
FIG. 2 is a schematic representation of a circuit for controlling the
volume of a remotely located amplifier utilizing the basic circuit shown
in FIG. 1;
FIG. 3 is a diagrammatic representation of a combined control switch and
adaptor which may be utilized with the present invention;
FIG. 4 is a schematic representation of a second embodiment of the present
invention, and
FIG. 5 is a schematic representation of a tuner circuit which may be
utilized with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings in detail wherein like reference numerals
have been used throughout the various figures to designate like elements,
there is shown in FIG. 1 a schematic representation of a remote control
circuit for controlling electronic musical instrument equipment and
designated generally as 10. The circuit 10 utilizes the existing guitar
pickup 12 which, as is well known in the art, is a mechanical to
electrical transducer. The output of the guitar pickup 12 is normally
connected to the guitar amplifier through an audio cable 14. In accordance
with the present invention, however, a switch 16 preferably carried by the
guitar is connected in the audio cable line.
The audio cable 14 continues on and is connected to a remotely located
guitar amplifier (not shown) in the conventional manner. Located adjacent
the guitar amplifier and remote from the guitar is a low-noise buffer 18.
Buffer 18 isolates the rest of the circuit from the guitar amplifier to
prevent signals from the remaining parts of the circuit from feeding back
into the amplifier or from loading the amplifier. The output of the
low-noise buffer 18 is connected to the audio input of a tuner circuit 20.
The output of low-noise buffer 18 is also connected to the input of a
low-noise, high-gain amplifier circuit 22. Following the low-noise
amplifier 22 is a retriggerable one shot 24 which has its output, in turn,
connected to the control input of the tuner circuit 20. Tuner circuit 20
is of the type which has a frequency generator therein capable of
selectively generating one of a number of preselected frequencies. The
particular frequency generated is selected by a counter at the input of
the tuner circuit which is responsive to the control signal from the
retriggerable one shot 24. Such a tuner circuit is shown, for example, in
FIG. 9 of Applicant's co-pending application Ser. No. 120,061, now U.S.
Pat. No. 4,320,689, filed Feb. 11, 1980.
The tuner circuit which is more fully described in Applicant's co-pending
application is illustrated in present FIG. 5 and is comprised of a counter
100 having its input connected to the output of the retriggerable one shot
24. Thus, for each pulse of the control signal, counter 100 is
incremented. The count is decoded by decoder 102 which is connected to a
seven-segment display 104. The display 104 will display, for example, one
of the letters "E," "A," "D," "G" or "B" representing the strings of a
guitar depending on the number of pulses from the retriggerable one shot
24 which, of course, is also equal to the number of times that the switch
16 is depressed.
Counter 100 is also connected to a memory such as a ROM 106 which will then
cause the pulse generator 108 to generate the appropriate frequency
corresponding to the frequency of the string represented by the letter
displayed by the display 104. The output of the pulse generator 108 is
also connected to one side of the frequency comparator 110.
The tuner circuit 20 also includes an amplifier 112 which has its input
connected to the audio signal from the guitar which, in FIG. 1, is the
output of the low noise buffer 18 as illustrated. The output of amplifier
112 is converted to a pulse form by square wave generator 114. Frequency
comparator 110 compares the output of the pulse generator 108 which is the
desired frequency to the output of the square wave generator 114 which
represents the actual frequency of the vibrating string. If the frequency
of the vibrating string is too high, diode 116 is energized and if the
frequency of the vibrating string is too low, diode 118 is energized. As
is known in the art, the tension on the string is then adjusted until it
is brought into tune.
The circuit shown in FIG. 1 operates in the following manner. Switch 16 is
preferably a momentary contact switch which, when depressed, disconnects
the guitar pickup output from the audio cable leading to the guitar
amplifier and the remaining parts of the circuit. This may be done either
by simply opening the circuit between the guitar pickup 12 and the cable
14, by simply shorting or grounding the audio cable 14 or by a combination
thereof, i.e. by shorting the audio cable while simultaneously
disconnecting the guitar pickup.
Regardless of the particular manner of operation of switch 16, there will
be an absence of any significant audio signal or noise level in audio
cable 14 whenever switch 16 is depressed. The noise referred to is
normally present on line 14 and is a result of the normal output of the
pickup 12 even when the guitar is not being played. When there is audio
signal or noise on the line 14, it will be amplified by high-gain
amplifier 22. However, when the switch 16 is depressed, the output of
amplifier 22 will go low. Retriggerable one shot 24 is responsive to the
output of amplifier 22 so as to be continuously retriggered by the
presence of any noise or audio signal level and will alternatively
generate a pulse or control signal each time the switch 16 is depressed
and the noise or audio signal is removed. This control signal is utilized
to select the desired frequency within the tuner circuit 20.
FIG. 2 illustrates the manner that the circuit shown in FIG. 1 may be
utilized to control the volume of an amplifier. This is accomplished by
utilizing a DC voltage-controlled amplifier 26. The amplification factor
of amplifier 26 is controlled by ramp circuit 28 in a known manner. The
ramp duration is controlled by the control signal coming from the output
of retriggerable one shot 24. Ramp circuit 28 is therefore controlled by
depressing switch 16. Holding switch 16 depressed increases the pulse
width of the control signal which in turn controls the ramp duration and
thus the volume of amplifier 26.
It would, of course, also be desirable to decrease the amplification factor
of amplifier 26 and to again increase the same if needed. This can be
accomplished by also controlling the direction of the ramp in ramp circuit
28. To accomplish this, the control signal from the output of
retriggerable one shot 24 is also fed to a flip-flop 30 which, in turn, is
connected to the ramp direction input of the ramp circuit 28. Thus, each
time switch 16 is depressed the direction of the ramp in ramp circuit 28
and therefore the direction of the amplifier (increase or decrease) volume
also changes. It may also be desirable to include a visual indicator to
distinguish when the volume of the amplifier 26 is being increased or
decreased.
The switch 16 may be built directly into the guitar. However, substantially
all electric guitars are equipped with a standard phone jack into which is
plugged a standard phone plug from the audio cable leading to the guitar
amplifier. Shown diagrammatically in FIG. 3 is an adaptor 32 which may be
used in line between the guitar and the audio cable and which includes a
switch which will function as switch 16.
Adaptor 32 includes a forward standard phono plug portion 34 which is
adapted to be plugged directly into an electric guitar. The rear portion
of the adaptor 32 includes a socket portion 36 which is adapted to accept
a standard phono plug 38 at the end of a standard audio cable 40 leading
to the guitar amplifier and associated circuitry. The adaptor 32 carries a
momentary push-button switch 42 which, as shown schematically, shorts or
grounds the jack 36 and thus, as explained above, eliminates the noise
signal on the audio cable 40.
By utilizing the adaptor 32 shown in FIG. 3, no modifications need be made
to the guitar. All that is necessary is that the adaptor 32 be plugged
into the existing phono jack in the guitar and the audio cable leading to
the amplifier then be plugged into the adaptor. The switch 42 on the
adaptor may then be used as switch 16 in the circuitry described above.
Another embodiment of the control circuitry of the present invention is
shown in FIG. 4. In this embodiment, a signal source other than the audio
signal or noise (or absence of such) is utilized as the control signal.
This other signal is supplied by a high frequency oscillator 44. The
frequency of the oscillator 44 should be somewhat above the frequencies
normally encountered with an electric guitar and associated audio
equipment.
When switch 46 (which may be similar to switch 16) is depressed, the output
of the high frequency oscillator 44 is delivered to the audio cable 14.
Passive low pass filter 48 and low pass filter 50 prevent the signal from
the high frequency oscillator 44 from passing to the guitar amplifier or
to the tuner input. High pass filter 52 prevents the audio signal or noise
from the guitar from passing to the retriggerable one shot 24. High pass
filter 52, however, does allow the output of the high frequency oscillator
44 to pass to the high-gain amplifier 22 which controls the retriggerable
one shot 24 in the same manner as the audio signal or noise described
above with respect to FIG. 1.
From the foregoing descriptions, it should be readily apparent that the
present invention allows for the control of remotely located audio
equipment such as an amplifier or a tuner device utilizing the existing
audio cable. The only modification which need be made to the guitar (or
other device such as a microphone or the like) is the inclusion of a
switch or with respect to FIG. 4 a switch and a high frequency oscillator.
When the adaptor shown in FIG. 3 is utilized, the "modifications" to the
guitar are easily performed. All of the rest of the control circuitry
shown in the figures is located remote from the guitar and adjacent the
audio equipment being controlled and the only connection between the two
is the existing audio line.
The present invention may be embodied in other specific forms without
departing from the spirit or essential attributes thereof and accordingly,
reference should be made to the appended claims rather than to the
foregoing specification as indicating the scope of the invention.
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