JPS5841600Y2 - Oscillator for keyboard instruments - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an oscillator for a keyboard instrument, and is particularly designed to obtain an oscillation signal with a stable frequency relative to an input signal from a keyboard.

A conventional oscillator for a keyboard instrument is constructed as shown in FIG.

In FIG. 1, 1 is a group of keyboard switches.

This keyboard switch group 1 is connected between each voltage division point and the positive voltage terminal (+) of a resistor ladder circuit 2 constituted by a resistor group R of the same resistance value, and the resistor ladder circuit 2 is connected by operating the keyboard. Apply positive voltage to each voltage dividing point.

One terminal of the resistor ladder circuit 2 is operated by a keyboard to sequentially turn on and off the keyboard switch group 1 from one end to the other, thereby changing the terminal terminal exponentially, i.e. A voltage corresponding to the musical scale can be obtained.

This voltage is amplified by an amplifier 5 as required, and the amplified output is applied to the base of a transistor 4 through an input terminal 3.

The emitter of the transistor 4 is grounded, and the collector is connected to a current terminal 7 of an oscillator 6 which oscillates a frequency proportional to the current.

This oscillator 6 is a sawtooth wave oscillator composed of a capacitor C and a switch element S, and the impedance between the collector and emitter of the transistor 4 is controlled by a control signal applied to the terminal 3, thereby operating the keyboard switch group 1. It oscillates a frequency that changes exponentially with respect to the 12-tone scale, and oscillates a frequency that corresponds to each note name of the 12-tone scale.

The oscillation output is taken out from an output terminal 8 derived from the collector of the transistor 4.

On the other hand, since the signal source of an electronic keyboard instrument uses an electric circuit, it is easy to produce various special effect sounds such as vibrato or tremolo.

This special effect sound is produced by applying a modulation signal such as a triangular wave or a sine wave of several Hz from the vibrato signal source 9 or tremolo signal source 10 to the terminal 3, modulating the oscillation frequency of the oscillator 6 at a low frequency, and producing the special effect. I'm trying to get some sound.

Such a conventional musical instrument oscillator has the disadvantage that the collector current value of the transistor 4 fluctuates due to changes in humidity, resulting in deviations in pitch due to humidity.

For this reason, conventionally, although not particularly shown in the drawings, a resistor is inserted between the emitter of the transistor 4 and a common potential point for humidity compensation to reduce fluctuations in the collector current.

However, if a resistor is inserted into the emitter of the transistor 4, the temperature characteristics will be stabilized, but there will be a drawback that it will be difficult to modulate the signals provided from the signal sources 9 and 10.

Of course, even if temperature compensation is performed, it does not mean that the pitch deviation will be completely zero.

The purpose of this invention is to provide an oscillator for a keyboard instrument with a simple structure and stable temperature characteristics.

An embodiment of this invention will be described below.

FIG. 2 shows an embodiment of this invention.

In this invention, the emitters of a pair of transistors 4 and 4' are commonly connected, the commonly connected emitters are connected to the output terminal of the DC amplifier 11, and one transistor 4' is connected to the output terminal of the DC amplifier 11.
The collector is led out to the first input terminal 3 and also connected to the inverting input terminal (to) of the DC amplifier 11 .

The other transistor 4' of transistors 4 and 4'
oscillator 6 that oscillates the collector of at a frequency proportional to the current.
Connect to current terminal 7 of

The base of this transistor 4' or the base of one of the transistors 4 In the illustrated example, the base of the transistor 4' is led out to the second input terminal 12, and this second input terminal 12 is used as the input terminal for the modulation signal and is normally used as the base of the transistor 4'. The potential of the input terminal 12 is held at the potential of a common potential point, the base of the transistor 4 is connected to the common potential point, and a signal from the keyboard is supplied to the first input terminal 3.

Here, a resistor 13 is inserted in series between the first input terminal 3 and the inverting input terminal of the DC amplifier 11.

With this configuration, when a voltage is applied to the first input terminal 3 by operating the keyboard switch group 1, the DC amplifier 11 amplifies the input voltage, and the output with inverted polarity is sent to the transistor 4. and 4' emitter.

Here, the input voltage applied to input terminal 3 is ■1, the input voltage applied to input terminal 12 is ■2, the collector current of transistor 4 is 11, the collector current of transistor 4' is Let the base voltage be VBB7, the base voltage seen from the emitter of transistor 4' be ■BE2, the reverse saturation current of transistors 4 and 4' be Is, the Boltzmann constant be, and the humidity be T1. If the electron charge is q, then ■■ 5-eXp・(q・VBEt/kT) --・
−・−mI2=Is−exp・(q・VBE2/kT)
-(2) holds true.

Here, assuming that the base of transistor 4 is connected to a common potential, transistors 4 and 4'
The relationship between the voltage VBEI and VBE2 looking at the base of is ■BE2-■BE1+■2 ・・・・・・・・・
・・・・・・・・・・・・(3)

Therefore, equation (2) is ■22■5-eXp(q(■2+■BE1)/kT)■
5-eXp(q・■2/kT)・eXp(q・■BE1
/kT) ・・・・・・・・・・・・・・・・・・(4)

Solving equation (1) for Is and substituting it into equation (4), we can rearrange it by ■22■1・exp (q・■2/kT)...
(5) Here, if the input terminal 12 is connected to the common potential, ■2=0, so ■2 - ■1.

Assuming that the DC amplifier 11 is an ideal amplifier, it can be assumed that no current flows through the inverting input terminal.

Therefore, if the resistance value of the resistor 13 is r, it can be expressed as 1l-V-1.

Therefore ■2-V-1 ・・・・・・・・・・・・
(6) The output current (2) is proportional to the input voltage (2) and does not depend on the temperature.

Therefore, while the second input terminal 12 is held at the potential of the common potential point, ie, zero potential, the collector current of the transistor 4' becomes 2-V-1 and changes in proportion to the signal 1 from the keyboard.

Therefore, an oscillation signal having a frequency corresponding to the note name is obtained from the output terminal 8.

However, while the voltage 2 at the second input terminal 12 is O2, the collector current I2 of the transistor 4' does not depend on temperature changes.

Therefore, if the voltage of the second input terminal 12 is normally maintained at O■, the oscillation frequency of the oscillator 6 can provide a stable scale signal with no pitch deviation regardless of temperature changes.

A modulation signal is supplied to the second input terminal 12 from a modulation signal source such as the vibrato signal source 9 or the tremolo signal source 10 when necessary, so that modulation can be easily applied.

Note that this second input terminal 12 may be derived from the base of the transistor 4.

In that case, the base of transistor 4' is connected to a common potential point.

FIG. 3 shows another embodiment of this invention.

In this example, a current source 14 is inserted between the input terminal 3 and the input terminal of the DC amplifier 11, and a current corresponding to the voltage 1 applied to the input terminal 3 is supplied from the current source 14. show.

Further, this example shows a case where an inverter is used as the DC amplifier 11.

As explained above, according to this invention, it is possible to obtain a stable scale signal with no frequency shift due to temperature changes, thereby increasing the reliability of the keyboard instrument.

Moreover, since the structure is simple, it has the advantage that it can be manufactured at a lower cost than conventional temperature compensation circuits.

[Brief explanation of drawings]

Fig. 1 is a connection diagram for explaining a conventional keyboard instrument oscillator, Fig. 2 is a connection diagram showing one embodiment of this invention, and Fig. 3 is a connection diagram showing another embodiment of this invention. . 1: keyboard switch group, 3: first input terminal, 4-one transistor, 4': other transistor, 6: oscillator,
7: Current terminal, 11: DC amplifier, 12: Second input terminal.

Claims (1)

[Scope of utility model registration request] The emitters of a pair of transistors are commonly connected, and the commonly connected emitters are connected to the output terminal of a DC amplifier.
The collector of one of the transistors is led out to a first input terminal and connected to the inverting input terminal of the meandering amplifier, and the collector of the other of the transistors is connected to the current terminal of an oscillator that emits at a frequency proportional to the current. ,
The base of the transistor or the base of one of the transistors is led out to a second input terminal, and the second input terminal is used as an input terminal for a modulation signal, and the second input terminal is normally held at a potential of a common potential point. , an oscillator for a keyboard instrument, wherein the first input terminal is supplied with a DC voltage that varies exponentially and is obtained by selecting a keyboard.