JPS5941590B2 - control signal generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control signal generator that controls the transmission amplitude of an AC signal using a variable resistor and at the same time obtains a DC control signal when the transmission amplitude of the AC signal is zero. It is.

Conventionally, when controlling the transmission amplitude of an AC signal using a variable resistor, it was desired to detect when the transmission amplitude of the AC signal was zero in principle and control something else. However, the circuits required to achieve this purpose are extremely complex, and are currently hardly ever put into practical use.

The present invention provides an inexpensive control signal generator capable of controlling the transmission amplitude of an AC signal and at the same time obtaining a DC control signal by operating a series of variable resistors.

Embodiments in which the present invention is applied to electronic musical instruments will be described below with reference to the drawings.

In FIG. 1, reference numerals 4 and 5 indicate oscillators constituting a musical tone signal source, which are connected to the transistor opening/closing gate 6 and the emitter of □, respectively.

The opening/closing gates 6 and T are connected to the gate control voltage Vk via key switches 19, 20, etc.
Opening/closing is controlled by 0 etc. The respective outputs of the switching gates 6 are connected in common, and are connected to a +20V power supply via a resistor 22 and a transistor 8. Similarly, a plurality of outputs of the switching gates T are connected in common, and are connected to a +20V power supply via a resistor 23 and a transistor 9. In addition, here, the group of opening/closing gates 6 is assumed to be an 8-foot section 1,
The group of opening/closing gates T is assumed to be a 4-foot section 2. The musical tone signal output of the 4-foot section 2 is supplied to an amplifier 10, and its output is connected to one terminal 31 of a sliding resistor 30 of a variable resistor 3 via a capacitor 11.

The sliding terminal 3 of the variable resistor 3 is connected to a downstream amplifier 18 via a capacitor 14, and the signal amplified here is used as a musical tone signal. + is connected to one terminal 31 of the sliding resistor 30 and the sliding terminal 33 through resistors 12 and 13, respectively.
A 20V DC power supply is connected, and as a result, DC voltages of the same potential are applied to both terminals 31 and 33. The switch terminal 32 of the variable resistor 3 is the sliding resistor 30
It is connected to a high input resistance control signal generation circuit 21 consisting of a high resistance 15 of about 1 MΩ, a transistor 16, and a load resistance 17. The output of this control signal generating circuit 21 is the transistor 9 of the 4-foot section 2.
connected to the base of. In this embodiment, as is clear from the drawings, the sliding terminal 33 of the variable resistor 3
is closer to one terminal 31 of the sliding resistor 30, the amplifier 18
The musical tone output amplitude is large, and as it approaches the switch terminal 32, the musical tone output amplitude becomes smaller.

Therefore, depending on the sliding position of the sliding terminal 33, the transmission amplitude of the musical tone signal, which is an alternating current signal, can be freely controlled. On the other hand, when the sliding terminal 33 is connected to the switch terminal 32 and disconnected from the sliding resistor 30, the amplifier 1
8's musical tone output is theoretically infinitesimal.

At the same time, the control signal generation circuit 21, which has been off until now,
transistor 16 is turned on, a zero V DC output signal appears at its output, and this output signal is applied to transistor 9.
turn off. As a result, the gate transistor 7 in the 4-foot section 2 will not operate even if the key switches 19, 20, etc. are pressed. Therefore, the musical tone signal of 4-foot section 2 is +2
Not only does it leak into the 0V power supply line and do not flow, but it also does not reach the subsequent stages. Note that similar control is performed for the 8-foot section 1 as well. As in this embodiment, when the movable resistor 3 is set so that all musical tones are not output, if the musical tones are cut off at the sound source section, the power supply line, parasitic capacitance coupling, etc. In addition, the 4-foot section 2
It is possible to completely eliminate the unpleasant leakage of the musical tone of the 8-foot section 1, which is one octave lower than the musical tone, when the musical tone of 1 is being generated.

In addition, when the gate section is integrated circuit, in order to sufficiently reduce the leakage caused by the musical tones of other foot rows coming around from the power supply line, the impedance of the power supply line is usually made sufficiently low and the power supply line is In the past, it was necessary to make the power line thicker to lower the impedance, but with this embodiment, the impedance of the power supply line does not have to be so small, and therefore the power line can be made thinner, making it easier to integrate. This makes it possible to reduce the chip area of the circuit and also contributes to lowering its cost.

Note that in this embodiment, the control signal generation circuit 21 was configured using an inverting circuit with a grounded emitter due to the polarity of the control.
A common high-resistance input control signal generation circuit, such as an emitter follower, may also be used.

Further, in the present invention, the high resistance 15 is inserted on the input side of the control signal generation circuit 21 for the following reason. That is, if the high resistance 15 were not provided, a large direct current would flow through the sliding terminal 33 at the moment the sliding terminal 33 of the variable resistor 3 was connected to the switch terminal 32, and as a result, a click sound would appear in the musical tone. However, if the input resistance of the active element circuit 21 is made sufficiently large by inserting the high resistance 15, the click sound will not appear in the musical tone. In the above embodiment, the present invention was applied to an electronic musical instrument.
The present invention can also be used in other signal processing devices such as audio mixers. Further, although some specific numerical values were used in the above embodiments, the present invention is not limited to these numerical values. As described above, according to the present invention, it is possible to easily control the amplitude of an AC signal and generate a DC voltage by using a series of variable resistors equipped with a switch terminal, and also to generate a DC voltage. By making the input resistance of the control signal generation circuit sufficiently large, it is possible to prevent clicking noise from appearing in the AC signal at the moment the sliding terminal of the variable resistor is connected to the switch terminal. Excellent effects can be obtained.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing an embodiment of the present invention. 1...8 foot section, 2...4 foot section, 3...variable resistor, 4,5...
Oscillator, 6, 7... Opening/closing gate, 8, 9...
...Transistor, 10,18...Amplifier,
21...Control signal generation circuit.

Claims (1)

[Claims] 1 A sliding resistor constituting a variable resistor, a switch terminal insulated from the sliding resistor, and a sliding terminal that is in sliding contact with the sliding resistor and also in contact with the switch terminal. , a control signal generation circuit having a high input resistance connected to the switch terminal, means for applying an alternating current signal to one end of the sliding resistor, and one end of the sliding resistor and the sliding terminal having the same potential. means for applying a DC voltage, the transmission amplitude of the AC signal is controlled by sliding the sliding terminal on the sliding resistor, and by bringing the sliding terminal into contact with the switch terminal. . A control signal generation device, characterized in that the DC voltage is applied to the control signal generation circuit, and a DC control signal is obtained at an output terminal thereof.