JPS5837556B2 - Vibrato device for electronic musical instruments - Google Patents

Description

[Detailed description of the invention] The present invention relates to a vibrato device for an electronic musical instrument.

In electronic musical instruments, vibrato devices that add vibrato to musical tones are constructed by frequency modulating the sound source signal generated using a voltage-controlled oscillator. 1
A circuit as shown in the figure has been proposed.

This circuit uses charging and discharging of the capacitor 6 to oscillate a sawtooth wave as shown in FIG. 2a from the output terminal Tout.

The transistor 1 and the operational amplifier 2 form a voltage-current conversion circuit, and if the control voltage applied to the non-inverting input terminal of the operational amplifier 2 is R, then the value of the resistor 3 on the emitter side of the transistor 1 is R. A constant current Ic1 in accordance with the control voltage Vc flows through the collector.

In addition, transistors 5a and 5 forming a current switch
b and the operational amplifier 4 generate a reference constant current Ire corresponding to the reference voltage Vref applied to the non-inverting input terminal of the operational amplifier 4.
It forms a constant current circuit that flows f.

Therefore, when the transistor 5a is on, the reference constant current I
The capacitor 6 is charged by the difference current Iref-Ic between ref and the constant current Ic, and when the transistor 5a is off, the capacitor 6 is discharged by the constant current Ic.

The voltage of the capacitor 6 is applied to the comparator 8 via the buffer field effect transistor 7, and when the voltage of the capacitor 6 falls to the comparison reference lower limit voltage vth, the converter 8 outputs the signal "'1"' and becomes monostable. The multivibrator 9 is driven to generate a pulse with a time width τ.

(See Figure 2b) The output pulse of the monostable multi-bibreak 9 is applied to the base of the transistor 5b, turning it off.

Therefore, the transistor 5a is turned on and the difference current ■re
Capacitor 6 is charged by f-Ic.

When the output of monostable multi-bi break 9 becomes ``0'' (
When the time τ ends), the transistor 5b is turned on, the transistor 5a is turned off, and the capacitor 6 is discharged by the constant current Ic.

In this way, a sawtooth wave as shown in FIG. 2a is output from the output terminal Tout.

If the peak voltage generated in the capacitor 6 is vpp and the capacitance of the capacitor 6 is C, there is a relationship during charging, so from equations (1) and (2), the oscillation frequency f of this circuit is given by:

A vibrato device for an electronic musical instrument using the voltage-controlled oscillator described above is constructed by vibrating a control voltage Vc in accordance with a predetermined vibrato frequency and varying a constant current Ic.

However, in order to cause the constant current Ic to oscillate around a predetermined current, it is necessary to make the transistor 1 differential, which has the drawback of complicating the circuit.

This invention was made to eliminate the above-mentioned drawbacks.
In the voltage-controlled oscillator described above, the frequency signal (sawtooth wave) corresponding to the control voltage Vc is frequency-modulated by oscillating the oscillation pulse width τ of the monostable multi-by-break with a low-frequency oscillator, which has a simple configuration and improves auditory sense. It is an object of the present invention to provide a vibrato device for an electronic musical instrument that can add good vibrato.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 3 shows an embodiment of a vibrato device for an electronic musical instrument according to the present invention. In this embodiment, the voltage-controlled oscillator shown in FIG. 1 is used, and the common parts are the same as in FIG. 1. It is represented by the symbol.

A low frequency oscillator 12 is connected to the monostable multivibrator 9 via a capacitor 10 and a vibrato switch 11.

The low frequency oscillator 12 oscillates a vibrato signal, and the frequency and amplitude of the oscillator 12 are controlled by adjusting the variable resistor 13, thereby adjusting the speed and depth of the vibrato.

The monostable multi-vibrato break 9 is composed of a circuit as shown in FIG. 4, and when the vibrato switch 11 is turned on, a vibrato signal from a low frequency oscillator 12 is applied, and the pulse time width τ is changed according to this vibrato signal. changes.

When the voltage of the capacitor 6 (FIG. 3) becomes lower than the comparison reference lower limit voltage vth due to discharge, a signal at 1 pp is applied from the converter 8 (FIG. 3) to the reset terminal H of the flip-flop 91 of the monostable multivib break 9. Reset.

As a result, the output Q of the flip-flop 91 becomes t'O'', turning off the transistor 92 and starting charging the capacitor 93.

Charging of the capacitor 93 is performed by a constant current (2) from a constant current source formed by an operational amplifier 94 and a transistor 95.

The voltage on capacitor 93 is applied to comparator 96;
Reference voltage V determined by resistor 9T and variable resistor 98
The voltage of the capacitor 93 compared with o is the comparison reference voltage ■.

When the flip-flop 91 is reached, a signal "1" is output from the comparator 96, and this signal "1" is applied to the flip-flop 91 to set the flip-flop 91.

As a result, the transistor 92 is turned on, and the charge in the capacitor 93 is discharged.

Therefore, the pulse time τ outputted through the inverter 99 is determined by the constant current ■, the capacitance value Co of the capacitor C, and the comparison reference voltage Vo, and is given by the following equation.

By the way, since this monostable multivibrato break 9 is configured to add the vibrato signal JV from the low frequency oscillator 12 to the comparison reference voltage Vo by turning on the vibrato switch 11, the pulse time width τ' when adding vibrato Hato becomes.

In this way, by turning on the vibrato switch 11, the oscillation pulse time width τ' of the monostable multivibrator 9 can be varied in accordance with the vibrato signal from the low frequency oscillator 12.

In FIG. 3, the control voltage Vc applied to the non-inverting input terminal of the operational amplifier 2 is determined according to the frequency of each sound, for example.
(proportional) pitch voltage is used.

If the vibrato switch 11 is off, the capacitor 6 is charged with the difference current Iref-Ic for the time τ, discharged with the constant current Ic according to the control voltage (tone pitch voltage) Vc, and the output terminal From Tout, the above formula (3)
A sawtooth wave with a frequency f expressed by is output.

When the vibrato switch 11 is turned on, the pulse width generated by the monostable multi-vibrato break 9 becomes τ' expressed by the above equation (5) according to the output of the low frequency oscillator 12, and the oscillation frequency f' generated at the output terminal Tout is The frequency is modulated according to the output of the low frequency oscillator 12, vibrato is added, and the control voltage (sound pitch voltage) is
A frequency signal corresponding to Vc can be obtained.

Note that the voltage controlled oscillator used in the above embodiment discharges the capacitor with a constant current Ic according to the control voltage Vc,
The capacitor is charged by the difference current between the constant current Ic and another reference constant current Iref, but in contrast, the voltage control type charges the capacitor by the constant current Ic and discharges by the difference current. The same applies to using an oscillator.

As explained above, according to the present invention, it is possible to realize a vibrato device for an electronic musical instrument with a simple configuration, and it is also possible to obtain a vibrato effect that is better audibly than when the control voltage Vc (Ic) is varied. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a voltage controlled oscillator, FIG. 2 is an explanatory diagram of the operation of FIG. The figure is a circuit diagram showing an example of a monostable multi-by-break in the same embodiment. 6... Capacitor, 8... Comparator, 9... Monostable multi-vibration break, 11...
...Vibrato switch, 12...Low frequency oscillator.

Claims (1)

[Claims] 1. A capacitor is discharged (or charged) by a controlled constant current defined by a human control voltage, and when the terminal voltage of the capacitor reaches a predetermined voltage, a predetermined pulse is generated from the monostable multi-by-break, and the pulse causes the controlled constant current to increase. In the circuit, the capacitor is charged (or discharged) by a current difference between the current and another reference constant current, and the charging and discharging of the capacitor generates a sawtooth wave having a frequency according to the input control voltage. A vibrato device for an electronic musical instrument, which adds vibrato to the sawtooth wave by varying the width of a pulse generated from a stable multivib break in accordance with the output of a low frequency oscillator.