JPS5837557B2 - 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.

Transistor 1 and operational amplifier 2 form a voltage-current conversion circuit, and if the control voltage applied to the non-inverting input terminal of operational amplifier 2 is vc1, and the value of resistor 3 on the emitter side of transistor 1 is R, then the collector of transistor 1 is Control Vc A constant current I c-R flows according to the control voltage Vc.

In addition, transistors 5a and 5 forming current switches
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
Difference current Iref − I between ref and the constant current Ic
The capacitor 6 is charged by the 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 comparator 8 outputs a signal "1" and the monostable multi-by-break 9 to generate a pulse with a time width τ.

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

Therefore, the transistor 5a is turned on and the difference current Ire
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.

The peak voltage generated in the capacitor 6 is ■pp1.If the capacitance of the capacitor 6 is C, there is a relationship between charging and discharging, so the oscillation frequency f of this circuit is given by formula (1).
, given by (2).

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 above voltage controlled oscillator, the reference voltage Vref applied to the operational amplifier 4 is oscillated by a low frequency oscillator, and the reference constant current I ref is oscillated, so that it is possible to add a vibrato that is simple in structure and has good audibility. The present invention aims to provide a vibrato device for electronic musical instruments.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying 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 capacitor 13 is connected to a connection point 12 between resistors 10 and 11 that provides a reference voltage Vref to the non-inverting input terminal of the operational amplifier 4.
A low frequency oscillator 15 is connected via a vibrato switch 14.

The low frequency oscillator 15 oscillates a vibrato signal, and by adjusting the variable resistor 16, the oscillation frequency and vibration of the oscillator 15 are varied to adjust the speed and depth of the vibrato.

As the control voltage Vc applied to the non-inverting input terminal of the operational amplifier 2, a tone pitch voltage corresponding to (proportional to) the frequency of each tone is used.

Therefore, the current IC=1 flowing through the Vc collector of transistor 1 has a value proportional to the pitch voltage.

When the vibrato switch 14 is off, the reference constant current Iref is a value corresponding to the reference voltage Vref, ie, the bare transistor 5a. Resistor 1 on the emitter side of 5b
7 is R2, and similarly to the above, the output terminal T out outputs a sawtooth wave with a frequency f expressed by the above equation (4) which is proportional to the control voltage Vc (pitch voltage).

When the vibrato switch 14 is turned on, the operational amplifier 4
The reference voltage applied to the non-inverting input terminal of the low frequency oscillator 15
The fluctuating voltage JV is adjusted and the voltage Vref f J
It becomes V.

Therefore, the reference current I'ref flowing through the resistor 17 is as follows.

As a result, the oscillation frequency f' generated at the output terminal Tout is frequency-modulated according to the output of the low-frequency oscillator 15, and generates a sawtooth wave with vibrato added and a frequency corresponding to the control voltage Vc (tone pitch voltage). Obtainable.

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 was charged by the difference current between the constant current Ic and another reference constant current Iref, but in contrast, a voltage-controlled oscillator is used that charges the capacitor by the constant current Ic and discharges by the difference current. The same applies.

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 drawings]

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. 1, and FIG. 3 is a circuit diagram showing an embodiment of a vibrato device for an electronic musical instrument according to the present invention. 6... Capacitor, 9... Monostable multivibrator, 14... Vibrato switch, 15... Low frequency oscillator.

Claims (1)

[Claims] 1. A capacitor is discharged (or charged) by a control constant current defined by a human control voltage, and when the terminal voltage of the capacitor reaches a predetermined voltage, the capacitor is discharged by the difference current between the control constant current and another reference constant current. In a circuit that generates a sawtooth wave with a frequency according to the input control voltage by charging (or discharging) the capacitor, the other reference constant current is varied according to the output of the low frequency oscillator. A vibrato device for an electronic musical instrument, which adds vibrato to the sawtooth wave.