JPS58139186A - Envelope generation circuit for electronic musical instrument - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an envelope generation circuit for an electronic musical instrument, in which the pulse generator is not activated no matter where the variable resistor that variably adjusts the duty ratio and frequency of the output pulse of the pulse generator is set. An envelope generating circuit for an electronic musical instrument is capable of stabilizing the operation, and is also capable of effectively obtaining changes in decay time by significantly changing the duty ratio and frequency of the output pulse relative to the variable ratio of the variable resistor. The purpose is to provide.

FIG. 1 shows a circuit diagram of an example of an output circuit of a general electronic musical instrument. In the figure, a sound source signal e1 having a frequency of a certain sound that has entered terminal l is supplied to a sound source signal switching circuit 2. On the other hand, the power supply VCC of the terminal 3 is converted into the key-on signal VK shown in FIG. 2 (6) by the switch S which opens and closes in response to the pressing of the key, and is supplied to the envelope generating circuit 4 via the folding wire Hru. Ru.

The envelope generating circuit 4 is provided with a pulse generator 5, from which the H level period T is long and the L level periods T and I are low, as shown in FIG.
is being taken out. (H level voltage of pulse vp)
(H level voltage of key-on signal ■1), R2< R□
Therefore, during period T2, the point-large voltage is τ2! through the resistor "1 + "l. ; While being discharged with a time constant of kL20, the point A in period Tl
The voltage is discharged only through the resistor R1 with a time constant of v1=R, 10. As a result, the envelope generating circuit 4 generates an envelope signal VENV as shown in FIG.
(The broken line indicates the average value) is taken out and supplied to the switching circuit 2.

The sound source signal e8 from the terminal 1 is switched in the switching circuit 2 according to the envelope vENv from the envelope generating circuit 4, and is converted into a signal eg as shown in FIG. 2(c) having an amplitude according to the envelope VENV.
It is taken out from the output terminal 6.

The duty ratio of the output pulse vp of the pulse generator 5 is varied by a variable resistor whose resistance value is varied according to the operation of a tone selection lever provided on the operation panel as described later. (2) By varying the duty ratio of (2), the attenuation waveform of the envelope VW shown in (q) in the same figure is varied (that is, the attenuation rate of the envelope is varied), and the tones of various instruments can be selectively extracted. The envelope attenuation generally needs to be varied over a wide range.

Here, the pulse generator 5 of the conventional envelope generating circuit 4 is constituted by a well-known free-run multivibrator as shown in FIG. 3, and its output terminals 51. As is well known, the period T1°T of the pulse V extracted from
T□#R3・C1・ln2, T,=R4-02・ln2
To be determined.

However, in this case, when adjusting the variable resistor R1, for example, if the resistance value is maximized, the transistor Q! There is no guarantee that the base current will stop flowing and the pulse Vp will stop at an H level or an L level.
The operation is unstable, and if the resistance value is minimized, the base current of the transistor Q3 becomes large and there is a risk of destroying it.

By the way, let us consider changes in the duty ratio and frequency of the pulse vp and changes in the decay time of the envelope.

Generally, it is necessary to change the waveform of the envelope signal over a wide range, but even if the duty ratio and frequency of the pulse (2) are slightly changed, the envelope signal V
Changes in the ENV attenuation waveform are small, and therefore changes in the attenuation time are difficult to hear to the ears. For this reason, it is generally possible to more effectively obtain changes in the decay time by changing the duty ratio and the frequency at a relatively large rate relative to the variable rate of the resistor R3. However, in this conventional circuit, the rate at which the resistance value of the resistor R3 is varied and the rate at which the duty ratio and frequency of the pulse V are varied are linear, so it is not possible to effectively obtain a change in the decay time. There were drawbacks such as.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described with reference to FIG. 4 and the following figures.

Figure 4 shows a circuit diagram of a main part (pulse generator) of an embodiment of an envelope generating circuit for a screw musical instrument according to the present invention.

In the figure, 7 is an amplifier whose inverting input terminal is grounded via a capacitor C3, and connected to the power supply VCCI via a resistor -R, while a diode D
1 to the output terminal 5□. The non-inverting input terminal of the amplifier 7 is connected to the power supply VCC! via a resistor R6 and a variable resistor R3. while connected to output terminal 5! via diode D, connected to a. In addition, Vccs
>Vcct.

In the figure, the voltage from the power supply vcct is applied to the capacitor C3 via the resistor R1 to charge it, but during the period when the capacitor C3 is not being charged, the relationship between the two input terminal voltages Va + Vb of the amplifier 7 changes. is Vb>■a, and the voltage va has a waveform as shown in FIG. on the other hand,
The voltage vb is the fifth voltage according to the adjustment position of the first resistor M)'L,
It is an H level voltage as shown in the figure), and the output terminal 5! a
An H-level voltage as shown in (0) of the same figure is taken out from.

Capacitor C3 is gradually charged and voltage ■a becomes voltage vb
When the voltage Vb is reached, the state of the amplifier 7 is reversed, the output V of the output terminal 52a is set to the L level, and the voltage vb is also set to the L level as shown in FIG. Due to the inversion of the amplifier 7, the charge in the capacitor C8 is discharged through the diode D, and the voltage va gradually decreases as shown in (5) of the same figure. When voltage va falls to the L level of voltage vb, amplifier 7
is inverted again and returns to its original state, and the output ■ of the output terminal 5□3 becomes H level again.

The operation like .mu.F is repeated, and a pulse (2) with a predetermined duty ratio and frequency is taken out from the output terminal 52a.

Here, assume that the resistor R3 is adjusted to vary the duty ratio and the voltage Vb is set to, for example, the voltage Vb (51st case). Similarly to the above case, when the voltage va becomes the voltage Vb, the amplifier 7 is inverted and the voltages Vb, v, 5
(to) the same figure, (as shown in El, the amplifier 7 becomes L level, and when the voltage va becomes the L level voltage v6, the amplifier 7 is inverted again, and as a result, from the output terminal 5□, the same figure (G) A Y-mouthed pulse vd shown in is outputted.When other voltages and voltages (Vb', Vb'', ) are set, the level of the pulse is inverted at the timing corresponding to the set voltage. In this case, the voltage va becomes the resistance M
The voltage set by R,3 (vb, vbi*Vb
' + ・) The time for multiple connections varies depending on each set voltage (periods T1. T1', . . . are determined); on the other hand, when the capacitor 0. Since the discharge time is approximately constant (period T2), pulses with different duty ratios and frequencies can be obtained depending on the set voltage. Moreover, the voltage v
Since a is a curve that changes exponentially, the duty ratio can be changed exponentially by changing the voltage setting number.

Next, let us consider the operational stability of this pulse generator 5m. When the resistance value of resistor R3 is set to the minimum (voltage Vbmin), the voltage Vbmi in FIG. 5(2)
. is at the low level line, which causes the pulse Vb
The duty ratio of min s Vp is approximately 50%, for example, and the oscillation operation is repeated stably in this state. Or, depending on the value of voltage Vbmin, Vbmin,
'■ remains at L level. When set in this way, the circuit is more stable than the conventional circuit shown in FIG. 3, in which the base current of the transistor Q8 becomes large.

On the other hand, when the resistor R1 is set to the maximum (voltage Vbmax), the voltage Vbmax in FIG. 5 becomes larger than the voltage va regardless of the charging state of the voltage va, and the pulse
x + Vp remains at H level. This setting is more stable than the conventional circuit in which no current flows to the base of the transistor Q2 and there is no guarantee whether the output pulse will stop at the H level or the - level.

As mentioned above, the envelope generation circuit for a child musical instrument according to the present invention connects a pulse generator to an inverting input terminal of an amplifier and a charging circuit that is charged with a voltage from a source. A power source with a voltage higher than the voltage of the power source is connected to the non-inverting input terminal of the amplifier via a variable resistor that changes the duty ratio and frequency of the output pulse, and the inverting input terminal and output terminal of the amplifier are connected to each other. Since a diode is connected between the terminal and the non-inverting input terminal and its output terminal, the resistance value of the variable resistor is reduced and the voltage at the non-inverting input terminal of the amplifier is changed to the charging circuit's charging IIE11t voltage. That is, when the inverting input terminal voltage of the amplifier is set to a certain level, the amplifier repeats the inverting operation alternately, thereby extracting a pulse with a certain duty ratio, or lowering the non-inverting input terminal voltage to below the inverting input terminal voltage. When set to , the amplifier does not perform an inverting operation and its output remains at L level. On the other hand, when the resistance value of the variable resistor is set to the maximum, the voltage at the non-inverting input terminal of the amplifier/- is at the inverting input terminal. voltage, and the output of the amplifier remains at H level.In this way, no matter which position the variable resistor is adjusted to, the oscillation operation remains stable, and the conventional circuit using a free-run multivibrator In addition, since the amplifier compares the charging voltage of the charging circuit, that is, the voltage that changes exponentially, with the voltage set by the variable resistor, the duty ratio of the pulse and The frequency can be changed exponentially, and the attenuation rate of the envelope can thereby be changed greatly with respect to the variable rate of the variable resistor, and the variable resistor of the free-running child vibrator can change the adjustment rate and the duty of the output pulse. Compared to conventional circuits in which the ratio and rate of change in frequency can only be obtained linearly, this circuit has the advantage of being able to effectively obtain changes in decay time.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of an example of the output circuit of a general electronic musical instrument, Figures 2 to 3 are signal waveform diagrams for explaining the operation of the circuit shown in Figure 1,
FIG. 3 is a circuit diagram of an example of a conventional pulse generator, FIG. 4 is a circuit diagram of an embodiment of the circuit of the present invention, and FIG. It is a signal waveform diagram. 4...Working envelope generation circuit, 5*"2...Pulse output i, 523"...Output terminal, 7...Amplifier, VCCI, VCC2""Power supply, R, 11@ 11 town resistor, l'l' +R2*)tS + R6...
・Resistance, 0, O8...Capacitor, Dl, D2
...Diode ◇ 1 Figure 3 Figure 4 Spots

Claims (1)

[Claims] A pulse generator equipped with a variable resistor that variably adjusts the duty ratio and frequency of the output pulse is provided with two discharges that are discharged with a certain time constant during the H level period and the L level period of the output pulse from the nuclear pulse generator, respectively. connect the circuit,
In an envelope generation circuit for an electronic musical instrument that generates an attenuation envelope by repeating each discharge, the pulse generator is connected to an inverting input terminal of an amplifier with a charging circuit that is charged with a voltage from a power supply, and the amplifier is A power source with a voltage higher than the voltage of the power source is connected to the non-inverting input terminal of the amplifier via a variable resistor, and the voltage is connected between the inverting input terminal and the output terminal of the amplifier, and between the non-inverting input terminal and the output terminal. An envelope generating circuit for an electronic musical instrument, characterized in that the envelope generating circuit is configured by connecting diodes between the two.