JPS5855433Y2 - envelope signal generator - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an envelope signal generator for an electronic musical instrument.

When an electronic musical instrument generates a striking sound like a piano, a percussive envelope signal is applied to an opening/closing circuit when a key is pressed.

In order to generate this percussive envelope signal, a device that utilizes the charging and discharging of a capacitor as shown in FIG. 1 has conventionally been used.

In FIG. 1, KSW is a key switch, and a capacitor C1 and a resistor R1 constitute a differentiating circuit, and the number of times is set to be extremely small.

C2 is a capacitor for generating an envelope signal, Tr is connected to base resistor R2 and emitter resistor R3, and when key switch KSW is turned on, it is turned on for a short time and resistor R4 is connected.
This is a transistor that together with the capacitor C2 forms a charging circuit.

When the transistor Tr is off, the resistor R3 and the resistor R4 form a discharge circuit for the capacitor C2.

Note that the resistance value of the resistor R4 is selected to be sufficiently smaller than that of the resistor R3.

Vl is a first voltage source (ground voltage), -v2 is a second voltage source, and OUT is an output terminal for an envelope signal.

In such a circuit, the key switch K is activated by pressing the key.
When SW is turned on, capacitor C1 is charged in a short time, and a short pulse-like negative voltage appears at the connection point between capacitor C1 and resistor R1.

This negative voltage is applied to the base of the transistor Tr via the resistor R2, the transistor Tr becomes conductive instantaneously, and the capacitor C2 is rapidly charged by the current in the direction of arrow A through the resistor R4 and the transistor Tr, and its output voltage is The emitter voltage of the transistor Tr almost reaches the value of the second voltage source -V2, but as soon as the transistor Tr becomes non-conductive, it starts discharging as shown by arrow B through the resistors R4 and R3, and its terminal voltage gradually decreases. The first voltage source V1 returns to the ground voltage, ie, zero.

As shown in Figure 2, the envelope signal generated in this way has a sharp peak at its waveform (in this example, it is a negative voltage signal, but in a negative direction), that is, the part where the attack curve changes to the attack curve. The waveform will change.

Therefore, when such an envelope signal is added to the opening/closing circuit to control the sound source signal, due to the relationship between the phase of the sound source signal and the rise time of the envelope signal, the attack level AL of the envelope signal differs from the actual sound source signal. The attack level AL' changes.

That is, the value of the attack level changes depending on whether the apex of the sound source signal waveform exactly matches the apex of the envelope signal waveform or when they do not overlap.

This effect is particularly noticeable in the low frequency range of the sound source signal C, which has the disadvantage that the sense of attack varies and is not stable.

This idea was made in view of the above points, and in order to provide a stable and uniform envelope,
The present invention provides an envelope signal generator that slices the attack level of a percussive envelope signal formed by charging and discharging a capacitor so that the slice portion contains at least one wave of a sound source signal.

Embodiments of this invention will be described below with reference to the accompanying drawings.

FIG. 3 is a circuit diagram showing an embodiment of the envelope signal generator according to this invention, which is obtained by adding an attack level slice circuit to the conventional example shown in FIG. 1.

In Fig. 3, the same parts as in Fig. 1 are given the same reference numerals.
Since their operations are the same, the explanation will be omitted.

In this example, the voltage at the connection point between capacitor C2 and resistor R4 is not directly output, but is output via resistor R5 to output terminal OU.
Connect it to T to take it out, and then connect it to the output terminal OUT.
is connected to the third voltage source -3 through a diode D.

Third voltage source - ■3 is the first voltage source (ground) Vl and the second
Resistors R6 and R7 connected in series between the voltage source -V2
Therefore, the voltage value is an intermediate value between the first voltage source V1 and the second voltage source -V2.

This embodiment will now be described with reference to FIG.

When the key switch KSW is turned on, a negative percussive envelope signal is generated at the connection point between the capacitor C2 and the resistor R4, as in the conventional example described above.

However, in the attack curve of this signal, when the voltage value in the negative direction falls below the third voltage source -V3, the diode D becomes conductive.

Therefore, if the resistance value of the resistor R5 is selected to be sufficiently high compared to that of the resistors R6 and R7, the voltage portion higher than the voltage -v3 generated at the terminal of the capacitor C2 will be dropped by the resistor R5 and will not appear at the output terminal OUT. do not have.

Then, the voltage value at the mechanical carburetor opening is -
■When the voltage becomes higher than 3, diode D returns to a non-conducting state.

Therefore, as shown in FIG. 4, the attack level of the voltage waveform taken out from the output terminal OUT is sliced by voltage -v3, and the portion between time t becomes flat.

This time t is preferably set to one wave to several waves of the sound source signal, and is determined by the value of the third voltage source −■3, but depending on the key range, the time t may be shorter in the low range than in the high range. If this output voltage formed as described above is used as a percussive envelope signal, there will be no variation in the attack level due to the phase relationship even if the sound source signal is in the low frequency range.

FIG. 5 is a circuit diagram showing another embodiment of this invention,
The same parts as in FIG. 1 or 3 are given the same reference numerals.

In the figure, SWl and SW2 are key switches that operate simultaneously in conjunction with key presses.

In this embodiment, the width of the time t sliced by the diode D in the generated envelope waveform is changed according to the strength of the key touch force to increase the sense of attack, and the attenuation curve is corrected. This is an envelope signal generator with effects.

Capacitor C3, resistor 8, 9 and key switch SW
1 is constantly charged with a fourth voltage source -v4 whose absolute value is larger than the second voltage source -v2,
This is a touch response circuit that utilizes changes in the terminal voltage of a capacitor C3 that is discharged through a resistor R8 in accordance with the moving time of the movable contact of the key switch SW1 when a key is pressed.

And capacitor C3 when switch SW1 is switched
The terminal voltage of resistor R9, key switch SW1, resistor R
2 to the base of the transistor Tr, and also controls the conduction time of the transistor Tr in accordance with the key touch force.

Here, -V4->-V2- is closed by -V4-knee V
This is to make the dynamic range of the touch response larger than when it is set to 2-, and if it is set to -V4->-v2-, the absolute value of the movable contact of key switch SW1 changes from the state shown in the figure. It is possible to increase the voltage of the movable contact that is attenuated to a maximum of v2 or higher, and at that time)・
This is to make the emitter voltage of the transistor Tr as close to the voltage -V2 of the second voltage source as possible.

Capacitors C4 and C5 are capacitors for generating envelope signals in place of capacitor C2 in FIG. 1 or FIG. 3, and are connected in series between the emitter of transistor Tr and the ground, and resistors R1o and R1 for discharging, respectively. , are connected in parallel and their time constants are different.

For example, time constant 04. Increase Rlo, time constant C5, R1
If □ is kept small, the attenuation curve due to discharge when the transistor Tr is turned off can be made to have a steep tendency in the first half and a gentle tendency in the second half, and the turning point is the capacitor C4.
It can be determined by the capacity ratio of and 05.

That is, the attenuation curve can be corrected.

The transistor Tr' has its collector connected to the second voltage source -■
2, and its emitter is connected to the first voltage source V1 via a resistor R, and the buffer converts the voltage at point a, which is input to its base, into impedance and outputs it to point b. Is it something that has the effect of
This can also be omitted.

A diode D1 is inserted between the series circuit of capacitors C4 and C5 and the ground, and a forward bias is applied to this diode D1 through a resistor R12, so that the voltage drop when the diode D1 is conductive causes a voltage drop between the emitter and the base of the transistor Tr'. The voltage is guaranteed.

The variable resistor VR is connected between the fifth voltage source +V and the first voltage source (ground voltage), and the resistor R14 is connected from its variable terminal to the fifth voltage source +V and the first voltage source (ground voltage).
A positive voltage is applied in advance to capacitors C4 and C5 via diode D3 to adjust the sustain common to all keys in order to change the signal decay time, and diode D3 is used to prevent influence on other keys. This is an insert.

Further, a series circuit including a key switch SW2, a diode D2, and a resistor R13 is connected in parallel between both terminals of the capacitors C4 and C5.

This is because when the switch SW2 is turned on when the key is off, the charging voltage of the capacitors C4 and C5 is rapidly discharged by the resistor R13 with a small resistance value, and a so-called damper effect is created that stops the continuation of the sound source signal. It is something.

The operation of the above-described embodiment configured in this manner will be explained with reference to FIG. 6.

When the key switch SW1 is switched from the illustrated state by pressing a key, a pulse having a peak value corresponding to the switching speed, that is, the key pressing speed is applied to the base of the transistor Tr, and the transistor Tr is turned on.

Thereby, the capacitors C4 and C5 are rapidly charged by the second voltage source -2 through the charging circuit formed by the transistor Tr, the resistor R4, and the diode D1, and the voltage at point a in FIG. Form the attack curve shown in A in the figure.

The attack level AL at this time varies depending on the time the transistor Tr is on, that is, the magnitude of the pulse applied to the base of the transistor Tr in accordance with the key pressing speed.

When the transistor Tr is turned off, the capacitors C4 and C
5 starts discharging by the discharge circuits of resistors R1o and R1, respectively, but the voltage at point a initially forms a decay carp mainly determined by the smaller discharge time constant C5・R1□, and then the larger one Discharge time constant 04・Rlo
The ground voltage of the first voltage source V1 (actually, it is a voltage lower than the ground voltage by the forward voltage drop of the diode D1, but since this voltage is small, it is shown in FIG. 6 and In the following explanation, the ground voltage is used.

). The voltage at point a in FIG.
The impedance is converted by
The voltage at UT is clamped to the voltage at a third voltage source -V3.

Therefore, the envelope signal waveform output to the output terminal OUT becomes a waveform in which the attack level AL is sliced by the voltage -V3 to become AL', as shown by the solid line in FIG. 6, and the time t for this slicing is It will change depending on the key press speed.

Here, if a positive voltage from the fifth voltage source 1 V is applied to point e via the variable resistor VR in FIG. 5, the final value of the energizer bar in FIG. When the voltage at point e becomes the voltage Ve, and the voltage at point a becomes positive, the transistor Tr' turns off, so the decay curve appearing at the output terminal OUT is clamped at the ground voltage, and as shown by the broken line 2 in Figure 6. The sustain time will be shortened.

In this way, the sustain time can be adjusted by varying the variable resistor VR.

Furthermore, when the key is released during sustain, switch SW2 also returns to the state shown in Figure 5 in conjunction with key switch SW1, so diode D2 and resistor R13 (resistance value is small)
The residual charges in the capacitors C4 and C5 are rapidly discharged through the series circuit of the capacitors C4 and C5.

Therefore, the force curve becomes as shown by the broken line E in FIG. 6, and a damper effect is obtained.

In addition, although the above embodiment shows the case where the first voltage source is grounded, the second voltage source may also be grounded.
There is no problem in using an NPN (NPN) transistor instead of a transistor and changing the connection direction of the diode, the polarity of the voltage source, etc.

Furthermore, the time constants of the charging and discharging circuits are not limited to the combination of two, but can also be set to three or more, thereby making it possible to change the attenuation curve in a more complex manner.

Furthermore, it goes without saying that other unidirectional elements may be used instead of the slicing diode D.

As explained above, according to this invention, it is possible to generate a percussive envelope signal that can always provide a stable and consistent envelope when keys are pressed under the same conditions.

In addition, according to the embodiment shown in Fig. 5, it is possible to change the attack depending on the strength of the key touch, correct the attenuation curve, and obtain a damper effect when the key is off, which can be applied to the musical tone control of electronic musical instruments. If so, the effect is great.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional envelope signal generator, Figure 2 is a circuit diagram of a conventional envelope signal generator.
The figure is a waveform diagram showing the relationship between the output signal and the sound source signal controlled by it, Figure 3 is a circuit diagram showing an embodiment of this invention, Figure 4 is an output signal waveform diagram, and Figure 5 is a waveform diagram showing the relationship between the output signal and the sound source signal controlled by it. A circuit diagram showing another embodiment of this invention, and FIG. 6 is an output signal waveform diagram thereof. C1-C5... Capacitor, R1-R15... Resistor, D, D. ~D3...Diode, Tr, Tr'...Transistor, KSW, SWl, SW2...Key switch,
Vl...first voltage source, -■2...second voltage source,
-V3...Third voltage source, -■4...Fourth voltage source, OUT...Output terminal.

Claims (1)

[Scope of utility model registration request] A first voltage source, a second voltage source, a key switch, and a charging circuit that is connected between the first and second voltage sources through a charging circuit that is closed for a short time when the key switch is turned on. a percussive envelope signal that rises when the key switch is turned on and then attenuates from the output terminal of the capacitor. In the envelope signal generator, a resistor is connected between the terminal of the capacitor and the output terminal, and a third voltage source having a voltage intermediate between the first and second voltage sources is provided. 3. A unidirectional element is connected between a third voltage source and the output terminal, and the percussive envelope signal is sliced by the voltage of the third voltage source.