JPS591273Y2 - Switching circuit device for electronic musical instruments - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an opening/closing circuit device for opening and closing a musical tone signal to form an envelope in response to key presses in an electronic musical instrument.

In electronic musical instruments, in order to obtain a musical tone signal close to a sine wave, such as the sound of a flute, from a sound source signal containing many harmonic components such as a square wave, a low-pass filter is used to remove the harmonic components. There is a need to.

In this case, since the musical tone signal in the high frequency range is attenuated by the low pass filter, its level must be set higher than that of the musical tone signal in the low frequency range.

Therefore, conventionally, the output of the switching circuit is provided with a volume correction circuit composed of a series resistor and a switching element that short-circuits the series resistor as appropriate depending on the octave.

FIG. 1 is a circuit diagram showing such a conventional switching circuit device, in which 1 is an envelope signal forming circuit, 2 is a switching circuit,
3 is a volume correction circuit.

The envelope signal forming circuit 1 includes a capacitor C for forming an envelope, a switching FET Qa whose opening/closing is controlled by a key-on signal KOH, and a resistor R1 forming a charging circuit for the capacitor C connected to the ground and a negative power source of -8. A resistor R2 is connected in series between the capacitors C and in parallel to the capacitor C to form a discharge circuit.

Then, an envelope signal is formed by the terminal voltage of capacitor C at point a in FIG.

The switching circuit 2 consists of two switching FETs Qb and Qc connected in series between the output terminal (point a) of the envelope signal forming circuit 1 and the ground, and an inverter IN. FETQc is gate-controlled by an inverted signal φ2 from the inverter IN that inverts the musical tone input signal φ1, and the open/close output is taken out from the connection point (output point) b between FETQb and QC. .

Therefore, when the musical tone input signal φ1 is at a low level O, FETQb is turned off and FETQc is turned on, so that the output point becomes the ground potential, and when the musical tone input signal φ1 is at a high level 1, FETQb is turned on.

FETQc is turned off, and the voltage at point a of the envelope signal forming circuit 1 appears as is at the output point.

As a result, the input musical tone signal φ1 is controlled to open and close according to the envelope signal, thereby forming an envelope.

The volume correction circuit 3 includes series resistors ra, rb, and rc connected in series from the output point of the switching circuit 2, an FET Q2 that shorts the resistor ra, and an FET that shorts the resistors ra and rb.
Q3, FETQ4 short-circuiting resistors ra-rc, and each FETQ2 to Q4 is connected to an octa-butcher OC.
Gate control is performed by 2 to OC4.

For example, in a four-octave electronic musical instrument, when the first octave from the lowest pitch is OC1, none of the FETs is turned on, and when the second octave is OC2, FET Q1 is turned on,
FETQ3 is turned on at the octaft OC3, and -FETQ4 is turned on at the fourth octaft OC4.

In such an opening/closing circuit device, when a musical tone input signal φ1 as shown in FIG. 2A is input to the opening/closing circuit 2, the inverted signal φ2 is as shown in the figure.

Now assume that the keys of the second, third, and fourth octaves are pressed in sequence, and a key-on signal KON as shown in FIG. 2 is input to the envelope signal forming circuit 1.

As a result, the envelope signal (2) formed at point a becomes as shown in FIG.

However, in the volume correction circuit 3, the second octave OC
At the second octave, FET Q2 is turned on, so that it is attenuated only by the resistors rb and rc, and at the third octave, FET Q3 is turned on, so it is attenuated only by the resistor rc.

Furthermore, at the fourth octave, FET Q4 turns on, so there is no attenuation.

Therefore, the level of the musical sound output signal (2) outputted through the volume correction circuit 3 is corrected by the octave as shown in FIG.

However, in such conventional circuits, if a new key of a different octave is pressed while the output of the musical tone signal of the previously pressed key is attenuating, the octave data changes at that time and the volume correction circuit 3 Since the FETs that are turned on change at different times, the level of the musical tone output signal (2) changes rapidly as shown by the arrow N in FIG. 2 (E).

This has the drawback of generating click noise.

This invention was made to eliminate the above-mentioned drawbacks, and by controlling the maximum amplitude value of the envelope signal supplied to the opening/closing circuit according to the octave, it is possible to avoid generating click sounds by adjusting the maximum amplitude value of the envelope signal supplied to the opening/closing circuit according to the key range. The present invention provides an opening/closing circuit device capable of performing sound volume correction.

An embodiment of this invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 is a circuit diagram showing one embodiment of this invention.
In place of the volume correction circuit 3 in the conventional example shown in the figure, an amplitude control circuit 4 for controlling the amplitude value of the envelope signal according to the octave is provided.

The amplitude control circuit 4 includes a resistor r2, which divides the power supply voltage -8V for forming an envelope signal. r3゜r4 series circuit, and a switching FET Q1゜Q2. for selecting the power supply voltage at one of the voltage dividing points c, d, e, or f and supplying it to the envelope forming circuit 1. Q3. It consists of Q4.

These FETs Q1 to Q4 each have octave data OC1 to
Gated by OC4.

Therefore, in the 1st octaft OCl, ``is FETQ
When l is turned on, the smallest voltage at point 0 is output to point g, and 2
At the octaft OC2, FETQ2 is turned on and d
At OC3 in the third octave, FET Q3 is turned on and the voltage at point e becomes FET, and at OC4 in the fourth octave, the voltage at point e becomes FET.
ETQ4 is turned on, and the voltage of 18 V at point f is outputted to two points, respectively, and supplied to envelope signal forming circuit 1.

In this way, a higher negative voltage is supplied to the envelope signal forming circuit 1 as the octave becomes higher.

The configuration of the envelope signal forming circuit 1 and the switching circuit 2 is as follows.
Since it is the same as the conventional example shown in the figure, its explanation will be omitted.

Next, the effects of the above embodiment will be explained with reference to the waveform diagram of FIG.

As in the case of the conventional example described above, the keys of the second, third, and fourth octaves are now pressed in order, and a key-on signal KON as shown in FIG. 4A is input to the envelope signal forming circuit 1. Suppose that

At this time, FETQ2. Q3.
Q4 is turned on according to the order in which each key is pressed, and the g point is sequentially turned on, and the d point is turned on.
The voltages at points e and f are output.

The maximum amplitude value of the envelope signal (2) formed at point a of the envelope signal forming circuit 1 is controlled by the voltage at point g, as shown in the fourth column.

When the musical tone input signal φ1 as shown in FIG. 2A is input to the opening/closing circuit 2, it becomes the envelope signal
The musical tone output signal (2) is opened and closed and an envelope is formed as shown in FIG. 4 (C).

Therefore, for example, as shown in Figure 4, even if the key of the third octave OC3 is pressed while the musical tone output signal of the second octave OC2 is being sustained, the envelope signal ■ will change with the time constant of the C-R process. Therefore, the level of the musical sound output signal does not suddenly change at that time, so no click sound is generated.

Since the amplitude value of the envelope signal changes depending on the octave data, the volume of the musical tone is corrected accordingly.

The same applies to other octaves.

In the above embodiment, the maximum amplitude value of the envelope signal supplied to the opening/closing circuit is controlled according to the octave, but it may also be controlled according to an appropriate key range every half octave and every two octaves. Of course.

As described above, according to this invention, when obtaining a musical tone signal close to a sine wave such as a flute through a low-pass filter by correcting the volume according to the key range, an octave change is performed while the previous signal is attenuated. Click noise does not occur even when a new, different signal is input, so you can enjoy a comfortable performance.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional switching circuit device with a volume correction circuit.
2A to 2H are signal waveform diagrams of various parts to explain the operation of FIG. 1, and FIG. 3 is a circuit diagram showing an embodiment of this invention.
4A to 4C are signal waveform diagrams of various parts for explaining the operation of FIG. 3. 1... Envelope signal forming circuit, 2...
...Opening/closing circuit, 3...Volume correction circuit, 4...
...Amplitude control circuit.

Claims (1)

[Claims for Utility Model Registration] 1. In an opening/closing circuit that controls opening/closing of a musical input signal according to an envelope signal, means is provided for controlling the maximum amplitude value of the envelope signal supplied to the opening/closing circuit according to a key range, An opening/closing circuit device for an electronic musical instrument, characterized in that the volume is corrected according to the key range. 2. The means for controlling the amplitude value of the envelope signal according to the key range includes a series circuit of a plurality of resistors that divides the power supply voltage for forming the envelope signal, and a voltage at one of the voltage division points or the power supply voltage. It consists of multiple switching elements that select and supply the signal to the envelope signal forming circuit.
The switching circuit device for an electronic musical instrument according to claim 1, wherein the plurality of switching elements are controlled by a key range band.