JPS6149678B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electronic musical instrument that has a plurality of key switches corresponding to a plurality of keys, and can generate a single-tone frequency signal according to the position of the operated key by operating the key switch. It relates to a sound source device.

First, a conventional sound source device for this type of electronic musical instrument will be explained with reference to FIG. A constant current source circuit 1 is connected to the power supply +B, and the constant current from this constant current source circuit 1 is supplied to a resistance voltage divider in which a plurality of resistors of the same value are connected in series, and when each resistor is connected, Key switch 3 corresponding to multiple keys at the point, namely 3
A, 3b, 3c, . . . are connected, and the other ends of each key switch 3a, 3b, 3c, . Therefore, on the input side of the sampling and holding circuit 4, a higher DC voltage is obtained as the key switch 3 closer to the constant current source circuit 1 in FIG. 1 is turned on. And these key switches 3a, 3b, 3c,...
The closer the constant current source circuit 1 is to the key, the higher the pitch of the key. The pulse generator 5 generates a pulse signal based on the output voltage obtained when the key switch corresponding to the pressed key of the key switch 3 is turned on. Since a pulse signal is generated, the pulse signal is generated at a point when a stable DC voltage is obtained, which is slightly delayed from the first point at which the pulse signal is turned on. The pulse signal from the pulse generator 5 is then supplied to the sampling and hold circuit 4, and the DC voltage from its input terminal is sampled. Therefore, in the sampling hold circuit 4, the key switch 3
By turning on, a stable DC voltage can be obtained. The output of this sampling hold circuit 4 is then supplied to an antilogarithmic function signal generation circuit 6. This anti-logarithmic function signal generation circuit 6 converts the linear signal into an anti-logarithmic function signal according to the position of the key corresponding to the key switch 3, and converts the linear signal into an anti-logarithmic function signal according to the frequency of 12 pitches within one octave. This is a circuit that generates a voltage. The output of the anti-logarithmic function signal generation circuit 6 is then supplied to a variable oscillator (voltage controlled variable oscillator) 7, which generates a frequency signal corresponding to the position of the key described above. The output of this variable oscillator 7 is supplied to an amplitude modulation circuit 9 through a variable wave generator (voltage controlled variable wave generator) 8. Note that the variable wave generator 8 is controlled by the output of the pulse generator 5. Furthermore, the pulse generator 5
The output of the timbre-determining envelope signal generator 10 is triggered by the pulse signal to generate an envelope signal of a predetermined waveform. This envelope signal is then supplied to the amplitude modulation circuit 9, where the input frequency signal is amplitude-modulated by the envelope signal, and the output terminal 11 outputs the desired frequency of the envelope corresponding to the desired tone. frequency signal is generated. If this is supplied to a speaker via an amplifier or the like, a single tone will be generated from the speaker in response to turning on the key switch 3 in response to key operation.

FIG. 2 shows an example of the waveform of the envelope signal generator 10 described above, in which A represents the attack time, D represents the decay time, S represents the sustain level, and R represents the release time. An appropriate waveform is selected depending on the timbre of the frequency signal to be generated.

By the way, in the conventional electronic musical instrument sound source device shown in FIG. 1, the initial chatter of the key switch 3 does not lead to malfunction due to the presence of the pulse generator 5, but if chattering occurs thereafter, there is a risk of malfunction. be. Furthermore, since the anti-logarithmic function signal generating circuit 6 utilizes the anti-logarithmic function characteristic of the base-emitter voltage versus collector current of the transistor, the frequency signal obtained from the output terminal 11 changes due to temperature-dependent changes in the characteristic. There is a possibility that the frequency may change depending on changes in temperature.

In the electronic musical instrument sound source device shown in FIG. 1, when multiple keys are pressed at the same time, multiple key switches 3
If both are turned on at the same time, the key switch closest to ground has priority. Therefore, if the key switch 3 closer to the constant current source circuit 1 is made to respond to higher tones as described above, priority will always be given to keys with lower tones.

In view of this, the present invention seeks to propose a sound source device for an electronic musical instrument that is free from malfunctions caused by key switch chatter.

In the following, one embodiment of the present invention will be described in detail with reference to FIG. In addition, in FIG. 3, parts corresponding to those in FIG. 1 will be described with the same reference numerals. Reference numeral 3 denotes a plurality of key switches corresponding to a plurality of keys, and 3a, 3b, . . . 3n correspond to keys from high to low tones, respectively. Reference numeral 12 denotes a timing signal generation circuit that generates a timing signal according to the position of an operated key by the operation of the key switch 3, and in this example, it is composed of the key switch 3, a clock oscillator 13, and a shift register 14. ing. clock oscillator 1
3 is an oscillator that generates a pulse signal of several tens of kHz, for example 20 kHz. The shift register 14 is a wired-OR shift register, and
The output of the clock oscillator 13 is supplied to the clock signal input terminal C, and the serial input terminal IN is grounded. is an inverted reset signal input terminal.
Oa, Ob, ..., On are parallel output terminals, and OUT is a series output terminal. And key switch 3a, 3
One end of the key switches 3a, 3b, . . . , 3n is connected to the parallel output terminals Oa, Ob, . 28. This output terminal 28 and the serial output terminal OUT of the shift register 14 are connected to an AND circuit 22.
connected to each input terminal. The output terminal of the AND circuit 22 is connected to the inverted reset signal input terminal of the shift register 14 and also to the input side of the pulse generator 15. The output terminal of the pulse generator 15 is connected to an exponential function signal generation circuit 16.
The output terminal of the exponential function signal generating circuit 16 is connected to the input terminal of the sampling hold circuit 1.
The output terminal of the sampling hold circuit 17 is connected to the input terminal of the voltage controlled variable oscillator 18.
The output terminal of the variable oscillator 18 is connected to the input terminal of an amplitude modulation circuit 19, and the output terminal of this amplitude modulation circuit 19 is connected to the output terminal 23. Further, the output terminal 28 is connected to a sampling signal input terminal of the sampling hold circuit 17. 20 is an RS flip-flop circuit, and an output terminal 28 is connected to the flip-flop circuit 20.
The serial output terminal OUT of the shift register 14 is connected to the inverted reset signal input terminal of the shift register 14. The output terminal Q of the flip-flop circuit 20 is connected to the input terminal of an envelope signal generator 21, and the output terminal of the envelope signal generator 21 is connected to the modulation signal input terminal of the amplitude modulation circuit 19. The RS flip-flop circuit 20 is a control circuit for controlling the operation of the envelope signal generation circuit 21.

The specific circuit _of the _above -mentioned exponential function signal generation circuit 16 is as shown in FIG. The connected resistors R ₁ and R ₂ are connected, and the connection midpoint of the resistors R ₁ and R ₂ is connected to the base of the transistor Q ₁ . The emitter of transistor _Q1 is grounded, and its collector is connected to the power supply +B through resistor _R4 -resistor _R3 . The emitter of transistor Q ₂ is connected to the power supply +B, and its base is connected to the midpoint between resistors R ₃ and R ₄ . The collector of transistor Q ₂ is connected to resistor R ₅ and capacitor
It is grounded through a parallel circuit of _C1 , and an output terminal 26 is led out from its collector. In this exponential function signal generation circuit 16, when a positive pulse is supplied to the input terminal 25, the transistor Q ₁
and _Q2 are both turned on, charging the capacitor _C1 , and the voltage at its terminal instantly rises to the voltage of the power supply +B. After that, when no pulse is supplied to the input terminal 25, both transistors Q ₁ and Q ₂ are turned off, and the charge stored in the capacitor C ₁ is discharged through the resistor R ₅ , and the charge stored in the capacitor C ₁ and the resistor R ₅ is discharged. The terminal voltage of the capacitor _C1 decreases with a time constant determined by the capacitance and resistance value, respectively, and an exponential function signal is generated at the output terminal 26.

Next, referring also to Figures 5 and 6, this third
The operation of the sound source device of the electronic musical instrument shown in the figure will be explained. 5A to 5G and FIGS. 6A to 6G each show waveforms at corresponding portions in FIG. 3. 5A and 6A show the waveform of the clock signal supplied to the clock signal input terminal C of the shift register 14, and in the figures, it is a rectangular wave signal with a duty of 50%. In this shift register 14,
When any one of the key switches 3 is turned on, the voltage at the output terminal 28 changes from "1" to "0", and any key switch 3 is turned on during one cycle of the shift register 14. If not, the voltage at the series output terminal OUT changes from "1" to "0" at an appropriate time one cycle later. Furthermore, since the shift register 14 can be wired-ORed, the key switch located on the left among the key switches 3a, 3b, . operations are given priority. Further, an AND circuit 22 is provided so that the output of the output terminal 28 and the output of the serial input terminal OUT of the shift register 14 are supplied to the AND circuit 22, and the output thereof is supplied to the inverting reset input terminal. Therefore, even if the output of the output terminal 28 or the serial output terminal OUT changes from "1" to "0", this shift register 14 is reset in a short time, and eventually the output terminal 28 and the serial output terminal OUT change from "1" to "0".
Negative pulse signals as shown in FIG. 5B and FIG. 6G are output from OUT, respectively.

If a suitable key switch among the key switches 3 is turned on, a negative pulse is generated at the output terminal 28 as shown in FIG. 5B.
The pulse generator 15 is triggered by the negative pulse shown in FIG. 5B, and a pulse signal as shown in FIG. 5C is generated. This pulse signal is a rectangular wave signal having a predetermined time width determined by the time constant of the pulse generator 15, for example, when it is constituted by a monostable multivibrator. This pulse signal shown in FIG.
As is clear from the circuit of FIG. 4 mentioned above, the output voltage immediately reaches the power supply voltage E as shown in FIG. 5D, and after the pulse in FIG. 5C disappears, the output voltage becomes exponential. It gradually decreases with functional characteristics. This exponential function signal generation circuit 16
The output of is supplied to the sampling and hold circuit 17, but in the previous cycle of the exponential function signal generating circuit 16, when the transistors _Q1 and _Q2 were off and the charge in the capacitor _C1 was gradually discharging. When a pulse as shown in FIG. 5B is generated from the output terminal 28, the output voltage of the exponential function signal generation circuit 16 at that time is sampled and held, and the output voltage of the sampling and hold circuit 17 is as shown in FIG. 5E. A constant output voltage as shown is obtained. The oscillation frequency of the variable oscillator 18 is set to the frequency corresponding to the operated key by the DC voltage as shown in FIG. The signal is supplied to the amplitude modulation circuit 19. When a pulse signal as shown in FIG. 5B is obtained at the output terminal 28, it is supplied to the inverted reset signal input terminal of the flip-flop circuit 20, so that the fifth As shown in Figure F, the output voltage changes from "0" to "1". This triggers the envelope signal generation circuit 21, which generates an envelope signal, which is transmitted to the amplitude modulation circuit 19.
The oscillation signal from the variable oscillator 18 is amplitude-modulated. Then, a frequency signal having a frequency and tone corresponding to the pressed key is generated at the output terminal 23. Note that while the key switch 3 is pressed, no output is obtained from the serial output terminal OUT of the shift register 14, so the output terminal Q of the flip-flop circuit 20 is always "1" as shown in FIG. 5F. . Therefore, the envelope signal generator 21 continues to operate, and the output terminal 23 continues to generate a frequency signal corresponding to the operated key.

Next, the operation when the pressed key is released will be explained. When the key switch 3 is released from the press, the voltage at the output terminal 28 remains at "1" as shown in FIG. 6B. However, if none of the key switches 3 are pressed during one cycle period of the shift register 14, the state shown in FIG.
As shown in the figure, the negative polarity pulse signal is connected to the series output terminal.
OUT, which allows the pulse generator 15
is triggered. As a result, the pulse generator 15
From this, a pulse signal as shown in FIG. 6C is generated.
Then, this pulse signal is transmitted to the exponential function signal generator 1.
6, transistors Q ₁ and Q ₂ of the circuit of FIG. 4 are both turned on, and the voltage of capacitor C ₁ reaches the voltage E of power supply +B. Then, when this pulse signal of FIG. 6C disappears,
The charge on the capacitor _C1 gradually decreases through the resistor _R5 , and an output having a waveform as shown in FIG. 6D is obtained from the exponential function signal generating circuit 16. Incidentally, since none of the key switches 3 are pressed, the voltage at the output terminal 28 is "1" as shown in FIG. 6B, so the output voltage of the sampling hold circuit 17 is "0". Therefore, the variable oscillator 18 will not oscillate. In addition, when none of the key switches 3 is pressed, the signal from the serial output terminal OUT of the shift register 10 to G in FIG.
A pulse signal of negative polarity as shown in FIG. As shown in FIG. F, the signal changes from "1" to "0" and the envelope signal generator 21 is not triggered. Therefore, no signal is supplied to the amplitude modulator 19 from the envelope signal generator 21, and no output is obtained from the output terminal 23.

According to the acoustic device of the electronic musical instrument of the present invention described above,
A timing signal is generated according to the position of the operated key by the operation of multiple key switches corresponding to multiple keys, and the exponential function signal from the exponential function signal generation circuit is sampled and held using this timing signal, and the hold output is Since the oscillation frequency of the variable oscillator is controlled, malfunctions due to key switch chattering do not occur.

In the above, a shift register capable of wired OR is used as the shift register, but if a shift register not capable of wired OR is used, an OR circuit may be provided externally to each parallel output terminal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional electronic musical instrument sound source device, FIG. 2 is a characteristic curve diagram, FIG. 3 is a system diagram showing an embodiment of the present invention, and FIG. 4 is a diagram similar to that of FIG. Circuit diagrams showing some specific configurations, Figures 5 and 6
The figure is a waveform diagram. 3 is a plurality of key switches, 12 is a timing signal generation circuit, 13 is a clock oscillator, 14 is a shift register, 16 is an exponential function signal generation circuit, 17
18 is a sampling hold circuit, 18 is a variable oscillator, 19 is an amplitude modulation circuit, 20 is a flip-flop circuit as a control circuit, and 21 is an envelope signal generation circuit.

Claims (1)

[Claims] 1. A plurality of key switches corresponding to a plurality of keys, an exponential function signal generation circuit that generates an exponential function signal of a predetermined period, and a function corresponding to the position of the key operated by the operation of the key switch, a timing signal generation circuit that generates a timing signal within a predetermined period; a sampling and hold circuit that supplies the exponential function signal from the exponential function signal generation circuit and samples and holds it based on the timing signal from the timing signal generation circuit; A variable oscillator whose oscillation frequency is controlled by the output of the sampling and hold circuit, and the variable oscillator generates a frequency signal having a frequency corresponding to the position of the operated key. Sound source device for electronic musical instruments.