JPS6042951B2 - Electronic musical instrument sound source device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention converts a voltage signal (hereinafter referred to as pitch voltage) generated in response to each key operation on the keyboard into a current, thereby generating a frequency corresponding to the pitch voltage. This relates to a sound source device for an electronic musical instrument that is equipped with a voltage-controlled oscillator that generates a sound source signal, and in particular, when switching between tones, etc., multiple resistors and electronic The present invention relates to a sound source device for an electronic musical instrument in which errors in the converter are removed by making the connection terminal potential of a switch equal to a preset reference potential.

An outline of a sound source device having a voltage-controlled oscillator used in a conventional electronic musical instrument will be explained using FIG. 1 as an example.
This sound source device converts a tone pitch voltage KV generated in response to the pitch of an operating key on a keyboard into a current using a voltage/current converter 1, and uses this converted output current to connect the converter 1 to a constant voltage. source 2
Controls charging of the capacitor 3 connected between the two.

The charging voltage of this capacitor 3 is supplied to a Schmitt trigger circuit 5 via a buffer amplifier 4, and in this Schmitt trigger circuit 5, when this charging voltage reaches a certain voltage value, a transistor 6 connected in parallel to the capacitor 3 is activated. The capacitor 3 is made conductive and the charging voltage of the capacitor 3 is discharged. Then, the capacitor 3 is charged again in accordance with the output current of the voltage/current converter 1, and thereafter, such charging and discharging is repeated. The terminal voltage that changes as the capacitor 3 is charged and discharged is sent out as a sound source signal from an output terminal 7 provided on the output side of the buffer amplifier 4. By the way, the voltage/current converter 1 includes an operational amplifier 11,
It is composed of a current amplifying transistor 12 and a resistor 13.

Therefore, a current I proportional to the pitch voltage and set by the resistor 13 flows through the transistor 12. This current I becomes the output current of the voltage/current converter 1 and controls the charging of the capacitor 3 as described above. In such an oscillator, the oscillation frequency f is determined by the pitch voltage K■, the capacitance C of the capacitor 3, and the value R of the resistor 13.
That is, the oscillation frequency f is proportional to the current 1 flowing through the capacitor 3, the current amplifying transistor 12, and the resistor 13.

Further, since this current 1 is proportional to the pitch voltage KV, the oscillation frequency f changes in proportion to the pitch voltage KV, and the frequency f is inversely proportional to the value R of the resistor 13. In a sound source device having such an oscillator, when changing the sound range of the sound source signal, generally the capacitance C of the capacitor 3 is fixed and the value R of the resistor 13 is changed.

That is, conventionally, as shown in FIG.
A plurality of resistors 13a, 13b, . . . having different values are provided in parallel as resistors connected to the emitter side of the
By switching the changeover switch 8, a single resistor (13a
, 13b, 13c, and 13d). Therefore, the resistance values R1 to R4 of the resistors 13a to 13d are set to, for example, R1=2・R2=4・R3=8.
・Set to the relationship of R4, and use the selector switch 8 to connect each resistor 13a.
When ~13d is selected, the oscillation frequency f becomes Fl, 2fl,
4fl and 8fl, and by setting the selector switch 8, an arbitrary range (octave) can be obtained. It is conceivable to provide a plurality of such sound source devices and simultaneously generate a plurality of sounds in response to performance operations on the keyboard section.

In such electronic musical instruments, all the changeover switches of each sound source device must be linked, but reliability is impaired due to changes in electrical characteristics caused by the contacts, and the operation of the movable contacts requires a relatively large amount of effort. This is not preferable in terms of circuit configuration, since operability is impaired as a result of this necessity. For this purpose, a third switch is used instead of a mechanical switch as the changeover switch 8.
Some devices include an electronic switch circuit as shown in the figure. This electronic switch circuit connects, for example, an N
Electronic switches 9a to 9d such as pn transistors are connected, and each fixed contact of the changeover switch 10 is connected to each base of the electronic switches 9a to 9d so as to selectively control conduction of each electronic switch 9a to 9d. . In this case, the voltage ゜゜+■゛ is supplied to the common contact of the changeover switch 10. In such a sound source device, each of the electronic switches 9a to 9d has resistors 13a to 9d connected to the current path.
13d, so when the changeover switch 10 makes the electronic switch 9a conductive as shown in the figure, the converted current 1 flowing in the output current path of the converter flows between the collector and emitter of the transistor 9a. When the voltage is Vce, it is expressed by the following equation. However, as is clear from this equation, the converted current 1 is
It is affected by the terminal voltage Vce of ~9d.

Therefore, the converted current 1 is no longer proportional to the pitch voltage KV, and especially when the pitch voltage KV is small, Vce can no longer be ignored, resulting in the inconvenience that the sound source signal of the originally intended frequency cannot be obtained. . The purpose of this invention was to reduce the error in the sound source signal frequency by making the current converted by the voltage/current converter accurately proportional to the input pitch voltage. The present invention provides a sound source device for an electronic musical instrument that enables the following.

In order to achieve such an object, the sound source device of the present invention adds the voltage at the connection end between the electronic switch and the resistor connected to the output current path of the voltage/current converter to the sound pitch voltage to calculate the voltage. - The connection terminal voltage is canceled by supplying it as an input signal to a current converter.
Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is an electrical circuit diagram of a main part showing the principle of the sound source device of an electronic musical instrument according to the present invention. In the figure, the same parts as those in FIG. That is, in the same figure, the input terminal of voltage/current converter 1 is connected to adder 2.
One input terminal 20a of this adder 20 is supplied with a tone pitch voltage KV, and the other input terminal is connected to an electronic switch of a first electronic switch circuit 21, which will be described later. Terminal voltage between the collector and emitter of 21a is supplied. In this first electronic switch circuit 21, an electronic switch 21a such as a transistor is connected in series between one end of a resistor 13 connected to the output current path of the voltage/current converter 1 and ground, and the collector of this electronic switch 21a is is connected to the drain of an electronic switch 22a, such as a MOS transistor, constituting the second electronic switch circuit 22. The source of this electronic switch 22a is connected to the other input terminal 20b of the adder 20. The first of these
The electronic switches 21a and 22a of the second electronic switch circuits 21 and 2 are configured to be supplied with a predetermined bias value so as to be rendered conductive at the same time by the drive voltage “゜+V” supplied to the changeover switch 23. In this case, the base of the electronic switch 21a is connected to the fixed contact 23a of the changeover switch 23 through a resistor 21r1, and is grounded through a resistor 21r2.The gate of the electronic switch 22a is , is connected to the fixed contact 23a through a diode 22d1 and a resistor 22r1, and is also grounded through a resistor 22r2.The cathode of this diode 22d1 is connected to the driving voltage ゜"1" through a resistor 22r3. has been done. In the sound source device configured in this way, when the movable contact of the changeover switch 23 is set to the fixed contact 23a as shown in the figure, each electronic switch 2 of the first and second electronic switch circuits 21 and 22
1a and 22a are supplied with a predetermined bias voltage at the drive voltage "°+V" supplied to the changeover switch 23, and are rendered conductive at the same time.

When the tone pitch voltage KV is supplied to one input terminal 20a of the adder 20 during this conduction, the electronic switch 21a which is in the conduction state is supplied to the other input terminal 20b of the adder 20.
Since the collector-emitter terminal voltage Vce of the adder 20 is supplied through the electronic switch 22a, the adder 20
Let KV'' be the additional voltage of KV'', this additional voltage KV'' is expressed by the following equation. When this added voltage K'' is supplied to the input terminal 1a of the voltage/current converter 1, the voltage/current converter 1 obtains an output voltage ``,'' at its output terminal 1b, and this output voltage ``5'' is Since it operates so as to be equal to the added voltage KV'', if the output current converted by the converter 1 is I, this output current 1 is expressed by the following equation.

In this equation (4), R1 is the resistance value of the resistor 13.

Therefore, the output current 1 can be calculated using the above formula (4).
3) By calculating the expression by proxy, it is expressed as the following expression. As is clear from this equation (5), the voltage-to-current converter 1 cancels out the voltage VCE between the terminals of the electronic switch 21a connected to the current path, so the voltage-to-current converter 1 can accurately proportion the pitch voltage XV. can be converted into a current of 1.

FIG. 5 is an electrical circuit diagram of a main part showing a specific example of the sound source device of an electronic musical instrument according to the present invention. In the figure, the same parts as those in FIG. 4 are denoted by the same numbers and their explanations are omitted.

That is, in the figure, a plurality of independent sound source devices (
In the figure, one sound source device is used as an example) to switch a four-octave sound range. In this case, the first electronic switch circuit 21 includes four wires between one end of each of the resistors 13 to 16 connected to the output current path of the voltage/current converter 1 and ground.
The second electronic switch circuit 22 is connected to the other input terminal 20b of the adder 20 and the electronic switches 21a to 21d.
Four electronic switches 22a to 22d are connected between each collector side of 1d. Further, the changeover switch 23 includes the electronic switches 21a to 21b and 22a to 22.
Four fixed contacts 23a so as to selectively control conduction of d.
23d to 23d are commonly connected to each base and source. Therefore, according to the sound source device configured in this way, by setting the changeover switch 23 arbitrarily, it is possible to send out a sound source signal in the range (octave) corresponding to the setting position. In the voltage/current converter 1, an adder 20 adds the sound pitch voltage KV and the terminal voltage of one electronic switch selected from among the electronic switches 21a to 21d of the first electronic switch circuit 21. Since the output voltage is supplied as an input signal, this converter 1 can output a current 1 that is accurately proportional to the pitch voltage KV, as shown in equation (5) above.

Although octave switching has been described in the above embodiment, it can also be used for operations such as transposition by appropriately selecting the resistance value of the current path.

As explained above, the sound source device of the present invention adds the voltage between the terminals of the electronic switch connected to the output current path of the voltage/current converter to the sound pitch voltage, and uses this added output as the output current of the voltage/current converter. Since the inter-terminal voltage is canceled by supplying it as an input signal, conversion errors due to this inter-terminal voltage can be removed. As a result, the voltage/current converter can convert the pitch voltage into a current that accurately corresponds to the pitch voltage, so that it has the effect of generating a sound source signal with a frequency that corresponds to the pitch voltage.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the main parts of a sound source device used in a conventional electronic musical instrument, Fig. 2 is a partial circuit diagram of the main parts when switching the tone range in the sound generator shown in Fig. 1, The figure is the first
FIG. 4 is a partial circuit diagram of the main parts when an electronic switch is used instead of a mechanical octave changeover switch when using a plurality of sound source devices shown in the figure. FIG. 4 is a principle of the sound source device of an electronic musical instrument according to the present invention FIG. 5 is a circuit diagram showing a specific example of the sound source device shown in FIG. 4. 1...Voltage/current converter, 13-16...
...Resistor, 20...Adder, 21...First electronic switch circuit, 21a-21d...Electronic switch, 22...Second electronic switch circuit ,2
3... Selector switch.

Claims (1)

[Claims] 1. A voltage/current converter that converts the pitch voltage into a current, and an oscillator whose oscillation frequency is controlled by the output current of the voltage/current converter to generate a sound source signal with a frequency corresponding to the pitch voltage. , a plurality of series circuits each including a resistor and an electronic switch are connected in parallel between the output current path of the voltage/current converter and a predetermined potential source, and the voltage/current is adjusted in accordance with the resistance value of the resistor. a frequency adjustment circuit that adjusts the oscillation frequency of the oscillator by controlling the output current of the converter; and a changeover switch that selectively controls conduction of each electronic switch of the frequency adjustment circuit to switch and adjust the frequency of the sound source signal. In the sound source device for an electronic musical instrument, the tone pitch voltage and the connection terminal potential of each of the electronic switches and each of the resistors are added to the input side of the voltage/current converter, and the output voltage is converted to the voltage/current. A sound source device for an electronic musical instrument, characterized in that it is provided with an adder circuit that supplies the signal as an input signal to a converter.