JPS5843285Y2 - slice circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a slice circuit that can be effectively used as a musical tone forming means in, for example, an electronic musical instrument.

In electronic musical instruments, a sound source circuit generates a sound source signal corresponding to each pitch, selects and derives the sound source signal corresponding to the pitch of the operated key as a key is operated, and creates a timbre in a timbre forming circuit consisting of a filter circuit, etc. It forms a musical tone signal.

That is, the timbre of a performance sound is specified, for example, by setting the frequency characteristics of a timbre forming circuit, and the timbre of a performance sound is constant from its rise to decay.

However, actual performers of natural instruments have a unique envelope set for that instrument, and the timbre changes as the envelope changes, and as a result, it is not possible to obtain a performance sound that is rich in musicality. be.

In consideration of these points, for example, two series of sound source signal circuits are formed in which the tones are different depending on the key operation, and each of the sound source signal circuits is controlled by a separate gate circuit. It has been proposed to control the opening and closing of this gate circuit using an envelope signal from an envelope forming circuit that is controlled in accordance with key operations.

In other words, the gate circuits to which the two series of sound source signals are combined are controlled with different envelopes to form two series of musical tone signals with different envelopes and tones, and these are synthesized. Correspondingly, the timbre changes from the rise of the musical tone until it decays.

However, with such means, it is necessary to form multiple envelope signals in a mutually related manner in response to one key operation, which complicates the configuration, and especially when converting to an IC, the number of pins increases. etc. will increase, making it ineffective.

This invention was made in view of the above points, and it is intended to be able to be effectively used to change the sound source signal envelope from multiple series of sound source signal circuits, for example, in a tone forming circuit of an electronic musical instrument. It is intended to provide a slice circuit that is particularly effective for IC implementation, and is characterized by constant current control of a field effect transistor to which an input signal is coupled.

An embodiment of this invention will be described below with reference to the drawings.

Figure 1 shows an example in which the circuit is used in a musical tone forming circuit for an electronic musical instrument. For example, three sound source signals with different feet temperament are generated corresponding to each pitch, and
1a to 11c, respectively.

This input sound source signal is divided into two systems and supplied to the first and second waveform conversion circuits 12 and 13. In this embodiment, the first waveform conversion circuit 12 is connected to the sound source signal from the terminals 11a to 11c. The second waveform converting circuit 13 is constituted by an AND circuit to which the sound source signals from the terminals 11a and 11c are coupled.

Then, different sound source signals having different harmonic components with different duties are taken out from the waveform conversion circuits 12 and 13, respectively.

The output sound source signals from the first and second waveform conversion circuits 12 and 13 are taken out through gate circuits 14 and 15, respectively, and synthesized through filter circuits 16 and 17 that form timbre. To obtain a musical tone signal output.

The gate circuits 14 and 15 are the envelope forming circuit 1
The waveform conversion circuit 12 is controlled by the envelope signal from 9.
．． A gate circuit 14 includes field effect transistors TI, T2 and T3, T4 for switching the sound source signal from the transistors TI, T2, and a field effect transistor T5. to amplify and extract it.

Furthermore, in the gate circuit 15, the transistor T3
, T4 is further taken out via the slice circuit 20 according to the present invention comprising a field effect transistor T6°TI, which is appropriately amplified and taken out by a field effect transistor T8.

It should be noted that among the field effect transistors T1 to T8 in the figure, those with a "+" symbol attached to the old type are depletion type transistors, and the others are enhancement type transistors.

As shown in FIG. 2, the slice circuit 20 has a first field effect transistor T6 to which the input sound source signal Vin is coupled to the gate electrode, and a potential VDD is coupled to the drain electrode of the transistor T6. At the same time, the source electrode is connected to the drain electrode of the second field effect transistor T7 constituting the constant current circuit.

Then, the output sound source signal ``o'' is obtained from the connection point between the source and drain electrodes of the transistor T6 and TI.

Further, the constant current circuit is configured such that the gate electrode and source electrode of the transistor TI are connected to each other, and a control voltage v8 from, for example, a constant voltage source is coupled to the source electrode.

The envelope forming circuit 19 generates an envelope signal in response to a key operation, and includes a key switch KS that is switched and driven in accordance with the operation of a key of a corresponding pitch.

The fixed terminal on the normally closed side of this key switch KS is connected to a constant voltage power supply vE, the movable terminal is connected to a capacitor C1, and a resistor R forming a discharge circuit for this capacitor C1.
1. Diode D1 is connected and grounded via diode D2.

Then, the capacitor C1 is normally charged to the set potential by the power supply vE.

Further, the normally open side fixed terminal of the key switch KS is connected to the base of the transistor Tr, and this transistor T
A storage capacitor C2 is connected to the emitter circuit of r, and a first discharge circuit to which a predetermined potential Vr is applied to the capacitor C2 via a diode D3 and a resistor R2, a diode D4, a resistor R3, and the key A second discharge circuit is connected using a normally closed switch S that is opened in conjunction with the operation of the switch KS.

Then, the terminal voltage of the capacitor C2 is read out as a gate command envelope signal to the gate circuits 14 and 15 via the high input impedance circuit.

That is, when the key is operated, the key switch KS is switched and driven, and when its movable contact leaves the normally closed fixed terminal, the charging circuit of the capacitor C1 is cut off, and the capacitor C1 is set by the resistor R1. When the movable terminal is inserted into the normally open fixed terminal, the base of the transistor Tr is controlled according to the terminal voltage of the capacitor C1 at that time.

The terminal voltage of the capacitor C1 at this time is inversely proportional to the time it takes for the movable contact to move from the normally closed side to the normally open fixed contact, and this is in a state proportional to the operating speed of the key.

That is, a voltage signal proportional to the key operation speed (key touch) is coupled to the base of the transistor Tr.
A potential proportional to the key touch is stored in the capacitor C2.

Immediately after charging, the capacitor C2 charged in this way is discharged to the potential Vr through the first discharge circuit (resistance R2), and the terminal voltage of the capacitor C2 changes as the key is operated. It is set to a potential corresponding to the operating speed, and is thereafter discharged at a time constant set together with the resistor R2.

Note that when the key is released, switch S closes and capacitor C
2 (corresponding to potential Vr) is rapidly discharged to zero potential via the second discharge circuit (resistance R3).

Therefore, the gate circuits 14 and 15 are coupled with an envelope signal which rises and then attenuates in proportion to the key touch.

That is, the gate circuits 14 and 15 are controlled to open and close in response to the envelope signal, and a sound source signal corresponding to the envelope is extracted in response to a key operation.

In addition, in the slice circuit 20 shown in FIG. 2, the drain current D flowing through the field effect transistor T7 is due to the potential vG8 between its gate electrode and source electrode. Because the source electrodes are commonly connected, “vG8
=O".

Therefore, the drain current ■D takes a constant value (■) as shown in FIG.

onst Furthermore, the drain current of the field effect transistor T6 ■
D is the potential VG8 between its gate electrode and source electrode
A is shown in Fig. 4 with A as a parameter.

As shown by B, C, etc., the drain current ID of the transistor T7 flows directly through this transistor T.

Therefore, the drain current ID of the transistor T6 has a constant value (const), and this drain current I
Potential ■ between the gate electrode and the source electrode to obtain D (=■const).

8 is the current ■ shown by A in FIG. The value corresponds to onst.

In addition, as shown in FIGS. 3 and 4, ■T' and ■o are transistors T7. T6 threshold (thr
eshold) Voltage level;h level.

In this way, when the drain current ID of the transistor T6 is kept constant (■D-Iconst), the potential VGs between the gate electrode and the source electrode of the transistor T6 is
is the value corresponding to the above drain current ■D, that is, constant (
■G8-■.

onst).

Therefore, if the gate input Vi of transistor T6 goes high, the output V from the source electrode of transistor T6.

Also, the value of vin is high (it becomes high by the amount that it becomes, and conversely input ■in
The lower the value, the lower the output ■o will be.

That is, the output signal ■ follows the input signal vin.

begins to change. (Here, the gain of the transistor T6 is "1".

) In this case, when the input signal vin becomes smaller than "v+VT+■o'", the drain current ■D of the transistors T 6 and T 7 becomes zero, and in this case, the output signal V.

also becomes zero. That is, the operating characteristics (human output characteristics) of the slice circuit 20 consisting of the field effect transistors T6 and TI are as shown by curve A in FIG.

Therefore, the sound source signal ■ derived by the transistor T 3 s T 4 corresponding to the above envelope signal
When in is in the state shown in the figure, the output sound source signal is V as shown in FIG.

ut, and the sound source signal is obtained by slicing the level portion below "■8+■TvT'".

That is, the sound source signal obtained from the first waveform conversion circuit 12 is derived according to the envelope obtained from the envelope forming circuit 19, and the sound source signal is further sliced by the slicing circuit 20 to be processed by the second waveform conversion circuit. The sound source signals from 13 are mixed.

In this case, since the two systems of sound source signals have different harmonic components, the tones of the musical tone signals obtained from the filter circuits 16 and 17 will be different, and therefore the musical tone signal output will have characteristics, especially at the rise of the sound. This makes it possible to make the liquid performance of an electronic musical instrument rich in musicality and effective.

In other words, if a slice circuit with the above configuration is used, it can be constructed in a state that is particularly easy to integrate into an IC by combining simple field effect transistors, and it is possible to effectively perform envelope conversion of, for example, a sound source signal whose envelope has been set. It can be used as a means for forming electronic musical tones, and its practical effects are remarkable.

In this slice circuit, if the control power supply VS is constructed from a variable resistance circuit or the like, slice level conversion control can be performed effectively.

Furthermore, in the case of musical tone formation, if the timbre is changed in the filter circuit section, there is no need to specifically vary the harmonic components by waveform conversion.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating musical tone forming means using a slice circuit according to an embodiment of the invention, FIG. 2 is a diagram showing the slice circuit section taken out, and FIGS. 3 and 4 are diagrams illustrating the slice circuit section. Diagram 5 explaining the characteristics of the transistor used
The figure is a characteristic diagram illustrating the above-mentioned slice circuit. 11a to 11c... Input terminals, 12, 13...
... Waveform conversion circuit, 14, 15... Gate circuit, 16°17... Filter circuit, 19...
...Envelope forming circuit, 20...Slice circuit, T6...First field effect transistor, TI...Second field effect transistor.

Claims (1)

[Scope of utility model registration request] A slice circuit comprising a field effect transistor whose gate electrode is supplied with an input signal, and a constant current circuit connected to the source electrode of the transistor, and configured to extract an output signal from the source electrode of the field effect transistor.