JPS5834476Y2 - Tremolo circuit for electronic musical instruments - Google Patents

Description

[Detailed description of the invention] This invention produces an output signal whose amplitude changes periodically by mixing a musical tone signal whose phase is periodically changed by a low-frequency signal and a musical tone signal whose phase does not change. This invention relates to a circuit that obtains a so-called tremolo effect.

Conventionally, in this type of tremolo circuit, multiple stages of C-E split type transistor phase shift circuits were used as a circuit to change the phase of the musical tone signal, as necessary, but this circuit can also be used to change the phase of the musical tone signal. It is difficult to uniformly shift the phase of the musical tone signal, and in reality, the internal bass of the musical tone signal of an electronic musical instrument is phase-shifted by nearly 30 degrees, and the highest tone is phase-shifted by about 270 degrees.
Using this as a reference phase, the phase is further periodically shifted by a low frequency signal.

However, the standard phase of the musical tone signal near IKHz is approximately 180°, and if this is mixed with the original musical tone signal with no phase change, the output level of the musical tone signal becomes extremely low, which is difficult to achieve when using an electronic musical instrument. The problem has been that the output level changes depending on the pitch of the musical tone signal played.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional drawbacks, the object of the present invention is to provide a tremolo circuit for an electronic musical instrument, which can obtain a tremolo music volume of 1 to tremolo music with an equal output level over all pitches of the electronic musical instrument.

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

In FIG. 1, 1 is an input terminal to which musical tone signals of various pitches (frequencies) arrive in response to the operated keys of the electronic musical instrument, 2 is a changeover switch whose movable terminal is connected to input terminal 1, and 3 is a changeover switch whose movable terminal is connected to input terminal 1. The amplifier has an input end connected to a first fixed terminal 2a of a changeover switch 2, and an output end connected to an output terminal 5 via a resistor 4.

6 is a first transistor, its base electrode is connected to the second fixed terminal of the changeover switch 2, its collector electrode is connected to the positive power supply (T) through a resistor, and its emitter electrode is connected to ground through a resistor. It is connected.

Further, the collector electrode is connected to an emitter electrode via a capacitor 7 and a drain/source electrode of a field effect transistor 8 (hereinafter referred to as FET) which operates as a variable resistance element in series.

9 is a low frequency oscillator connected to the D1 to electrodes of FET8.

10 is a second transistor, its base electrode is connected to the common connection point of the capacitor 7 and FET 8, its collector electrode is connected to the positive power supply (1) through a resistor, and its emitter electrode is connected to the resistor. are connected to ground through the respective terminals.

In addition, its collector electrode is a capacitor 11 and a FET 12.
is connected to the emitter electrode through the solaine source electrode in series.

Note that the gate electrode of the FET 12 is connected to the low frequency oscillator 9.

The first transistor 6, capacitor 7, and FET 8 constitute a first phase shift circuit, and the second transistor 10 and capacitor ILFET 12 constitute a second phase shift circuit.

15 is an amplifier, the input side of which is connected to the capacitor 1
At the common connection point between 1 and FET 12, there is a resistor 16 on the output side,
They are connected to the output terminal 5 via a bandpass filter circuit 17 and a resistor 18, respectively.

19 is an amplifier, the input side of which is connected to the changeover switch 2;
The output side of the second fixed terminal 2b is connected to the input side of the bandpass filter circuit 17 via a resistor 20.

21 is a common output terminal of the first signal transmission path including the first and second phase shift circuits 13 and 14, and the second signal transmission path including the amplifier 19.

The operation of the above configuration will now be described with reference to FIGS. 2 and 3.

In a state where the movable terminal of the changeover switch 2 is connected to the second fixed terminal 2b side as shown in the figure, when a musical tone signal arrives due to the performance of the electronic musical instrument, the signal from the low frequency oscillator 9 causes the second and second fixed terminals to be connected. FET8 in phase shift circuit 13.14,
Since the resistance value of 12 changes periodically, the musical tone signal is periodically phase-shifted in this phase shift circuit 13, 14 based on a constant phase angle determined by the frequency of the musical tone signal. On the other hand, the musical tone signal is outputted to the common output terminal 21 via the amplifier 19 as it is.

The resistors 16 and 20 are for making the output levels of musical tone signals outputted from the first signal transmission path including the phase shift circuit 13 and 14 and the second signal transmission path including the amplifier 19 substantially equal. It is.

By the way, the musical tone signal in both the first and second phase shift circuits 13 and 14 changes from about 30 degrees to about 270 degrees according to its frequency as shown by the broken line in FIG. 2 (the keyboard range of an electronic musical instrument is about 100 degrees). 2 KHz), and using this as a reference, the signal from the low frequency oscillator 9 further periodically shifts the phase in the range shown by the solid line in FIG. As is clear, the musical tone signal around 1 KHz is phase-shifted by about 180 degrees, and when this musical tone signal is mixed with the musical tone signal output from the second signal transmission path,
Since both are substantially in opposite phase, the output signal level becomes extremely low.

The characteristics of the output signal level with respect to the frequency of this musical tone signal are as shown in FIG.

Therefore, the musical tone signal having the output signal level shown in FIG. 3 is passed through the bandpass filter circuit 17 having the frequency characteristic opposite to the characteristic shown in FIG. The level is corrected and output to the subsequent stage.

Next, when the movable terminal of the changeover switch 2 is connected to the first fixed terminal 2a side, the musical tone signal arriving at the input terminal 1 is outputted as it is to the subsequent stage via the amplifier 3, so no tremolo effect is added. .

As described in detail above, in this embodiment, the musical tone signal that has been conventionally considered to be a drawback in a circuit that obtains a tremolo effect by mixing a periodically phase-shifted musical tone signal and an original musical tone signal that is not phase-shifted can be improved. Fluctuations in the output signal level due to differences in pitch of the signal are prevented by using a bandpass filter circuit 17 having frequency characteristics in which the high and low tones are attenuated compared to the middle tones, thereby eliminating inconveniences in performance.

As mentioned above, in the present invention, there is no inconvenience that the volume of the sound varies depending on the pitch of the outputted musical tone signal during tremolo performance, and the effect is great.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram for explaining one embodiment of the present invention, Fig. 2 is a characteristic diagram of the phase shift circuit, and Fig. 3 is a characteristic of the output signal level of the musical tone signal input to the bandpass filter circuit. It is a diagram. In the figure, 1 is an input terminal, 13 is a first phase shift circuit, 14 is a second phase shift circuit, 17 is a bandpass filter circuit, and 21 is a common output terminal.

Claims (1)

[Scope of utility model registration request] The base electrode is connected to the musical tone signal input terminal, the collector electrode is connected to the emitter electrode through a variable resistance element whose resistance value changes periodically and a capacitor in series, and the common connection between the variable resistance element and the capacitor. a first signal transmission line including a transistor phase shift circuit whose point is connected to an output terminal; a second signal transmission line connected in parallel to the first signal transmission line and transmitting the musical tone signal as it is; Said first,
A tremolo circuit for an electronic musical instrument, comprising: a bandpass filter circuit connected to the rear stage of a common output terminal of a second signal transmission path, and having a frequency characteristic in which high and low frequencies are attenuated compared to midrange.