JPS6149677B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable delay device suitable as an audio vibrato device used in electronic musical instruments, acoustic devices that reproduce singing voices from speakers, and the like.

Conventionally, it is generally known that an audio vibrato device can be realized using a variable delay circuit whose delay time can be controlled by the repetition period of a clock pulse. It has been proposed to use a CTD (charge transfer device) such as a CCD (charge coupled device).

However, when constructing a vibrato device using such a variable delay circuit, as will be explained later, if you change the vibrato frequency, that is, if you change the modulation frequency of the clock pulse, the range of change in frequency pitch will inevitably change. When attempting to apply vibrato to musical instrument sounds or voices, unnatural phenomena occur, causing discomfort to the listener.

As shown in FIG. 1, the delay circuit 1 is set to _a constant delay time τ ₀ by a constant clock pulse supplied from the clock oscillation circuit 2.
If an input signal Sa of Asinωt is supplied, the time axis of the output signal So is shifted by a delay time _τ0 , and the output signal So becomes Asinω(t- _τ0 )...(1). Furthermore, as shown in FIG. 2, if a modulation signal is supplied from the modulation signal oscillator 3 to the clock oscillation circuit 2 and the frequency of the clock pulse that determines the delay time τ ₀ of the variable delay circuit 1' is modulated, the delay time will naturally increase. τ ₀ will undergo modulation. Now, if the maximum delay time deviation (width of change in delay time) is △τ, and the delay time changes in a sinusoidal manner, then the change in delay time is τ ₀ +△τsinω _n t...(2) (However, ω _n is the modulation angular frequency of the delay time). Note that in this case, if the modulation signal is a sine wave, the delay time change will not be sinusoidal.

In this way, compared to the delay time τ ₀ when no modulation is applied, the delay time when modulated is ±△τ around τ ₀ .
Varies within the range of . Therefore, the delay circuit has ₀
The output signal _n (t) when adding the input signal (t) = Asinωt is given by the delay time τ in equation (1) instead of ₀ .
(2) can be used, so _n (t) = Asinωt
{t-(τ ₀ +△τsinω _n t)}...(3).

Therefore, if the ratio Δτ/τ ₀ between the center value τ ₀ of the delay time and the maximum delay time deviation Δτ is m, and this is called the modulation depth, equation (3) can be written as follows.

_n (t)=Asinωt
{t-τ ₀ (1+msinω _n t)}...(4) However, △τ/τ ₀ = m...(5) Also, input signal ₀ (t) and output signal _n (t)
The relationship between the two is illustrated in Figures 3A and 3B.

That is, the output signal _n (t) is the input signal ₀
(t) is frequency modulated and the input signal _{is 0.}
The frequency spectrum of (t) changes over time. Also, if the modulation frequency is sufficiently low relative to the input signal frequency, the instantaneous frequency can be defined,
The output signal can be thought of as this instantaneous frequency varying over time.

Next, find this instantaneous frequency. If equation (4) is divided into a frequency term and a phase term, it can be written as _n (t) = Asin (θ + φ ₀ ) ... (6).

However, θ=ω(t-τ ₀ msinω _n t) ...(7) φ ₀ =-ωτ ₀ ...(8) At this time, the time differential of the frequency term in equation (6) divided by 2π, that is, 1 /2π dθ/dt is perceived as an instantaneous frequency. For example, input signal ₀ (t) = sinω
The instantaneous frequency of t is 1/2π d/dt(ωt) = ω/2π, which is constant with respect to time, but the instantaneous frequency F(t) of the output signal in equation (4) is F(t) from equation (7). =1/2π dθ/dt=ω/2π(1−τ
₀ mω _n cosω _n t)...(9).

Therefore, if the frequency of the input signal is =ω/2π, the equation (9) becomes F(t) = (1−τ ₀ mω _n cosω _n t) ...(10), and the frequency pitch of the source signal is the input signal. It can be seen that it changes by ±τ ₀ mω _n around the signal frequency. This situation is shown in FIG. 3C.

From this, the width of change in frequency pitch is given by the modulation depth m and the modulation angular frequency ω _n of the delay time, assuming that the input signal frequency and the delay time τ ₀ at the time of no modulation are constant.
It can be seen that it is proportional to the product of

Here, from equations (2) and (5), the modulation depth m and modulation angular frequency ω _n are quantities that indicate the state of change in the delay time itself, and do not represent the amplitude or angular frequency of the modulation signal. There is a relative relationship between the change in the delay time and the change in the delay time; as the amplitude of the modulation signal increases, the change in the delay time also increases, and the period of the modulation signal corresponds to the period of change in the delay time. Therefore, the variation width of the instantaneous frequency F(t) is the modulation signal _n (t)
It is approximately proportional to the product of the amplitude and the frequency.

Therefore, the present invention aims to control the modulation signal frequency and modulation depth of the modulation signal oscillation circuit to keep the frequency change range of the input signal of the delay circuit constant.

Embodiments of the present invention will be described below with reference to FIG. 4 and subsequent figures.

First, in the first embodiment shown in FIG.
is a variable delay circuit consisting of CTD such as BBD and CCD,
12 is a clock oscillation circuit, and 13 is a modulation signal oscillation circuit, each of which is provided with a frequency control terminal a. Reference numeral 14 denotes an amplifier circuit that amplifies or attenuates the amplitude of the modulated signal from the modulated signal oscillation circuit 13 and supplies it to the clock oscillation circuit 12, and is provided with a control terminal b for controlling the degree of amplification or the amount of attenuation.

With the above configuration, the modulation signal generated in the modulation signal oscillation circuit 13 is supplied to the clock oscillation circuit 12 through the amplifier circuit 14, and modulates the oscillation frequency of the clock pulse generated by the clock oscillation circuit 12. The clock pulses φ ₁ and φ ₂ frequency-modulated in this manner are in an antiphase relationship with each other, and are applied to the variable delay circuit 11.
The input signals supplied to the terminal 1 are sequentially transferred and taken out as output signals. At this time, the modulation signal frequency of the modulation signal oscillation circuit 13 and the gain of the amplifier circuit 14 are changed by supplying control signals to the frequency control terminal a and the amplification degree control terminal b. In this control, when the oscillation frequency of the modulation signal of the modulation signal oscillation circuit 13 is increased, the gain of the amplifier circuit 14 is adjusted to lower, so that the frequency change range of the input signal of the variable delay circuit 11 is almost constant. .

Next, an embodiment in which the modulation signal frequency and modulation depth of the modulation signal oscillation circuit are controlled simultaneously will be described with reference to FIGS. 5 to 7.

In the second embodiment shown in FIG. 5, a voltage controlled oscillation circuit is used as the modulation signal oscillation circuit 13, and a variable resistor 16 is connected between the control input terminal a and the power supply 15. The oscillation frequency of the modulation signal is determined by the voltage value determined by . In other words, the closer the contact 16a of the variable resistor 16 is to "1", the lower the oscillation frequency of the modulation signal is. The signal is supplied to the oscillation circuit 12. Further, the clock oscillation circuit 12 is oscillated at a constant frequency when the contact 17a of the variable resistor 17 is at "3";
The clock pulse is modulated in such a manner that the modulation depth of the clock pulse by the modulation signal increases as 7a approaches "1". On the other hand, the variable resistors 16 and 17 are coaxially linked, and therefore the curves of the rotation angles and resistance values of the variable resistors 16 and 17 or the voltage values and oscillation frequencies of the clock oscillation circuit 12 and the modulation signal oscillation circuit 13 If the relationship is appropriately selected, the modulation depth m of the delay time of the variable delay circuit 11 and the modulation angular frequency ω _n
The product mω _n becomes constant, and the frequency change range of the input signal of the variable delay circuit 11 can be made constant regardless of the modulation signal oscillation frequency.

The third embodiment shown in FIG. 6 uses a voltage-controlled amplifier circuit as the amplifier circuit 14, in which the gain of the amplifier circuit can be directly controlled by the voltage value. That is, the oscillation frequency of the modulation signal oscillation circuit 13 and the amplification circuit 14
The gain of the modulation signal oscillation circuit 1 is controlled by the voltage value of the variable power supply 15', and as the voltage value increases, the gain of the modulation signal oscillation circuit 1
The oscillation frequency of the amplifier circuit 14 is increased and the gain of the amplifier circuit 14 is decreased. Therefore, by appropriately selecting the characteristics of the modulation signal oscillation circuit 13 and the amplification circuit 14, the modulation frequency of the clock pulse of the clock oscillation circuit 12 can be arbitrarily and continuously changed by changing the voltage value of the power supply 15'. The frequency change range of the input signal can be kept constant.

Further, the fourth embodiment shown in FIG. 7 uses an effective value detection circuit 18 in place of the variable power supply 15' in the third embodiment shown in FIG.
The input signal of the variable delay circuit 11 is supplied to the variable delay circuit 8. That is, in this example, the oscillation frequency of the modulation signal oscillation circuit 13 and the amplifier circuit 1
The gain of No. 4 is controlled by the input signal level of the variable delay circuit 11, so that the modulation frequency of the clock pulse of the clock oscillation circuit 12 can be automatically changed. It is possible to keep the frequency change range constant.

In each of the embodiments shown in FIGS. 5 to 7 described above, the two adjustments of the oscillation frequency of the modulation signal oscillation circuit 13 and the gain of the amplifier circuit 14 are performed simultaneously and in conjunction, so that the operation is simple.

As described above, according to the present invention, when the delay time of the variable delay circuit is modulated by a modulation signal, the modulation frequency and modulation depth of the modulation signal are controlled and adjusted, so that the frequency of the input signal of the variable delay circuit changes. The range can be kept constant, and especially when used as an audio vibrato device, it has the effect of applying optimal vibrato to singing voices, musical instrument sounds, etc., and obtaining sound effects with breadth and depth. .

[Brief explanation of the drawing]

Fig. 1 is a principle system diagram of a delay device, Fig. 2 is a system diagram of a delay device using a variable delay circuit, Fig. 3 is a waveform diagram for explaining Fig. 2, and Figs. 4 to 7 are 1 is a system diagram of an embodiment of a variable delay device according to the present invention; FIG. In the figure, 11 is a variable delay circuit, 12 is a clock oscillation circuit, 13 is a modulation signal oscillation circuit, and 14 is an amplifier circuit.

Claims (1)

[Claims] 1. A variable delay circuit whose delay time can be controlled by a clock frequency, a voltage-controlled clock oscillator that drives the variable delay circuit, and a modulation signal oscillation circuit that controls the oscillation frequency of the clock oscillator. and an amplifier circuit, and modulates the modulation signal by controlling both the circuits simultaneously so that when the oscillation frequency of the modulation signal oscillation circuit is raised (lowered), the gain of the amplifier circuit is reduced (increased). A variable delay device characterized by controlling signal frequency and modulation depth.