JPS5859611A - Digital type sound effect device - Google Patents

Abstract

PURPOSE:To prevent sharp variation in characteristic and occurrence of clicking sounds, by changing the characteristics of a digital equalizer by using an up- down counter. CONSTITUTION:As a result of change of the level and sharpness at a prescribed frequency of digital signals inputted into a variable coefficient digital filter 1, a desired frequency characteristic is obtained. Coefficients are changed by up- down counters 9, 10, and 11. Each of the up-down counters 9, 10, and 11 is equipped with an up-switch and a down-switch. The up-down countes 9, 10, and 11 are installed to control the frequency, level, and sharpness with their outputs. The coefficients are changed one bit by one bit by operating the up or down switch. The output of the up-down counter is operated by a microcomputer 8 and given to the digital filter 1.

Description

[Detailed Description of the Invention] The present invention relates to an audio effect device using a digital equalizer, and an object of the present invention is to prevent the characteristics from changing abruptly when changing parameters, and to prevent the occurrence of click sounds. It is something to do.

FIG. 1 shows a conventional digital parametric equalizer.

In FIG. 1, 1 is a variable coefficient digital filter, and the digital signal input to this digital filter 1 is converted to a level L and a sharpness Q at a predetermined frequency F by this digital filter 2/...1.
changes, and a desired frequency characteristic can be obtained. Next, a circuit configuration for controlling the frequency F, level L, and sharpness Q of the digital filter 1 will be explained. R is a rotary or sliding variable resistor to which voltage V is applied;
2, 3.4 is a MuD converter that converts the branch voltage Vc from the variable resistor R into a digital quantity, 5) 6.7 is a MuD converter that decodes the digital quantity from 2゜3.4). teF,
L.

A decoder 8 outputs the value of Q, and 8 is a coefficient calculation unit by a microcomputer, and the output of this coefficient calculation unit 8 sets the characteristics of the digital filter 1, that is, the frequency F, the level circle L, and the sharpness Q. . Variable resistor R
By varying , the characteristics of the digital filter 1 change.

The transfer function H(z) of the parametric equalizer 1 is expressed as:

Each coefficient of the above equation (1) is as follows. However, e wo ``'2 K F + K '' 10
It is 1.

If F, L, and Q are given, the coefficient C is obtained from equations a) 2 to β).

Mu1. Mu2,! h, B2 are determined, and the characteristics of equation 0) are obtained.0 In the conventional example shown in FIG. 4 output) fluctuated, leading to deterioration in sound quality. Furthermore, in the conventional example described above, when the variable resistor R is moved relatively quickly, many placement steps are skipped, which causes the characteristics of the digital filter to change rapidly, resulting in a problem such as a clicking sound.

In order to eliminate the above-mentioned drawbacks of the conventional method, it is necessary to take measures such as providing a dead zone near the localization level and interpolating with the digital filter 1, which makes the device complicated and expensive.

The present invention eliminates the above-mentioned drawbacks of the conventional art, and one embodiment of the present invention will be described below with reference to FIG. 2. In FIG. 2, the same parts as in FIG. 1 are given the same numbers.

In FIG. 2, 9 is an up/down counter for setting frequency F, 1o is an up/down counter for setting level L, and 11 is an up/down counter for setting sharpness Q, and each counter 9, 1o.

11 is provided with an up switch and a down switch,
By pressing this up switch or down switch, the count up or down is performed. If you keep pressing the up or down switch, the counter will automatically go up or down to 40.
One set of coefficients is set every 1111 to 200 m5, and the characteristics of the filter 1 gradually change every 401118 to 200 m5.

In the above example, the frequency F is 200H2~18d
37 points in the range of B to -18 dB, 12 points in the range of sharpness Q of 2 to 13, and 24 points each for F, L, and Q.
If we want to display a bit fixed-point number, (32+37
+12) A decoder can be configured with a small memory capacity of X3 bytes - 243 bytes.

FIG. 3 shows the configuration of the up/down counter in the above embodiment. In FIG. 3, 12 is an up switch, 13 is a down switch, 14 is a count up control circuit, 16 is a count down control circuit, and 16 is an up/down counter circuit. The count-up control circuit 14 and count-down control circuit 16 each include a chattering prevention circuit 17117', a pulse oscillator 18,18' that outputs a pulse with a period τ, and a monostaple multivibrator 19s19'.

4(-, (b), (C) show the control timing at the time of count-up in FIG. 3.
a).

When pressed by (≦τ), a count up pulse is output from the pulse oscillator 18, and after T1, a reset pulse is output from the monostaple multivibrator 19.
Pulse oscillator 18 is reset. That is, in this case, only one count-up pulse is input to the count-up terminal U of the up-down counter circuit 160, and the counter advances by one count.

When the up switch 12 is pressed for a time T2()τ), the pulse oscillator 18 outputs a count-up pulse with a period τ, and the counter continues to advance until the pulse oscillator 18 is reset after T2.

By the way, when the coefficient calculation unit 8 for calculating coefficients from the above equations (1) to (6) is configured with a microcomputer, a set of coefficients C, M1. Mu2, Ih, and B2 can be calculated at approximately 20 mg. On the other hand, the time T1 during which the up switch 12 (or down switch 13) is pressed down with the fingertip is about 40 m19 at the shortest, during which time a set of coefficients is calculated and the characteristics of the digital filter 1 are adjusted to the nearest characteristic. can be moved to. If the characteristics of the digital filter 1 are sequentially changed at this speed, sudden changes in the characteristics can be prevented and click noises will not occur.

In the above embodiment, since the pulse oscillators 18 and 18' that generate pulses with a constant period τ are used, it may take too much time to make a large change in the characteristics. In order to eliminate this inconvenience, as shown in FIG. 4(d), a pulse generator may be used in which the period of continuous pulses becomes gradually shorter when T2>τ.

For example, a pulse generator may be used that can initially output pulses at a period of 200 m5 and gradually shorten this period to 40 mB. If such a pulse generator is used, even when it is desired to greatly change the characteristics of the digital filter 1-, it can be controlled in a short time. Moreover, it can be easily realized by such a pulse jet.

The present invention has the above-mentioned configuration, and because it does not require complicated and expensive parts such as an AD converter or a digital filter for interpolation, an inexpensive audio effect device can be obtained. Further, according to the present invention, since the characteristics of the digital equalizer are changed according to the count number of the up/down counter, there is an advantage that the characteristics do not change suddenly and no click sound is generated. Furthermore, since the present invention does not use an AD converter, stable control is possible without fluctuations in control signals due to noise, etc., and there is no deterioration in sound quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional digital audio effects device, FIG. 2 is a block diagram of a digital audio effects device according to an embodiment of the present invention, and FIG. 3 is a block diagram of main parts of the device. FIGS. 4(IL) to (11) are explanatory diagrams of the operation of the device. 1...Digital filter, 5. ! , 7
...De1 o, ... Korg, 8 ... Coefficient operation section, 9.10.11.
...Up/down counter, 12... Up switch, 13... Down switch, 14
...Count-up control circuit, 15...
・Countdown control circuit, 16...Up-down counter circuit, 17117'...Chattering prevention circuit, 18.18'・River...Pulse oscillator, 1
9,19'...Monostaple multivibrator. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3

Claims (1)

[Scope of Claims] 0) A digital audio effect device equipped with a digital equalizer whose parameters change according to the number of up/down color counts. ? ) The digital audio effect device according to claim 1, which uses an up/down counter with a counting speed of 4011B to 200 ms.