JPS58103215A - Amplitude controller - Google Patents

Abstract

PURPOSE:To prevent the distortion of a higher harmonic wave or the cross modulation due to the saturation of an audio device, by dividing the input signal into plural bands, limiting the amplitudes of the signals divided into those bands and then synthesizing and delivering those limited signals. CONSTITUTION:The prescribed level of an amplitude control means 3 is set at a level which is slightly lower than the saturating level of an amplifier or a speaker which is connected to the output side. As a result, only the frequency component of a high level receives a limitation of amplitude less than the prescribed level through an amplitude control means 3 for the frequency components of the supplied major input signal. While other frequency component receives no limitation of amplitude and pass through to be synthesized by a signal synthesizing means 4. Therefore the level of an output terminal 5 receives more limitation of amplitude than the original level. This can prevent the saturation of an amplifier or a speaker. Thus only the distortion of a higher harmonic wave or the cross modulation due to saturation can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplitude control device used in audio equipment, etc., and an object of the present invention is to remove harmonic distortion and cross-modulation distortion caused by amplifier clipping, speaker saturation, etc. at the time of large input. do.

All devices that handle audio signals, such as audio amplifiers and speakers, have a limit to the signal level they can handle, and signals exceeding that level will saturate and generate distortion. The input signal at that time is a single note.

Alternatively, in the case of only overtones, even if the distortion occurs, the only component is the overtones, so it does not cause much discomfort.

However, the input signal has multiple sounds (chords, etc.) that are not related to overtones.
In this case, the distortion produces a sound unrelated to the input signal or its harmonics, that is, cross-modulation distortion, resulting in a very unpleasant sound.

Soft clipping and automatic volume control have traditionally been used to improve the above problems.

Soft clip suppresses the occurrence of high-order harmonic distortion by slowly saturating the amplifier, etc.
This is intended to suppress the irritating sound caused by sudden lips. However, even with the soft clipping method, low-order distortion occurs, and since the amplifier gradually enters the nonlinear region from a point lower than the original clip level, the distortion characteristics in that region will be different from the original. There was a problem that it got worse than the characteristics.

Furthermore, automatic volume control lowers the gain when the signal level approaches the clip level to prevent clipping. However, this method has the problem of reducing the overall gain even if the signal level of only a part of the frequency band of the input signal is high, which impairs the power of the sound. If there is a time lag in between, the volume immediately after a large input may be suppressed to a low level, or the noise may disappear immediately after a large input, but then appear after a while, resulting in an unnatural feeling. There was a problem.

The present invention provides an amplitude control device that solves the above problems.

A first embodiment, which is the basis of the present invention, is shown in FIG. 1st
In the figure, 1 is an input end, 2 is a plurality of filters 2a~
Band dividing means 2n divides the input signal into a plurality of frequency bands; 3 comprises a plurality of amplitude controllers 3a to 3n, and amplitude control controls the amplitude of each band-divided signal to a predetermined level or less; Means 4 synthesizes each amplitude-controlled signal.

6 is an output terminal. Incidentally, here, the amplitude controllers 3a to 3n are constituted by AGC circuits.

In the above configuration, if the predetermined level of the amplitude control means 30 is set to a level slightly lower than the saturation level of the amplifier or speaker connected to the output side, when a large input signal is input, Among the frequency components, only the frequency components with high levels are amplitude limited to below a predetermined level by the amplitude control means 3, and the other frequency components pass through without being subjected to amplitude limitation and are synthesized by the signal synthesis means 4. Therefore, the amplitude of the level at the output end 5 is limited compared to the original level, and saturation of the amplifier and speaker can be prevented.

As mentioned above, the configuration shown in Figure 1 alone can prevent saturation of the amplifier and speakers to some extent, but even if the level of each frequency component is low, depending on their phase relationship, the synthesized signal The level becomes louder and may even exceed the saturation level of the amplifier or speaker. In order to prevent this, if the level controlled by each amplitude controller 18a to 3n is set sufficiently low, then when a single note is input, the level will be lower than the 4IP sum level of the amplifier and speaker.
The problem arises that you are restricted to a much smaller level.

A second embodiment of the present invention that solves the above problems is shown in FIG. The level of the output terminal 7 of the amplifier 6 connected to the output terminal 5 of the signal synthesizing means is detected by the level detecting means 8, and when the level approaches the clip level of the amplifier 6, the level is controlled by the amplitude control means. The amplitude is limited to a point where the amplifier 6 does not clip. Moreover,
Since the control amplitude of the amplitude control means 3 is set at a sufficiently high level until the level of the amplifier 6 approaches the clip level, the above-mentioned level shortage does not occur even for a single note input. In the embodiment shown in FIG. 2, the level detection is
Although this is done at the output end of the amplifier 6, it may be done at the input end of the amplifier 6.

By the way, in the embodiment shown in FIG.
However, unless the control levels of a large number of amplitude controllers 3a to 3n are controlled in conjunction with each other, the process becomes quite complicated.

Therefore, a third embodiment of the present invention is shown in FIG. 3, which realizes the same function as the embodiment shown in FIG. 2 more simply. This is done by fixing the level of each amplitude controller 3a to 3n of the amplitude control means 3, and changing the level at the input side of the band dividing means 2 and the output side of the signal combining means 4 in mutually opposite directions. First thing to do. Second variable level means 9, 1o are provided, and when the level of the amplifier 6 approaches the clip level, the level of the first variable level means 90 on the input side increases, and by that much,
Conversely, by controlling the level detecting means 8 so that the level of the second variable level means 10 on the output side becomes small, the levels of all the amplitude controllers 3a to 3n in each band are equally controlled. It was designed to do so.

Next, a method for preventing speaker saturation will be explained.

When a large input is applied to a speaker, its saturation mode is
Depends on frequency. Regarding the low frequency range of each speaker unit, a large input can cause the voice coil to jump out of the magnetic field, or the damper or edges to become stiff, causing a phenomenon called bottoming out. Also, regarding the high range,
Distortion is likely to occur at the changing frequency of the split resonance mode.

Furthermore, in a speaker system configured by combining a plurality of speaker units, there are many distortion modes. The level at which these distortions occur varies greatly depending on the frequency.

Therefore, in the configuration of the present invention shown in FIG.
By setting the levels a to 3n to levels corresponding to the distortion generation limit level at each frequency of the speaker used, it is possible to prevent distortion from occurring in the speaker.

You can set each level by connecting an oscillator to the input, changing its level and frequency, and listening to the distorted sound with your ears, but this method is very time-consuming and
Difficult to set accurately.

Therefore, the fourth aspect of the present invention is to automatically perform this process.
An example of this is shown in FIG. This takes advantage of the fact that when distortion occurs in a speaker, a distortion component appears in the current.
First, the oscillator 11 sequentially oscillates signals with frequencies corresponding to the energization band frequency of the band dividing means 2, drives the speaker 12, detects the current with the resistor 13, and converts the detected signal into the oscillation frequency component. The distortion component of the speaker current is detected by passing it through the band removing means 14 in which the current is removed, and when the distortion component exceeds a predetermined level, the level of the amplitude controller corresponding to that band is controlled to be reduced. This limits the level of each frequency component to below the distortion generation level of the speaker.

Such sequential switching of the oscillation frequency and band elimination frequency, control and maintenance of each amplitude controller 3a to 3n, switching of the input from the oscillator 11 to the input end 1 after setting, and the resistance for speaker current detection Commands such as short circuit 13 are issued by control means 15 such as a microcomputer. In addition, in Fig. 4, 16 is an input changeover switch, 17
is a resistor short switch.

In the embodiment of FIG. 4, the oscillator 11
is provided and its oscillation frequency is sequentially switched, but the circuit of the band dividing means 2 may be switched and used as an oscillator that oscillates at the passband frequency.

The above explanation deals with the case where there is only one amplitude control device, but normal audio equipment has two systems like a stereo.
Consists of a system or more.

For example, in the case of stereo, there is a problem in that the operation of the amplitude control device of the present invention changes the balance between left and right sound volumes, thereby changing the localization of the sound image. In order to solve such a problem, amplitude control of corresponding frequency bands of each channel of the amplitude control device of the present invention may be performed in conjunction with each other.

In the case of the embodiment shown in FIG. 3, the first variable level means 9 and the second variable level means 1 of each channel
The above problem can be solved by interlocking the 0 comrades.

The amplitude control device according to the present invention not only prevents distortion caused by the saturation of amplifiers and speakers as described above, but also can be used in front of audio equipment such as recorders, record canting devices, and broadcast modulators. It is also possible to prevent distortion due to saturation at the time of large input.

14'. As described above, the present invention divides an input signal into a plurality of bands, controls the amplitude of each band-divided signal to be below a predetermined level, and synthesizes and outputs each amplitude-controlled signal. Therefore, if applied to an audio device, it is possible to prevent harmonic distortion and cross-modulation distortion due to saturation of the audio device, and to realize an audio device without level fluctuations or noise fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a first embodiment of the present invention, FIG. 2 is a block diagram of a second embodiment of the present invention, FIG. 3 is a block diagram of a third embodiment of the present invention, and FIG. The figure is a block diagram of a fourth embodiment of the present invention. 2...Band division means, 3...Amplitude control means, 4...Signal synthesis means, 6...Amplifier, 8...... Means for detecting the signal synthesis output level, 9...First variable level means, 10.
...Second variable level means, 111+4・→-#
h--oscillator, 12・■...speaker, 13...
- Band removal means, 15... Means for controlling and setting a predetermined level of each amplitude control. Name of agent: Patent attorney Toshio Nakao (1st person)
FA Figure 2 3-

Claims (1)

[Claims] (1) Band division means for dividing an input signal into a plurality of frequency bands, amplitude control means for controlling the amplitude of each of the frequency bands to a predetermined level or less, and An amplitude control device comprising signal synthesis means for synthesizing each signal. (2. Claim 1 is characterized in that the predetermined level controlled by the amplitude control means is set to a level slightly lower than the clip level of the amplifier connected to the output side of the signal synthesis means. (3) Band division means for dividing an input signal into a plurality of frequency bands; amplitude control means for controlling the amplitude of each of the frequency bands to a predetermined level or less; It is composed of a signal synthesizing means for synthesizing signals, and a level detecting means for detecting the output level of the signal synthesizing means, and as the detection level of the level detecting means increases, the output level is adjusted to a predetermined level controlled by the amplitude controlling means. (4) band dividing means for dividing an input signal into a plurality of frequency bands; and amplitude control for controlling the amplitude of each band-divided signal to be below a predetermined level. means for synthesizing the amplitude-controlled signals; first variable level means connected to the input side of the band dividing means; An amplitude control device characterized in that the variable level of the second variable level means is increased and the level of the second variable level means is decreased.(6) Band dividing means for dividing the input signal into a plurality of frequency bands; Amplitude control means consisting of a plurality of amplitude controllers that control the amplitude of each band-divided signal to a predetermined level or less, a signal synthesis means that synthesizes each of the amplitude-controlled signals, and control by the plurality of amplitude controllers. (6) In claim 6, the control level setting means is provided on the input side of the amplitude control means. a signal generating means connected to the circuit and generating a signal having a frequency corresponding to the passing frequency of each band; and a speaker driven by the output signal of the signal synthesizing means; means for detecting the current of the speaker; A band removing means for removing the frequency component generated by the signal generating means, and a control means for controlling and setting a predetermined level controlled by each amplitude controller according to the output signal of the band removing means. (7) An amplitude control device according to claim 6, characterized by comprising an oscillator that oscillates at the pass frequency of each band of the signal synthesizing means and the band dividing means. (8) The amplitude control device according to claim 6, characterized in that the output signal of each pass band obtained by switching a plurality of filters of the band dividing means is used as the output signal of the signal generating means. (9) In claim 6, the control means controls each output signal frequency of the signal generation means, the band removal frequency,
An amplitude control device characterized in that an amplitude controller corresponding to each frequency is automatically switched and set in conjunction with each other, and the setting state is stored and held. (1o) band division means for dividing an input signal into a plurality of frequency bands; amplitude control means for controlling the amplitude of the band-divided signal to below a predetermined level; and signal synthesis for combining the amplitude-controlled signals. 1. An amplitude control device characterized in that a plurality of systems are provided, and the amplitude control means for corresponding frequency bands of each system are controlled in conjunction with each other. (11) Band division means for dividing the input signal into a plurality of frequency bands, amplitude control means for controlling the amplitude of each of the divided signals to below a predetermined level, and synthesis of each of the amplitude-controlled signals. a first variable level means connected to the input side of the band dividing means; and a second variable level means connected to the output side of the band combining means; A plurality of systems are provided for increasing the first variable level and decreasing the level of the second variable level means as the output level of the variable level means becomes larger than a predetermined level,
An amplitude control device characterized in that the first variable level means and the second variable level means of each system are variable in conjunction with each other.