JPH04196705A - Digital audio equipment - Google Patents

Abstract

PURPOSE:To obtain the digital audio equipment in which sound volume is not reduced by increasing a gain of a power amplifier when a compressor circuit is acted. CONSTITUTION:First, 2nd and 3rd switches 202, 204 and 209 are controlled entirely by a changeover switch 212, and when a compressor circuit 203 is acted, each switch is thrown to the position of a terminal C, and when the compressor circuit 203 is acted, each switch 212 is thrown to the position of a terminal D. Thus, suppose that a voltage reduction ratio is 0dB while each switch is thrown to the position of a terminal D and the compressor circuit 203 is inactive, each switch is thrown to the position of a terminal C, and when the compressor circuit 203 is acted, an input signal level being an upper limit level RU or over keeps 0dB and the gain of the input signal of the level below the upper limit level is increased. Thus, when the compressor circuit 203 is acted, the reduction in the sound volume at the level less than the upper limit level is prevented.

Description

[Detailed Description of the Invention] Summary 1 In a digital audio device that uses a compressor circuit that makes the attenuation ratio of information below a predetermined level relatively small among the information reproduced from a digital sound source, the compressor circuit is made to function. increase the gain of the power amplifier to prevent the volume from decreasing beyond a predetermined level.

[Industrial Field of Application] The present invention relates to a digital audio device that reproduces a digital sound source, and more particularly to a digital audio device that automatically corrects the gain of a power amplifier when a compressor circuit is operated.

[Prior Art 1] So-called digital sound sources such as compact discs or digital audio tape recorders have come to be commonly used as sound sources for audio, particularly car audio.

Such digital sound sources have a wide dynamic range, but so-called analog devices such as power amplifiers and speakers have a narrower dynamic range than digital sound sources, and if all the information recorded in the sound source is reproduced at its original level, it will be very small. I can't hear the sound.

Furthermore, in the field of car audio, the sound of running cars makes it even harder to hear small sounds.

In order to solve this problem and make it easier to hear small sounds, so-called compressor circuits have been put into practical use that digitally correct the loudness of sounds below a predetermined level to increase the output level.

FIG. 3 is an input/output characteristic diagram of the compressor circuit, with the horizontal axis representing the input signal level and the vertical axis representing the output signal level.

The relationship between the input and output signals when the compressor circuit is not functioning is shown by a straight line a, assuming that the attenuation ratio is 0 decibel.

If the damping ratio is -50 desobel, the input/output relationship can be expressed by a straight line parallel to straight line a.

When the compressor circuit is operated and the attenuation ratio is set to 0 decibels, the relationship between the input and output signals is a straight line C.

That is, if the input signal level is below the lower limit level RL, it has the same characteristics as the straight line a, and if it is above the upper limit level RU, it is uniformly attenuated by about 10 decibels.

If the input signal level is below the upper limit level RU and above the lower limit level RL, the output signal level changes in proportion to the input signal level.

[Problem to be Solved by the Invention] Therefore, when the compressor circuit is made to function, if the damping ratio is kept constant, an output signal with the set damping ratio can be obtained at a very small input signal level. At a certain input signal level, the attenuation ratio will increase.

In other words, the small input signal level becomes relatively large compared to the general signal level, but to the user it sounds like the overall volume has decreased, and an operation such as increasing the volume is required to return to the original volume. Become.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a digital audio device in which the volume does not decrease even when the compressor circuit is activated.

[Means for Solving the Problems 1] FIG. 1 is a basic configuration diagram of a digital audio device according to the present invention, which includes a digital sound source 101 and an input signal having a predetermined level or less among the outputs of the digital sound source 101. A compressor circuit 102 that compensates for , and increases the input signal relative to a predetermined level or higher.
, a digital-analog converter 103 that converts the digital signal output from the compressor circuit 102 into an analog signal, a power amplifier 104 that amplifies the power of the output of the digital-analog converter 102, and a power amplifier 1.
04 output into audible sound, a switch 106 that switches whether or not to make the compressor circuit 102 function, and a switch 106 that changes the gain of the power amplifier 104 when a function command is output to the compressor circuit 102 by the switch 106. an increasing gain increasing circuit 107;
It consists of

[Function] In the digital audio device configured as described above, when the compressor circuit is operated, the gain of the power amplifier is increased.

[Embodiment 1] FIG. 2 is a block diagram of one embodiment of the present invention, in which a compact disc player, for example, is used as the digital sound source 201.

The output of compact disc player 201 is input to first switch 202 .

One output 202C of the first switch 202 is input to the compressor circuit 203, and the other output 202D is input directly to the switch 202 of the cylinder 2 via the bypass circuit 205.
204D.

The output of the compressor circuit 203 is connected to the second switch 204
is connected to the other input 204C of the .

The output of the second switch 204 is input to a digital-to-analog converter 206 that converts the digital signal to an analog signal.

The output of digital-to-analog converter 206 is led to attenuator 208 via buffer amplifier 207.

The attenuator 208 is composed of, for example, a resistive voltage divider circuit, and the third
When the switch 209 selects the first terminal 209C, the attenuation ratio is 0 decibel, and when the second terminal 209D is selected, the attenuation ratio is determined by the values of the two resistors 208a and 208b.

The output of the third switch 209 is power amplified by a power amplifier 210, and then is converted into audible sound by driving a speaker 211.

The first, second and third switches 202, 204 and 209 are collectively controlled by a changeover switch 212,
When making the compressor circuit 203 function, each C
terminal is selected, and when the compressor circuit is not to function, the D terminal is selected.

Furthermore, in the attenuator 208, two resistors 208a and 20
The value of 8b is selected as follows.

Rb/ (Ra+Rb)=t (1) Here, Ra is the resistance value of the first resistor 208a, Rb is the resistance value of the second resistor 208b, and ε is the resistance value of the input signal above the upper limit level RU when the compressor circuit is functioning. Attenuation rate Therefore, if the D terminal of each switch is selected and the attenuation ratio is 0 dB when the compressor circuit is not functioning, then the C terminal of each switch is selected and the compressor circuit is functioning. In this case, the input signal level above the upper limit level RU is maintained at O decibel, and the gain of the input signal below the upper limit level is increased to above 0 decibel.

That is, it becomes possible to obtain the input/output characteristics shown in d of FIG. 3 as a whole.

[Effects of the Invention] In the digital audio device configured as described above, when the compressor circuit is activated, the volume at a general level is prevented from decreasing, and the user does not have to readjust the volume. .

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a configuration diagram of an embodiment, and FIG. 3 is a graph showing input/output characteristics of a compressor circuit. 101...Digital sound source 102...Compressor circuit 103...Digital-to-analog converter 104...
Power amplifier 105...Speaker 106...Switch 107...Gain increase circuit

Claims (1)

[Claims] 1. A digital sound source (101), and digitally corrects input signals below a predetermined level among the outputs of the digital sound source (101) to compensate for input signals above a predetermined level. a compressor circuit (102) that increases
a digital-analog converter (103) that converts a digital signal output from the digital-analog converter (102) into an analog signal; a power amplifier (104) that amplifies the power of the output of the digital-analog converter (102);
a speaker (105) that converts the output of (104) into audible sound;
and a switch (106) for switching whether or not to make the compressor circuit (102) function, the switch (106) causing the compressor circuit (102) to function.
a gain increase circuit (104) that increases the gain of the power amplifier (104) when a function command is output to the power amplifier (104);
07) is added.