JP2000031768A - Graphic equalizer circuit and audio equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and inexpensive audio equipment. SOLUTION: The graphic equalizer circuit 12 of the audio equipment 10 includes an adder 121 that receives an audio signal at its one input and an output signal of a band pass filter whose gain is adjusted by a gain adjustment resistor 124 is given to the other input of the adder 121. An output of the adder 121 is given to an inverting amplifier 125, where the signal is inverted. A switch 122 is used to select whether the audio signal is given to the band pass filter 123 or an output signal of the inverting amplifier 125 is given to the band pass filter 123. Thus, the band pass filter 123 is used in common for a graphic equalizer filter and for a spectral analyzer filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphic equalizer circuit for an audio device, and more particularly to a graphic equalizer circuit used for an audio device including a so-called spectral alanizer for displaying a frequency signal level, and an audio device using the same.

[0002]

2. Description of the Related Art In a conventional audio apparatus 1 shown in FIG. 1, an audio signal passes through a graphic equalizer 2, is level-adjusted by a volume 3, and is output to a speaker 5 through an amplifier 4. The same audio signal is also input to a microcomputer 7 through a bandpass filter 6 for a spectrum analyzer (spectral analyzer) and a detection circuit (not shown). The microcomputer 7 processes the signal from each detection circuit and displays a frequency level. Each frequency level is displayed on the device 8 in the form of, for example, a bar graph.

[0003]

In the prior art shown in FIG.
Since the filter in the graphic equalizer is used not only as a bandpass filter but also as a notch filter, it has been difficult to share the filter as a filter for a spectrum analyzer. For this reason, despite the fact that the same audio signal is processed, two types of filters are used for the graphic equalizer and the spectrum analyzer.

It is therefore a primary object of the present invention to provide a simple and inexpensive audio device.
Another object of the present invention is to provide a graphic equalizer circuit suitable for an audio device having a spectrum analyzer.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a graphic equalizer circuit used in an audio device having a graphic equalizer function section and a spectrum analyzer function section, wherein one of the input means receives an audio signal at one input, a band-pass filter, Gain adjusting means for receiving an output signal of the band-pass filter and providing a gain-adjusted output signal to the other input of the adding means, inverting means for inverting the output signal of the adding means, and applying or inverting the audio signal to the band-pass filter Is a graphic equalizer circuit comprising switch means for switching whether or not to apply the output signal of (1) to the band-pass filter.

The present invention also provides an adder for receiving an audio signal at one input, a band-pass filter, a gain adjuster for receiving an output signal of the band-pass filter and providing an output signal gain-adjusted to the other input of the adder, An inverting means for inverting an output signal of the means, and a graphic equalizer circuit having a switch means for switching between applying an audio signal to a bandpass filter or applying an output signal of the inverting means to the bandpass filter, and outputting the bandpass filter output signal. Is an audio device further provided to the spectrum analyzer function unit.

[0007]

When the gain is set by the gain adjusting means and the audio signal is given to the band-pass filter by the switch means, the output of the adding means becomes [1+
G], and when the output signal of the inverting means is given to the bandpass filter by the switching means, the output of the adding means becomes [1 / (1 + G)].

The output of the band-pass filter is supplied to a spectrum analyzer function unit, that is, a detection circuit (microcomputer).

[0009]

According to the present invention, the band-pass filter of the graphic equalizer circuit can be used both as a filter for a graphic equalizer or as a filter for a spectrum alanizer. Therefore, the configuration is simpler and less expensive than the conventional audio device using different filters, and sound quality control and frequency level display can be performed under the same characteristics.

[0010] Other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An audio apparatus 10 according to an embodiment shown in FIG.
A graphic equalizer circuit 12 for receiving an audio signal from a signal source (not shown); a signal passed through the graphic equalizer circuit 12 is output to a speaker 18 via a volume 14 and an amplifier 16;
It is given to the microcomputer 20. The microcomputer 20 processes the signal that has passed through the graphic equalizer circuit 12 and the detection circuit (not shown), and displays the level of each frequency component on the frequency level display device 22 as a bar graph.

The feature of this embodiment is that a filter included in the graphic equalizer circuit 12 is also used as a filter for a spectrum analyzer. The graphic equalizer circuit 12 is provided corresponding to each of a plurality of frequencies that can be adjusted by the graphic equalizer. However, in FIG. 2 and the following description, only one graphic equalizer circuit 12 is typically used. Note that it is shown and described in advance.

The graphic equalizer circuit 12 is an adder 12 which receives the audio signal as it is as one input.
1, and the audio signal is also provided to the bandpass filter 123 via the switch 122. The output of the band-pass filter 123
, To the other input of the adder 121. Therefore, the adder 121 adds the audio signal directly input from the signal source and the frequency component that has passed through the band-pass filter 123 and has been gain-adjusted by the resistor 124.
The output of the adder 121 is provided to the volume 14 described above. Then, the output of the band-pass filter 123 is given to the microcomputer 20, that is, a detection circuit (not shown).

The output of the adder 121 is also supplied to the inverting amplifier 1
The output of the inverting amplifier 125 is input to the bandpass filter 123 via the switch 122. That is, the bandpass filter 123 is connected to the switch 1
22 is controlled to receive the audio signal from the signal source or to receive the output of the inverting amplifier 125.

The band-pass filter 123 is shown in FIG.
As shown in (1), it is composed of, for example, a multiple feedback type active filter. However, a band-pass filter having another arbitrary configuration may be used. Also, the switch 122
This is a switch for switching the use of the graphic equalizer circuit 12 as a boost circuit or a cut circuit in a time-division manner. For example, as shown in FIG. 4, two analog switches (three-state switches) 122
a and 122b, switches 122a and 12b
2b, for example, the microcomputer 20
Is provided. That is, the microcomputer 20 controls the graphic equalizer circuit 12
When this is used as a boost circuit, this switch control signal is output as a high level signal. The analog switches 122a and 122b are supplied with an audio signal from a signal source and a signal from the inverting amplifier 122 as a boost signal and a cut signal, respectively. When the microcomputer 20 outputs the high-level control signal, the analog switch 122a is turned on, and the analog switch 122a is turned on.
2b is turned off. Therefore, the analog switch 12
An audio signal is supplied to the band pass filter 123 via 2a. Conversely, when the microcomputer 20 outputs the low level control signal, the analog switch 122b is turned on and the analog switch 122a is turned off. Therefore, an output signal from the inverting amplifier 125 is supplied to the bandpass filter 123 via the analog switch 122b.

In the embodiment shown in FIG.
4 sets the gain G. Then, when an audio signal (boost signal) is given to the band-pass filter 123 via the analog switch 122a, the output of the band-pass filter 123 has a gain (G) and the adder 12
1 is input. Therefore, the [1 + G] signal is obtained at the output of the adder 121. That is, the frequency component is boosted up. Analog switch 1
When the output (cut signal) of the inverting amplifier 125 is given to the band-pass filter 123 via 22b, the output of the band-pass filter 123 becomes [1 / (1 + G)]. This is because the output of the adder 121, that is, the inverting amplifier 12
This is because the input of 5 is [1 + G]. Therefore, the frequency component is cut.

In the embodiment shown in FIG.
That is, since the detection circuit (not shown) always receives the output of the band-pass filter 123, the frequency level can be displayed on the frequency level display device 22 by the microcomputer 20 as a bar, as in the related art. Note that when switching between the boost circuit and the cut circuit, the bandpass filter 12
Although the output of No. 3 greatly changes, it is sufficient that the output is adjusted by the level calculation by the microcomputer 20 to drive the frequency level display device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a conventional audio device.

FIG. 2 is a block diagram showing one embodiment of the present invention.

FIG. 3 is a circuit diagram showing a bandpass filter in the embodiment of FIG.

FIG. 4 is a circuit diagram showing a switch in the embodiment of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Audio device 12 ... Graphic equalizer circuit 14 ... Volume 20 ... Microcomputer 121 ... Adder 122 ... Switch 123 ... Bandpass filter 124 ... Gain adjustment resistance

Claims (2)

[Claims] 1. A graphic equalizer circuit used in an audio device having a graphic equalizer function section and a spectrum analyzer function section, wherein one of an input means for receiving an audio signal at an input, a band-pass filter, and an output signal of the band-pass filter. Gain adjusting means for receiving the gain-adjusted output signal to the other input of the adding means; inverting means for inverting the output signal of the adding means; and applying the audio signal to the band-pass filter or outputting from the inverting means. A graphic equalizer circuit, comprising: switch means for switching whether to apply a signal to the bandpass filter. 2. An addition means for receiving an audio signal at one input, a band-pass filter, a gain adjustment means for receiving an output signal of the band-pass filter and providing an output signal whose gain has been adjusted to the other input of the addition means, Using a graphic equalizer circuit comprising: inverting means for inverting an output signal of the means; and switch means for switching between applying the audio signal to the bandpass filter or applying the output signal of the inverting means to the bandpass filter. An audio device, wherein an output signal of a pass filter is further provided to the spectrum analyzer function unit.