JPH0450647Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a bass volume adjustment circuit in an audio reproduction system.

BACKGROUND ART FIG. 5 shows a conventional example of a bass volume adjustment circuit. In this device, an audio signal is supplied to a non-inverting input terminal of an operational amplifier 1 via a resistor 2, and a variable resistor 3 is provided between the non-inverting input terminal and the inverting input terminal of the operational amplifier 1. Variable resistor 3
A resonant circuit 4 is connected between the movable element and ground. Further, a feedback resistor 5 is connected between the inverting input terminal and the output terminal of the operational amplifier 1.

In such a conventional bass volume adjustment circuit, the amplification gain changes around the low frequency ₁ set in the resonant circuit 4, and the range of change in the amplification gain decreases as the frequency moves up or down from the center frequency ₁ . do. When the variable resistor 3 operates as a bass control volume and moves the mover of the variable resistor 3 in the direction of arrow A, the input level to the non-inverting input terminal of the operational amplifier 1 decreases, and the amplification gain by the operational amplifier 1 decreases. decreases, resulting in a bass cut (down). Also, mover of variable resistor 3 is indicated by arrow A.
If it is moved in the opposite direction, the input level to the non-inverting input terminal of the operational amplifier 1 increases, or the amplification gain of the operational amplifier 1 increases, resulting in a bass boost (increase). Therefore, by adjusting the variable resistor 3, variable frequency characteristics can be obtained in the bass range as shown in FIG.

In addition, in such a conventional bass volume adjustment circuit, when the gain is increased by adjusting the variable resistor 3, the gain at the center frequency ₁ increases and the frequency bands before and after it, for example, ₂₀₀
The gain in the ~300Hz band also increases, although it is smaller than the gain increase at the center frequency ₁ . This band of 200 to 300 Hz is a band that increases due to the transfer characteristics in a narrow reproduction environment such as inside a car, and the increase in gain in this band causes the sound to be heard as muffled. Furthermore, when the Q in the resonance characteristics of the resonant circuit 4 shown in Fig. 7 is increased, the gain in the band around frequency ₂ decreases compared to when Q is low, but the gain in the deep bass range around frequency ₃ also decreases, resulting in low It has the disadvantage of feeling lacking.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a bass volume adjustment circuit that can prevent muffled sounds and lack of bass in a narrow reproduction environment such as inside a vehicle interior.

The bass volume adjustment circuit of the present invention includes a first resonant circuit that generates a first resonance signal in response to an input audio signal within a first low frequency range, and a first low frequency a second resonant circuit that generates a second resonant signal in response to an input audio signal within a second low frequency range included in the second resonant signal; an adjusting means that changes the level of the first and second resonant signals in opposite directions and outputs the same; and an amplifying means for amplifying the input audio signal according to frequency characteristics corresponding to respective levels of the first and second resonance signals outputted from the means, and a band excluding a second low frequency of the first low frequency. It is characterized in that the gain increases and decreases in the second low frequency band change in directions opposite to each other.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the bass volume adjustment circuit shown in FIG. 1, which is an embodiment of the present invention, the same parts as those in the conventional circuit shown in FIG.
A resistor 7, a variable resistor 8, and a resistor 9 are connected in series between both ends of the resistor 7. The resistance value of resistor 7 is resistor 9
resistance value. A resonant circuit 10 is connected between the movable element of the variable resistor 8 and ground. Further, the variable resistor 10 and the variable resistor 3 are designed to be interlocked. The rest of the configuration is the same as the circuit shown in FIG. Note that the resonance center frequency of the resonance circuit 4 is 100Hz or _less , and the resonance center frequency of the resonance circuit 10 is around 150 to 300Hz.
It is set to ₂ . Further, the Q of the resonant circuit 10 is set higher than that of the resonant circuit 4.

In the bass volume adjustment circuit according to the present invention having such a configuration, in the band centered around frequency ₂ , the change in amplification gain due to the variable resistor 3 and the resonant circuit 4 is caused by the resistors 7, 9, the variable resistor 8, and the resonant circuit 10. It acts in such a way that it is canceled out.

That is, the level of the first resonance signal generated from the resonance circuit 4 is adjusted by the variable resistor 3, and the level of the second resonance signal generated from the resonance circuit 10 is adjusted by the variable resistor 8. Now, if the movable element of variable resistor 3 is moved in the direction of arrow B,
In conjunction with this, the movable element of the variable resistor 3 moves in the direction of the arrow C. As a result, the input level to the non-inverting input terminal of the operational amplifier 1 is increased by the variable resistor 3 and the resonant circuit 4, and the amplification gain of the operational amplifier 1 is increased, resulting in a bass boost.
However, the resistors 7 and 9, the variable resistor 8, and the resonant circuit 10 lower the input level to the non-inverting input terminal of the operational amplifier 1 in the band centered on frequency ₂ , and also reduce the amplification gain of the operational amplifier 1. Therefore, as shown by the solid line in Fig. 2, as the mover is moved, the amplification gain increases in the first low range centered on frequency ₁ , other than the second low range centered on frequency ₂ . 2. In the low range, the amplification gain is almost non-existent or slightly reduced.

Further, when the movable element of the variable resistor 3 is moved in the direction opposite to the arrow B, the movable element of the variable resistor 3 is moved in the opposite direction to the arrow C in conjunction with the movement. As a result, the input level to the non-inverting input terminal of the operational amplifier 1 decreases, and the amplification gain of the operational amplifier 1 decreases, resulting in a bass cut. However, the resistors 7 and 9, the variable resistor 8, and the resonant circuit 10 increase the input level to the non-inverting input terminal of the operational amplifier 1 in the band centered on frequency ₂ , and also increase the amplification gain of the operational amplifier 1. As shown by the broken line in Figure 2, as the mover is moved in the opposite direction, the amplification gain decreases in the first low range centered on frequency ₁ , other than the second low range centered on frequency ₂ . However, in the second low frequency range, the amplification gain is almost non-existent or slightly increased.

3 and 4 show other embodiments of the invention. In the bass volume adjustment circuit shown in FIG. 3, the non-inverting input terminal of the operational amplifier 1 is grounded via a resistor 11 and a resonant circuit 10, and one end of the resonant circuit 10 on the resistor 11 side is connected to a variable resistor 12,
It is grounded via the resonant circuit 4, and only bass boost is possible using a single variable resistor 12. Further, in the bass volume adjustment circuit shown in FIG. 4, switches 13a and 13b are used to switch between bass boost and bass cut.

In addition, in each embodiment of the present invention described above,
Although only one channel is shown, for example, if the circuit in Figure 1 is applied to a two-channel stereo, the same circuit will be provided for each channel, and a four-channel system will be installed so that the four variable resistors are interlocked. things are used. Further, when the circuit of FIG. 3 or 4 is applied, a double variable resistor is provided.

Effects of the invention As described above, the bass volume adjustment circuit of the invention can, for example, increase the low-frequency audio signal level centered on frequencies below 100Hz, and
Since it is controlled to cancel out the rise in the level of the mid-low range between 200 and 300 Hz, it is possible to prevent muffled sound in a narrow playback environment such as the inside of a car, and it is possible to obtain high-quality bass. Furthermore, as shown in FIG. 2, the cut in the middle and low ranges does not adversely affect the deep bass range, making it possible to prevent a lack of bass.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the operating characteristics of the circuit in FIG. 1, and FIGS. 3 and 4 are circuit diagrams showing other embodiments of the present invention. Fifth
FIG. 6 is a circuit diagram showing a conventional example of a bass volume adjustment circuit, FIG. 6 is a diagram showing operating characteristics of the circuit of FIG. 5, and FIG. 7 is a diagram showing resonance characteristics of a resonant circuit. Explanation of symbols of main parts, 1... operational amplifier,
3, 8, 12... variable resistor, 4, 10... resonant circuit.

Claims (1)

[Scope of utility model registration request] the first for the input audio signal within the first low frequency range.
a first resonant circuit that generates a resonant signal; and a second resonant signal generated in response to an input audio signal within a second low frequency range that is greater than the resonant center frequency of the first resonant circuit and that is included in the first low frequency range. a second resonant circuit; an adjusting means for changing the level of the first and second resonant signals in opposite directions and outputting the same; an amplifying means for amplifying the input audio signal according to frequency characteristics, and the gain increase/decrease in the first low frequency band excluding the second low frequency band and the second low frequency band change in opposite directions to each other. A bass volume adjustment circuit characterized by: