JPH0644176Y2 - Volume and sound quality adjustment device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a device for adjusting the volume and sound quality of an acoustic signal.

2. Description of the Related Art A sound signal output from a record player, a compact disc player, a tuner, or the like is adjusted in volume and sound quality by an amplification device according to a listener's preference, and is reproduced by a speaker or the like.

FIG. 5 is a block diagram of a configuration of a conventional audio device. A sound signal output from a reproducing device 51 such as a record player, a compact disc player, or a tuner is given to a volume adjusting circuit 52, and the intensity of the volume reproduced by a speaker 53 is set.

The volume adjusting circuit 52 is composed of a ladder circuit 52a, a current setting circuit 52b and an operational amplifier 52c, and an acoustic signal output from the reproducing device 51 is given to the ladder circuit 52a and corresponds to the setting state of the current setting circuit 52b. Current value is operational amplifier 5
Given to 2c. As the ladder circuit 52a, for example, a circuit called an R-2R type ladder resistor for an electronic volume is well known, and the circuit is composed of a plurality of resistors connected in parallel and a switch connected in series with each resistor. The current value is set according to the switching mode. The operational amplifier 52c converts the input current value into a corresponding voltage signal and sends it to the sound quality adjustment circuit 54.

The sound quality adjustment circuit 54 is a well-known circuit called a CR-NF type bass train circuit, and includes a treble circuit 54a that adjusts sound quality in a high frequency region and a bus circuit 54b that adjusts sound quality in a low frequency region.
And an operational amplifier 54c. The sound quality adjustment circuit 54 varies the frequency characteristic of the sound quality adjustment circuit 54 by negatively feeding back a signal component in a specific frequency region included in the output signal of the operational amplifier 54c to the inverting input terminal of the operational amplifier 54c. That is, the treble circuit 54a
By moving the contact C of the variable resistor 54a1 in the direction of the maximum emphasis position A, the amount of the high frequency component negatively fed back to the operational amplifier 54c is reduced, so that the high frequency component included in the acoustic signal can be emphasized. it can. Further, by moving the contact C in the direction of the maximum attenuation position B, the amount of the high frequency component negatively fed back to the operational amplifier 54c increases, so that the high frequency component included in the acoustic signal can be attenuated. Similarly, in the bus circuit 54b, the contact C of the variable resistor 54b1 is moved toward the maximum emphasis position A or toward the maximum attenuation position B to emphasize or attenuate the low frequency component included in the acoustic signal. be able to.

The sound signal output from the sound quality adjustment circuit 54 is a power amplification circuit.
The power is amplified by 55 and then reproduced by the speaker 53.

Problems to be Solved by the Invention In the above-described conventional volume and sound quality adjusting circuit, the operational amplifier is provided in each of the volume adjusting circuit and the sound quality adjusting circuit, which makes the circuit configuration complicated and raises the cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a volume and sound quality adjusting device that simplifies the circuit configuration by omitting an operational amplifier, reduces the area of a printed circuit board on which circuit components are mounted, and reduces the cost.

The present invention has a volume control circuit that adjusts the volume of an acoustic signal by varying the amount of attenuation of the acoustic signal, and an input terminal. An output from the volume control circuit is given to this input terminal. And an audio quality adjustment circuit that is connected in parallel to the output of the operational amplifier, adjusts the acoustic component in a predetermined frequency region, and negatively feeds back to the input terminal of the operational amplifier. It is a volume and sound quality adjusting device.

In the present invention, the volume of the acoustic signal input to the volume adjusting circuit is adjusted by changing the attenuation amount of the acoustic signal in the volume adjusting circuit. The output of the volume adjusting circuit is given to the operational amplifier and amplified to the volume set by the volume adjusting circuit. The sound quality adjustment circuit is connected in parallel with the output of the operational amplifier, and a predetermined frequency component of the sound quality adjustment circuit is negatively fed back to the operational amplifier.

Embodiment FIG. 1 is a block diagram showing the configuration of an audio device using a volume and sound quality adjusting device according to the present invention. An acoustic signal output from the reproducing device 1 such as a record player, a compact disc player or a tuner is sent to the volume adjusting circuit 2, and an acoustic signal current corresponding to the setting state of the volume setting circuit 3 is given to the operational amplifier 4.

The volume adjusting circuit 2 is a well-known circuit called a so-called R-2R type ladder circuit, and the sound signal sent from the reproducing apparatus 1 is set in accordance with the contact mode of the switches S1 to Sn set by the volume setting circuit 3. A current value corresponding to the switching mode of the switches S1 to n is applied to the operational amplifier 4 by shunting the resistors 211 to 21n and the resistors 221 to 22n. The contact mode of the switches S1 to Sn is determined by the volume setting circuit 3, and for example, the switches are
The common contact S1c of S1 is selected as either the individual contact S1a or the individual contact S1b.

The operational amplifier 4 is a circuit for converting the current value sent from the volume adjusting circuit 2 into a voltage value, and the output thereof is input to the sound quality adjusting circuit 5 composed of the treble circuit 5a and the bus circuit 5b. The treble circuit 5a and the bus circuit 5b feed back a specific frequency component contained in the acoustic signal output from the operational amplifier 4 to the inverting input terminal of the operational amplifier 4 via the feedback resistor 6.

The sound signal whose sound quality is adjusted by the sound quality adjustment circuit 5 is power-amplified by the power amplification circuit 8 to drive the speaker 7.

Next, the operation of the sound quality adjustment circuit 5 will be described in more detail. The treble circuit 5a and the bus circuit 5b have the same basic idea of operation, except for the arrangement of the resistors and capacitors that are included in the treble circuit 5a. Therefore, the operation of the treble circuit 5a will be described in detail below.

The treble circuit 5a changes the amount of negative feedback to the inverting input terminal of the operational amplifier 4 via the feedback resistor 6 by changing the set resistance value of the variable resistor 5a3, so that the high frequency component included in the audio signal is changed. Signal can be enhanced or attenuated.

Next, the transfer function of the sound quality adjustment circuit 5 is obtained. The transfer function calculated below is calculated for the treble circuit 5a.
Therefore, the transfer function obtained below does not include the bus circuit 5b.

The output voltage of the operational amplifier 4 is e ₀ , of the capacitor 5a5 of the treble circuit 5a and the variable resistor 5a3, the current flowing through the resistor 5a1 on the capacitor 5a5 side is i ₁ , the combined impedance of the capacitor 5a5 and the resistor 5a1 is Z ₁ , and variable. Resistor 5a3 capacitor 5
If the resistance on the a4 side is 5a2, the current flowing through the resistance 5a2 and the capacitor 5a4 is i ₂ , and the combined impedance of the resistance 5a2 and the capacitor 5a4 is Z ₂ , the first expression is satisfied.

e ₀ = i ₁ · Z ₁ + i ₂ · Z ₂ (1) Next, when the current flowing through the feedback resistor 6 is i _f , the second equation holds.

i ₁ = i ₂ + _if (2) Further, when the resistance value of the feedback resistor 6 is R _f , the potential of the inverting input terminal and the potential of the non-inverting input terminal of the operational amplifier 4 are substantially equal to each other, and the non-inverting inverting input Since the terminal is grounded,
Formula 3 is established.

e ₀ = i ₁ · Z ₁ + _if · R _f (3) Substituting i _{2 in} the second equation into the first equation and rearranging it yields the fourth equation.

e ₀ = i ₁ · (Z ₁ + Z ₂ ) −i _f · Z ₂ (4) When the third equation is modified and i ₁ is obtained, the fifth equation is derived.

Substituting the fifth equation into the fourth equation and rearranging it yields the sixth equation.

Here, the capacitance of the capacitor 5a5 is C ₅ , and the resistance value of the resistor 5a1 is
Set the resistance value of R ₁ and resistor 5a2 to R ₂ and the capacitance of capacitor 5a4.
Assuming C ₄ , the impedances Z ₁ and Z ₂ are expressed by the seventh equation.

Then, by substituting the impedances Z ₁ and Z ₂ shown in the equation 7 into the equation 6 and rearranging them, the equation 8 is obtained.

In the equation (8), the current _if can be considered as the set current of the volume adjusting circuit 2 input to the operational amplifier 4. Therefore, the terms after the equation ( _if) in the equation (8) are the transfer function of the treble circuit 5a. Become. Assuming that the variables M and N are as shown in the equation 9, the frequency characteristic of the treble circuit 5a changes depending on the magnitude relation of the variables M and N.

Hereinafter, it will be described that the frequency characteristic of the treble circuit 5a changes depending on the magnitude relation between the variables M and N.

FIG. 2 is a frequency characteristic diagram in the case where the variables M and N have the relationship of Expression 10.

M> N (10) In FIG. 2, lines 1 to 13 are currents of the formula 8
current value i _f, that is, the output of the operational amplifier 4 by changing the current value set by the volume control circuit 2 which means that the change in the vertical in FIG. 2.

When the variables M and N have the relationship of Expression 10, it means that the high frequency is emphasized.

FIG. 3 is a frequency characteristic diagram when the variables M and N have the relationship of Expression 11.

M = N (11) Lines l4 to l6 are the same as those described with reference to FIG. 2, and the output voltage of the operational amplifier 4 changes according to the current value set by the volume adjusting circuit 2, and in FIG. It means to move up and down in parallel.

When the variables M and N have the relationship of the eleventh equation, the high range emphasis or attenuation is not performed.

FIG. 4 is a frequency characteristic diagram when the variables M and N have the relationship of Expression 12.

M <N (12) Lines l7 to l9 are the same as above, and variables M and N are the first
When there is a relationship of two equations, it indicates that the high range is attenuated.

Although the frequency characteristics of the sound quality adjustment circuit 5 have been described above with respect to the treble circuit 5a, the same applies to the bus circuit 5b, and enhancement or attenuation in the low frequency band can be realized. Further, even when the treble circuit 5a and the bus circuit 5b are connected in parallel, the high frequency region and the low frequency region can be emphasized or attenuated by the principle of superposition.

As described above, in the present embodiment, the well-known circuit CR-
By feeding back the output of the NF type bus circuit to the inverting input terminal of the operational amplifier via the feedback resistor, the frequency characteristics of the high frequency band and the low frequency band of the acoustic signal can be changed.

As described above, according to the present invention, the operational amplifier can be omitted by sharing the operational amplifier provided in the conventional volume adjusting circuit and the sound quality adjusting circuit, respectively. The simplification can be achieved and the mounting area of the volume and sound quality adjustment circuit portion on the printed circuit board can be reduced. Further, the cost can be reduced by simplifying the circuit configuration.

[Brief description of drawings]

FIG. 1 is a block diagram of the configuration of an audio device using a volume and sound quality adjusting device according to the present invention, and FIGS. 2 to 4 are variables.
FIG. 5 is a frequency characteristic diagram of the treble circuit 5a when M and N are changed, and FIG. 5 is a configuration block diagram of a conventional audio device. 2 ... Volume adjusting circuit, 3 ... Volume setting circuit, 4 ... Operational amplifier, 5 ... Sound quality adjusting circuit, 5a ... Treble circuit, 5b ... Bus circuit, 6 ... Feedback resistor

Claims (1)

[Scope of utility model registration request] 1. An operational amplifier having a volume adjusting circuit for adjusting the volume of an acoustic signal by varying an attenuation amount of the acoustic signal, an input terminal, and an operational amplifier to which an output from the volume adjusting circuit is given to the input terminal, A sound volume and sound quality adjusting device, which is connected in parallel to the output of the operational amplifier, and which adjusts an acoustic component in a predetermined frequency region and negatively feeds back to the input terminal of the operational amplifier. .