JPS6143302Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a sound quality adjustment device that can increase or decrease the output level of a specific frequency band, and particularly relates to a sound quality adjustment device that can increase or decrease the level of an arbitrary frequency band.

2. Description of the Related Art Conventionally, there is a sound quality adjustment device as shown in FIG. 1 that can vary the output level of an arbitrary frequency band. This sound quality adjustment device is composed of a sound quality adjustment circuit 2 and a series resonant circuit 4, and the series resonant circuit 4 includes a capacitor 6 and a simulated inductance circuit 8.
(hereinafter referred to as the simulated L circuit).

The simulated L circuit 8 includes an operational amplifier 10a, a variable resistor 12, a variable resistor 14, and a capacitor 16. The output terminal of the operational amplifier 10a is connected to an inverting input terminal 9a, and this inverting input terminal 9a is connected to a variable resistor 12 and a capacitor 1.
6 to the non-inverting input terminal 11a. This non-inverting input terminal 11a is connected to the variable resistor 1
It is grounded via 4. Variable resistor 12 and variable resistor 14 are linked. Further, a resonance capacitor 6 is connected to the connection point between the variable resistor 12 and the capacitor 16, and this capacitor 6 is connected to the sound quality adjustment circuit 2.

The sound quality adjustment circuit 2 includes an operational amplifier 10b, a variable resistor 18, a resistor 20, and a resistor 22, and an inverting input terminal 9b of the operational amplifier 10b.
A variable resistor 18 is connected between the input terminal 11b and the non-inverting input terminal 11b. The middle point of this variable resistor 18 is grounded, and the movable contact is connected to the capacitor 6. The non-inverting input terminal 11b of the operational amplifier 10b is connected to the input terminal 24 via the resistor 22, and the output terminal of the operational amplifier 10b is connected to the external output terminal 26.
and is connected to the inverting input terminal 9b via the resistor 20.

Now, it is assumed that the movable contact of the variable resistor 18 of the sound quality adjustment circuit configured as described above is moved to the a side, and the series resonant circuit 8 is connected to the inverting input terminal 9b of the operational amplifier 10b. In this state, input terminal 24
When a signal with the same frequency as the resonant frequency _p of the series resonant circuit 8 is applied to the inverting input terminal 9b, the inverting input terminal 9b is grounded through the resonant impedance Z _p , and the negative feedback applied to the operational amplifier 10b becomes small, so the output level decreases. Obtain rising peak characteristics. Conversely, if the movable contact of the variable resistor 18 is moved to the b side, the resonant impedance Z _p is connected to the non-inverting input terminal 11b, and the signal input to the non-inverting input terminal 11b is becomes smaller, the output level decreases, and a dip characteristic is obtained. Therefore, by moving the movable contact of the variable resistor 18, the output level in the frequency band centered around the resonance frequency _p can be increased or decreased as shown in FIG.

However, this conventional sound quality adjustment circuit has the following drawbacks.

Now, the value of the variable resistor 12 in the simulated L circuit 8 is
R ₁ , the value of variable resistor 14 is R ₂ , capacitor 16
If the value of is C ₁ , the voltage at point C is V _C , the terminal voltage of the inverting input terminal 9a is V _I , and the terminal voltage of the non-inverting input terminal 11a is V _N , then the current i ₁ flowing through the variable resistor 12 is And the current i ₂ flowing through the capacitor 16 is i ₁ =V _C −V _I /R ₁ ...(1) The impedance Z _L of the simulated L circuit seen from point C is becomes.

Here, since the output terminal of the operational amplifier 10a is connected to the inverting input terminal 9a, the inverting input terminal 9a
The terminal voltage V _I of is almost equal to the terminal voltage V _N of the non-inverting input terminal 11a, It is expressed as

Substituting this equation (4) into equation (3), we get becomes.

Expanding this formula (5), Z _L = R ₁ + (ωC ₁ R ₁ ) ² R ₂ + jωC ₁ R ₁ R ₂
−jωC ₁ R ₁ ² /R ₁ ² ω ² C ₁ ² +1... (5)'.

Here, since R ₁ <<1/ωC ₁ , the formula (5)' becomes Z _L = R ₁ + (ωC ₁ R ₁ ) ² R ₂ + jωC ₁ R ₁ R ₂ (6).

Moreover, the impedance _{Z of the series resonant circuit 4 composed of the simulated L circuit 8 and the capacitor 6 as seen from the point d is Z=1/jωC 2 +} Z _L =R ₁ +( ωC ₁ R ₁ ) ² R ₂ +j(ωC ₁ R ₁ R ₂ −1/ωC ₂ ) ...(7).

The resonant frequency _p , resonant impedance Z _p and Q of this series resonant circuit 4 are as follows: Therefore, if the linked variable resistor 12 and variable resistor 14 are changed to change the resonant frequency _p , Q can be kept constant, but the resonant impedance Z _p changes as shown in Figure 3 and remains constant. I can't do it. This resonant impedance Z
Since _p becomes smaller as the resonance frequency _p becomes higher, the frequency band in which the output level can be adjusted by the variable resistor 18 of the sound quality adjustment circuit 2 expands as the resonance frequency _p becomes higher, and the amount of change in the level becomes larger. It had the disadvantage of becoming.

This invention aims to provide a sound quality adjustment device in which the amount of change in the output level and the frequency bandwidth do not change even if the frequency band in which the output level can be adjusted is varied.

This invention will be explained below based on an illustrated embodiment. Note that the same parts as in the conventional example are given the same reference numerals, and the description thereof will be omitted.

In FIG. 4, 28 is a compensation circuit, and this compensation circuit 28 is inserted between the tone quality adjustment circuit 2 and the capacitor 6. Compensation circuit 28 is operational amplifier 10
c, resistor 32, resistor 34 and variable resistor 30
It consists of The output terminal of the operational amplifier 10c is connected to the inverting input terminal 9c of the operational amplifier 10c, and the inverting input terminal 9c is connected to the resistor 32 and the resistor 3.
4. Non-inverting input terminal 11 via variable resistor 30
connected to c. The connection point between the variable resistor 30 and the non-inverting input terminal 11c is connected to the capacitor 6, and the connection point between the resistor 32 and the variable resistor 30 is as follows.
It is connected to the movable contact of the variable resistor 18. The variable resistor 30 is linked with the variable resistor 12 and the variable resistor 14, so that when the resistance values of the variable resistor 12 and the variable resistor 14 become smaller, the resistance value of the variable resistor 30 becomes smaller. . Note that resistors 12a and 14a connected in series to the variable resistor 12 and the variable resistor 14 are protection resistors for the operational amplifier 10a.

Now let the value of the resistor 32 be _R3 , the sum of the resistance values of the resistor 34 and the variable resistor 30 be _R4 , the voltage applied to point e _be Ve, and the impedance of the series resonant circuit 4 seen from point d be Z. , the terminal voltage of the inverting input terminal 9c of the operational amplifier 10c is V′ _I , and the non-inverting input terminal 1
If the terminal voltage of 1c is _V'N , the current _i3 flowing through the resistor 32 is _i3 =Ve _{- V'I} / _R3 (11). Similarly, the current i ₄ flowing through the resistor 34 and the variable resistor 30 is i ₄ =V _e /R ₄ +Z (12).

The combined impedance Z _e of the series resonant circuit 4 and the compensation circuit 28 viewed from point e is Z _e =V _e /i ₃ +i ₄ (13).

Substituting equations (11) and (12) into equation (13), Z _e becomes becomes.

Here, since the output terminal of the operational amplifier 10c is connected to the inverting input terminal 9c, the inverting input terminal 9
The terminal voltage V' _I of c is approximately equal to the terminal voltage V' _N of the non-inverting input terminal 11c, and is expressed as V' _I =V' _N =Z/R ₄ +ZV _e (15).

Substituting equation (15) into equation (14), we get It is expressed as

Here, if R ₄ >>R ₃ , then equation (16) can be expressed as Z _e ≈R ₃ (R ₄ +Z)/R ₄ =R ₃ +R ₃ /R ₄ Z (17).

Here, the resonant impedance Z of the series resonant circuit 4
From equation (9), _p is R ₁ (variable resistor 14 and resistor 14a
Therefore, the resonant impedance Z _ep seen from point e is Z _ep =R ₃ /R ₄ R ₁ (1+C ₁ /C ₂ )+R ₃ (18).

Here R ₃ is a fixed resistance and variable resistor 30
and variable resistor 14 are linked, so R ₄ and
The ratio of R ₁ takes a constant value, and Z _ep takes a constant value regardless of R ₁ and R ₄ as shown in FIG.

Therefore, even if the resonant frequency _p is changed, e
Since the resonant impedance Z _ep seen from a point is constant, by changing the resonant frequency _p as in the conventional example, the frequency band in which the output level can be adjusted expands and the amount of change in the output level increases. Nor.

According to this invention, as explained above, it is possible to realize a sound quality adjustment device in which the amount of change in the level and the frequency bandwidth do not change even if the frequency band in which the output level can be adjusted is varied.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional sound quality adjustment device, Fig. 2 is a frequency characteristic diagram of the conventional sound quality adjustment circuit, and Fig. 3 is an impedance characteristic diagram as seen from point d of the series resonant circuit in the conventional sound quality adjustment circuit. FIG. 4 is a circuit diagram of a sound quality adjustment device based on this invention, and FIG. 5 is an impedance characteristic diagram of the composite impedance of the compensation circuit and the series resonant circuit of the sound quality adjustment circuit based on this invention, viewed from point e. 2...Sound quality adjustment circuit, 4...Series resonance circuit, 6
... Capacitor, 8 ... Simulated inductance circuit, 24 ... Input terminal, 26 ... Output terminal, 28
...Compensation circuit.

Claims (1)

[Scope of utility model registration request] A capacitor; a series resonant circuit is formed together with this capacitor, and the Q of the series resonant circuit is kept constant by interlocking the first and second variable resistors so that the ratio of their resistance values is constant. an operational amplifier in which the capacitor is connected to the non-inverting input terminal, the inverting input terminal is connected to the output terminal, and a fixed circuit having one end connected to the inverting input terminal; an impedance compensation circuit including a resistor, a third variable resistor having one end connected to the non-inverting input terminal side, and a series circuit having the other ends connected to each other; the fixed resistor and the third variable resistor; a sound quality adjustment circuit connected to the interconnection point with the series resonant circuit and configured to make the gain in a frequency band centered on the resonant frequency of the series resonant circuit different from the gain in other frequency bands; The first and third variable resistors are configured to be linked so that the ratio of their resistance values is constant, and the resistance value of the third variable resistor is selected to be larger than the resistance value of the fixed resistor. A sound quality adjustment device that is characterized by: