JPS6336563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an audio tone control circuit.

Recently, there has been an increase in the number of audio multiplexed programs on television, and accordingly there is a demand for increased functionality and functionality. Furthermore, as television receivers become increasingly remote-controlled, the need for audio-related remote control is increasing.

This invention is a simple circuit that can be easily integrated into a circuit, and is capable of boosting and cutting high and low frequencies using direct current, and is also suitable for remote control.

FIG. 1 shows an example of a circuit according to the present invention, in which an input signal from a terminal 10 is directly supplied to an adder 20.
In addition, the input signal from the terminal 10 is filtered through a filter 31,
It is supplied to a boost signal path consisting of an amplifier 32 and a gain control circuit 33, and its output signal is sent to an adder 20.
supply to. Furthermore, the input signal from the terminal 10 is passed through a filter 41, an amplifier 42 and a gain control circuit 43.
The output signal is supplied to the adder 20. And adder 20
, adds the signal passed through the boost signal path to the input signal, subtracts the signal passed through the cut signal path,
The output signal is taken out to the terminal 60. Then, the voltage V _c obtained from the volume 50 is applied to the gain control circuit 3.
3 and 43 as gain control voltages.

In this circuit, if the filters 31 and 41 are high-pass filters, it is possible to boost and cut the high frequency range. If the filters 31 and 41 are low-pass filters, it is possible to boost or cut low frequencies. Normally, the boost and cut characteristics of the high range are the 3rd type.
What is required is as shown in the figure, and the amount of boost is
The amount of attenuation is about 10 dB, and the amount of attenuation is made infinite at infinite frequencies. According to the circuit of the present invention, such required characteristics can be easily obtained.

That is, the gain control circuit 33 is set so that the gain becomes zero when the control voltage V _c is in the range from the center value V _p to zero. Conversely, the gain control circuit 43 is set so that the gain becomes zero when the control voltage V _c is in the range from the center value V _p to the maximum value 2V _p . Therefore, when the control voltage V _c is at the center value V _p , the output signals of the gain control circuits 33 and 43 are both zero, the input signal is obtained as is at the terminal 60, and the frequency characteristics are flat.

When the control voltage V _c changes from the center value V _p to the maximum value 2V _p , the gain of the gain control circuit 33 increases, and the gain becomes 1 at the maximum value 2V _p . Therefore, in this state, the gain of the amplifier 32 is
When A ₁ is set, the gain of the boost signal path is A ₁ as shown in FIG. 4, so a high boost of A ₁ +1 is obtained. Of course, A ₁ >0.

Conversely, when the control voltage V _c changes from the center value V ₀ toward zero, the gain of the gain control circuit 43 increases so that the gain becomes 1 at zero. Therefore, in this state, when the gain of the amplifier 42 is _A2 , the gain of the cutting signal path is _A2 as shown in FIG. 5, resulting in a high cut of 1- _A2 .
If 0<A ₂ ≦1 and A ₂ =1, the amount of attenuation can be infinite.

Boosting and cutting can also be achieved in the same way by replacing the filters 31 and 41 with low-pass filters.

According to this circuit, since the control curves can be freely set in both the boost direction and the cut direction, it is possible to easily obtain aurally preferable characteristics.

As in the example shown in FIG. 2, the filter 31 can also be used for boosting and cutting. However, in this case, it is difficult to obtain symmetry between the boost and cut characteristics.

In order to be able to perform treble and bass independently, as shown in Figure 6, there is only one signal path that takes out the input signal as is.
A high-frequency boost signal path consisting of a high-pass filter 31H, an amplifier 32H, and a gain control circuit 33H, a high-frequency cut signal path consisting of a high-pass filter 41H, an amplifier 42H, and a gain control circuit 43H, a low-pass filter 31L, and an amplifier 32L. and a reduction boost signal path consisting of a gain control circuit 33L, a low-pass filter 41L, and an amplifier 42.
It is sufficient to provide a reduction cutting signal path consisting of L and gain control circuit 43L in parallel. 50H is a treble volume, and 50L is a bass volume.

FIG. 7 shows a specific example of the circuit of the present invention, which is for treble control. On the one hand, the input signal from the signal source 11 is supplied as is to the transistor Q ₀ . The high boost block consists of transistors _Q1 to _Q8 . The high-cut block consists of transistors _Q11 to _Q18 .

Here, the input signal from the signal source 11 is supplied as is to the base of the transistor _Q1 ,
On the other hand, a high-frequency component signal current flows through the transistors Q ₁ and _{Q 2 by} being supplied to the base of the transistor Q ₂ via a low-pass filter consisting of a resistor R ₁ and a capacitor C 1 . Then, the signal current is taken out through transistor _Q6 ,
High frequency components are added.

Similarly, the input signal from the signal source 11 is supplied as is to the base of the transistor _Q12 ,
On the other hand, the base of transistor Q ₁₁ is supplied via a low-pass filter consisting of resistor R ₂ and capacitor C ₂ , so that transistors Q ₁₂ and Q ₁₁
A high-frequency component signal current flows through. Then, the signal current is taken out through transistor _Q16 , and the high frequency component is subtracted.

When the control voltage V _c is greater than the center value V ₀ , transistors Q ₇ and Q ₁₈ are on, transistors Q ₈ and Q ₁₇ are off, current flows through transistor Q ₆ , and no current flows through transistor Q ₁₆ . , becomes high boost. In this case, transistor Q ₇
The gain is determined by the current _I1 of the constant current source on the emitter side of _Q8 .

Conversely, when the control voltage V _c is smaller than the center value V ₀ , transistors Q ₈ and Q ₁₇ are on, transistors Q ₇ and Q ₁₈ are off, current flows through transistor Q ₁₆ , and current flows through transistor Q ₆ . It becomes high-cut. In this case, the gain is determined by the current I ₂ of the constant current source on the emitter side of the transistors Q ₁₇ and Q ₁₈ .

According to this invention, boosting and cutting of high and low frequencies can be performed using a single DC volume. In particular, the control curve can be set freely and completely flat characteristics can be created. In addition, it can be integrated into an integrated circuit by removing the filter capacitor, making it suitable for remote control.

[Brief explanation of the drawing]

Figures 1 and 2 are system diagrams of an example of the circuit of the present invention, Figures 3 to 5 are diagrams showing its characteristics, and Figure 6 is a diagram showing the characteristics of the circuit.
The figure is a system diagram when treble and pass are performed independently, and FIG. 7 is a connection diagram of a specific example. 31 and 41 are filters, and 33 and 43 are gain control circuits.

Claims (1)

[Claims] 1. A first transistor composed of a first transistor and a second transistor.
a differential amplifier, third and fourth transistors whose bases are connected to the collectors of the first and second transistors and whose emitters are connected to each other, and a fifth and sixth transistor. a differential amplifier; seventh and eighth transistors whose bases are connected to the collectors of the fifth and sixth transistors, respectively, and whose emitters are connected to each other; emitters of the third and fourth transistors and seventh and eighth transistors; 7,
each connected to the emitter of the eighth transistor,
first and second gain control circuits that differentially control the emitter currents of the third and fourth transistors and the emitter currents of the seventh and eighth transistors; and a volume supplying a common control voltage to the control circuit and a collector connected to the collectors of the fourth and eighth transistors;
a ninth transistor whose base is connected to the bases of the first, second, fifth, and sixth transistors; and a filter circuit; The output signal is supplied to the base of the second and fifth transistors via the filter circuit, and an output signal is obtained from the collector of the ninth transistor. A tone control circuit that controls the frequency characteristics of the frequency characteristics and switches the control mode of the frequency characteristics.