JPS5830765B2 - Tone control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tone control circuit using an amplifier in an audio device.

Conventionally, tone control circuits include CR attenuation type, BAX type, and negative feedback type tone control circuits shown in Figures 1, 2, and 3.The OCR type tone control circuit is shown in Figure 1. As shown, resistance 1.2,
3, 4, 5, 6, variable resistor 7.8, capacitor 9, 1
0, 11.12, and by giving frequency selectivity to the attenuation characteristics using a resistor and a capacitor, the high and low frequencies can be raised or lowered.

At frequencies where the reactances of capacitors 9, 10, 11, and 12 are large enough to be considered open circuits, the circuit shown in Figure 1A is formed, and at frequencies where the reactances of capacitors 9, 10, 11, and 12 are small enough to be considered short circuits, the circuit shown in Figure 1B is obtained. The equivalent circuit is

The transfer functions of the equivalent circuits shown in Figures 1A and 1B are completely different, and when using variable resistors with the same resistance value change rate characteristics, the boost and The cut ratio is completely different, and the change in boost and cut amount is determined by the frequency f on the horizontal axis, the output ratio dB of the tone control circuit on the vertical axis, and the sliding of the variable resistor as a parameter. The rotation angle of the child differs between the low range and the high range as shown in Fig. 1C.

It also had the drawbacks of high circuit insertion loss and low input impedance.

The BAX type tone control circuit also includes resistors 13, 14, 15, 16, variable resistor 17,
18, consists of capacitors 19, 20, 21 and an inverting amplifier 22, and has an input impedance between the input terminal IN and the inverting input terminal of the amplifier 22, and an input impedance between the output terminal OUT and the inverting input terminal of the amplifier 22. The ratio to the feedback impedance of the circuit determines the gain and frequency characteristics of the circuit.

Now, the equivalent circuit at a frequency where the capacitors 19, 20, 21 have a large actance and can be considered as an open circuit is as shown in Figure 2A, and at a frequency where the capacitors 19, 20, 21's actance is small and can be considered as a short circuit, the equivalent circuit is as shown in Figure 2A. The equivalent circuit is shown in the figure.

As is clear from FIGS. 2A and 2B, when using variable resistors with the same resistance value change rate characteristic curve without determining the transfer function, the position of the slider of the variable resistor is The boost and cut ratios are different.

It also has the drawbacks of phase inversion between the input signal and output signal and low input impedance.

In addition, as shown in Fig. 3, the negative feedback type tone control circuit consists of resistors 23, 24, 25, 26°27, variable resistors 28, 29, and capacitors 30°3L32, 33. A circuit of the same type as the conventional tone control circuit is connected to the negative feedback circuit of the non-inverting amplifier 34 to raise or lower the high and low frequencies.

This tone control circuit only has the boost and cut reversed from the CR type tone control circuit shown in Figure 1, and when using a variable resistor with the same resistance value change rate characteristics, the slider of the variable resistor The disadvantage is that the changes in boost and cut amounts with respect to the position of are different between high and low frequencies, and that there is gain.

The present invention has been made in view of the above, and an object of the present invention is to eliminate the above-mentioned drawbacks and provide a tone control circuit in which the phase of the output relative to the input is not inverted and the gain is 1 when the frequency characteristic is flat. .

The present invention will be explained below using examples.

FIG. 4 is a block diagram of the tone control circuit according to the first embodiment of the present invention.

In FIG. 4, reference numeral 40 is an ideal amplifier with sufficiently high input impedance, sufficiently low output impedance, and sufficiently large gain, and is a non-inverting type amplifier.

The input signal voltage applied to the input terminal IN is applied to the amplifier 40, the output voltage of the amplifier 40 is applied to a series circuit of impedance networks 41 and 42 for voltage division, and the voltage applied to the impedance network 42 is applied to the amplifier 40. 40, the output voltage of the amplifier 40 is applied to the series circuit of the impedance networks 43 and 44, and the common connection point of the impedance networks 43 and 44 is connected to the output terminal 0T.
It is configured to connect to the IJT and output a voltage applied to impedance network 44 .

The impedance networks 41 and 42 constitute a high-frequency circuit or a low-frequency circuit, and the impedance networks 43 and 44 constitute a low-frequency circuit or a high-frequency circuit.

Now, in the tone control circuit configured as described above, the impedance values of the impedance networks 41, 42, 43, and 44 are set, for example, at the midpoint position of the variable elements in each high-frequency and low-frequency circuit. Zl, Z2, Z3 and Z4,
Zl(S)=αZ2. The relationship is set as Z32αZ4.

Transfer function Tf of the tone control circuit shown in Fig. 4
(S) becomes.

Therefore, at the midpoint position of the variable element, the transfer function has a constant value l at any frequency, resulting in flat characteristics for all frequencies.

That is, the gain of the tone control circuit is 1 when the frequency characteristic is flat.

Furthermore, the phase of the output relative to the input is not reversed.

Next, a second embodiment will be explained.

FIG. 5 is a block diagram of a tone control circuit according to a second embodiment of the present invention.

In FIG. 5, numeral 40 is an ideal amplifier, which is a non-inverting type amplifier, as in the case of FIG. 4.

The input signal voltage applied to the input terminal IN is applied to a series circuit consisting of impedance networks 45 and 46 to divide the voltage, the voltage applied to the impedance network 46 is applied to the amplifier 40, and the output voltage of the amplifier 40 is In addition to being the output of the tone control circuit, the output voltage of the amplifier 40 is applied to a series circuit consisting of impedance networks 47 and 48 for voltage division, and the voltage applied to the impedance network 48 is negatively fed back to the amplifier 40. Configure.

The impedance networks 45 and 46 constitute a high-frequency circuit or a low-frequency circuit, and the impedance networks 47 and 48 constitute a low-frequency circuit or a high-frequency circuit.

In the tone control circuit configured as shown in FIG. 5, each impedance network is 45, 46, 4
The impedance values of 7 and 48 are Z5 , Z6 ,
Z7 and Z8 represent variable elements in the high-frequency and low-frequency circuits, for example, at the midpoint position of the variable elements, Z
5(S)=αZa(S), Z, , (S)αZ8(S).

S is j2πf. f is the frequency.

Transfer function Tf of the tone control circuit shown in FIG.
(S) becomes.

Therefore, at the midpoint position of the variable element, the transfer function has a constant value of 1 at any frequency, resulting in a flat frequency characteristic for all frequencies.

That is, the gain of the tone control circuit is 1 when the frequency characteristic is flat.

Furthermore, the phase of the output relative to the input is not reversed.

Next, an application example of the first embodiment will be explained.

FIG. 6 is a circuit diagram of an application example of the tone control circuit according to the first embodiment of the present invention.

In FIG. 6, 40 is an ideal amplifier and a non-inverting amplifier.

A resistor 50, a capacitor 51, a variable resistor 52, a capacitor 53, and a resistor 5 are connected between the output terminal of the amplifier 40 and the ground terminal.
A resistor 55 is connected between the output terminal of the amplifier 40 and the sliding piece of the variable resistor 52, and a resistor is connected between the sliding piece of the variable resistor 52 and the ground terminal. 56 are connected to each other, and the sliding portion of the variable resistor 52 is connected to the inverting input terminal of the amplifier 40 to form a high-frequency circuit, and the voltage applied to the resistor 56 is configured to be negatively fed back to the amplifier 40. .

On the other hand, a resistor 57 is connected between the output terminal of the amplifier 40 and the ground terminal.
, a series circuit of a variable resistor 58 and a resistor 59 is connected between the common connection point of the resistor 57 and the resistor of the variable resistor 58 and the slider of the variable resistor 58, and between the resistor 59 and the variable resistor. Capacitors 60 and 61 are respectively connected between the common connection point of the resistor of the amplifier 58 and the slider of the variable resistor 58, and the output terminal of the amplifier 40 and the slider of the variable resistor 58 are connected separately. A resistor 62 is connected between the resistor 62 and a resistor 63 is connected between the slider of the variable resistor 58 and the ground terminal to form a low-frequency circuit, so that the voltage applied to the resistor 63 is guided to the output terminal OUT. Configure.

Now, the resistance values of resistors 50, 54, 55, 56, 57, 59° 62 and 63 are R1, R2, R3, R4° R5, R
6, R7 and R8, capacitor 51°52.60
and 61 capacities as C1, C2, C3 and C4,
The resistance value between the slider of the variable resistor 52 and one end of the resistor of the variable resistor 52 connected to the capacitor 51 is rl,
The resistance value between the resistor of the variable resistor 52 and the other end connected to the capacitor 52 and the slider of the variable resistor 52 is r2,
Similarly, the resistance value of the resistor between the slider of the variable resistor 58 and the common connection point between the resistor of the variable resistor 58 and the resistor 57, and the resistance value of the resistor between the common connection point with the resistor 59. The resistance value of r3. Let it be r4.

The variable resistors 52 and 58 have a line-symmetrical resistance change rate with respect to the rotation angle as shown in FIG.

For example, if the variable resistor 52 has a C-type resistance change characteristic, the variable resistor 58 has an A-type resistance change characteristic.

Now, the resistance values r1 to r4 of the variable resistors 52 and 58 when the variable resistors 52 and 58 are at the mechanical center with respect to the rotation angle, that is, when the slider of each variable resistor 52 and 58 is at the 50% position, are respectively calculated. rCl + rC2p r
Select C3 and rC4 as ivy.

Therefore, when the variable resistors 52 and 58 are at their mechanical midpoints, the transfer function Tf(S) in FIG.゛In becomes 1.

Also, by changing the position of the slider of the variable resistor 52 or 58, the resistance value rl, r2 or r3. Boosting and cutting the high and low frequencies by changing the ratio of r4 is the same as before.

Now, the variable resistors 52 and 58 whose resistance change rate with respect to the rotation angle is axisymmetric as shown in FIG. 7 are used. This is to obtain a boost characteristic in the low range, and a cut characteristic by rotating it to the left.

Therefore, as long as the direction of rotation of the variable resistor for obtaining the boost and cut characteristics is not limited to the above, the variable resistor may have a variable resistor whose resistance value change rate is not line symmetrical but has the same rate of change.

Next, in the tone control circuit shown in FIG. 6, the equivalent circuit at a frequency where the reactance of capacitors 51, 53, 60 and 61 can be considered to be large and open is represented by the circuit shown in FIG. 6A, and the capacitor 5L5
An equivalent circuit at a frequency where the reactances of 3, 60 and 61 are small and can be considered as a short circuit is represented by the circuit shown in FIG. 6B.

Note that the resistors 62' and 63' are parallel resistors of resistors 57 and 62 and parallel resistors of resistors 59 and 63, respectively.

As is clear from FIGS. 6A and 6B, the transfer functions of the equivalent circuits shown in both figures are the same, and at point A in FIGS. 6A and 6B, the feedback side circuit and the output side circuit If they are selected so that they are completely separated, the characteristics of high-frequency boost and low-frequency cut, high-frequency cut and low-frequency boost will change almost the same as the change in the resistance value of the variable resistor. do.

Therefore, variable resistors 52 and 58 are now of C type or A type.
If you use a variable resistor that has the characteristic that the rotation angle of the mold and the rate of change in resistance value change at a constant rate, the characteristics of boost and cut in the low range and boost and cut in the high range will be as follows.
As shown in FIG. 8, the frequency f is plotted on the horizontal axis, the output ratio dB of the tone control circuit is plotted on the vertical axis, and the rotation angle of the variable resistor is plotted as a parameter. Characteristics that change at approximately the same rate are obtained.

Furthermore, if the variable resistors 52 and 58 are used as variable resistors 52 and 58, which have C-type and A-type resistance change rates with respect to rotation angles, as described above, the rotation angles of variable resistors 52 and 58 boost and cut characteristics that change at approximately the same rate are obtained, and the variable resistors 52 and 5
Boost or cut characteristics can be obtained for the same rotation direction of 8.

Next, a modified embodiment of the tone control circuit shown in FIG. 6 will be described.

FIG. 9 is a circuit diagram of a modified embodiment of the tone control circuit shown in FIG. 6, and the tone control circuit shown in FIG. 9 is a high-frequency circuit and a low-frequency circuit of the tone control circuit shown in FIG. The low-frequency circuit consists of a resistor of 64°65.66.68 and a variable resistor of 67.
, a circuit consisting of capacitors 69 and 70 and having the same shape as the low-frequency circuit of the circuit shown in FIG. It consists of resistors 71.75, 76.77, variable resistor 73, and capacitor 72.74, and is constructed with the same circuit as the high-frequency circuit of the circuit shown in FIG. Configure it to output to .

Also in the tone control circuit shown in FIG. 9, resistors 66, 68, 64, 65, and 71 are used.

75.The resistance values of 76 and 77 are Rlo, R11, R1
□.

Assuming R13, R14, R15, R16 and R1□, the capacitance of capacitor 69°70.72 and 75 is C1o, C
1□, C12 and C13, and the connection point between the resistor of the variable resistor 67 and the resistors 66 and 68 when the slider of the variable resistor 67 is located at the mechanical midpoint, and the variable resistor 67 Let rloC and rllc be the resistance values of the resistor between the slider of the variable resistor 73 and the capacitor 72 when the slider of the variable resistor 73 is located at the mechanical midpoint. The resistance values of the resistors between the connection points with and 74 and the slider of the variable resistor 73 are set to r12c and r13.
If selected in case c, the gain of the tone control circuit will be 1 when the frequency response is flat, similar to the tone control shown in Figure 6, and the boost and cut characteristics of the high and low frequencies will be controlled by the variable resistor. A variable resistor having type A or type C characteristics in which the change in resistance value of the variable resistors 67 and 73 is almost the same as that of the resistors 67 and 73, and the rotation angle versus resistance change rate of the variable resistors 67 and 73 changes at a constant rate. If used, the same boost and cut characteristics as in FIG. 8 can be obtained.

Next, an application example of the second embodiment will be explained.

FIG. 10 is a circuit diagram of an application example of the l-on control circuit according to the second embodiment of the present invention.

In FIG. 10, 40 is an ideal amplifier and a non-inverting amplifier.

A series circuit of a resistor 78, a capacitor 79, a variable resistor 80, a capacitor 81, and a resistor 82 is connected between the input terminal IN and the ground terminal, and a slider of the variable resistor 80 is connected to the input terminal IN and the ground terminal. resistance 83 between
and 84 are connected separately, the slider of the variable resistor 80 is connected to the non-inverting input terminal of the amplifier 40, and the input signal voltage applied between the input terminal IN and the ground terminal is divided and the amplifier 40 Configure a high-frequency circuit by applying
On the other hand, the output of the amplifier 40 is led to the output terminal OUT, and a series circuit of a resistor 87, a variable resistor 88, and a resistor 89 is connected between the output terminal OUT and the ground terminal.
Resistors 85 and 86 are connected between the slider of the variable resistor 88 and the output terminal OUT and the ground terminal, respectively, and resistors 85 and 86 are connected between the slider of the variable resistor 88 and both ends of the resistor of the variable resistor 88, respectively. The capacitors 90 and 91 are connected separately, the slider of the variable resistor 88 is connected to the inverting input terminal of the amplifier 40, and the output of the amplifier 40 is divided into voltages.
A low-frequency circuit is constructed so as to provide negative feedback to the

Also in the tone control circuit shown in FIG. 10, the resistance values of resistors 78.82.83, 84.85°86.87 and 89 are set as
, R, R and lR3g, Conde 34 35
36 37 The capacity of sensors 79, 81, 90 and 91 is C3□.

C3°, C33 and C34, and the connection point of the resistor of the variable resistor 80 with the capacitor 80 and the capacitor 81
The resistance value between the connection point and the slider of the variable resistor 80 when the slider is at the mechanical midpoint is r3□.

, r3□. The resistance value between the connection point of the resistor of the variable resistor 88 with the resistors 87 and 89 and the slider of the variable resistor 88 when it is at the mechanical midpoint is r33 (+
r34C, and if the variable resistors 80 and 88 are C-type or A-type variable resistors with rotation angle vs. resistance change rate characteristics, the same effect as the application example shown in FIG. 6 can be obtained. Obtainable.

Next, a modified embodiment of the tone control circuit shown in FIG. 10 will be described.

FIG. 11 is a circuit diagram of a modified embodiment of the tone control circuit shown in FIG. 10, in which the high-frequency circuit and low-frequency circuit of the tone control circuit shown in FIG. The area circuit is resistors 92, 94, 98, 99
, consisting of a variable resistor of 93 degrees and a capacitor of 95.96 degrees, consisting of a circuit of the same shape as the low-frequency circuit of the circuit shown in Fig. 10,
The high frequency circuit consists of resistors 100, 101, 102, 106, variable resistor 104, and capacitors 103, 105.
It consists of a circuit of the same type as the high-frequency circuit of the circuit shown in Figure 0.

In the tone control circuit shown in Fig. 11, a C-type or A-type variable resistor with rotation angle versus resistance change rate characteristics is used for each variable resistor, and the resistance value of each resistor and the capacitance ratio of the capacitor are shown in Fig. 10. If the selection is made in the same manner as in the case of the tone control circuit shown in FIG. 10, it will have the same effect as the tone control circuit shown in FIG. You can obtain the same high and low frequency boost and cut characteristics as shown in .

As explained above, according to the present invention, since a non-inverting amplifier is used, the phase of the output with respect to the input is not inverted.

Furthermore, since the gain is 1 when the frequency characteristic is flat, it is easy to set the gain when inserting into a preamplifier or the like in which a large number of amplifiers are connected in series.

Further, there is no interference between the high-frequency circuit and the low-frequency circuit, and the high-frequency circuit and the low-frequency circuit can be considered completely separate, making it easy to set each constant.

In addition, by selecting the resistance value of the resistor that makes up the high-frequency circuit and the low-frequency circuit, the capacitance of the capacitor, and the rotation angle versus resistance change rate characteristics of the variable resistor, the amount of boost and cut in the high and low frequencies can be changed. Another advantage is that it can be easily made the same in the high-frequency circuit and the low-frequency circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional CR attenuation type tone control circuit. 1A and 1B are equivalent circuits of the tone control circuit of FIG. 1. FIG. 1C is a characteristic curve of the tone control circuit shown in FIG. Figure 2 is a circuit diagram of a conventional BAX type tone control circuit. 2A and 2B are equivalent circuits of the tone control circuit of FIG. 2. FIG. 3 is a circuit diagram of a conventional negative feedback tone control circuit. FIG. 4 is a block diagram of a tone control circuit according to a first embodiment of the present invention. FIG. 5 is a block diagram of a tone control circuit according to a second embodiment of the present invention. FIG. 6 is a circuit diagram of a tone control circuit according to an application example of FIG. 4. 6A and 6B are equivalent circuits of the tone control circuit of FIG. 6. Figure 7 is a characteristic curve of rotation angle versus resistance value change rate of a variable resistor. Figure 8 shows the characteristic curve of the tone control circuit shown in Figure 6. FIG. 9 is a circuit diagram of a modified embodiment of the tone control circuit of FIG. 6. FIG. 10 is a circuit diagram of a tone control circuit according to an application example of FIG. 5. FIG. 11 is a circuit diagram of a modified embodiment of the tone control circuit of FIG. 10. 40; Non-inverting amplifier, 41, 42, 43, 44° 45.
46, 47 and 48; impedance network, 52,
58, 67.73, 80, 88, 93 and 104: Variable resistor, 5t, 53, 60° 61.69, 70, 7
2,74,79,81,90゜91.95,96,10
3 and 105: capacitor.

Claims (1)

[Scope of Claims] 1. A negative feedback tone control circuit, in which first and second impedance circuit networks for dividing the output voltage of the non-inverting amplifier are connected to the output terminal of the non-inverting amplifier, and and a second impedance network constitute a high-frequency or low-frequency circuit, and the voltage applied to the second impedance network is fed back to the non-inverting amplifier, and the output voltage of the non-inverting amplifier is divided. a third and a fourth impedance circuit network that are connected to each other, and when the first and second impedance network are high-frequency circuits, the third and fourth impedance circuit networks are configured with a low-frequency circuit; When the first and second impedance circuit networks are low-frequency circuits, they are configured as high-frequency circuits, and the voltage applied to the fourth impedance network is the output of the tone control circuit, and the frequency of the tone control circuit is When the characteristics are flat, the impedance ratio of the first and second impedance networks and the impedance ratio of the third and fourth impedance networks are both configured to be the same real number excluding zero. Features a tone control circuit. 2 A negative feedback type tone control circuit, in which first and second impedance circuit networks that divide the input voltage applied to the input terminal are connected, and the first and second impedance circuit networks are used to control the high frequency range or configuring a low-pass circuit, applying the voltage applied to the second impedance network to a non-inverting input terminal of a non-inverting amplifier, and making the output of the non-inverting amplifier an output of the tone control circuit; Third and fourth impedance networks for dividing the output voltage are connected to the output terminal of the non-inverting amplifier, and the third and fourth impedance networks are connected to the first and second impedance networks. When is a high-frequency circuit, it is composed of a low-frequency circuit, and when the first and second impedance networks are low-frequency circuits, it is composed of a high-frequency circuit, and the voltage applied to the fourth impedance network is fed back to the inverting input terminal of the non-inverting amplifier, and when the frequency characteristic of the tone control circuit is flat, the impedance ratio of the first and second impedance circuit networks and the impedance ratio of the third and fourth impedance circuit networks are determined. A tone control circuit characterized in that the impedance ratio and the impedance ratio are configured to be the same real number excluding zero.