JPS6056326B2 - Tone control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a tone control circuit having turnover frequency and roll-off frequency switching functions.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tone control circuit in which the number of changeover switches required for switching the turnover frequency and roll-off frequency and the number of capacitors that define the turnover frequency and roll-off frequency are reduced. .

FIG. 1 shows a turnover frequency and a roll-off frequency (hereinafter referred to as turnover frequency) of an embodiment of the tone control circuit shown in FIG. 2, which was previously filed by the applicant.

) This is a tone control circuit with a switching function. The tone control circuit shown in FIG. 2 is a circuit that is the basis of the tone control circuit shown in FIG.
The voltage applied to N is applied to the non-inverting input terminal of operational amplifier 1, and resistor 2 and capacitor 4 are connected to the output terminal of operational amplifier 1.
a first parallel circuit with a resistor 3 and a second parallel circuit with a capacitor 5
one end of the parallel circuit is connected, and the other ends of the first and second parallel circuits are bridged by a first series circuit consisting of a resistor 6, a variable resistor 8, and a resistor 7, and the first series circuit Resistors 9, 11, capacitor 13, variable resistor 15 in parallel with
, a second series circuit consisting of a capacitor 14 and resistors 12 and 10 is connected, the sliders of variable resistors 8 and 15 are respectively grounded, and the common connection point of resistors 9 and 11 is connected to the output terminal 0U.
The common connection point of resistors 10 and 12 is connected to operational amplifier 1 at T'.
Connect to the inverting input terminal of the

The first and second parallel circuits and the first series circuit are low-frequency side circuits, and the variable resistor 8 is for low-frequency control, and the second series circuit excluding resistors 9 and 10 is a high-frequency side circuit. The variable resistor 15 is for high frequency control.

The tone control circuit shown in FIG. 1 above consists of an output circuit between the output terminal of the operational amplifier 1 and the output terminal 0UT, which is configured in the upper part of Figure 2 with the ground terminal as the border, and the lower part of Figure 2. The feedback circuit between the output end and the inverting input end of the operational amplifier 1 is symmetrical, and the variable resistors 8 and 15 are constructed astride the output circuit and the feedback circuit, respectively. By changing the position of the slider 15, the attenuation amount is changed in the output circuit and the feedback amount is changed in the feedback circuit, and tone control characteristics are obtained by adding the attenuation amount and the feedback amount.

In the tone control circuit shown in Figure 2 above, the capacitors that determine the cutoff frequency on the low side are 4 and 5, and the capacitor that determines the cutoff frequency on the high side is 1.
3 and 14.

In particular, the resistance values and capacitances of the pair of resistors and capacitors are selected to be equal, for example, the resistance values of resistors 2 and 3 are equal, the capacitances of capacitors 4 and 5 are equal, and the following is similarly selected. 15 and the resistance value of the resistor is the same, and the slider is placed at the midpoint of each. When using variable resistors 8 and 15, the resistance value of the resistor of variable resistors 8 and 15 is divided into two when set at the position, and the resistance change rate characteristic with respect to the position of the slider has a linear characteristic such as type B. As shown in Fig. 3, the tone control characteristic is such that when the sliders of variable resistors 8 and 15 are at their midpoint positions, the attenuation amount of the output circuit and the feedback amount of the feedback circuit are equal, and the gain becomes ■B. Completely flat, unundulating characteristics can be obtained. Also, when the offset position from the center point of the slider of variable resistor 8 or 15 is the same, the same amount of cut and the same amount of boost can be obtained,
A tone control characteristic that is completely symmetrical with respect to the frequency axis can be obtained. Therefore, the tone control circuit shown in FIG. 1 is constructed by adding movable pieces to the tone control circuit shown in FIG. Connected interlocking switch 1
8 and 19, and by switching the changeover switches 18 and 19, the capacitors 4 and 5 and 16 and 17 are connected.
so that capacitors 4 and 5 or capacitors 16 and 17 are connected in parallel to resistors 2 and 4 separately, and between capacitor 13 and the resistor of variable resistor 15 and between capacitor 14 and variable resistor. Changeover switches 22 and 23 operate in conjunction with the resistor of 15.
are provided separately for each, and by switching the changeover switches 22 and 23, the capacitors 13 and 14 are combined as a pair to form the capacitor 2.
It is configured so that it can be switched between 0 and 21.

When the tone control circuit shown in FIG. 1 is used, the changeover switches 18 and 19 switch the capacitors 4 and 5 and 17 and 18 as a pair to change the low frequency cutoff frequency and change the low frequency turnover frequency, etc. The capacitors 13 and 14 and 20 and 21 are switched as a pair by the changeover switches 22 and 23 to change the high-frequency cutoff frequency and change the high-frequency turnover frequency, etc., as indicated by the solid line and broken line in FIG. The tone control characteristics shown were obtained. However, in the tone control circuit shown in FIG. 1, two sets of changeover switches 18 and 19 are operated in conjunction when switching the turnover frequency, etc.
, 22, and 23, and also requires twice the number of capacitors 16, 17, 20, and 21 as the number of turnover frequencies, etc., resulting in a complicated circuit configuration.

Therefore, in order to eliminate the above-mentioned drawbacks, the present invention has developed a capacitor that determines the turnover frequency of the low frequency range in parallel to the variable resistance for the low frequency range, and a slider of the variable resistance for the high frequency range that determines the turnover frequency of the high frequency range. A selector switch is used to selectively connect to ground through a capacitor that determines overfrequency.

The present invention will be explained below using examples. FIG. 5 is a circuit diagram of an embodiment of the present invention.

The tone control circuit of this embodiment further includes a resistor of variable resistor 8 and a resistor of resistor 7 in addition to the tone control circuit of FIG.
The movable piece of the changeover switch 25 is connected to the common connection point with the changeover switch 25, and the capacitor 24 is connected between the contact point 25-2 of the changeover switch 25 and the common connection point of the resistor 6 and the resistor of the variable resistor 8. When the movable piece 25 is brought into contact with the contact 25-2, the capacitor 24 is connected in parallel to the resistor of the variable resistor 8, and the movable piece is connected to the ground between the slider of the variable resistor 15 and the ground. Connect the changeover switch 27 with the two ends connected, connect the changeover switch's contact 27-1 to the slider of the variable resistor 15, connect the capacitor 26 between the contact 27-2 and the slider of the variable resistor 15, When the movable piece of the changeover switch 27 is brought into contact with the contact 27-1, the slider of the variable resistor 15 is directly grounded, and when the movable piece of the changeover switch 27 is brought into contact with the contact 27-2, the slider of the variable resistor 15 is grounded directly. The slider is configured to be grounded through a capacitor 26. Therefore, in this embodiment, when the movable piece of the changeover switch 25 is brought into contact with the contact 25-1, and the movable piece of the changeover switch 27 is brought into contact with the contact 27-1, the tone control circuit is the same as that shown in FIG. As a result, the tone control characteristics shown by the solid line in FIG. 6 can be obtained.

Furthermore, when the movable piece of the changeover switch 25 is brought into contact with the contact point 25-2, the capacitor 24 is connected in parallel to the resistor of the variable resistor 8, and the low-frequency cutoff frequency changes, as shown by the broken line on the left side of FIG. As shown in Fig. 2, characteristics such as the turnover frequency are switched.

For example, if the capacitance of capacitor 24 is selected to be the same as the capacitance of capacitor 4, its cutoff frequency will be approximately 112, which is the cutoff frequency when capacitor 24 is inactive. Further, when the movable piece of the changeover switch 27 is brought into contact with the contact point 27-2, the slider of the variable resistor 15 is grounded through the capacitor 26, and the high cutoff frequency changes.
As shown by the broken line on the right side of the figure, a characteristic in which the turnover frequency and the like are switched is obtained.

For example, if the capacitance of capacitor 26 is selected to be the same as the capacitance of capacitor 13, its cutoff frequency will be approximately twice the cutoff frequency when capacitor 26 is inactive. Note that the capacitances of the capacitors 24 and 26 may be selected to obtain a desired turnover frequency, respectively.

In this case, as is clear from the comparison with the tone control circuit shown in Fig. 1, the number of changeover switches and capacitors required for switching the turnover frequency, etc. is 112.
Therefore, its circuit configuration is also simple. Also, in the circuit of this embodiment, the symmetry of the output circuit and the feedback circuit is maintained, and in particular, if the resistance values and capacitances of the paired resistors, variable resistors, and capacitors are selected to be equal as described above, the tone can be improved. The control characteristic maintains its flatness and line symmetry with respect to the frequency axis.

Next, a modified example of this example will be described.

FIG. 7 is a circuit diagram of a modified embodiment of one embodiment of the present invention.

The tone control circuit of this modified embodiment further includes a resistor 7 and a variable resistor 8 in addition to the tone control circuit shown in FIG.
The movable piece of the changeover switch 29 is connected to the common connection point with the resistor of the resistor 6 and the variable resistor 8, and one of the capacitors 28-1, 28-2, . are commonly connected to the electrodes of capacitors 28-1, 28-2,
...28-n is connected to the contacts 29-1, 29-2, ...29-n of the changeover switch 29, respectively, and the capacitor 3 is connected to the slider of the variable resistor 15.
0-1, 30-2, . . 30-n one electrode.
The other of the capacitors 30-1, 30-2, . . . 30-n is connected to each contact 31-1, 31-2, . In addition to connecting the electrodes separately, selector switch 3
1 contact 31-0 directly connects the variable resistor. It is connected to the slider of the resistor 15, and is constructed in the same manner as in the circuit shown in FIG. 5, in which a plurality of different capacitors 24 and 26 are provided and each is switched by a changeover switch.

Therefore, in the case of this modified embodiment, each switching switch J29
, 31, the cut-off frequency on the low-frequency side and the cut-off frequency on the high-frequency side change depending on the positions of the contacts brought into contact by the movable pieces of the changeover switches 29 and/or 31.
By switching the high-frequency side and/or low-frequency side turnover frequency, etc., tone control characteristics as shown in FIG. 8 can be obtained.

Also in the circuit of this modified embodiment, the changeover switch 29
, 31, the symmetry between the output circuit and the feedback circuit is maintained at each switched position. In particular, if the resistance values and capacitances of the paired resistors, variable resistors, and capacitors are selected to be equal as described above, The flatness of the tone control characteristic and line symmetry with respect to the frequency axis are also maintained. Note that in the circuits of this embodiment and modified embodiments,
Resistors 6 and 7 may be short-circuited and another resistor may be connected between the slider of variable resistor 8 and the ground, or resistors 9 and 10 may be short-circuited.
, 11 and 12 are short-circuited to form a slider of variable resistor 15;
Common connection point A between capacitor 26 and contact 27-1 or slider of variable resistor 15 and capacitors 30-1, 30-2
, . . . , another resistor may be connected between the common connection point A of 30-n. Alternatively, capacitors 4 and 5 may be short-circuited, and another capacitor may be connected between the slider of variable resistor 8 and the ground, or capacitors 13 and 14 may be short-circuited, and variable resistor 15 is Other capacitors may be connected between the slider and point A.

Next, other embodiments of the present invention will be described. FIG. 9 is a circuit diagram of a tone control circuit according to another embodiment of the present invention. The tone control circuit of this embodiment has an input terminal 1N and an output terminal of the operational amplifier 1, that is, an output terminal 0UT.
A first parallel circuit consisting of a resistor 41 and a capacitor 43 between them, a first series circuit consisting of a resistor 46, a variable resistor 48 and a resistor 47, and a second parallel circuit consisting of a resistor 42 and a capacitor 44. are connected in series, and a resistor 49, a resistor 51, a capacitor 53,
Variable resistor 55, capacitor 5, resistor 52, and resistor 50
The slider of the variable resistor 48 is directly grounded, and the resistor of the variable resistor 48 is selectively connected in parallel with the capacitor 56 by a changeover switch 57. The slider of the resistor 55 is the changeover switch 5
9 is configured to be selectively grounded directly or through a capacitor 58, and the common connection point of resistors 49 and 51 is connected to the non-inverting input terminal of operational amplifier 1, and resistors 50 and 52
The common connection point with the inverting input terminal of the operational amplifier 1 is connected to the inverting input terminal of the operational amplifier 1.

The first and second parallel circuits and the first series circuit are low frequency side circuits, and the variable resistor 48 is for low frequency control.
The second series circuit excluding resistors 49 and 50 is a high frequency side circuit, and variable resistor 55 is for high frequency tone control.

The tone control circuit shown in FIG. 9 above includes an input circuit between the input terminal 1N and the non-inverting input terminal of the operational amplifier 1, which are formed in the upper part of FIG. 9 with the ground terminal as the boundary; The feedback circuit between the output terminal 0UT and the inverting input terminal of the operational amplifier 1 is arranged symmetrically, and the variable resistors 48 and 55 are arranged astride the input circuit and the feedback circuit, respectively. By changing the positions of the sliders of the variable resistors 48 and 55, the attenuation amount in the input circuit and the feedback amount in the feedback circuit are changed, respectively, and tone control characteristics are obtained by adding the attenuation amount and the feedback amount.

Therefore, according to this embodiment, when the movable piece of the changeover switch 57 is brought into contact with the contact 57-1 and the movable piece of the changeover switch 59 is brought into contact with the contact 59-1, the tone control characteristics shown by the solid line in FIG. can get.

Further, when the movable piece of the changeover switch 57 is brought into contact with the contact 57-2, the capacitor 56 is connected in parallel to the resistor of the variable resistor 48, and the low cutoff frequency changes to the sixth
As shown by the broken line on the left side of the figure, a characteristic in which the turnover frequency and the like are switched is obtained.

When the movable piece of the changeover switch 59 is brought into contact with the contact 59-2, the slider of the variable resistor 55 is grounded through the capacitor 58, and the high cutoff frequency changes as shown by the broken line on the left side of FIG. It is possible to obtain characteristics in which the turnover frequency and the like are switched as shown in FIG.

Note that the capacitances of the capacitors 56 and 58 may be selected to obtain a desired turnover frequency, respectively.

In addition, even in this case, the symmetry between the input circuit and the feedback circuit is maintained at each position of the changeover switches 57 and 59, and in particular, the resistance values and capacitances of the paired resistors, variable resistors, and capacitors are maintained as described above. If equal values are selected, the tone control characteristic maintains its flatness and line symmetry with respect to the frequency axis.

This is the same as in the previous embodiment. Furthermore, if a plurality of turnover frequencies are provided and it is desired to switch them, the circuit shown in FIG. 9 may be replaced with a circuit having the same relationship as that shown in FIGS. 5 and 7.

As explained above, according to the present invention, the number of changeover switches for changing over frequency, etc. and the number of capacitors for determining turnover frequency, etc. can be reduced to 11, which is the conventional number.
2, which has the effect of simplifying the circuit configuration.

Therefore, the tone control circuit can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional tone control circuit having a switching function such as turnover frequency. FIG. 2 is a circuit diagram of a tone control circuit that is the basis of the tone control circuit shown in FIG. FIG. 3 is a tone control characteristic diagram of the tone control circuit of FIG. 2. FIG. 4 is a tone control characteristic diagram of the tone control circuit of FIG. 1. FIG. 5 is a circuit diagram of a tone control circuit according to an embodiment of the present invention. FIG. 6 is a tone control characteristic diagram of an embodiment and a modified embodiment of the present invention. FIG. 7 is a circuit diagram of a tone control circuit according to a modified embodiment of the present invention. FIG. 8 is a tone control characteristic diagram of the tone control circuit of FIG. 7. FIG. 9 is a circuit diagram of a tone control circuit according to another embodiment of the present invention. 1... operational amplifier, 18,
19, 25, 27, 29, 31, 57 and 59...
- Changeover switch, 8, 15, 48 and 55...variable resistance.

Claims (1)

[Claims] 1. An output circuit including high-frequency and low-frequency tone control variable resistors whose respective sliders are grounded, and formed between an output terminal and the ground and the output terminal of the amplifier; A feedback circuit is formed symmetrically with the output terminal of the amplifier between the ground and the inverting input terminal of the amplifier. In a tone control circuit that obtains tone control characteristics by adding attenuation amount and feedback amount according to the position of the slider of the tone control variable resistor for high frequency, the slider of the tone control variable resistor for high frequency is A selector switch selectively connects the high frequency turnover and roll-off frequency to ground through or without passing through the capacitor, and a second selector switch selectively connects the low frequency tone control variable resistor to ground. A tone control circuit characterized in that a capacitor for determining a range turnover and roll-off frequency is connected in parallel. 2. An input circuit including high-frequency and low-frequency tone control variable resistors whose respective sliders are grounded, and formed between the input terminal, the ground, and the non-inverting input terminal of the amplifier;
A feedback circuit is formed symmetrically with the input circuit between the output end of the amplifier, the ground, and the inverting input end of the amplifier. In a tone control circuit that obtains tone control characteristics by adding attenuation amount and feedback amount, the slider of tone control variable resistor for high frequency range is changed according to the position of the slider of tone control variable resistor for high frequency range. A first selector switch selectively connects the high frequency turnover and roll-off frequency through or without a capacitor to ground, and a second selector switch selects the resistor of the low frequency tone control variable resistor. A tone control circuit characterized in that a capacitor for determining a low frequency turnover and roll-off frequency is connected in parallel.