JPH0134427Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tone quality adjustment circuit having loudness adjustment means.

Conventional audio signal amplifiers include amplifiers (so-called control amplifiers) that are capable of adjusting loudness in addition to volume control and tone quality control. A conventional example of such an amplifier is shown in FIG.

In FIG. 1, 1 indicates a signal input terminal, and this signal input terminal 1 is a non-inverting input terminal 2 of an amplifier 2.
a and the output terminal 2o of the amplifier 2
is connected to the inverting input terminal 2b via the negative feedback resistor 2f. Reference numeral 3 indicates a tone quality adjustment circuit, and this tone quality adjustment circuit 3 is of a negative feedback type, and is connected in parallel to the negative feedback resistor 2f as a whole. That is, a first variable resistor 31 for treble adjustment (hereinafter referred to as treble adjuster) is connected between the output terminal 2o of the amplifier 2 and the ground, and a slider 31s of this treble adjuster 31 is connected to a small capacitor 32. and is connected to the inverting input terminal 2b of the amplifier 2 via a DC blocking capacitor 33. On the other hand, a resistor 34, a second variable resistor for bass adjustment (hereinafter referred to as bass regulator) 35, and a resistor 36 are connected in series between the output terminal 2o and the ground. A large capacity capacitor 37 is connected in parallel. A slider 35s of the bass adjuster 35 is connected to the inverting input terminal 2b of the amplifier 2 via a DC blocking capacitor 33.

Reference numeral 4 denotes a loudness adjustment circuit, in which a variable resistor 41 with a center tap for volume adjustment is connected between the output terminal 2o of the amplifier 2 and the ground. A movable contact 42c of the loudness switching switch 42 is connected to the loudness switching switch 42, and a second small capacitor 43 is connected between one fixed contact 42a of the switch 42 and the output terminal 2o of the amplifier 2.
A second large capacity capacitor 44 is connected between the other fixed contact 42b and the movable contact 42c of the switch 42, and a resistor 45 is connected between the other fixed contact 42b and ground. 5 indicates a signal output terminal, and this signal output terminal 5 is connected to the variable resistor 4.
1 slider 41s.

In the sound quality adjustment circuit shown in FIG. 1, when the slider 31s of the treble adjuster 31 moves to the ground side, the amount of negative feedback in the treble range decreases, so the treble range is strengthened, and the slider 31s moves to the amplifier 2. When moving toward the output terminal 2o side, the amount of negative feedback increases and the high frequency range is attenuated. Furthermore, when the slider 35s of the bass adjuster 35 moves toward the resistor 36 on the ground side, the bass range is enhanced, and when it moves toward the resistor 34 on the amplifier 2 side, the bass range is attenuated. Slider 31s or 35s
is at the center position of the treble adjuster 31 or the bass adjuster 35, respectively, the treble or bass range is neither enhanced nor attenuated.

As shown in FIG. 1, the movable contact 42c of the loudness changeover switch 42 is connected to one fixed contact 42a.
When connected to the sound quality adjustment variable resistor 4
When the first slider 41s is located closer to the ground than the center tap 41c, a second small capacitance capacitor 43 is connected in parallel from the center tap 41c of the variable resistor 41 to the amplifier 2 side in the high frequency range. Since it is connected, the treble range is enhanced. Furthermore, in the bass range, the second large capacitance capacitor 44 and the resistor 45 connected in series are connected in parallel to the ground side part from the center tap 41c of the variable resistor 41, so that the attenuation for the bass range is less than that for the middle range. It is smaller than attenuation, and the bass range is relatively enhanced.

Note that when the slider 41s of the variable resistor 41 is located closer to the amplifier 2 than the center tap 41c, and when the movable contact 42c of the switch 42 and the other fixed contact 42b are connected, the loudness cannot be adjusted.

In the conventional loudness adjustment circuit described above, a special variable resistor having a center tap had to be used as a variable resistor for volume adjustment. In addition to this, when the loudness adjustment is not in operation, the center tap 41c of the variable resistor 41 is connected to the resistor 45.
Since the slider 41s is near the center tap 41c, the slider 41s
Another drawback was that the change in output signal level with respect to displacement (rotation or sliding) of the resistor 45 was smaller than in the case without the resistor 45.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a sound quality adjustment circuit having a loudness adjustment means that eliminates the drawbacks of conventional loudness adjustment circuits.

An embodiment of the present invention will be described with reference to FIG. In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals and redundant explanation will be omitted.

In FIG. 2, reference numeral 6 indicates a variable resistor for adjusting sound quality (hereinafter referred to as a sound quality adjuster). Connected to output terminal 5.

One fixed contact 42a of the loudness selector switch 42 is connected to ground through a second small capacitor 43, and the other fixed contact 42b is connected in parallel to the amplifier 2 of the bass adjuster 35 with a large capacitor 37. The sides are connected. Resistor 3
A second large-capacity capacitor 44 is inserted between the switch 42 and the bass adjuster 35, and the connection point between the resistor 34 and the capacitor 44 is connected to the movable contact 42 of the switch 42.
connected to c.

In this example, when the loudness changeover switch 42 is in the switching state shown in FIG. Since the two small-capacity capacitors 43 are connected in parallel, the signal current supplied from the amplifier 2 to the treble adjuster 31 is reduced compared to when the switch 42 is in the reverse switching state as shown in FIG. Therefore, the amount of negative feedback in the treble range is also reduced, and the treble range is enhanced. Also, in the low frequency range, the second large capacity capacitor 44 is connected to the resistor 3.
4 and the bass adjuster 35, the impedance of the capacitor 44 reduces the amount of negative feedback in the bass range, thereby enhancing the bass range.

The circuit constants of this example are as follows.

Variable resistor 31: 50KΩ, 35: 50KΩ Resistor 34: 30KΩ, 36: 30KΩ Capacitor 32: 3300pF, 37: 0.068μF 〃 43: 2200pF, 44: 0.01μF In this example, the volume controller 6 and the loudness adjustment circuit are used. Since they are separated, there is no need to use a special variable resistor with a center tap, and furthermore, changes in the output signal level in response to displacement of the slider of the volume adjuster can be sufficiently large and smooth.

Next, another embodiment of the present invention will be described with reference to FIG.

In FIG. 3, reference numeral 7 indicates a slider position detection circuit, which detects the position of the slider 6s of the volume adjuster 6 corresponding to a predetermined volume and switches the loudness changeover switch. 42. The rest of the structure is the same as that of the embodiment shown in FIG. 2, so detailed explanation will be omitted.

As the slider position detection circuit 7, various known means can be used. For example, the position of the slider of a volume controller at low volume may be detected optically, or two variable resistors may be connected and a signal is supplied to one of them to function as a volume controller, while the other is supplied with a DC voltage. It may also be used for detecting rotational position by supplying voltage.

According to this example, loudness adjustment can be performed at a predetermined sound volume.

As described in detail above, according to the present invention, the volume controller and the loudness adjustment circuit can be separated, and there is no need for a special variable resistor with a center tap as the volume controller. The range of change in the output signal level with respect to the displacement of the mover can be made sufficiently wide, and the change can also be made smooth.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram showing an example of the configuration of a conventional sound quality adjustment circuit, Fig. 2 is a wiring diagram showing an embodiment of the sound quality adjustment circuit according to the present invention, and Fig. 3 is another embodiment of the sound quality adjustment circuit according to the present invention. It is a wiring diagram showing an example. 2 is an amplifier, 31 is a treble adjuster, 32 is a small capacitor, 35 is a bass adjuster, 37 is a large capacitor, 42 is a loudness selector switch, 43
is a second small capacitance capacitor, and 44 is a second large capacitance capacitor.

Claims (1)

[Scope of utility model registration request] It has first and second variable resistors for treble and bass adjustment, respectively, connected between the output terminal of the amplifier and the ground, and the slider of the first variable resistor is connected to a first small capacitor. A negative feedback connection is made to the input terminal of the amplifier through a capacitor, a slider of the second variable resistor is connected to the input terminal of the amplifier by negative feedback, and a first In the sound quality adjustment circuit formed by connecting large capacity capacitors in parallel, a second large capacity capacitor is inserted between the output terminal of the amplifier and the second variable resistor, and one end is grounded. A second small capacitance capacitor and a loudness switching switch are provided in which the other end of the second small capacitor is connected to one fixed contact, and the other fixed contact of the switch is connected to the second variable resistor. and a connection point of the second large-capacity capacitor, and a movable contact of the switch is connected to the output terminal of the amplifier.