JPH055691Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a sound quality adjustment circuit incorporated in audio equipment such as a head-on stereo or a tape recorder with a radio. (b) Conventional technology Audio equipment that plays back and listens to signals such as music recorded on magnetic tape has become widespread, but some of these innovative equipment are equipped with a sound quality adjustment circuit called a graphic equalizer. There is something. An innovative sound quality adjustment circuit is disclosed in Japanese Utility Model Application Publication No. 62-57427, but there are problems in that it is expensive because there are many frequencies to adjust the sound quality, and it is not easy to adjust the sound quality. . As a technique that improves the novel points, a circuit as disclosed in Japanese Utility Model Application Publication No. 62-181028, ie, a technique that adjusts the level of only the low frequency signal, has been developed. (c) Problems to be solved by the invention The above-mentioned Japanese Utility Model Application Publication No. 181028/1983 discloses a technology for enhancing low frequency signals, but such a circuit does not require a dedicated amplifier circuit for enhancing low frequency signals. Because of this, there is a problem that the circuit configuration becomes complicated and expensive. The present invention aims to provide a sound quality adjustment circuit that solves this problem. (d) Means for Solving the Problems In the sound quality adjustment circuit of the present invention, the slider is connected to the output terminal of the preamplifier circuit, one end is grounded, and the other end is connected to the input terminal of the main amplifier circuit. a variable resistor connected to the variable resistor; a low frequency boosting circuit consisting of a resistor and a capacitor connected in parallel to the variable resistor and connected in series with each other; It is comprised of switching means for short-circuiting both ends of the capacitor when the booster is not in operation. (E) Effect The present invention connects a low-frequency boost circuit consisting of a resistor and a capacitor in parallel to a variable resistor that adjusts the volume, and controls the low-frequency boost operation by controlling the operation of the capacitor. This is what I did. (F) Embodiment The illustrated circuit is an embodiment of the sound quality adjustment circuit of the present invention. In the figure, 1 is a magnetic head that reproduces signals recorded on a magnetic tape, 2 is a preamplifier circuit to which the signal reproduced by the magnetic head 1 is input and amplified, and 3 is a volume control circuit. A slider 6 which is a variable resistor for adjustment and is connected to the output terminal of the preamplifier circuit 2 via a resistor 4 and a capacitor 5, a ground terminal 7 which is grounded, and a signal terminal from which a signal is output. It is equipped with 8. Reference numeral 9 denotes a main amplification circuit into which a signal output from the signal terminal 8 of the variable resistor 3 is input through a capacitor 10 and amplifies the signal; 11 a main amplification circuit for amplifying the signal; The signal is applied through the speaker and emits the signal. Reference numeral 13 designates a low-frequency boost circuit connected between the signal terminal 8 of the variable resistor 3 and the ground, and is formed by a series circuit of a resistor 14 and a capacitor 15, which functions to set the amount of change in low-frequency boost. It is configured. Reference numeral 16 denotes a switching transistor for controlling the operation/non-operation of the low-frequency enhancement circuit 13 , the collector of which is connected to the connection point A between the resistor 14 and the capacitor 15, and the emitter of which is grounded. 17 is a sound quality changeover switch that is switched during the sound quality adjustment operation;
a common terminal a connected to a power source, a first terminal b connected to the common terminal a when inactive for low frequency enhancement and also connected to the base of the switching transistor 16 via a resistor 18; and a low frequency enhancement. A second terminal c is provided which is connected to the common terminal a during operation. In this circuit configuration, the capacitors 5, 10, and 12 are DC blocking capacitors, and the resistor 4 is connected to the output terminal of the preamplifier circuit 2 when the variable resistor 3 is adjusted to the minimum position, that is, to the ground terminal 7 side. This is a resistor to prevent grounding. The sound quality adjustment circuit of the present invention is constructed as described above, and its operation will be explained next. First, the operation when the tone quality changeover switch 17 is in the illustrated position, that is, in the low frequency enhancement non-operation position will be described. When the tone quality changeover switch 17 is in the position shown, a bias current is supplied to the base of the switching transistor 16 through the switch 17 and the resistor 18, so that the switching transistor 16 is in a conductive state. When the switching transistor 16 is in a conductive state, a connection point A between the resistor 14 and the capacitor 15 constituting the low frequency enhancement circuit 13 is grounded. Therefore, the capacitor 15 has no effect on the signal. In such a state, when the slider 6 of the variable resistor 3 is displaced, the level of the signal input to the main amplifier circuit 9 through the variable resistor 3 changes, so that the volume of sound emitted from the speaker 11 is adjusted. I can do it. When the slider 6 of the variable resistor 3 is moved to the ground side, the resistance value between the slider 6 and the signal terminal 8 increases, so the signal level due to the resistor 14 constituting the low frequency enhancement circuit 13 increases. The level of decline in However, since the signal level is reduced for all frequencies, no low frequency enhancement operation is performed. As described above, the operation is performed when the tone quality changeover switch 17 is in the low-frequency enhancement non-operating position.Next, the operation when the tone quality changeover switch 17 is switched to the low-frequency enhancement operating position will be explained. When the tone quality changeover switch 17 is moved to the low frequency enhancement operating position opposite to the illustrated position, the bias current to the base of the switching transistor 16 is cut off, so that the switching transistor 16 is reversed to a non-conducting state. When the switching transistor 16 becomes non-conductive, a series circuit of a resistor 14 and a capacitor 15 is connected between the signal terminal 8 of the variable resistor 3 and the ground. Therefore, in such a state, the signal whose level is lowered by the resistor 14 becomes a high frequency signal, and the signal level of a low frequency band is not lowered. When the slider 6 of the variable resistor 3 is moved to the ground side, that is, when the volume is decreased, the resistance value between the slider 6 and the signal terminal 8 increases, so the signal level at high frequencies increases. The amount of decrease becomes large. On the other hand, when the slider 6 is moved toward the signal terminal 8 side, that is, when the volume is increased, the resistance value between the slider 6 and the signal terminal 8 decreases, and the amount of decrease in the signal level at high frequencies decreases. becomes smaller. In this way, the operation is carried out when the sound quality selector switch 17 is in the low-frequency enhancement operation position, but in such a state, the signal emitted from the speaker 11 has a lower frequency signal than a high-frequency signal. This results in a signal with a high level, that is, a signal with an enhanced low frequency range. When such an operation is performed, the resistor 14 constituting the low frequency enhancement circuit 13
acts to set the amount of change in low frequency enhancement, so by selecting the resistance value of the resistor 14, it is possible to freely set the amount of change in low frequency enhancement associated with volume adjustment. In addition, in this embodiment, the operation of the low frequency enhancement circuit 13 is
Although a transistor is used as a switching means for controlling non-operation, it is also possible to use a mechanical switch such as a relay. Further, although the case where the present invention is applied to a tape recorder has been described, it is of course possible to apply the present invention to a radio or the like. (g) Effects of the invention The sound quality adjustment circuit of the invention applies the output signal of the preamplifier circuit to the slider of a variable resistor used for volume adjustment, and also connects a resistor and a capacitor between the signal terminal and ground. In this case, a low-frequency boosting circuit consisting of the following is connected, and whether or not the low-frequency boosting operation is performed is controlled by whether or not both ends of the capacitor are shorted.In other words, a special amplifier circuit is provided. The practical value of the present invention is very high because the bass enhancement operation can be performed without any noise. In addition, in the present invention, the low frequency enhancement circuit is formed by a series circuit of a resistor and a capacitor, and the resistor is configured to act to set the amount of change in low frequency enhancement, so the resistance value of the resistor can be selected. This has the effect that the amount of change in low frequency enhancement accompanying volume adjustment can be freely set.

[Brief explanation of the drawing]

The illustrated circuit is an embodiment of the sound quality adjustment circuit of the present invention. Explanation of main drawing numbers, 2... Preamplifier circuit, 3 ...
Variable resistor, 6...Slider, 9...Main amplifier circuit,
13...Low frequency enhancement circuit, 16...Switching transistor, 17...Sound quality selection switch.

Claims (1)

[Scope of utility model registration request] The slider is connected to the output terminal of the preamplifier circuit, the ground terminal which is one end of the resistor is grounded, and the signal terminal which is the other end of the resistor is connected to the input terminal of the main amplifier circuit. a variable resistor, a low-frequency boost circuit consisting of a resistor and a capacitor connected in series between the signal terminal of the variable resistor and the ground; 1. A sound quality adjustment circuit comprising switching means for short-circuiting both ends of the capacitor when the enhancement is not in operation, the amount of change in low frequency enhancement being set by a resistor constituting the low frequency enhancement circuit.