JPS6158048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a sound quality adjustment device for audio equipment such as a television receiver.

Conventionally, sound quality adjustment has been carried out using a well-known adjustment circuit that passes audio signals through sound quality adjustment variable resistors 1 and 2, as shown in FIG. However, since such a variable resistor for adjustment is generally installed at the front of the TV set, it is necessary to pass the audio signal through a long signal line between it and the chassis. There was a problem in that it was susceptible to induced interference by signals and noise was mixed in. For this reason, as a means of controlling sound quality using DC voltage, only the high frequencies are leveled using a circuit configuration in which the current distribution of a differential amplifier 4 equipped with a low-pass filter 3 is controlled by a control voltage Vc, as shown in Figure 2. Although it has been done to reduce the frequency due to its characteristics, this method also has the disadvantage that it is not possible to increase or decrease the high and low frequencies independently.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sound quality adjustment circuit that can independently increase or decrease the characteristics of high and low frequencies using a DC control voltage. Hereinafter, one embodiment of the present invention will be described with reference to FIGS.

First, FIG. 3 shows an example of a circuit configuration. Transistors 5, 6, diode 7, and resistors 8-11 are a bias circuit. Transistors 12-14 and resistors 15-19 constitute a differential amplifier 20 for flat characteristics, and transistors 21-27 and resistors 28-3
2 constitutes a differential amplifier 33 for high frequency control, and transistors 34 to 40 and resistors 41 to 45 constitute a differential amplifier 46 for low frequency control. 47 is a high-pass filter, 48 is a low-pass filter, 49 is a load resistor, 50 is a signal input terminal, and 51 is a signal output terminal.

The base of the transistor 25 receives a high-frequency signal that has passed through a high-pass filter 47, the base of the transistor 13 receives a signal that is uniform across the entire range, and the base of the transistor 39 receives a low-frequency signal that has passed through a low-pass filter 48. has been added. Therefore, the negative phase component of the high frequency signal is output to the collector of the transistor 25, and the positive phase component thereof is output to the collector of the transistor 26. The positive phase component of the flat signal is output to the collector of the transistor 12, and the negative phase component thereof is output to the collector of the transistor 13. The positive phase component of the low frequency signal is output to the collector of the transistor 38, and the negative phase component thereof is output to the collector of the transistor 39. The differential amplifiers 33 and 46 are each configured as a double-balanced differential amplifier, and the collectors of the transistors 12, 21, 23, 34, and 36 are connected in common, and their respective output signals are added to the load. Output terminal 51 from resistor 49
The output signal is extracted.

Transistors 21 and 24 and transistor 22
and 23 are connected in common, and a high frequency control voltage is applied from high frequency control voltage input terminals 52 and 53. Similarly, a low range control voltage is applied to the bases of the transistors 34 and 37 and the transistors 35 and 36 from low range control voltage input terminals 54 and 55.

In such a configuration, if the same voltage is applied to the terminals 52 and 53, the transistor 21
Equal amounts of the positive-phase component and negative-phase component of the high-pass signal current flow through the collectors 23 and 23, and they cancel each other out at the load resistor 49, so that no high-pass signal is output. By varying the control voltages at terminals 52 and 53, transistors 21 and 2
It is possible to control the ratio of the high-pass signal current flowing through the transistor 13, and to add a high-pass signal amount of a positive phase component or a negative phase component to the flat signal current from the transistor 13 by controlling the magnitude thereof. can. When more positive phase components are added, the high frequency range increases, and when more negative phase components are added, an output signal with reduced high frequency frequencies is obtained.

Similarly, by controlling the low frequency control voltages applied to terminals 54 and 55, the low frequency component in the output signal can be increased or decreased.

In this way, the high-frequency characteristics and the low-frequency characteristics can be increased or decreased independently, and the sound quality can be controlled. The maximum amount that can be increased or decreased is resistance 30,
31 and the resistance ratio of resistors 17 and 18 and the resistor 43,
44 and the resistors 17 and 18, and the maximum amount of change in the current distribution ratio of the double balanced differential amplifiers 33 and 46.

Figure 4 shows the above circuit configuration in a block diagram.
FIG. 5 shows the control state of the low frequency signal using a vector diagram. Low-pass signal L obtained by passing the input signal N through the low-pass filter 48
Since the phase of is slightly different from the phase of the flattened input signal N, the addition is as shown in FIG.

In Fig. 4, K and Kh are respectively differential amplifiers 3
3 and 46, and a<K
<b, a<Kh<b, -1<a<0, 0<b. Within this range K and Kh are controlled by control voltages to control terminals 52, 53 and 54, 55, respectively. Furthermore, as can be seen in FIG. 5, the low-pass signal L that has passed through the low-pass filter 48 is inevitably phase-shifted by the phase φ with respect to the original flattened signal N, and this is used to determine the polarity and amplitude. It is unavoidable that the phase of the output signal which is controlled and added is also shifted compared to the flattened signal N. Although FIG. 5 shows only the control of the low-frequency characteristics, the same applies to the high-frequency characteristics.

FIG. 6 shows examples of frequency characteristics of various output signals when sound quality is controlled by such a circuit.

As detailed above, according to the present invention, both the high-frequency characteristics and the low-frequency characteristics can be adjusted independently and arbitrarily by using the DC control voltage, and even if the control voltage is changed, the DC Thus, it is possible to obtain a useful sound quality adjustment device that does not involve minute fluctuations.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams of a conventional sound quality adjustment device, FIG. 3 is a circuit diagram of a sound quality adjustment device according to an embodiment of the present invention, FIG. 4 is a block diagram thereof, and FIG.
The figure is a vector diagram to explain the control operation.
FIG. 6 is a characteristic diagram showing the adjusted state. 20... Differential amplifier for flat signal, 33... Differential amplifier for high frequency signal, 46... Differential amplifier for low frequency signal, 47... High pass filter, 48...
Low-pass filter, 49...Load resistance, 50...
Signal input terminal, 51... Signal output terminal, 52, 5
3...High range control voltage input terminal, 54, 55...Low range control voltage input terminal.

Claims (1)

[Claims] 1. One side of a differential amplifier whose emitter is connected to a constant current source through a resistor, with the high-frequency signal extracted by applying the input audio signal to a high-pass filter and equally biased by a voltage source through a resistor. The input audio signal is applied to a low-pass filter, and the extracted low-frequency signal is biased equally through a resistor by the above voltage source. The output emitter is connected to one side of a differential amplifier connected to a constant current source through a resistor so that a positive phase component and a negative phase component are supplied to each collector. are configured to serve as positive-phase and negative-phase signal sources for each of the double-balanced differential amplifiers, and the bases of the two double-balanced differential amplifiers are connected to a DC control voltage for high-frequency adjustment and a DC control voltage for low-frequency adjustment. The input audio signal is biased equally by the voltage source through the resistor, and the emitter is biased at a constant current through the resistor. A double-balanced differential connected to one side of the differential amplifier connected to the source to control the ratio of the positive-phase component side and the negative-phase component of the high-frequency and low-frequency signals with its positive-phase component side collector. A sound quality adjustment device in which the collector of an amplifier is connected to a common load, and the high and low frequencies are adjusted independently using a DC control voltage.