JPS6148211A - Sound quality adjusting circuit - Google Patents

Abstract

PURPOSE:To attain minute sound quality adjustment with lever operation of a variable resistor by providing the variable resistor to the slider of which plural circuits having frequency dependant impedance are given. CONSTITUTION:Coils 15, 18, capacitors 16, 19 and resistors 17, 20 form respectively a high resonance circuit and a low resonance circuit. When a slider 14a of the variable resistor 14 is placed at one end 14b of the variable resistor 14, the resistor 13 and the high and low resonance circuits are connected in parallel. Thus, a large frequency characteristic (a) having the gain at high and low frequencies is obtained. In moving the slider 14a, the effect of the resonance circuits is reduced to form a flat frequency characteristic (b). When the slider 14a comes to the other end 14c, since the resonance circuit is connected to an output terminal of an amplifier 11, a frequency characteristic (c) having a small gain at high/low frequencies is obtained. When the slider 14a is placed at the midpoint of the resistor 14, a frequency characteristic (d) is obtained by the effect of a capacitor 21. Thus, minute sound quality is adjusted by the lever operation of the variable resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sound quality adjustment circuit such as a no-fi amplifier in a stereo device.

(Conventional configuration and its problems) In recent years, stereo devices used for listening to records, etc. have become widespread in households and are being used by people of a wide range of age groups. There is an increasing demand to provide.

A sound quality adjustment circuit commonly used in conventional hi-fi amplifiers will be described below.

Figure 1 is generally called the CR type sound quality adjustment circuit, and since it is a well-known circuit, we will not explain its operation, but 1 and 2 are variable resistors, which increase and decrease the bass and treble regions, respectively. can be adjusted independently.

FIG. 2 shows a simplified sound quality adjustment circuit that adjusts only the amount of attenuation in the treble range, and since this is also a general circuit, a description of its operation will be omitted.

When adjusting sound quality using the circuit described above, the circuit shown in Figure 1 can increase or decrease the treble and bass parts independently, but the circuit is complicated due to the large number of parts, and if the user is a child, etc. Difficulties arise in adjusting the two variable resistors. In the circuit shown in FIG. 2, there is only one variable resistor, and anyone can easily operate it, but the adjustment content is only high frequency attenuation, and advanced sound quality adjustment is not possible.

(Objective of the Invention) The present invention solves the above-mentioned problems of the conventional art, and enables fine-grained sound quality adjustment according to various kinds of music by operating the levers of two variable resistors. The purpose is to provide a circuit that can be obtained for hi-fi amplifiers.

(Structure of the Invention) The present invention comprises an output terminal of a negative feedback amplifier, a feedback terminal of the amplifier, a feedback resistor connected from the output terminal to the feedback terminal, and a variable voltage amplifier having fixed terminals connected to both ends of the feedback resistor. The conventional method is equipped with a resistor and a circuit whose impedance changes depending on at least two frequencies connected between the movable end of the variable resistor and ground, and by operating a lever that moves one movable end. It is possible to easily adjust the sound quality according to the music being listened to and the room by increasing or decreasing the treble and bass, rather than just attenuating the treble like a circuit.

(Explanation of Examples) FIG. 3 shows an embodiment of the present invention.

This is part of the circuit of a high-fidelity amplifier, and in FIG. 3, 3 is an amplifier, and 4 and 5 are resistors, which form a negative feedback circuit for the amplifier 3. 6 is a variable resistor, the center point 6a of which is connected to the output terminal 7 via a filter 8. Impedance elements 9 and 10 are connected to the movable piece 6b of the variable resistor 6.

Figure 4 shows a more specific example, 11
is an amplifier similar to amplifier 3, 12 and 13 are resistors similar to resistors 4 and 5, respectively, and 14 is a variable resistor similar to variable resistor 6, whose total resistance value is much larger than the resistance value of resistor 4. This is a large value. In FIG. 3, the impedance element 9 is made up of a coil 15, a capacitor 16, and a resistor 17, and the impedance element 10 is made up of a coil 18. It consists of a capacitor 19 and a resistor 20, which have series resonance at a reduced arbitrary frequency. The filter 8 in Figure 3 is the capacitor 2 in Figure 4.
1, the high range series resonance frequency of the above-mentioned coil 15, capacitor 16, and resistor 17 passes through, and the coil 18
, the capacitor 19, and the resistor 20 function to block the low-range series resonance frequency.

The operation of the sound quality adjustment circuit of the embodiment configured as described above will be described below. In FIG. 4, the gain of the amplifier 11 is determined by the resistance values of the resistors 12 and 13 of the negative feedback circuit.
It is generally known that the resistance value of R8 is expressed by the following equation.

Gain=20Log. (RfAe) (dB) ・-(
1) However, in reality, a variable resistor 14 is connected in parallel to the resistor 12.
is connected, but as mentioned above, its resistance value is 1
Since it is sufficiently larger than 2, no error is given to the above gain calculation.゛Coil 15, capacitor 16, resistor 17 and coil 1
8, a capacitor 19, and a resistor 20, the series resonant circuit has a resonant frequency f as shown in FIG. The impedance is the minimum at 9, and its value r is equal to the resistance values of the resistors 17 and 20, respectively. Here, the resonance frequency f. is generally known to be expressed by the following formula.

f = 1/(2πφte)...(2) L: Inductance of the coil C: Capacitance of the capacitor Now, a series resonant circuit consisting of the coil 15, capacitor 6, and resistor 17, which have a resonance frequency in the high range. (hereinafter referred to as a high-frequency resonant circuit) and a series resonant circuit (hereinafter referred to as a low-frequency resonant circuit) consisting of each component of a coil 18, a capacitor 9, and a resistor 20 having a resonant frequency in the low frequency range are connected in parallel. When the movable piece 14a of the variable resistor 14 is connected to one end 14b of the variable resistor 14, R8 in the gain calculation formula described above is calculated not only from the resistance value of the resistor 13 but also from the high-frequency and low-frequency resonant circuits. When connected in parallel, at the resonant frequency of the resonant circuit, the combined impedance is approximately the resistance 17.
When the resistance value of the resistor 17 and 20 is made smaller than the resistance value of the resistor 13, the shear gain with a small value of R8 increases. In other words, the frequency characteristic is such that the high and low frequencies are increased (characteristics a, . . . in FIG. 6).

When the movable piece 14a is moved from one end 14b to the other end 14c, the resistance between 14a and 14b is connected in series to each resonant circuit, and as the resistance value increases, the value of R8 gradually becomes influenced by the resonant circuit. The amount of increase in the high and low range of the frequency response decreases, and the resistance value of resistor 13 becomes 14'a~
When the resistance value between 14b becomes sufficiently large, the gain is determined by equation (1) again without affecting the resonant circuit, and becomes the resistance value of Re-resistor 13, resulting in a flat frequency characteristic as shown in the characteristic curve of FIG.

When the movable piece 14a is further moved and comes to the other end 14c, the two resonant circuits mentioned above are connected to the output terminal of the amplifier 11, and the resonant circuit is connected as a load resistance of this amplifier. The output voltage is determined by the dividing resistance between the output impedance and the impedance of the resonant circuit, and the impedance of the two resonant circuits is extremely small in the high and low ranges, so the output voltage is small in the high and low ranges (characteristic curve in Figure 6). C).

When this movable piece 14a is moved again and connected to the midpoint 14d of all the resistances of the variable resistor 14, two resonant circuits are connected here from the output terminal of the amplifier 11 through the capacitor 21, and in this case, resonance occurs. The influence of the circuit is that the impedance of the capacitor 21 is large near the low-frequency resonant frequency and becomes small near the high-frequency resonant frequency, so that only the high-frequency resonant circuit is affected, as shown by the characteristic curve C in Figure 6 above. From this, a characteristic curve d in FIG. 6 with a flattened low range is obtained.

In this way, by moving the movable piece of one variable resistor, the sixth
It is possible to obtain an amplifier with four different frequency characteristics as shown in the characteristic curves a, b, e, and d in the figure, and the movable piece can be moved to any position until each characteristic is obtained. Needless to say, it is possible to continuously obtain characteristics between the respective characteristics.

(Effect of the invention) The present invention has one end as an amplifier signal circuit, the other end as a negative feedback circuit,
By equipping the hi-fi amplifier with a variable resistor connected to at least two circuits whose impedance changes depending on the frequency, the movable end can be adjusted to various frequencies by one lever that operates the movable end of the variable resistor. The characteristics can be easily obtained, and the circuit configuration is simple without requiring two variable resistors unlike conventional independent sound quality adjustment for treble and bass, and its effects are very large. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional CR type sound quality adjustment circuit, FIG. 2 is a diagram showing a conventional simplified sound quality adjustment circuit, and FIGS. 3 and 4 are diagrams showing a sound quality adjustment circuit according to an embodiment of the present invention. , FIGS. 5 and 6 are diagrams for explaining the operation of the same embodiment. 3.11...Amplifier, 4. ．． 5.1'2, 13.17
゜20...Resistor, 7...Amplifier output terminal, 8.
...Filter, 6+14...Variable resistor, 9.10.
...Impedance element, 15.18...Coil, 1
6,19゜21... Capacitor. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] The output terminal of the negative feedback amplifier, the feedback terminal of the amplifier,
A feedback resistor connected from the output terminal to the feedback terminal, a variable resistor with fixed terminals connected to both ends of the feedback resistor, and at least two connected between the movable end of the variable resistor and ground. A sound quality adjustment circuit characterized by comprising a circuit whose impedance changes.