JPH054336Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a sound quality adjustment device, and is used, for example, in a radio cassette recorder.

(Prior Art) A conventional sound quality adjustment device has a method in which the volume of the sound quality boosted by the sound quality adjustment boost circuit is directly added to the volume for volume adjustment.

(Problems to be Solved by the Invention) For this reason, there was a problem in that when the volume for adjusting the volume was set to the maximum, that is, at the maximum volume output point, abnormal conditions such as howling phenomenon were likely to occur.

(Means for Solving the Problems) In order to solve the above problems, the sound quality adjustment device of the present invention changes the variable range of sound quality adjustment depending on the state of the volume adjustment volume. An adjustment volume, a frequency filter that extracts only low frequencies connected to the sliding terminal of this sound quality adjustment volume, a transistor that converts the output of this frequency filter into impedance and amplifies it, and the output of this transistor and the volume adjustment. and a resistor for synthesizing the output of the sound volume adjustment volume, and when the volume adjustment volume has a maximum output, the variable range of the boost amount by the sound quality adjustment volume is small, and the output of the volume adjustment volume becomes small. Accordingly, the variable range of the boost amount by the sound quality adjustment volume is increased.

(Function) The signal input from the input terminal passes through the sound quality adjustment volume, only a predetermined low frequency band is selected by the frequency filter, and then the input impedance and phase are matched by the transistor, and the resistor It is combined with the output of the volume control via. Therefore, if the impedance of the device is set so that when the volume for volume adjustment is set to maximum output and the volume for sound quality adjustment is set to maximum output, the variable width of the boost amount is set to the minimum. It becomes possible to change the variable range of the boost amount of the frequency band that has been set by adjusting the volume adjustment volume.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of the sound quality adjustment device of the present invention.

In the figure, 1 is a preamplifier, 2 is a sound quality adjustment boost circuit, 3 is a main amplifier, 4 is a speaker, and 5 is a volume adjuster.

Moreover, FIGS. 2a to 2c equivalently show the case where the above-mentioned sound quality adjustment boost circuit 2 is a low frequency boost circuit. Moreover, FIGS. 3a to 3d show the frequency characteristics of these circuits. However, Fig. 3a
The curve shown by the broken line in ~c shows the time when the bass volume is maximum.

FIGS. 2a and 3a show an equivalent circuit and frequency characteristics when the output of the volume adjustment volume 5 is at the maximum. In other words, at a frequency of 1kHz, the impedance is R ₁ , and at low frequencies, at the peak point, this R ₁ and the sound quality adjustment boost circuit 2
This is the combined resistance value with the impedance of Here, the impedance of the sound quality adjustment boost circuit 2 is
Assuming R _B , the maximum boost amount for a level with a frequency of 1kHz is: V _G1 = 20log low band amplification factor / 1KHz amplification factor = 20logR ₀ /R ₁ ×R _B /R ₁ +R _B +R ₀ /R ₀ /R ₁ +R ₀ =20logR ₁ +R ₀ /R ₁ ×R _B /(R ₁ +R _B ) +R ₀ [dB]
...(1) becomes.

Further, FIGS. 2b and 3b show an equivalent circuit and frequency characteristics when the volume adjustment volume 5 is at an intermediate value. In other words, at a frequency of 1kHz, the impedance is (R ₁ + R ₀ /2), and at low frequencies, the combined impedance with R _B is (R ₁ + R ₀ /2)・_RB / (R ₁ + R ₀ /2 + R _B ) Therefore, the maximum boost amount for a level with a frequency of 1kHz is V _G2 = 20log low range amplification factor / 1KHz amplification factor = 20logR ₀ /2 / (R ₁ + R ₀ /2) × R _B /R ₁ + R ₀ /2
R _B +R ₀ /2/R ₀ /2/R ₁ +R ₀ =20logR ₁ +R ₀ /(R ₁ +R ₀ /2)×R _B /R ₁ +R ₀ /
2+R _B +R ₀ /2
[dB] ...(2)

Furthermore, FIGS. 2c and 3c show an equivalent circuit and frequency characteristics when the volume adjustment volume 5 is at a value of 1/5. i.e. the frequency
At 1kHz, the impedance is (R ₁ + 4R ₀ /5), and at low frequencies, the combined impedance with R _B is (R ₁ + 4/5R ₀ ) × R _B / (R ₁ + 4/5R ₀ + R _B ) From this, the maximum boost amount for a level with a frequency of 1kHz is: V _G3 = Low-frequency gain / Gain at 1KHz = 20log
R ₀ /5/(R ₁ +4/5×R ₀ )×R _B /(R ₁ +4/5×R ₀ +
R _B )+R ₀ /5/R ₀ /5/R ₁ +R ₀ =20logR ₁ +R ₀ /(R ₁ +4/5R ₀ )×R _B /R ₁ +4/
5R ₀ +R _B +R ₀ /5
[dB] ...(3)

Here, in each of the above equations, the resistance values are temporarily determined as follows.

R ₁ = 20kΩ, R ₀ = 20kΩ, R _B = 10kΩ Substituting these resistance values into the above equations (1), (2), and (3), V _G1 ≒3.5dB V _G2 ≒7.2dB V _G3 ≒10.6dB.

In this way, if the impedance of the sound quality adjustment boost circuit 2 is set so that the boost amount is from 0 dB to 2 to 3 dB when the volume adjustment volume 5 is at its maximum, the sound quality adjustment boost will be adjusted depending on the state of the volume adjustment volume 5. The amount of boost provided by the circuit 2 can be varied. In other words, when the volume adjustment volume 5 is at its maximum output, the variable range of the boost amount by the sound quality adjustment boost circuit 2 is from 0 dB to 2 to 3 dB.
Therefore, when the volume adjustment volume 5 is at the intermediate value, the variable range of the boost amount by the sound quality adjustment boost circuit 2 is from 0 dB to 6 to 7 dB, and when the volume adjustment volume 5 is at the minimum value, the sound quality adjustment boost circuit 2 The variable range of boost amount is from 0dB.
It will be 10-13dB.

FIG. 4 shows an example of a specific circuit of the above-mentioned sound quality adjustment device.

In the figure, 11 is an input terminal, 13 is an output terminal, 14 is a volume for adjusting sound quality, 15 is a frequency filter that is a low-pass filter that extracts only low frequencies;
16 is a transistor constituting an emitter follower amplifier that acts as an impedance converter; 17 is a volume for adjusting the volume; and _R4 is a resistor for combining the output of the volume for volume adjustment 17 and the output of the transistor 16.

Next, the operation of the sound quality adjustment device having the above configuration will be explained.

The signal input from the input terminal 11 passes through the coupling capacitor C ₁ and is gain adjusted by the resistors R ₁ and R ₅ , then passes through the volume adjustment volume 17 and outputs from the output terminal 13, which has almost flat frequency characteristics. is output. On the other hand, coupling capacitor
The signal that has passed through C ₁ and sound quality adjustment volume 14 is selected by a frequency filter 15 to select only a predetermined low frequency band, and then is passed through transistor 1.
6, is outputted from the output terminal 13 through the resistor R ₄ and the capacitor C ₂ . Here, transistor 1
6 functions to match the input impedance and match the frequency phase.

Here, the relationship between the sound quality adjustment volume 14 and the volume adjustment volume 17 will be clarified by showing specific calculated values.

Now, to simplify the calculation, let's remove the resistance R ₅ as infinity (∽) and add the frequency filter 15.
The amplification factor (attenuation factor) of is set to 1. Further, the resistance value of the volume adjustment volume 17 is set to V _L17 , and the signal source side of the sliding terminal is set to V _LH , and the ground side is set to V _LL .
In addition, the input signal is V _i and the output signal is V ₀ , and the respective resistance values are R ₁ = 20kΩ, V _L17 = 20kΩ, R ₄ =
Set to 20kΩ. In addition, the signal has a low frequency.

In the above assumption, the volume adjustment volume 17
is set as the maximum value, and the amount of change between the minimum and maximum of the sound quality adjustment volume 14 at this time is calculated.

(1) When the sound quality adjustment volume 14 is at its minimum At this time, the output of the transistor 16 is zero,
Since the impedance is negligibly small compared to _R4 , the equivalent circuit in this case is as shown in FIG. Therefore, output terminal 1
The output voltage V ₀₁ of 3 is V ₀₁ =V _i ×V _L17 R ₄ /R ₁ +V _L17 R ₄ =V _i × [20 × 20 (20 + 20)] / 20 + [20 × 20 (20 +
20)] = 1/3V _i (2) When the sound quality adjustment volume 14 is at maximum At this time, the input signal V _i has an amplification factor of 1 in the frequency filter 15, and the output of the transistor 16, which is an emitter follower amplifier, is equal to the input signal Since V _i is output, the equivalent circuit at this time is as shown in FIG. Therefore, the output voltage of output terminal 13
V ₀₂ is V ₀₂ = V _i × V _L17 / R ₁ R ₄ + V _L17 = V _i × 20 / [20 × 20 (20 + 20)] + 20 = 2/3 V _i Therefore, the minimum time of volume 14 for sound quality adjustment The difference between V _G1 and the maximum time is V _G1 = 20logV ₀₂ /V ₀₁ = 20log2/3×V _i /1/3×V _i
=6[dB]...(4)

Next, the sliding terminal of the sound quality adjustment volume 17 is set at the 1/4 position, and the amount of change between the minimum and maximum of the sound quality adjustment volume 14 at this time is calculated. At this time, the values of V _LH and V _LL of the volume adjustment volume 17 are 15 kΩ and 5 kΩ, respectively.

(3) When the tone quality adjustment volume 14 is at its minimum At this time, R ₄ is handled in the same way as in the above case, and the equivalent circuit at this time is as shown in FIG. Therefore, the output voltage V ₀₃ of the output terminal 13 is V ₀₃ =V _i ×V _LL R ₄ /R ₁ +V _LL R ₄ = V _i × [5 × 20 (5 + 20)] / 20 + 15 + [5 × 20 (
5+20)] =4/39×V _i (4) When the sound quality adjustment volume 14 is at its maximum At this time, R ₄ is handled in the same way as in the above case, and the equivalent circuit in this case is as shown in Figure 8. . Therefore, the output voltage V ₀₄ of the output terminal 13 is V ₀₄ = _Vi × V _LL / (R ₁ + V _LH ) R ₄ + V _LL = _Vi × 5 / [(20 + 5) × 20] / (20 + 15 + 20) + 5
= 5/17.7 Therefore, the difference V _G2 between the minimum and maximum sound quality adjustment volume 14 is: V _G2 = 20logV ₀₄ /V ₀₃ = 20log5/17.7/4/39 = 8.8[
dB]...(5)

As is clear from the above equations (4) and (5), the amount of low-range boost when the volume adjustment volume 17 is at the maximum position is the same as the amount of low-range boost when the volume adjustment volume 17 is at the minimum position. It can be seen that the amount decreases.

In this calculation, the resistance value was determined for the purpose of explaining the principle, but by appropriately selecting the values of the resistor _R1 and the resistor _R4 , the boost amount as shown in FIG. 3 can be obtained.

In other words, when the volume adjustment volume 17 is set to maximum output and the sound quality adjustment volume 14 is set to maximum output, the variable width of the boost amount is 0 dB.
By setting the impedance of the device so that it is 2 to 3 dB from 1 to 3 dB, the boost width of the frequency band selected by the frequency filter 15 can be changed depending on the position of the volume control 17.

(Effects of the invention) As explained above, according to the sound quality adjustment device of the invention, when the volume adjustment volume is at its maximum output, the variable range of the boost amount by the volume adjustment volume is small; Since the variable range of the boost amount by the sound quality adjustment volume increases as the sound quality adjustment volume increases, it is possible to reliably prevent the occurrence of abnormal conditions such as howling at the maximum point of the volume output in the low frequency band.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of the sound quality adjustment device of the present invention.
Figures 2 a to c are circuit diagrams when the sound quality adjustment volume is varied, Figures 3 a to d are curve diagrams showing the frequency characteristics of these circuits, and Figure 4 is a specific example of the sound quality adjustment device of the present invention. The circuit diagrams shown in FIGS. 5 to 8 are equivalent circuit diagrams of various combinations of the positions of the volume adjusting volume and the position of the tone quality adjusting volume. 1... Preamplifier, 2... Sound quality adjustment boost circuit, 3... Main amplifier, 5, 17... Volume for volume adjustment, 14... Volume for sound quality adjustment,
15...Frequency filter, 16...Transistor, _R4 ...Resistor.

Claims (1)

[Scope of utility model registration request] The variable width of the sound quality adjustment is changed depending on the state of the volume adjustment volume, and the sound quality adjustment volume is connected to the input terminal, and the frequency filter that extracts only low frequencies is connected to the sliding terminal of the sound quality adjustment volume. A transistor for impedance-converting the output of the frequency filter and amplifying the output, and a resistor for synthesizing the output of the transistor and the output of the volume adjustment volume, and when the volume adjustment volume is at its maximum output. The variable range of the boost amount by the sound quality adjusting volume is small, and as the output of the sound volume adjusting volume becomes smaller, the variable range of the boost amount by the sound quality adjusting volume increases. Sound quality adjustment device.