JPH0870226A - Sound volume adjustment device - Google Patents

Abstract

PURPOSE: To secure an optimum S/N depending on the kind of a source and to realize excellent localization of a sound image. CONSTITUTION: A level of a signal from a source whose maximum input level is known such as a CD player is adjusted via an input terminal 1, an amplifier 4, an attenuator 6 and an output terminal 9. That is, the signal is amplified by an amplifier 4 before the signal is attenuated by the attenuator 6 to reduce the effect of noise caused in the attenuator 6. On the other hand, the level of a signal from other source is adjusted via input terminals 2, 3, the attenuator 6 and an amplifier 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a volume control device suitable for amplifying a sound signal.

[0002]

2. Description of the Related Art When amplifying an input audio signal and appropriately adjusting the volume, a structure in which an attenuator such as a volume is provided in a preceding stage and an amplifier is provided in a subsequent stage and a configuration in which an amplifier is provided in a preceding stage and an attenuator is provided in a latter stage You could think so. In the former case, the noise generated in the amplifier is output without being attenuated at all, so that there is a drawback that the S / N ratio is deteriorated especially when a small signal is output from the amplifier. On the other hand, in the latter configuration, when the input signal level is high and the amplifier is saturated, the distortion rate is extremely deteriorated and cannot be prevented.

Therefore, as a solution to both drawbacks, a circuit as shown in FIG. 3 has been proposed (Shokai Sho5).
1-113162, JP-A-63-86909, etc.). In the figure, 51 and 53 are attenuators, and 52 is an amplifier. The resistance values of the attenuators 51 and 53 are set in association with a volume knob (not shown), and volume control is performed while maintaining an appropriate S / N ratio and distortion rate to some extent. For example, the scale value of the volume knob is "0 dB (maximum value) to -18d.
In the case of “B”, the attenuation amount of the attenuator 51 is “0 dB to 18 d.
It is set in the range of "B", and the attenuation amount of the attenuator 53 is "0d.
B ”. Therefore, when the amplifier 52 is in the saturated state, the input signal level can be lowered by squeezing the volume knob to eliminate the saturated state.

When the scale value is "-18 dB" or less, the attenuation amount of the attenuator 53 becomes "18- (scale value) dB" while the attenuation amount of the attenuator 51 is kept at "18 dB". Is set. As a result, even when a small signal is output, the input signal level to the amplifier 52 can be raised to some extent, and a decrease in the S / N ratio can be prevented to some extent.

[0005]

By the way, in recent years, it has become common to perform various remote operations and automatic operations by digitizing parts such as the attenuators 51 and 53.
That is, A / D converter, digital volume and D
In some cases, these attenuators are configured by sequentially connecting the / A converter. However, the attenuator 51,
When 53 is digitized, quantization noise and error noise occur here. Since the generated noise is amplified through the amplifier 52, the S / N ratio of the volume adjusting device deteriorates.

Another problem has arisen when stereo reproduction is performed by providing two systems of the circuit shown in FIG. That is, since the attenuator inevitably has an attenuation error, the sound image slightly shifts depending on the volume position during stereo reproduction. FIG.
In the circuit (1), "two" attenuators 51 and 53 are provided for "one channel", which causes a problem that the "deviation" of the sound image due to the difference in attenuation error becomes significant.

On the other hand, the audio signal input to the volume adjusting device has various sources, and the maximum signal level may be known in some cases. For example, it is generally difficult to predict the maximum level of an input signal for a microphone input or a line input, but when the output signal of a CD player is used as the input signal, the maximum level is "2 [Vrms]. It is. Therefore,
For a source with a known maximum level, if the optimum signal path can be secured according to the source, S /
It is considered possible to raise the N ratio to the limit.
Furthermore, if the number of attenuators can be reduced by securing a signal path corresponding to each source, it is considered that excellent sound image localization can be realized. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a volume adjusting device that can secure an optimum S / N ratio according to the type of source and that realizes excellent sound image localization. .

[0008]

In order to solve the above-mentioned problems, the structure according to claim 1 is provided with an attenuator for attenuating and outputting a supplied audio signal, and an attenuator provided before the attenuator. A first amplifier, a second amplifier provided after the attenuator, and a switcher that amplifies the audio signal by one of the first and second amplifiers and bypasses the other. It is characterized by having.

According to the second aspect of the invention, an attenuator for attenuating the supplied audio signal and outputting it, and a first amplifier provided at a stage preceding the attenuator and having a predetermined gain A1. , A switch that appropriately bypasses the first amplifier, a second amplifier that is provided in a subsequent stage of the attenuator, and a gain of the second amplifier that is predetermined when the first amplifier is bypassed. While setting the gain A, the first
If the second amplifier is not bypassed, it is characterized by including a gain switching means for setting the gain of the second amplifier to a predetermined gain A2 (where A2 = A-A1).

[0010]

When the first amplifier is bypassed by the switch, the audio signal is attenuated by the attenuator and then amplified by the second amplifier. On the other hand, when the second amplifier is bypassed, the audio signal is
After being amplified by the amplifier, it is attenuated by the attenuator.

According to the configuration of claim 2, the first
If the amplifier is not bypassed, the audio signal will be the first
Is amplified by the gain A1 via the amplifier of A1, then attenuated by the attenuator, and further amplified by the gain A2 via the second amplifier. On the other hand, when the first amplifier is bypassed, the audio signal is attenuated by the attenuator and then amplified by the gain A through the second amplifier.

[0012]

【Example】

A. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to FIG. In FIG. 1, reference numerals 1 to 3 are input terminals to which audio signals are supplied from various sources. However, the input terminal 1 is an input terminal for a CD player. 4 is an amplifier,
"A = 20log (Vsat / Vi) [dB]" (however, Vsat [V]
Has a gain A of saturation voltage, Vi = 2 [Vrms]). That is, the amplifier 4 has an input signal level of "2 [Vr
ms] ”, the audio signal of“ Vsat [Vrms] ”is output. Next, 5 is a source switch, and its input terminal 5
In a to 5c, either the output signal of the amplifier 4 or the audio signal input from the input terminals 2 and 3 is selected and output.

Next, 6 is an attenuator, which is a source switcher 5.
The audio signal output from the device is appropriately attenuated and output. An amplifier 7 has the same gain A as the amplifier 4, and amplifies and outputs the audio signal output from the attenuator 6. Reference numeral 8 denotes a switching device, which works in conjunction with the source switching device 5 to select one of the signals supplied to its input terminals 8a to 8c and output it via an output terminal 9. That is, when the input terminal 5a is selected in the source switching device 5, the input terminal 8a is selected in the switching device 8, and similarly, the input terminal 5b is selected.
When the input terminal 8b is selected, the input terminal 8b is selected, and when the input terminal 5c is selected, the input terminal 8c is selected.

In the above configuration, when the input terminal 2 or 3 is selected by the source switcher 5, the supplied audio signal is attenuated by the attenuator 6, amplified by the amplifier 7, and then output by the output terminal 9. Is output. In such a case, attenuator 6
It is difficult to secure an extremely high S / N ratio because the noise generated in 1. is amplified by the amplifier 7. However, when the amplifier 7 is saturated, the attenuation rate of the attenuator 6 is increased to bring it into a saturated state. Can be avoided. On the other hand, when the input terminal 1 (amplifier 4) is selected by the source switcher 5, the supplied audio signal is amplified by the amplifier 4, attenuated by the attenuator 6, and then output by the output terminal 9. Is output.

Therefore, even if noise occurs in the attenuator 6, the noise level can be suppressed to a very low value compared with the amplified voice signal level. That is, assuming that the noise is caused only by the attenuator 6,
The S / N ratio can be improved by “A [dB]” as compared with the case where the audio signal is input from the input terminals 2 and 3. As described above, in this embodiment, when adjusting the volume of the input signal from the CD player or the like, it is possible to secure an extremely high S / N ratio. Further, even when two circuits of the circuit shown in FIG. 1 are provided and stereo reproduction is performed, only one "attenuator" 6 is provided for each system, so that the difference in attenuation error can be reduced, which is excellent. Sound image localization can be realized.

B. Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. In the figure, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and description thereof will be omitted. In the figure, 10 is an amplifier, which is connected between the input terminal 1 and the input end 5a,
It has a gain A1 (however, A1 <A). Reference numeral 13 is an amplifier, and 12, 15 to 17 are resistors for gain adjustment. The gain of the amplifier 13 is set by the switching state of the switch 8. That is, the gain of the amplifier 13 is A2 (where A2 = A−A when the input end 8a is selected).
It is set to 1), and is set to A when the input terminals 8b and 8c are selected.

In the above structure, the operation when the input terminal 2 or 3 is selected by the source switch 5 is the same as that of the first embodiment. That is, the supplied audio signal is attenuator 6
After being attenuated via, it is amplified by the amplifier 13,
Although the saturated state can be avoided, it is difficult to secure a high S / N ratio. On the other hand, when the input terminal 1 (amplifier 4) is selected by the source switcher 5, the supplied audio signal is amplified by the amplifier 10, attenuated by the attenuator 6, and further amplified by the amplifier 13. Is amplified.

Therefore, assuming that noise is caused only by the attenuator 6 as in the first embodiment, the S / N ratio is "A" as compared with the case where a voice signal is input from the input terminals 2 and 3.
Only 1 [dB] ”can be improved. The attenuator 6
When an analog volume is used as, the degree of improvement of the S / N ratio in this embodiment is slightly lower than that in the first embodiment. However, in the present embodiment, by reducing the maximum voltage level applied to the attenuator 6, it is possible to suppress the dynamic range thereof, which is extremely advantageous when the attenuator 6 is digitized. That is, by fully utilizing the effective bit width of the attenuator 6, it becomes possible to reduce the influence of quantization noise or the like on the S / N ratio.

Although the input terminal 1 is used for the CD player in the first and second embodiments, the same input terminal is provided for various sources whose maximum input levels are known, and the maximum input is provided. After amplifying with the gain according to the level,
It may be supplied to the attenuator 6. Further, in the first embodiment, the gain of the amplifier 4 is "20log (Vsat / Vi) [d"
Needless to say, it can be set lower than "B]".

[0020]

As described above, according to the volume control apparatus of the present invention, the order of amplification and attenuation of the audio signal can be changed as appropriate, so that depending on the type of source,
The audio signal can be amplified before being attenuated. Furthermore, the number of required attenuators for "1 system" is "1"
It is enough. Therefore, according to the present invention, an optimum S / N ratio can be secured according to the type of source, and
It is possible to achieve excellent sound image localization.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a volume adjusting device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a volume adjusting device according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional volume adjusting device.

[Explanation of symbols]

 Reference Signs List 4 amplifier (first amplifier) 5 source switching device (switching device) 6 attenuator (attenuator) 7 amplifier (second amplifier) 8 switching device (switching device, gain switching means) 13 amplifier (second amplifier)

Claims (2)

[Claims] 1. An attenuator that attenuates and outputs a supplied audio signal, a first amplifier provided before the attenuator, and a second amplifier provided after the attenuator. A volume control device comprising: a switch that amplifies the audio signal by one of the first and second amplifiers and bypasses the other. 2. An attenuator that attenuates and outputs a supplied audio signal, a first amplifier provided in a preceding stage of the attenuator and having a predetermined gain A1, and a switch for appropriately bypassing the first amplifier. And a second amplifier provided after the attenuator, and when the first amplifier is bypassed, the gain of the second amplifier is set to a predetermined gain A while the first amplifier is set to the predetermined gain A. When the amplifier is not bypassed, the gain of the second amplifier is set to a predetermined gain A2 (where A2 = A-A1).
And a gain switching means for setting the volume control device.