JP3637963B2 - Audio device and method for adjusting output level of audio signal thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an audio apparatus that reproduces an optical disk such as a CD or a DVD, and more particularly, to an audio apparatus that can be shipped by adjusting an analog audio output signal to a reference level at the time of manufacture and a voltage adjusting method thereof.
[0002]
[Prior art]
AV devices such as a CD player and a DVD player include a D / A converter that converts a digital audio signal into an analog signal.
As an example of such an audio apparatus, there is known a multi-channel D / A converter IC capable of arbitrarily selecting the number of systems for adjusting the multi-channel output amplitude (see Japanese Patent Laid-Open No. 5-191287).
In this device, the D / A converter IC is separated into a D / A converter and an amplitude controller. The D / A conversion unit includes a variable resistor and a bias resistor as an external device, and is provided with a reference voltage input terminal, a bias resistor connection terminal, and an amplitude adjustment output terminal.
[0003]
On the other hand, the amplitude control unit is provided with an adjustment input terminal and a signal output terminal. As a result, a combination of connections between a plurality of amplitude adjustment input terminals and a plurality of amplitude adjustment output terminals can be freely set, so that the number of systems for adjusting the output amplitude of multi-channels can be arbitrarily set. is there.
In addition, a D / A converter for controlling the amplitude of the output from the output terminal has been proposed (see Japanese Patent Application Laid-Open No. 5-129958).
In this D / A converter, the D / A converter changes the output amplitude in proportion to the voltage input to both ends of the first reference voltage input terminal and the second reference voltage input terminal. Yes.
[0004]
There is also known a D / A converter in which the input terminal of the minimum value reference voltage of the D / A converter is connected to the ground, and the input terminal of the maximum value reference voltage functions as an output proportional value analog input terminal. (See JP-A-6-132828).
According to this D / A converter, the slope of the output voltage with respect to the input data can be determined by adjusting the output voltage of the constant voltage power supply.
[0005]
[Problems to be solved by the invention]
By the way, the above-described conventional audio apparatus or the like generally has a variation in output performance of a finished product due to a difference in characteristics of circuit elements mounted at the time of manufacture or a manufacturing process.
That is, a D / A converter IC (Japanese Patent Laid-Open No. 5-191287) and a D / A converter (Japanese Patent Laid-Open No. 5-129958) adjust the output amplitude with a variable resistor, and the latter D / A converter. (JP-A-6-132828) adjusts the output voltage of a constant voltage power supply.
However, none of them are adjusted and controlled while detecting the output level at the final stage, so as described above, the output performance is shipped with variations, and the recorded information on the disk is actually reproduced to emit sound from the speaker. There was a problem that the sound was distorted or deteriorated.
[0006]
The present invention has been made in view of the above problems, is adjusted to a predetermined value the output level of the analog audio signal of the final stage in which the speaker is connected during the adjustment process, distortion Ya the audio to be output from the speaker An object of the present invention is to provide an audio device and a method for adjusting the output level of an audio signal that can solve the problem of deterioration.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an audio device according to a first aspect of the present invention comprises a digital circuit unit for processing a digital audio signal read out by reproducing a recording medium, and the digital circuit unit. a D / a converter for converting the digital audio signal into an analog audio signal inputted from filtering the analog audio signal by the audio signal output from the amplifier and the amplifier amplifies the analog audio signal from the D / a converter An audio DAC circuit including at least an analog circuit unit including a filter to be sent to a terminal; an external circuit including an amplifier connected to the audio signal output terminal; and an output side of the external circuit , A voltage level display device that displays the voltage level of the sine wave of the analog audio signal is detachably connected at the time of adjustment. A jack speakers are fixedly connected in place of the level display unit, a power supply circuit for supplying the de-I digital circuitry and power supply voltages of predetermined value to said analog circuit section, the power supply voltage output terminal of said power supply circuit And a manual operation for adjusting the voltage level being displayed to a predetermined value on the voltage level display device, which is connected between the power supply voltage input terminal of the analog circuit and the voltage level display device connected only at the time of adjustment. And a voltage adjusting unit that varies the power supply voltage output from the power supply output terminal and supplies the power supply voltage to the power supply voltage input terminal.
[0008]
Further, the analog in the audio DAC circuit D / A converter is provided between the output level adjustment method, a digital circuit and analog circuit portions of the audio signal of the audio device of the invention according to claim 2 the jack is provided through an external circuit to the circuit unit, prior to fixedly connecting the speaker, is connected with a voltage level display device detachably, by reproducing the recording medium, read from the recording medium A voltage level of a sine wave of an analog audio signal output from the jack via the audio DAC circuit and the external circuit is displayed on the voltage level display device, and the analog circuit unit has a power supply voltage of a predetermined value. a voltage adjustment means being interposed connected between the power supply input terminal of the analog circuit unit and the power output terminal of the power supply circuit for supplying the voltage level While manual operation based on the voltage level being displayed in the shown device, it is characterized by adjusting the voltage level to be displayed on the voltage level display device to a predetermined value.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the illustrated examples.
FIG. 1 is a block diagram showing an electrical configuration of an audio DAC circuit according to the present invention, and FIG. 2 is an electrical circuit diagram showing the audio DAC circuit.
This audio DAC circuit is applied to a CD player, and is configured to convert a digital signal reproduced from a CD into an analog audio signal and send it to a speaker side to emit music.
In the CD player, the servo control unit controls the motor and the optical pickup to rotate the CD, and sends the recording information optically read from the track of the CD to the signal processing unit.
The signal processing unit sends out a digital signal obtained by processing the read information to the audio DAC circuit 1 side.
[0010]
In FIG. 1, reference numeral 1 denotes an audio DAC circuit, and a digital circuit unit and an analog circuit unit operate by receiving a supply voltage from a power supply circuit 15.
Reference numeral 2 denotes an audio serial port (audio port). The output side of the signal processing unit is connected to an input terminal, and a digital signal is input from the signal processing unit.
In addition, a bit clock signal and a clock signal at the switching timing of the L and R channels are guided to the audio port 2, and the digital signal is processed based on these signals.
[0011]
Reference numeral 3 denotes a serial control port (serial port), and an output side of a control unit (not shown) is connected to an input terminal.
The serial port 3 receives the latch signal and the clock signal together with the control signal from the control unit, and controls the operation of the oversampling circuit 5.
A system clock manager (system clock) 4 receives a system clock signal from the oscillation circuit, and controls the operation time of the serial port 3 and the oversampling circuit 5 according to the system clock signal.
Reference numeral 5 denotes an oversampling digital filter (oversampling circuit) whose output is connected to the enhanced multilevel circuit 6.
[0012]
The oversampling circuit 5 samples (samples) the digital audio signal from the audio port 2 and outputs it to the enhancement multilevel circuit 6.
Reference numeral 6 denotes an enhanced multilevel delta-sigma modulation (enhanced multilevel circuit), and D / A converters 7 and 8 are connected to the output sides of the L channel and the R channel, respectively.
[0013]
The enhanced multi-level circuit 6 separates the digital audio signal into an L channel and an R channel, and outputs them to the D / A converters 7 and 8, respectively.
These D / A converters 7 and 8 are connected to amplifiers 9 and 10, respectively. The D / A converter 7 converts an L channel digital audio signal into an analog audio signal and sends it to the amplifier 9 side. .
On the other hand, the D / A converter 8 converts the L channel digital audio signal into an analog audio signal and sends it to the amplifier 10 side.
Low-pass filters 11 and 12 are connected to the amplifiers 9 and 10, respectively, and an analog audio signal is amplified and sent to the low-pass filters 11 and 12.
[0014]
Pin terminals 13 and 14 are connected to the low-pass filters 11 and 12, respectively, and an unnecessary band of the analog audio signal is cut and sent to the pin terminals 13 and 14 side.
These pin terminals 13 and 14 are audio signal output terminals, and the pin terminal 13 side is for L channel output and the pin terminal 14 side is for R channel output.
The pin terminals 13 and 14 are connected to external amplifier circuits 17 and 18, respectively. The amplifier circuits 17 and 18 amplify the L and R channel analog audio signals, and filters 19 and 20 are connected to the output sides of the amplifier circuits 17 and 18, respectively.
Jacks 21 and 22 are connected to the filters 19 and 20, and unnecessary components of the amplified analog audio signal are cut and sent to the jacks 21 and 22, respectively.
[0015]
A speaker is connected to the jacks 21 and 22 (not shown).
After the production of the CD player, an audio analyzer is connected to the jacks 21 and 22 to adjust the output of the audio signal.
This audio analyzer measures the voltage level of a sine wave of an audio signal. When an audio analog signal is introduced by connecting the input side to jacks 21 and 22, the current voltage measurement value is displayed on the display unit. It has become.
[0016]
A power supply circuit 15 receives a commercial AC voltage to an input terminal, and outputs DC power supply voltages of 3.3V and 5.0V from power supply voltage output terminals 15a and 15b after transformation, rectification, and smoothing, respectively . It is like that. Power supply voltage output terminal 15a for outputting a DC power supply voltage of 3.3V is coupled to a supply voltage input terminal 1a of the digital circuit portion of the audio DAC circuit 1. As a result, the audio port 2, the serial port 3, the system clock 4, the oversampling circuit 5, the enhanced multilevel circuit 6, and the digital signal input side of each of the D / A converters 7 and 8 in the digital circuit section are each 3.3V. DC power supply voltage is supplied. The power supply voltage output terminal 15b of 5.0V is coupled to a supply voltage input terminal 1b of the analog circuit portion in the audio DAC circuit 1 via a variable resistor 16.
[0017]
The variable resistor 16 includes a resistor and a slide portion that slides on the resistor. One end of the resistor is connected to the power supply voltage output terminal 15b, and the slide portion is connected to the power supply voltage input terminal 1b. The variable resistor 16, rotating the operation unit with a screwdriver, the slide portion slides the resistor, so that can vary the power supply voltage supplied to the power supply voltage input terminal 1b side. Thus, the 5.0 V power supply voltage output from the power supply voltage output terminal 15 b of the power supply circuit 15 is adjusted by the variable resistor 16, and then the analog signal output side of each D / A converter 7, 8, The signals are supplied to amplifiers 9 and 10 and low-pass filters 11 and 12 , respectively.
[0018]
Next, the output adjustment method of the CD player will be described with reference to the drawings. First, an audio analyzer is connected to the jacks 21 and 22 of the audio DAC circuit 1.
Next, a test CD is set on the disc tray and reproduction is started. Along with this, the recording information of the CD track is read, and the digital signal from the signal processing unit is sent to the audio DAC circuit 1 side.
In the audio DAC circuit 1, the audio digital signal is converted into an audio analog signal and then sent to the audio analyzer side via the jacks 21 and 22.
This audio analyzer displays the voltage level of the sine wave of the audio signal on the display unit.
[0019]
Here, when the voltage level is lower than the predetermined value, the driver is operated to slide the slide portion of the variable resistor 16.
Then, the 5.0 V DC voltage output from the power supply circuit 15 is adjusted by the variable resistor 16 and then supplied to the D / A converters 7 and 8, the amplifiers 9 and 10, and the low-pass filters 11 and 12. Is done.
At this time, if the voltage is adjusted while viewing the display value of the audio analyzer, the output level of the audio analog signal can be set to a desired value.
The maximum output level (VPP) is set to a power supply voltage (VCC) × 0.62.
[0020]
Accordingly, the output voltage of the L and R channel audio signals to be output to the speaker side is based on a value obtained by multiplying the 5.0 V DC voltage output from the power supply circuit 15 by 0.62, and therefore the audio analyzer What is necessary is just to adjust with the variable resistor 16 so that a display may become this voltage.
As a result, after the CD player is manufactured, errors (usually ± 5) that occur in the analog circuit portion of the audio DAC circuit 1 including the D / A converters 7 and 8, the amplifiers 9 and 10, the low-pass filters 11 and 12, etc. %) And external amplifier circuits 17, 18 and the like can be absorbed and adjusted to a constant voltage as specified.
Therefore, when a speaker is connected to the jacks 21 and 22 and the recorded information on the CD is actually reproduced and emitted from the speaker, there is no problem that the sound is distorted or deteriorated.
[0021]
【The invention's effect】
As described above, the audio device according to the first aspect of the present invention includes a voltage adjustment unit capable of variably adjusting the power supply voltage supplied from the power supply circuit to the analog circuit unit of the audio DAC circuit by manual operation, Prior to the connection of the speaker , it is equipped with a jack that can be detachably connected to the voltage level display device during the adjustment process . Therefore, in the adjustment process after manufacture , a voltage level display device such as an audio analyzer is connected to the jack. When a test recording medium is set and playback is performed, the digital audio signal read from the recording medium and input to the digital circuit portion of the audio DAC circuit is converted into an analog audio signal by the D / A converter. via the analog circuit portion is output from the jack, audio Anna Lai connected to this jack Since sine wave voltage level of the analog audio signal is displayed on, the voltage adjusting unit while watching the voltage level being displayed in the audio analyzer, for example, if manually operated variable resistor, a predetermined output voltage level of the analog audio signal The value can be variably adjusted. Since the analog audio signal to be adjusted is output from the jack connected to the speaker, the voltage fluctuation caused by the characteristics of each component of the analog circuit part of the audio DAC circuit or each component of the external circuit Even if this occurs, the output voltage level of the final stage analog audio signal supplied to the speaker can be kept at a predetermined value, so that there is an effect of preventing distortion and deterioration of the sound emitted from the speaker.
[0022]
According to a second aspect of the present invention, there is provided a method for adjusting an output level of an audio signal of an audio device, wherein a voltage level display device, for example, an audio analyzer is connected to a jack prior to connection of a speaker in an adjustment step after manufacture. From the power supply circuit, set the test recording medium and perform playback, and manually operate the voltage adjustment means, for example, the variable resistor while observing the voltage level of the sine wave of the analog audio signal displayed on the audio analyzer. Since the power supply voltage supplied to the analog circuit portion of the audio DAC circuit is variably adjusted, and the output voltage level of the analog audio signal is variably adjusted to a predetermined value, the analog audio signal to be adjusted is output from a jack connected to the speaker. Therefore, each component of the analog circuit section of the audio DAC circuit and the external circuit Even if voltage fluctuations occur due to the characteristics of each of the components, the output voltage level of the final stage analog audio signal supplied to the speaker can be maintained at a predetermined value, so that the sound emitted from the speaker This has the effect of preventing distortion and deterioration.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electrical configuration of an audio DAC circuit in an audio apparatus according to an embodiment of the present invention.
Figure 2 is an electrical circuit diagram showing a part of an audio DAC circuits above the.
[Explanation of symbols]
1 Audio DAC circuit
1a Digital circuit section power supply voltage input terminal 1b Analog circuit section power supply voltage input terminal 7, 8 D / A converter 9 , 10 Amplifier 11, 12 Filter 13, 14 Audio signal output terminal 15 Power supply circuit
15a Power supply voltage output terminal to the digital circuit section 15b Power supply voltage output terminal to the analog circuit section 17, 18 Amplifier 19, 20 Filter 21, 22 Jack

Claims (2)

A digital circuit unit that performs signal processing on a digital audio signal read out by reproducing a recording medium, a D / A converter that converts a digital audio signal input from the digital circuit unit into an analog audio signal, and the D / A An audio DAC circuit comprising at least an analog circuit unit including an amplifier for amplifying an analog audio signal from the converter and a filter for filtering the analog audio signal from the amplifier and sending the filtered signal to an audio signal output terminal ;
An external circuit including an amplifier connected to the audio signal output terminal;
A voltage level display device that is provided on the output side of the external circuit and displays the voltage level of the sine wave of the analog audio signal is detachably connected during adjustment, and a speaker is replaced in place of the voltage level display device after adjustment. A fixedly connected jack,
A power supply circuit for supplying a power supply voltage of a predetermined value to each of the de-I digital circuit unit and the analog circuit portion,
The voltage level displayed on the voltage level display device, which is connected between the power supply voltage output terminal of the power supply circuit and the power supply voltage input terminal of the analog circuit and is connected only at the time of adjustment , is adjusted to a predetermined value. manually by operation is performed, the audio device, characterized in that by varying the supply voltage output from the power output terminal and a voltage regulating means for supplying to said power supply voltage input terminal for. The jack is provided through an external circuit to the analog circuit section in the audio DAC circuit D / A converter is provided between the digital circuit and the analog circuit portion, to fixedly connect the speaker Prior to connecting the voltage level display device,
After reproducing the recording medium and reading from the recording medium, the voltage level of the sine wave of the analog audio signal output from the jack via the audio DAC circuit and the external circuit is displayed on the voltage level display device Let
Displaying voltage adjustment means connected between a power supply output terminal of a power supply circuit for supplying a power supply voltage of a predetermined value to the analog circuit section and a power supply input terminal of the analog circuit section on the voltage level display device A method for adjusting an output level of an audio signal in an audio device , wherein the voltage level displayed on the voltage level display device is adjusted to a predetermined value while being manually operated based on the voltage level of the audio device.

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