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JP2004214718

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DESCRIPTION JP2004214718
An object of the present invention is to enable high-quality voice output by eliminating
deterioration of signal quality in a transmission path. SOLUTION: An audio reproduction output
system 1 includes a disk reproduction device 10 and a headphone drive device 30, and the disk
drive device 10 performs a headphone drive device with a pulse width modulation signal
obtained by delta sigma modulation of a pulse code modulation signal. The headphone drive
device 30 performs waveform shaping on the pulse width modulation signal received from the
disk reproduction device 10 and amplifies the power to generate a drive signal for driving the
speaker 23 of the headphone 20. It is a thing. As a result, since resampling is performed in the
headphone driving device 30, deterioration in signal quality occurring in the transmission path
between the devices is eliminated, and high-quality sound output is possible. [Selected figure]
Figure 1
Audio reproduction output system, audio signal reproduction device, audio output drive device,
headphone
The present invention relates to an audio reproduction output system for reproducing and
outputting digitally recorded audio signals such as CDs and MDs, an audio signal reproduction
apparatus and an audio output drive apparatus constituting the same, and an audio output The
present invention relates to a headphone equipped with a driving device. 2. Description of the
Related Art In recent years, recording media for audio signals are digitally recorded as
represented by CD, MD and the like. The reproduction characteristics of the digitally recorded
audio signal do not deteriorate the sound quality due to the characteristics of the recording
medium such as a cassette tape, which is in the conventional analog recording medium, and have
high S / N, high dynamic range, low distortion, etc. Sound quality is possible. In order to
reproduce an audio signal from a digitally recorded recording medium, a disc reproducing
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apparatus such as a CD player or an MD player is used. Then, in order to finally output as a
sound, a speaker is often used when listening at a large volume at home, and a headphone is
often used outdoors. In addition, nowadays, there are many cases where even in a private room
at home, there are many cases using headphones. In digital sound sources, there are basically no
factors that affect the sound quality in the signal reproduction process. Therefore, when listening
to digitally recorded sound, the sound quality is determined at the stage of becoming an analog
signal, that is, substantially the speaker and the headphone. Therefore, conventionally, the
speaker has been improved in sound quality by accumulation of various methods and know-how.
On the other hand, headphones do not take into consideration the issue of high sound quality. As
shown in FIG. 6, the conventional disc reproducing apparatus 110 is configured to include a
signal processing circuit 111, a DA converter 112, and a headphone jack 113. The signal
processing circuit 111 performs a series of signal processing (demodulation, etc.) on a signal
(data) extracted by the optical pickup (not shown) from the disc D in which an audio signal such
as a CD or MD is digitally recorded. It performs error correction, data decompression and the like
in the case of compressed data, and outputs a PCM (pulse-code modulation) signal. The
processing up to this point is mainly digital signal processing, and the output PCM signal is
usually subjected to independent signal processing at Lch and Rch. In addition, since it is a digital
signal, it is not affected by the sound quality deterioration due to analog elements such as power
supply noise and substrate pattern. Next, the DA converter 112 converts the PCM signal output
from the signal processing circuit 111 into an analog signal.
After this, since the audio signal becomes an analog signal, there are various causes of sound
quality deterioration. That is, it is affected by power supply noise, the influence of the substrate
pattern, the influence of disturbance noise, and the like. This analog signal is output from the
headphone jack 113 to the headphone 120 (FIG. 7). The headphone jack 113 is usually a jack of
three terminals (L, R, G), and GND is common to Lch and Rch. Essentially, it is desirable that the
Lch audio signal and the Rch audio signal be processed independently, including the GND, so this
is also a factor in sound quality degradation. Further, as shown in FIG. 7, in the conventional
headphone 120, small speakers 123 and 123 for Lch and Rch are disposed at both ends of an
arm 124, and the headphones 123 and 123 are connected A headphone plug 121 is provided at
the end of the cable 122. The headphone plug 121 is used by being inserted into the headphone
jack 113 of the disc playback apparatus 110. Here, the headphone cable 122 is separated into
one for Lch and one for Rch. That is, GND is also provided separately for Lch and Rch. However,
in the headphone plug 121, as with the headphone jack 113, GND is common to Lch and Rch. As
prior art documents related to the present invention, there is the following patent document 1.
According to Patent Document 1, a remote control device for operating a recording information
reproducing apparatus is constituted by one switch, and is stored in an audio data ROM of a
shockproof unit of a disk reproducing apparatus according to its on / off pattern. There is
described a recorded information reproducing apparatus provided with a remote control device
capable of confirming a button operation by sound by outputting a signal specifying a voice
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message. [Patent Document 1] Japanese Patent Application Laid-Open Publication No. 2001283577 (release date: October 12, 2001) [0013] A system using a conventional disk reproducing
apparatus and headphones Then there were the following problems. (1) Since the transmission
path of the analog signal is included, there are various factors that cause the sound quality
deterioration from the stage when the reproduction signal becomes an analog signal. (2) In the
case of a stereo signal, originally, an Lch signal and GND for Lch are required for the signal
transmission line on the Lch side, and an Rch signal and GND for Rch are required for the signal
transmission line on the Rch side.
This is always the case with the speaker connection. However, in the case of headphones, the
GND for Lch and the GND for Rch are common, which causes the deterioration of separation of
Lch and Rch. Further, if the GND is common, BTL driving can not be performed, for example,
which gives a signal having a reverse polarity to the Lch signal instead of setting the GND side to
a fixed voltage, which is disadvantageous for low voltage large output driving. (3) The cable
connecting the headphone from the disk reproducing device is usually 1 m or more, but uses a
very thin wire to ensure flexibility. Therefore, the resistance value is relatively high, which leads
to the deterioration of the sound quality. The present invention has been made to solve the
above-mentioned problems, and its object is to provide an audio reproduction output system
capable of high-quality audio output, an audio signal reproduction apparatus comprising the
same, and an audio output. An object of the present invention is to provide a drive device and a
headphone equipped with an audio output drive device. SUMMARY OF THE INVENTION In order
to solve the above problems, an audio reproduction output system according to the present
invention includes an audio signal reproduction device and an audio output drive device, and the
audio signal reproduction device includes: A pulse width modulation signal obtained by
subjecting a pulse code modulation signal to delta sigma modulation is sent to the voice output
drive device, and the voice output drive device has a waveform for the pulse width modulation
signal received from the voice signal reproduction device. After shaping, power amplification is
performed to generate a drive signal for driving the audio output means. According to the above
configuration, in the audio signal reproduction device, the pulse width modulation signal (PDM
signal, PWM signal) generated from the pulse code modulation signal (PCM signal) is transmitted
to the audio output drive device, and After the pulse width modulation signal is waveformshaped, power amplification is performed to generate a drive signal for driving an audio output
unit such as a headphone. Thus, since the signal transmitted from the audio signal reproduction
device to the audio output drive device is a pulse width modulation signal, the signal waveform
can be shaped in the audio output drive device. Therefore, in the audio output driving device,
waveform shaping prior to power amplification of the pulse width modulation signal completely
eliminates signal deterioration due to jitter or fluctuation of data generated in the transmission
path between the devices or crosstalk. It becomes possible. Therefore, even if the transmission
path between the audio signal reproduction device and the audio output drive device is
lengthened, it does not become a factor of sound quality deterioration.
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Therefore, by providing an audio output driving device near the audio output means and
shortening the transmission path of the drive signal which is an analog signal, it is possible to
reduce the opportunity for sound quality deterioration, and high-quality audio output is possible.
. For example, even when listening to an audio signal reproduced by a portable MD reproducing
device with a headphone connected by a thin long headphone cable, by providing an audio
output driving device to the headphone, signal deterioration in the headphone cable can be
reduced. It can be removed to realize high-quality sound output. Also, even if the GND for Rch
and the GND for Rch are common in the path between the audio signal reproduction device and
the audio output drive device, they can be separated by the audio output drive device as in the
prior art. The separation of Lch and Rch does not get worse. In addition, since BTL drive can be
performed to generate a drive signal, it is possible to remove common mode noise and drive with
low voltage and large output. As described above, in the audio reproduction output system,
analog signal processing is performed by the audio output drive device using the L-bit and R-ch
independently, and based on the waveform-shaped jitter-free 1-bit signal. It will be. Therefore,
high-quality sound output is possible. Furthermore, in the audio reproduction output system
according to the present invention, the audio output drive device synchronizes based on the first
clock signal with first oscillation means for generating a first clock signal as a reference of
operation. A synchronization control signal generation unit that generates a control signal; and a
synchronization control signal transmission unit that transmits the synchronization control signal
to the audio signal reproduction device, and the second audio signal reproduction device uses the
second operation reference. And a synchronous oscillation means for generating the clock signal
in synchronization with the first clock signal based on the synchronous control signal received
from the audio output drive device. According to the above configuration, the phase and
frequency of the first clock signal of the audio output drive device and the second clock signal of
the audio signal reproduction device can be made the same. Therefore, the pulse width
modulation signal output from the audio signal reproduction device is a signal synchronized with
the oscillation clock of the audio output drive device, and the audio output from the audio signal
reproduction device is synchronized with the oscillation clock of the audio output drive device. A
pulse amplified signal can be sent to the drive. Accordingly, in the audio output drive device, the
waveform of the pulse width modulation signal can be shaped based on the first clock signal.
As a result, it is possible to completely remove the deterioration of the signal quality due to jitter
or fluctuation of data generated in the transmission path between both devices, crosstalk and the
like. Furthermore, in the audio reproduction output system of the present invention, the
synchronization control signal generation means includes an operation control signal for
controlling the operation of the audio signal reproduction device in the synchronization control
signal. It is characterized. According to the above configuration, the synchronization control
signal can further include an operation control signal for controlling the operation of the audio
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signal reproduction device. For example, the synchronization control signal may be continuously
transmitted, and the operation control signal may be transmitted together with the
synchronization control signal only when the operator transmits the operation control signal of
the audio signal reproduction device. Therefore, the transmission path of the synchronization
control signal and the transmission path of the operation control signal can be combined into
one. Furthermore, in the sound reproduction and output system of the present invention, the
synchronization control signal generation unit is configured to generate the synchronization
control signal by dividing the first clock signal. According to the above configuration, the
synchronization control signal may be a divided signal obtained by dividing the first clock signal.
Thereby, the transmission of the synchronization control signal can be reduced in power
consumption. Furthermore, in the audio reproduction output system according to the present
invention, the audio output drive device generates oscillation means for generating a clock signal
as a reference of operation, and clock signal transmission for transmitting the clock signal to the
audio signal reproduction device. And the audio signal reproduction device operates on the basis
of the clock signal received from the audio output drive device. According to the above
configuration, the first clock signal may be transmitted as it is as a synchronization control
signal. Thus, the audio output drive device can be realized with a simple device configuration. An
audio signal reproduction apparatus according to the present invention is characterized by
constituting the above-described audio reproduction output system. The audio output driving
device of the present invention is characterized by constituting the above-described audio
reproduction output system. A headphone according to the present invention is characterized by
including the above-described audio output driving device and a speaker driven by the audio
output driving device. DESCRIPTION OF THE EMBODIMENTS The following will explain one
embodiment of the present invention in reference to FIGS. 1 to 5.
In the present embodiment, a digital recording medium in which an audio signal is digitally
recorded is an MD (disc D), and an audio signal reproducing apparatus for reproducing an audio
signal from the digital recording medium is a portable MD reproducing apparatus (disc
reproducing apparatus 10). Explain as. As shown in FIG. 1, the audio reproduction output system
1 according to the present embodiment is configured to include a disc reproduction device (audio
signal reproduction device) 10 and a headphone drive device (audio output drive device) 30.
There is. And this headphone drive device 30 is mounted on the headphone 20 (FIG. 2). The
audio reproduction output system 1 transmits the audio signal of the disc D reproduced by the
disc reproduction device 10 to the headphone driving device 30 connected via the headphone
cable 22 and converts the audio signal into a driving signal by the headphone driving device 30.
Then, the speaker (voice output means) 23 outputs voice. Specifically, in the disk reproducing
apparatus 10, a pulse-code modulation (PCM) signal is subjected to delta sigma modulation to be
a PWM (pulse width modulation) signal or a PDM (pulse width modulation). After converting the
signal into a modulation (modulation) signal, the signal is transmitted to the headphone driver
30, and the headphone driver 30 drives the speaker 23 of the headphone 20 by waveform
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shaping the PWM signal or PDM signal and amplifying power by the switching driver. .
Hereinafter, the audio reproduction output system 1 will be described in detail. First, the disc
reproducing apparatus 10 transmits a PWM signal or a PDM signal obtained by delta sigma
modulation of the PCM signal to the headphone driving apparatus 30. Therefore, the disk
reproducing apparatus 10 includes a signal processing circuit 11, a 1-bit delta sigma modulation
circuit 12, a system microcomputer 14, a PLL (phase locked loop) circuit (synchronous
oscillation means) 15, and a headphone jack 13. It is configured. The signal processing circuit 11
demodulates, corrects errors, and compresses data (data) extracted from the disk D on which an
audio signal such as a CD or MD is digitally recorded by an optical pickup (not shown). In the
case of (1), a series of signal processing such as data decompression is performed to output a
PCM signal. The 1-bit delta sigma modulation circuit 12 delta sigma modulates the PCM signal
output from the signal processing circuit 11 and converts it into a 1-bit signal of a PWM signal
or a PDM signal.
The headphone jack 13 is a four-terminal jack provided with an L terminal, an R terminal, a G
terminal, and an REM terminal. The L terminal and R terminal output the Lch and Rch signals L
and R of the 1-bit signal generated by the 1-bit delta sigma modulation circuit 12, respectively.
The G terminal outputs the GND of a 1-bit signal commonly to Lch and Rch. The REM terminal
receives a remote control signal REM (described later) which is a control signal from the
headphone drive device 30. The system microcomputer 14 determines the pattern of the remote
control signal REM and controls the operation of the disc reproducing apparatus 10. The PLL
circuit 15 generates a clock signal (second clock signal) CLK2 with which the disk reproducing
apparatus 10 operates based on the synchronization control signal included in the remote
control signal REM received from the headphone driving apparatus 30. It synchronizes with
clock signal CLK1 of headphone drive 30, and generates it. Here, as shown in FIG. 2, the
headphones 20 have small speakers 23 and 23 for Lch and Rch at both ends of the arm 24 and
the headphone driving device 30 at appropriate positions on the arm 24 respectively. It is
arranged. The headphone driving device 30 is connected to the speakers 23 via the cables 25 via
the headphone cable 21 via the headphone cable 22. The headphone plug 21 is a four-terminal
plug provided with an L terminal, an R terminal, a G terminal, and an REM terminal, and is used
by being inserted into the headphone jack 13 of the disc reproducing apparatus 10. Here, as with
the headphone jack 13, the headphone plug 21 and the headphone cable 22 have the same GND
for Lch and Rch. Continuing on, as shown in FIG. 1, the headphone drive device 30 shapes the
waveform of the PWM signal or PDM signal received from the disk reproduction device 10,
amplifies the power, and drives the speaker 23 of the headphone 20. To generate a drive signal.
Therefore, the headphone drive device 30 includes a remote control signal generation circuit
(synchronization control signal generation means, synchronization control signal transmission
means) 31, a crystal transmission circuit (first oscillation means) 32, a battery / power supply
circuit 33, a flip flop 34, and a driver. It comprises 35 and an LPF (low pass filter) 36. The crystal
transmission circuit 32 generates a clock signal (first clock signal) CLK1 with which the
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headphone drive device 30 operates.
The remote control signal generation circuit 31 generates a remote control signal REM based on
the clock signal CLK 1, and transmits the remote control signal REM to the disk reproducing
apparatus 10. As described later, the remote control signal REM includes an operation control
signal and a synchronization control signal. The flip-flop 34, the driver 35 and the LPF 36 are
provided with two systems for Lch and Rch. Flip-flop 34 takes in a 1-bit signal, and shapes the
waveform based on clock signal CLK 1. The flip-flop 34 can eliminate signal degradation due to
jitter, crosstalk, fluctuation, etc. of a 1-bit signal. An inverter 38 for inverting the clock signal
CLK1 is provided in front of the flip flop 34 in order to detect the falling of the clock signal CLK1.
The driver 35 switches and amplifies the 1-bit signal whose waveform is shaped by the flip flop
34. The LPF 36 generates a drive signal by passing only the low frequency component of the
signal switched and amplified by the driver 35, and inputs this to the speaker 23 through the
cable 25. The battery / power supply circuit 33 is a battery and a power supply circuit for
driving the headphone drive device 30. Subsequently, operations of the disc reproducing
apparatus 10 and the headphone driving apparatus 30 will be described. In the disk reproducing
apparatus 10, the digital signal read from the disk D is converted to a PCM signal by the signal
processing circuit 11, and converted to a 1-bit signal of a PWM signal or a PDM signal by the 1bit delta sigma modulation circuit 12. Be done. Then, this 1-bit signal is supplied to the L and R
terminals of the headphone jack 13. Here, the processing until the signal processing circuit 11
outputs the PCM signal is mainly digital signal processing, and the output PCM signal is
subjected to independent signal processing in Lch / Rch. Therefore, since it is a digital signal, it is
not affected by the sound quality deterioration due to analog elements such as power supply
noise and a board pattern. Next, in the headphone driving device 30, the Lch and Rch 1-bit
signals (PDM signal or PWM signal) input from the headphone plug 21 are waveform-shaped by
the flip flop 34 and then amplified by the driver 35. , And are converted into an analog signal for
driving the speaker 25.
Here, the 1-bit signal has the property of being converted into an analog signal by passing
through the LPF as it is or after being amplified, though it is represented by a binary value of 1
and 0, Depending on the processing method, it has an analog element. Then, the deterioration of
the signal due to the jitter, crosstalk, fluctuation and the like of the 1-bit signal is removed by the
flip flop 34. As described above, by transmitting an audio signal in the form of a 1-bit signal from
the disc reproducing apparatus 10 to the headphone driving apparatus 30 of the headphone 20,
the deterioration of the signal quality in the transmission path is eliminated to achieve high
sound quality. Audio output can be obtained. Therefore, even when listening to the audio signal
reproduced by the portable MD reproducing apparatus with the headphone connected with the
thin and long headphone cable, the signal deterioration with the headphone cable can be
removed, and high-quality sound output is possible. Become. Next, the remote control signal REM
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generated by the remote control signal generation circuit 31 will be described with reference to
FIG. The remote control signal REM is generated by the remote control signal generation circuit
31 based on the oscillation clock (clock signal CLK1) of the crystal oscillation circuit 32 of the
headphone drive device 30. The remote control signal REM can be configured, for example, with
a waveform as shown in FIG. 3 in the case of serially transferring 3-bit data as an operation
control code. That is, the remote control signal REM is composed of a sync signal (sync pattern)
and a 3-bit data signal (operation control signal). The sync signal is composed of 4 clocks of Low
and 4 clocks of Hi. The sync signal is used by the system microcomputer 15 to detect the
beginning of data. The sync signal is also used by the PLL circuit 15 to generate the clock signal
CLK2 in synchronization with the clock signal CLK1. That is, the sync signal corresponds to the
synchronization control signal. Therefore, the remote control signal generation circuit 31
continuously supplies the remote control signal REM indicating "no input (code 0)" to the disc
reproducing apparatus 10 even when no operation control instruction is given. A data signal is
inserted between sync signals. As for the pattern of the data signal, the remote control signal
generation circuit 31 generates a pattern of the operation control code corresponding to the
pressed switch when an operator presses, for example, a push switch in the key switch circuit 37.
The data signal is used by the system microcomputer 14 for operation control according to the
pattern of the disc reproducing apparatus 10. As shown in FIG. 3, the pattern of the data signal
is, for example, “no input” for (0, 0, 0), “reproduction” for (0, 0, 1), (0, 1, 0) If it is
"Recording", if it is (0, 1, 1) "Up to tune",... Note that “1” is configured by Low for 2 clocks and
Hi for 2 clocks, and “0” is configured by Low for 4 clocks. The structures of the remote control
signal REM, that is, the sync signal and the data signal are not limited to the patterns shown in
FIG. 3, and can be arbitrarily set according to the specification of the audio reproduction output
system. As described above, the PLL circuit 15 generates the high frequency clock signal CLK2
synchronized with the remote control signal REM. Therefore, the oscillation clock signal CLK1 of
the headphone drive device 30 and the clock signal CLK2 generated by the disk reproduction
device 10 have the same phase and frequency. Then, the disk reproduction device 10 operates
with the clock signal CLK2 as a reference. Therefore, the 1-bit signal output from the 1-bit delta
sigma modulation circuit 12 is a signal synchronized with the oscillation clock of the headphone
driving device 30. Here, since the PLL operation is performed on the remote control signal REM
supplied via the headphone cable 22, the PLL circuit output (FIG. 4) contains a lot of jitter
components. The output of the 1-bit ΔΣ modulation circuit 12, which operates using the PLL
circuit output as the clock CLK2, also contains jitter. Further, since the signal reaches the flip-flop
34 via the headphone cable 22, the flip-flop input (FIG. 4) has a further increased jitter and
waveform rounding. However, the output CLK1 of the crystal oscillation circuit 32 is a waveform
with very little jitter in the vicinity of oscillation (FIG. 4) and is inverted by the inverter 38 to
perform latching at the timing when H and L of the flip flop input are determined. This makes it
possible to obtain a flip-flop output (FIG. 4) with extremely low jitter. That is, as shown in FIG. 4,
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when the flip-flop 34 resamples with the oscillation clock of the headphone driving device 30,
the output of the flip-flop 34 is shaped into a waveform without jitter.
Therefore, it is possible to remove the deterioration of the waveform generated while passing
through the headphone plug 21 and the headphone cable 22 by the flip flop 34. The crystal
oscillation circuit 32 is preferably disposed in the vicinity of the flip flop 34. As described above,
in the audio reproduction output system 1, in the headphone driving device 30, the analog signal
processing is performed independently on Lch and Rch and based on the waveform-shaped 1 bit
signal without jitter. To be done. That is, as in the conventional headphone 120 (FIG. 7), there is
no restriction that GND must be shared between Lch and Rch. Therefore, the speaker 23 can be
BTL (Bridged TransLess) driving (referred to as a full bridge in a digital amplifier). Therefore, it is
possible to remove in-phase noise, drive high output with low voltage, and the like. In the 1-bit
digital signal-analog signal conversion, clock jitter is the biggest problem in sound quality. In the
audio reproduction output system 1, the PDM signal or the PWM signal is transferred from the
disk reproduction device 10 in synchronization with the oscillation clock of the headphone drive
device 30. Therefore, signal deterioration is completely eliminated by resampling with the
oscillation clock of the headphone driver 30 against jitters and fluctuations of data generated in
the transfer path between both devices and deterioration of the signal quality due to crosstalk. It
is possible to In the above, the remote control signal REM is transmitted from the headphone
drive unit 30 to control the operation of the disc reproducing apparatus 10, and the PLL circuit
15 of the headphone drive unit 30 generates the clock signal CLK2 using this remote control
signal REM. The case of generating In this respect, in the case of a system in which it is not
necessary to control the operation of the disc reproducing apparatus 10 from the headphone
drive 30, the clock signal CLK1 of the headphone drive 30 or a signal obtained by dividing the
clock signal CLK1 is used instead of the remote control signal REM. The same function can be
realized by supplying the disk reproduction device 10. Specifically, as shown in FIG. 5, the
headphone driving device (audio output driving device) 30 ′ does not include the key switch
circuit 37 as compared with the headphone driving device 30 (FIG. 1), and A divider circuit
(synchronization control signal generation means, synchronization control signal transmission
means) 31 'is provided instead of the signal generation circuit 31.
The divider circuit 31 ′ divides the clock signal (first clock signal) CLK 1 of the headphone drive
device 30 generated by the crystal transmission circuit (oscillating means, clock signal
transmitting means) 32 to generate a divided signal. A DIV is generated, and this divided signal
DIV is transmitted as a synchronization control signal to the disk reproduction device (audio
signal reproduction device) 10 '. Then, in the disk reproduction device 10 ′, the clock signal
CLK2 which is used as a reference of operation of the disk reproduction device 10 ′ is
generated based on the frequency division signal DIV received by the PLL circuit 15 from the
headphone drive device 30 ′. In the disc reproducing apparatus 10 ', the system microcomputer
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14 (FIG. 1) is not provided because it is not necessary to control the operation in accordance with
an instruction from the headphone driving apparatus. Furthermore, the frequency division circuit
31 ′ may not be provided in the headphone drive device 30 ′, and the clock signal CLK1
generated by the crystal transmission circuit 32 may be supplied as it is to the disk reproduction
device 10 ′ as a synchronization control signal. The headphone drive devices 30 and 30 ′ may
be formed by using an IC (integrated circuit) or an LSI (large-scale integration), and the inside of
the arm 24 of the headphone 20 can be reduced. It is possible to mount it on the machine, which
is desirable in terms of size. Lastly, the present embodiment does not limit the scope of the
present invention, and various modifications can be made within the scope of the present
invention. For example, the present embodiment can be configured as follows. The audio
reproduction output system of the present invention includes a disc reproduction apparatus and
a headphone drive apparatus, the disc reproduction apparatus comprising: reading means for
reading a signal from a recording medium on which an audio signal is digitally recorded; The
headphone drive apparatus is provided with signal processing means for converting it into a
signal or a PWM signal, and transmitting means for transmitting the signal processed by the
signal processing means to the outside, and the headphone driving device receives the
transmission signal from the disc reproducing device. An oscillating means for generating a clock
of a fixed frequency, a waveform shaping means for regenerating the reception signal of the
receiving means with the clock, a switching amplification means for switching and amplifying the
signal whose waveform is shaped by the waveform shaping means, a switching amplification
Low-pass filter that passes only low-pass components from the signal amplified by And may be
configured. Furthermore, the above-mentioned sound reproduction output system may supply a
clock generated by the oscillating means of the headphone drive to the disk reproduction
apparatus to operate it.
Furthermore, the above-described audio reproduction output system may supply a clock
generated by dividing the clock generated by the oscillation unit of the headphone drive to the
disk reproduction apparatus to operate it. Furthermore, the above-described audio reproduction
output system supplies a clock obtained by dividing the clock generated by the oscillation unit of
the headphone drive to the disc reproduction apparatus, and the divided disc is input to the PLL
circuit in the disc reproduction apparatus. Thus, a clock of a higher frequency synchronized with
the divided clock may be generated and operated with this generated clock. Furthermore, in the
above-described audio reproduction output system, the headphone drive device has control
signal generation means for controlling the operation mode of the disc reproduction device, and
the control signal is generated by the oscillation means of the headphone drive device. The signal
train is synchronized with the clock to be supplied, and the control signal is supplied to the disk
reproducing apparatus, and the disk reproducing apparatus generates a clock of higher
frequency synchronized with the divided clock by inputting the control signal into the PLL
circuit. And may be operated by this generated clock. As described above, the audio reproduction
output system of the present invention includes an audio signal reproduction device and an audio
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output drive device, and the audio signal reproduction device performs delta sigma modulation
on the pulse code modulation signal. The pulse width modulation signal obtained is transmitted
to the audio output drive device, and the audio output drive device performs power shaping on
the pulse width modulation signal received from the audio signal reproduction device after
power shaping, A drive signal is generated to drive the audio output means. Therefore, since the
signal transmitted from the audio signal reproduction device to the audio output drive device is a
pulse width modulation signal, it is possible to shape the signal waveform in the audio output
drive device. Therefore, in the audio output driving device, waveform shaping prior to power
amplification of the pulse width modulation signal completely eliminates signal deterioration due
to jitter or fluctuation of data generated in the transmission path between the devices or
crosstalk. It becomes possible. Therefore, even if the transmission path between the audio signal
reproduction device and the audio output drive device is lengthened, it does not become a factor
of sound quality deterioration. Therefore, by providing an audio output driving device near the
audio output means and shortening the transmission path of the drive signal which is an analog
signal, it is possible to reduce the opportunity for sound quality deterioration, and high-quality
audio output is possible. It plays an effect.
Also, even if the GND for Rch and the GND for Rch are common in the path between the audio
signal reproduction device and the audio output drive device, they can be separated by the audio
output drive device as in the prior art. The effect is that the separation of Lch and Rch does not
deteriorate. In addition, since BTL driving can be performed to generate a driving signal, it is
possible to remove common mode noise and drive low voltage and large output. As described
above, in the audio reproduction output system, analog signal processing is performed in the
audio output drive device using the L-ch and R-ch independently and based on the waveformshaped jitter-free 1-bit signal. It will be. Therefore, high-quality sound output is possible.
Furthermore, in the audio reproduction output system according to the present invention,
synchronization is performed based on the first clock signal with first oscillation means for
generating the first clock signal as a reference of operation by the audio output drive device. A
synchronization control signal generation unit that generates a control signal; and a
synchronization control signal transmission unit that transmits the synchronization control signal
to the audio signal reproduction device, and the second audio signal reproduction device uses the
second operation reference. And a synchronous oscillation means for generating a clock signal of
the first clock signal in synchronization with the first clock signal based on the synchronization
control signal received from the audio output drive device. Therefore, further, the pulse width
modulation signal output from the audio signal reproduction device is a signal synchronized with
the oscillation clock of the audio output drive device, and the audio signal reproduction device is
synchronized with the oscillation clock of the audio output drive device. Can transmit the pulse
amplified signal to the audio output driving device. Therefore, in the audio output driving device,
the waveform of the pulse width modulation signal can be shaped based on the first clock signal.
As a result, it is possible to completely remove the deterioration of the signal quality due to jitter
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or fluctuation of data generated in the transmission path between both devices, crosstalk and the
like. Furthermore, in the sound reproduction output system of the present invention, the
synchronization control signal generation means includes an operation control signal for
controlling the operation of the sound signal reproduction device in the synchronization control
signal. Therefore, the synchronization control signal can further include an operation control
signal for controlling the operation of the audio signal reproduction device. Therefore, the
transmission path of the synchronization control signal and the transmission path of the
operation control signal can be combined into one.
Furthermore, in the sound reproduction and output system of the present invention, the
synchronization control signal generation means divides the first clock signal to generate the
synchronization control signal. Therefore, furthermore, the synchronization control signal may be
a divided signal obtained by dividing the first clock signal. As a result, transmission of the
synchronization control signal can be reduced in power consumption. Furthermore, in the audio
reproduction output system according to the present invention, the audio output drive device
generates oscillation means for generating a clock signal as a reference of operation, and clock
signal transmission for transmitting the clock signal to the audio signal reproduction device. And
the audio signal reproduction device operates on the basis of the clock signal received from the
audio output drive device. Therefore, further, the first clock signal can be transmitted as it is as
the synchronization control signal. Thus, the audio output drive device can be realized with a
simple device configuration. The audio signal reproduction apparatus of the present invention
constitutes the above-described audio reproduction output system. The audio output driving
device of the present invention constitutes the above-described audio reproduction output
system. The headphone according to the present invention is configured to include the abovedescribed audio output driving device and a speaker driven by the audio output driving device.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an outline of one
configuration of an audio reproduction output system according to an embodiment of the present
invention, that is, a disk reproduction device and a headphone drive device. FIG. 2 is an
explanatory view showing an outline of the configuration of a headphone equipped with the
headphone driving device shown in FIG. 1; 3 is a timing chart showing patterns of a clock signal
and a remote control signal generated by the headphone driving device shown in FIG. 1 and a
clock signal generated by the disk reproducing device. 4 is an explanatory view illustrating
waveform shaping of a 1-bit signal in the headphone drive device shown in FIG. 1; FIG. 5 is a
block diagram showing an outline of another configuration of the audio reproduction output
system according to the embodiment of the present invention, that is, the disk reproduction
device and the headphone driving device. FIG. 6 is a block diagram showing an outline of a
configuration of a conventional disk reproducing apparatus. FIG. 7 is an explanatory view
showing an outline of a configuration of a conventional headphone. [Description of the code] 1
audio reproduction output system 10, 10 'disk reproduction device (audio signal reproduction
device) 15 PLL circuit (synchronous oscillation means) 20 headphone 23 speaker (audio output
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means) 30, 30' headphone drive device (audio output Drive device) 31 remote control signal
generation circuit (synchronization control signal generation means, synchronization control
signal transmission means) 31 'divider circuit (synchronization control signal generation means,
synchronization control signal transmission means) 32 crystal oscillation circuit (first oscillation
means, first control means Oscillation means, clock signal transmission means) CLK1 clock signal
(first clock signal) CLK2 clock signal (second clock signal) DIV division signal (synchronization
control signal) REM remote control signal (synchronization control signal)
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