JPH0366297

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DESCRIPTION JPH0366297
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
digital amplifier and a speaker built-in amplifier system for digitally transmitting and processing
signals. In recent years, with the advent of analog-to-digital converters (hereinafter referred to as
A / D) and the spread of digital ICs, digitization of signals in the audio field is remarkable, and the
amplitude or phase frequency characteristics of audio signals are processed by digital signal
processing. A digital power amplifier incorporating a digital preamplifier which can be changed,
or a digital-analog converter (hereinafter referred to as D / A) has emerged. Hereinafter, an
example of the above-described conventional digital amplifier will be described with reference to
the drawings. FIG. 2 shows a conventional digital preamplifier. In FIG. 2, 10a, 10b, 10c and 10d
are modulated digital signal input terminals, 2 is an input signal selection means, 3a is an audio
signal demodulation means, 7a is a signal conversion means, 3C is a digital signal modulation
means, 10e. Is a modulated digital signal output terminal, 4a is a frequency characteristic input
means, and 9 is a signal conversion control means. In the conventional digital preamplifier shown
in FIG. 2, the frequency characteristic input means 4a obtains a signal conversion coefficient
suitable for the frequency characteristic input from the outside by selection or calculation from a
built-in coefficient table and outputs it to the signal conversion control means 9. Do. On the other
hand, the audio signal demodulated by the digital signal demodulation means 3a is subjected to
signal processing by the signal conversion means 7a in accordance with the signal conversion
coefficient set by the signal conversion control means 9. Thereafter, it is again modulated to a
signal suitable for transfer, and output to the outside from the modulated digital output terminal
10e. FIG. 3 shows a conventional digital power amplifier. In FIG. 3, 10f is a modulated digital
signal input terminal, 7b is a D / A means, 7c is an amplitude control means, 7d is a power
amplification means, 4b is an amplitude input means, and 9 is a signal conversion control means.
In the conventional digital power amplifier shown in FIG. 3, the amplitude input unit 4b outputs
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an amplitude conversion coefficient for realizing an amplitude value input from the outside to the
signal conversion control unit 9, and the signal conversion control unit 9 outputs the amplitude.
The amplitude value of the audio signal is converted using the amplitude conversion means 7c
based on the conversion coefficient, and the converted audio signal is power amplified and
output from the speaker drive signal output terminal 10g. SUMMARY OF THE INVENTION
However, in the digital preamplifier as described above, the audio signal before and after signal
processing is different, and the content of the signal processing is not transmitted later and the
information width of the digital audio signal is limited. When the signal processing to reduce the
signal is performed, a very small signal is completely lost, and it has a problem that it can not be
restored to the original signal again.
Also, in the digital power amplifier as described above, it is necessary to connect a cable from the
speaker drive signal output terminal to the speaker, but in order to vary the amplitude depending
on the listening condition, the digital power amplifier is at hand It is necessary to put it on the
board, and therefore has a problem that power loss in the cable is inevitable because the cable
wire is inevitably long, and the sound quality is disturbed by the noise. The present invention
provides the above-mentioned problems, and also provides a digital amplifier which can obtain
an audio signal completely equal to that before signal conversion even after the digital
preamplifier, and in the digital power amplifier, it is not necessary to newly perform amplitude
control input. It is Means for Solving the Problems In order to solve the above problems, the
digital preamplifier of the present invention selectively outputs one signal from a plurality of
modulated digital signal input terminals and a plurality of modulated digital signals input from
the input terminal. Input signal selection means, frequency characteristic input means, amplitude
input means, both or either one of the frequency characteristic input means and the amplitude
input means, and a signal conversion coefficient or amplitude representing the input frequency
characteristic or amplitude value Input characteristic conversion means for converting a
conversion coefficient into a digital information signal, audio signal demodulation means for
demodulating an audio signal from the signal outputted by the input signal selection means, the
demodulated digital audio signal and the input characteristic conversion means Digital signal
mixing means for mixing digital information signals output from the The in which again includes
a digital modulation means for digitally modulating and a modulated digital signal output
terminal for outputting the output of the digital signal modulating means to the outside. In order
to solve the above problems, the digital power amplifier according to the present invention
comprises a modulated digital signal input terminal in which a digital audio signal and a digital
information signal are mixed and modulated, and a digital audio signal and a digital information
signal from the input modulated signal. Digital signal demodulation means for demodulating,
control signal decoding means for obtaining a signal conversion coefficient and amplitude
conversion coefficient from the digital information signal, signal conversion means for changing
the frequency characteristic of an audio signal output from the digital signal demodulation
means, Digital / analog conversion means for converting a digital signal output from the signal
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conversion means into an analog signal, Amplitude conversion means for converting the
amplitude of the audio signal output from the digital / analog conversion means, and output from
the amplitude conversion means Power amplification means for amplifying the signal to be
Signal conversion control means for setting the signal conversion coefficient and the amplitude
conversion coefficient obtained by the signal decoding means in the signal conversion means and
the amplitude conversion means, and a speaker drive signal output for outputting the signal
power-amplified by the power amplification means And means.
The present invention converts these coefficients into digital information signals without actually
converting the audio signal with the preamplifier using the signal conversion coefficient or the
amplitude conversion coefficient obtained by the frequency characteristic input means and
obtained, and further, the audio The signal is mixed with the signal in an independent state and
transferred to the subsequent stage, and the signal conversion is performed using the conversion
coefficient in the power amplifier. Therefore, an original audio signal not subjected to signal
processing can be obtained as it is, and there is no need to newly input characteristics in the
digital power amplifier, so it is not necessary to install the digital power amplifier near the
listener. Since it is not necessary to lengthen the cable from the output terminal to the speaker,
audio reproduction with very little deterioration in sound quality is possible. Embodiment 1 The
object of the first embodiment is to convert an input signal into an audio signal obtained by
converting the signal conversion coefficient and the amplitude conversion coefficient to realize
input frequency characteristics and amplitude values as digital information signals. An object of
the present invention is to provide a digital preamplifier that performs digital mixing and digital
signal modulation and then outputs it to the outside. Hereinafter, a digital preamplifier according
to an embodiment of the present invention will be described with reference to the drawings. FIG.
1 is a block diagram of a digital preamplifier in an embodiment of the present invention. In FIG.
1, 10a, 10b, 10c and 10d are modulated digital signal input terminals, 2 is an input signal
selection means, 4 is a signal control unit, 4a is a frequency characteristic input means, 4b is an
amplitude input means, and 4c is an input. The characteristic conversion means 3 is an
amplitude processing unit, 3a is an audio signal demodulation means, 3b is a digital signal
mixing means, 3C is a digital signal modulation means, and 10e is a modulated digital signal
output means. The operation of the digital preamplifier configured as described above will be
described below with reference to FIGS. 1 and 4. In FIG. 1, the frequency characteristic input
means 4a inputs frequency characteristics such as amplitude and phase desired by the operator
by means of a zero volume or a switch, etc., and incorporates a signal conversion coefficient for
converting the signal into the inputted characteristics. It is selected from the coefficient table to
be calculated or calculated by calculation. The amplitude input means 4b also inputs an
amplitude value that determines the size of the reproduced sound by the same means, and
obtains an amplitude conversion coefficient for realizing the amplitude value. Both obtained
coefficients are sent to the input characteristic conversion means 4a, where the coefficients are
converted into digital information signals suitable for being transferred as digital signals.
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FIG. 4 simply shows how the information signal and the audio signal are mixed. The information
signal is mixed with the audio signal as shown in the figure for each sampling period. The
coefficient information that can be sent in one sample data is limited, and in order to send more
complex coefficients, for example, as shown in FIG. 4 (b), bits bO to b9 for four sample data of tota It is also possible to take a block data structure such as sending all the above coefficients in
data. As described above, according to the present embodiment, the audio signal is not actually
converted by the preamplifier using the signal conversion coefficient or the amplitude conversion
coefficient obtained by the one-frequency characteristic input means and thus not processed. It is
also possible to obtain the original audio signal as it is at a later stage. The object of the second
embodiment is to decode the modulated digital signal output from the digital preamplifier,
perform signal conversion and amplitude conversion of an audio signal based thereon, and
further amplify the power of the signal and output it. It is to provide. Hereinafter, a digital power
amplifier according to an embodiment of the present invention will be described with reference
to the drawings. FIG. 5 is a block diagram showing a digital power amplifier according to an
embodiment of the present invention. In FIG. 5, 6 is a digital signal demodulator, 7 is a signal
converter, 7a is a signal converter, 7b is a D / A converter, 7c is an amplitude converter, 7d is a
power amplifier, and 8 is a control signal. Decoding means 9 is a signal conversion control
means. The operation of the digital power amplifier configured as two or more will be described
below. In FIG. 5, the digital signal demodulation means 6 separates and demodulates the audio
signal and the digital information signal again from the mixed signal of the audio signal
modulated by the digital preamplifier and the digital information for signal conversion control.
And output to the control signal decoding means 8. The control signal decoding means 8 obtains
signal conversion coefficients and amplitude conversion coefficients to be used for signal
conversion from the digital information signal, and passes these coefficients to the signal
conversion control means 9. As shown in FIG. 6 (a), the signal conversion means 7a is constituted
by a continuous connection such as a cyclic or non-cyclic filter, and the signal conversion
coefficient is a coefficient of the filter. In the case of a biquad filter as shown in FIG. 3C, the
coefficients g1 to g5 of the biquad filters are set from the signal conversion control means 9.
The amplitude conversion means 7C is conceptually shown in FIG. 7, that is, a volume or the like
controlled by the signal conversion control means 9, and is mechanically or electrically
controlled. Further, the amplitude conversion means 7C may be between the signal conversion
means 7a and the D / A conversion means 7b. In this case, amplitude conversion control is
performed by digital signal processing. As described above, according to the present
embodiment, it is not necessary to keep the digital power amplifier at hand, since it is performed
by the digital preamplifier to change the amplitude in various ways depending on the listening
conditions. There is no need to increase the length of the cable, and the power loss in the cable
or the noise mixing will not disturb the sound quality. An object of the third embodiment is to
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provide a digital power amplifier in which each speaker of a speaker system in which an audio
band is reproduced by a plurality of speakers is driven by an independent power amplifier. FIG. 8
shows a block diagram of the digital power amplifier in the third embodiment, in which 7e is an
electronic band dividing means for driving a speaker having two speakers for high and low tones.
The power amplifiers 7dO and 7dl are independent and 34 independent power amplifiers 7dO
and 7dl are used to drive the speakers for bass and treble, respectively, so that a speaker using a
general band divider composed of a capacitor and a coil is used. Sound quality and input
resistance are improved. An object of the fourth embodiment is to provide a speaker system
incorporating a digital power amplifier. Hereinafter, the present invention will be described with
reference to the drawings with respect to a speaker system with a built-in digital power amplifier
according to one embodiment. FIG. 9 shows an embodiment of the present invention. In FIG. 9,
12 is a band divider, 13 is a bass speaker, and 14 is a treble speaker. The operation of the
speaker system with a built-in digital power amplifier configured as described above will be
described below. In FIG. 9, the modulated digital signal input from the modulated digital input
terminal 10f is subjected to signal conversion and power amplification by the digital power
amplifier, and the amplified signal is output to the band divider 12 which divides the signal into
two audio bands. Further, the respective bands are input to high tone and low tone speakers
13.14 for specialized reproduction. As described above, according to the present embodiment,
the digital power amplifier, the band dividing means for dividing the power amplified signal into
the high band and the low band, and the high-tone signal for reproducing the high band signal
divided by the band dividing means The distance between the power amplifier of the power
amplifier and the speaker can be minimized by providing the speaker for the low frequency and
the low frequency speaker reproducing the low frequency signal by the band division means, and
the power loss in the cable and the mixing of noise Greatly improved, the playback sound quality
is better than this.
As described above, the digital preamplifier of the present invention does not actually convert the
audio signal with the preamplifier using the signal conversion coefficient or the amplitude
conversion coefficient which is obtained by the frequency characteristic input means and thus
determined, thus the signal The original 56 audio signal which has not been processed can be
obtained as it is in the subsequent stage. Also, with the digital power amplifier according to the
present invention, it is not necessary to have the digital power amplifier at hand, since it is
performed by the digital preamplifier to change the amplitude in various ways depending on the
listening conditions, so the cable lines are necessarily long It has the effect that there is no need
to do this, and there is no loss of power in the cable or noise contamination that would interfere
with the sound quality. Furthermore, the speaker system with built-in amplifier according to the
present invention comprises the digital power amplifier according to the present invention, the
digital power amplifier, band dividing means for dividing the power amplified signal into high
band and low band, and the band dividing means. By providing a high frequency speaker for
reproducing the high frequency signal and a low frequency speaker for reproducing the low
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frequency signal by the band dividing means, the distance between the power amplification
means of the power amplifier and the speakers can be shortened to a minimum by a cable. Power
loss and noise mixing are greatly improved, which has the effect of improving the reproduction
sound quality.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram showing a digital preamplifier in an embodiment of the present
invention, FIG. 2 is a block diagram showing a conventional digital preamplifier, FIG. 3 is a block
diagram showing a conventional digital power amplifier, and FIG. FIG. 5 is a block diagram
showing a digital power amplifier according to an embodiment of the present invention, and FIG.
6 is a block showing an example of signal converting means of the digital power amplifier
according to the present invention. 7 and 8 are block diagrams showing one example of the
amplitude conversion means in the present invention, FIG. 8 is a block diagram showing a digital
power amplifier in one embodiment of the present invention, and FIG. 9 is one embodiment in
the present invention. It is a block diagram showing a digital power amplifier built-in speaker
system.
1 · · · · · · · Digital preamplifier, 2 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · digital preamplifier, 2 · · · input signal selection means, 3a · · · · audio
signal demodulation means, 3b · · · digital signal mixing means, 3c · · · ··· Digital signal modulation
means, 4a · · · · · · Frequency characteristic input means, 4b amplitude input means · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · · · · · · 4 digital signal modulation means 4 4 · · · · · · Digital signal
demodulation means, 7a · · · · · Signal conversion means, 7b · · · · D / A conversion means, 7c · · · · ·
· Amplitude conversion means, 7d · · · Power amplification means 7e Electronic band division
means 8 Control signal decoding means 9 Signal conversion / control means 10 Digital signal
input and output terminals.
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