Sharp SM-SX100 (serv.man2) Service Manual ▷ View online
SM-SX100
– 13 –
Figure 13-1 EXPLANATORY DIAGRAM OF
MODULATION
1 0 1 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 1 0 1 1 0 1 1 1 1 1 0 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 1
ANALOG 0v-
1 BIT
SIGNAL
SIGNAL
"0" Area
"1" Area
Integrator output : Lateral bar of thick line (-): 1
Lateral bar of doubled line (=): 0
Analog signal
waveform
waveform
The operation of the
modulation is explained using Fig. 13-1. Here, the analog signal component from the input section
is expressed with the black-filled vector, and the binary value negatively fed back is expressed with the white-blank vector.
In this block, the following operation is applied.
In this block, the following operation is applied.
1
If the output of the integrator is "positive", subtraction of "positive unit vector" is applied to the input side.
(In the figure, the downward white-blank vector is added.)
2
If the output of the integrator is "native", subtraction of "negative unit vector" is applied to the input side.
(In the figure, the upward white-blank vector is added.)
If the output of the integrator increases or the amplitude of the input signal increases, the figure shows that the negative
feedback is applied to suppress the increase.
In the other words, the continuous "positive" output of the integrator means that the amplitude of the input signal is large,
and the frequency of "1" coding increases.
On the contrary, the continuous "negative" output of the integrator means that the amplitude of the input signal is small,
and the frequency of "0" coding increases.
Thus, "binary codes corresponding to the amplitude" can be gained through the operation of the
feedback is applied to suppress the increase.
In the other words, the continuous "positive" output of the integrator means that the amplitude of the input signal is large,
and the frequency of "1" coding increases.
On the contrary, the continuous "negative" output of the integrator means that the amplitude of the input signal is small,
and the frequency of "0" coding increases.
Thus, "binary codes corresponding to the amplitude" can be gained through the operation of the
modulation.
Figure 13-2 EXPLANATORY DIAGRAM OF
MODULATION
Slant view of analog signal
Front view of analog signal
1 Bit Signal
1 Bit Signal
SM-SX100
– 14 –
2-2) 7th order
modulation circuit and devising
If any 1-bit signal is produced through the operation of the
modulation, the quantized noise is expelled to the high range.
This is well known as "noise shaping", and it is used to reduce the quantized noise of the target frequency band (example:
audible band). As the operation of "primary
audible band). As the operation of "primary
modulation" is described using Fig. 14-1, it is well known that the reduction
effect of the quantized noise is increased as the number of the order of the
modulation is increased.
Quantized noise
Audible band
0
fs/6
Frequency
7th order
5th order
3th order
0th order
Figure 14-1 NUMBER OF ORDER, AND NOISE SHAPING
The circuit here used to produce the 1-bit signal is practiced of "7th order
modulation algorithm" as shown in Fig. 14-
2. The strong noise shaping is applied to assure the wide dynamic range in the audible range.
Figure 14-2 7TH ORDER
MODULATION ALGORITHM
Q
Q
Z
–1
Z
–1
Z
–1
Z
–1
Z
–1
Y
Output
Quantization
Adder
Integrator
Multiplier
Delay unit
Quantizer (–1 or +1)
Input
X
a
1
b
1
a
2
a
3
b
2
a
4
a
5
a
6
b
3
"7th order
modulation LSI" gained by integrating the signal process circuit into one chip is shown in Fig. 14-3. As well
as the LSI can independently generate the 1-bit signals, the input terminal is provided to apply the feedback of the
modulation from the external in order to show the performance with the amplifying operation.
modulation from the external in order to show the performance with the amplifying operation.
Figure 14-3 7TH ORDER
MODULATION 1-CHIP LSI
SM-SX100
– 15 –
3. Application to amplifying circuit: 1-bit amplifier
3-1) Basic block and operational principle
The system classified as "Class C amplifier" among the amplification circuits switches the high voltage to control the ON
time in order to amplify the audio signal.
"PWM signal" which has the analog width in the time axis direction is generally used as the signal to control the switching.
time in order to amplify the audio signal.
"PWM signal" which has the analog width in the time axis direction is generally used as the signal to control the switching.
The operational principle of Class D amplifier is developed to apply the said 7th order
modulation 1-bit signal to the
signal which controls the signal. Thus, the 1-bit amplifier "SM-SX100" is introduced.
Figure 15 1-BIT AMP. SM-SX100 BLOCK DIAGRAM
Volume
Control
Control
Analog Signal
1-Bit Signal
Function Indicator
Function Switch
Analog Signal
Input
Input
Line 1 (RCA PIN)
Line 2 (Canon)
SACD (Analog)
SACD (1bit)
Digital 1(ST LINK)
Digital 2(RNC)
Digital 3(RCA)
Digital 4(TOS LINK)
1-Bit Signal Input
Multi-Bit Signal
Input Terminal
Input Terminal
Digital
Interface
Circuit
Sampling Rate
Converter
Circuit
Circuit of 1-Bit
Conversion
From Multi-Bits
Volume Indicator
LED Driver Circuit
LED Driver Circuit
Control
Microcomputer
1-Bit Amplification Signal Process Circuit
Power Switching
Circuit
Circuit
Digital Driver
Circuit
7th Order
∆∑
Modulation
1-Bit Signal
Generation Circuit
∆∑
Dynamic Feedback
–22V
DC Power
Supply Circuit
DC Power
Supply Circuit
Low-Pas Filter
Circuit
Bi-wiring Speaker
Terminal
Speaker
Fuse
Power
Switch
Switching
Power Circuit
+32V
–32V
+5V +5V
+5V
+12V –12V
Digital 1 Digital 2 Digital 3 Digital 4 SACD Analog 1
Analog 2
Digital 1 Digital 2 Digital 3 Digital 4 SACD Analog 1 Analog 2
Fig. 15 shows the basic block of the 1-bit amplifier. In the block diagram, the core of the amplifying operation is "1-bit
amplification signal process circuit", being composed of the following four circuits.
amplification signal process circuit", being composed of the following four circuits.
1
7th order
modulation 1-bit signal generation circuit
2
Digital driver circuit
3
Power switching circuit
4
Low pass filter circuit
In the circuit
1
, the input signal is processed through the high-speed sampling
modulation circuit to generate "1-bit
signal array" which is directly coded from the input information. (Said 7th order
modulation LSI)
Though the 1-bit signal is used as the control signal to switch the constant-voltage power supply at the timing of the quartz
precision, the digital driver circuit
precision, the digital driver circuit
2
controls the drive, suppressing the delay to the minimum since the full bridge power
switching circuit
3
composed of Power MOS-FET is operated at the high speed.
Though the constant voltage is supplied to the power switching circuit
3
, the fluctuation noise included in the power supply
and the error component of the power switching are included in the output section of
3
. Therefore, the "
dynamic
feedback" loop which negatively feeds the information of the output section back to "7th order
modulation 1-bit signal
generation circuit
1
" at the high speed is provided to compensate the above fluctuation noise and error component at the
real time. The feedback operation achieves "power amplification faithful to input signal" without influence of the power
fluctuation and so on.
Since the 1-bit signal of 64fs originally catches the analog signal at the sampling frequency of 64 x 44.1 kHz = 2.8224 MHz,
the information can be transferred to the band of approx. 1.4 MHz, a half of the sampling frequency as the principle.
In the practical circuit, the band is limited at 100 kHz as the result of the following being considered to determine the pass
band.
fluctuation and so on.
Since the 1-bit signal of 64fs originally catches the analog signal at the sampling frequency of 64 x 44.1 kHz = 2.8224 MHz,
the information can be transferred to the band of approx. 1.4 MHz, a half of the sampling frequency as the principle.
In the practical circuit, the band is limited at 100 kHz as the result of the following being considered to determine the pass
band.
1) The quantized noise of the 1-bit signal increases toward the high range, and it eliminates the band where the quantized
noise increases in the high range.
2) If any high frequency component of 100 kHz or more is included in the analog signal when an analog signal is taken out
of the 1-bit signal, an abnormality will occur in the circuit system and transfer system of the following step. (Example:
High frequency oscillation, unnecessary radiation, zwiter breakage, etc.)
High frequency oscillation, unnecessary radiation, zwiter breakage, etc.)
3) The frequency component of the acoustic signal which is present in the natural is distributed in the band up to 100 kHz.
In the low pass filter circuit
4
of the last step, the components up to 100 kHz are taken out from the the switching signal
for which the voltage is converted, and are output as the analog signal for the speaker drive.
SM-SX100
– 16 –
3-2) The feature of 1-bit amplifier
As described above, the amplification principle whose viewpoint is different from that of the existing analog amplifying
circuit assures S/N in the audible band, thus achieving the audio amplification which has the wider band.
Moreover, the operation which converts the voltage through the switching operation approximately halves the power
consumption during the ordinary operation in comparison with the existing analog amplifier, thus reducing the heating
amount of the amplifying section to approx. 1/5. In addition to the highly faithful replay of the audio source, it achieves both
energy saving and compactness/high power at the same time.
On the other hand, an countermeasure to suppress the noise in the power amplification with the switching operation
becomes inevitable. Particularly against the power line noise and unnecessary radiation, the countermeasure is taken from
both sides of the circuit (minimization of coring and circuit loop) and the structure (double shield of steep plate and copper
plate), thus clearing the technical standard of the electricity operation.
Moreover, the input terminal unit is provided with the originally specified 1-bit signal input terminal in addition to the three
analog systems and four digital audio interface systems. This terminal is provided to be connected to SACE player of our
company which will be put on sale in near future, being specified to transmit the 1-bit signal after the player is mutually
recognized as the countermeasure against the illegal copy.
The analog signals of the three systems are selected with the relay circuit by the function, and the attenuation level is then
set with the volume. This signal is connected to the analog input pin of the 7th order
circuit assures S/N in the audible band, thus achieving the audio amplification which has the wider band.
Moreover, the operation which converts the voltage through the switching operation approximately halves the power
consumption during the ordinary operation in comparison with the existing analog amplifier, thus reducing the heating
amount of the amplifying section to approx. 1/5. In addition to the highly faithful replay of the audio source, it achieves both
energy saving and compactness/high power at the same time.
On the other hand, an countermeasure to suppress the noise in the power amplification with the switching operation
becomes inevitable. Particularly against the power line noise and unnecessary radiation, the countermeasure is taken from
both sides of the circuit (minimization of coring and circuit loop) and the structure (double shield of steep plate and copper
plate), thus clearing the technical standard of the electricity operation.
Moreover, the input terminal unit is provided with the originally specified 1-bit signal input terminal in addition to the three
analog systems and four digital audio interface systems. This terminal is provided to be connected to SACE player of our
company which will be put on sale in near future, being specified to transmit the 1-bit signal after the player is mutually
recognized as the countermeasure against the illegal copy.
The analog signals of the three systems are selected with the relay circuit by the function, and the attenuation level is then
set with the volume. This signal is connected to the analog input pin of the 7th order
modulation 1-bit signal generation
circuit, and the aforementioned "signal process of 1-bit amplifier" is applied.
The digital signals (multi-bit signals) of the four systems are input in the format of the audio interface but the sampling
frequency corresponds to 32 kHz/44.1 kHz/48 kHz. These plural sampling frequencies are converted to 44.1kHz by
"sampling rate converter circuit". This signal is farther oversampled, and "64fs 1 bit signal" is generated by "multi-bit to 1
bit conversion circuit".
Since the 1-bit signal which is output includes the analog information coded in the original digital signal, the analog sound
volume level can be adjusted by controlling the wave height value of the 1-bit signal itself with the volume.
The signal is differentially connected to the digital input pin of the 7th order
The digital signals (multi-bit signals) of the four systems are input in the format of the audio interface but the sampling
frequency corresponds to 32 kHz/44.1 kHz/48 kHz. These plural sampling frequencies are converted to 44.1kHz by
"sampling rate converter circuit". This signal is farther oversampled, and "64fs 1 bit signal" is generated by "multi-bit to 1
bit conversion circuit".
Since the 1-bit signal which is output includes the analog information coded in the original digital signal, the analog sound
volume level can be adjusted by controlling the wave height value of the 1-bit signal itself with the volume.
The signal is differentially connected to the digital input pin of the 7th order
modulation 1-bit signal generation circuit,
and the aforementioned "signal process of 1-bit amplifier" is applied like the analog signal.
From the special terminal of SACD, the 64fs clock of the SACD player side is supplied.
As aforementioned, the analog sound volume level can be adjusted by controlling the wave height value of the signal itself.
The signal is differentially connected to the digital input pin of the 7th order
From the special terminal of SACD, the 64fs clock of the SACD player side is supplied.
As aforementioned, the analog sound volume level can be adjusted by controlling the wave height value of the signal itself.
The signal is differentially connected to the digital input pin of the 7th order
modulation 1-bit signal generation circuit,
and the aforementioned "signal process of 1-bit amplifier" is applied like the analog signal.
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