- 10 -
6. Power Amplification and Protection Circuit
6.1. Channels L&R Power Amplification Circuit: The L&R power amplifier employs
separate components. Taking the L channel as an example, its construction is shown
in Figure 7.
Differential
AMP Section
V401,V402
Voltage
AMP
Section
V404
Mirror Image
Constant Source
V403,V406,VD401,VD402
L Input
Temperature
Compensation
Section
V405
Compound
Power AMP ( PNP)
V409,V410,V412
Compound
Power AMP ( NPN)
V407,V408,V411
Speakers
AC Negative
Feedback
R419,R410,C407
.
(Figure 7)
.
V440
V441
Mute
The L channel signal is sent to the power amplification section by the electronic volume
adjusting circuit. A mute circuit installed in the input end. When press the MUTE button
on the remote control, a high level mute command is sent from the pin 1 of the electronic
volume adjusting IC N402. It makes V440 and V441 conductive to finish the mute control
function.
The L channel signal is coupled by the R403&C405 and sent to the base of the differential
AMP section V401. V401 and V402 compose the single-end input/output differential
amplification circuit. The audio signal is sent from the collector of V401 to the base of the
voltage amplification section V404 where its voltage is amplified and sent to the
compound power amplification section. V403, V406, VD401 and VD402 compose mirror
image constant circuit. VD401 and VD402 provide constant base current for V403 and
V405. V403's emitter resistor defines the current of the differential amplification section.
V406's emitter resistor defines the current of the voltage amplification section.
V407, V408 and V411 make up the NPN of compound power amplifier. V407 and V408 are
parallel connected. Their function equals a triode (able to amplify power). Then they mix
with V411 to constitute NPN compound tube (capable of enhance amplification times).
V409, V410 and V412 constitute the PNP of the compound amplifier. Its circuit
construction is the same as NPN. The temperature compensation section V405 has two
functions in the circuit: First it is a biasing of the NPN and PNP. Its working status defines
the static working current of the compound power amplification section. That is to say,
we can adjust the inductance degree of V405 to define the static working point of the
compound power amplification section. The usual way is to adjust the base resistor of
V405. It can also automatically adjust the working status of the compound power
amplification section when the temperature rises.
6.2 C, SR and SL power amplification circuit: These three channels employ the
exclusive power amplifier IC LM1875 (or TDA2030). It has five pins and is a good power
amplifier IC. The application circuit is very simple. It has 15W power output in the rated
condition. The pins 5 & 3 are the positive/negative power supplying pins and employ
2
¡À
2
V
.
T
h
e
p
in
1
is
th
e
s
ig
n
a
l
in
p
u
t
te
rm
in
a
l.
T
h
e
p
in
2
is
th
e
fe
e
d
b
a
c
k
in
p
u
t
te
rm
in
a
l.
T
h
e
p
in
4
is
th
e
o
u
tp
u
t
te
rm
in
a
l.
- 17 -
30
CD
CD11 25V220U±20%8×12 3.5
C415,C416
31
CD
CD11 35V470U±20%10×20 5
C423,C424
32
CD
CD11 50V1U±20%5×11 2
C411,C412
33
CD
CD11 50V10U±20%5×11 2
C435,C436,C437,C438,C417
34
CD
CD11 35V47U±20%6×12 2.5
C439,C440,C441,C442
35
CD
CD11 35V100U±20%8×12 3.5
C418
36
CD
LUA 35V6800U±20
£ ¥
30×45 10
C421,C422
37
DIODE
1N4004
VD407,VD408,VD419
38
DIODE
1N4148
VD401~VD406,VD418
39
DIODE
1N5404
VD410~VD413
40
VOLTAGE
REGULATOR
DIODE
12V 1/2W
VD415,VD414,VD409
41
VOLTAGE
REGULATOR
DIODE
6.8V 1/2W
VD417,VD416
42
TRIODE
2N5401
V404,V408,V414,V418,V429,V431,V433
43
TRIODE
2N5551
V401,V402,V403,V405,V407,V411~V413,V415,V417,
V428,V430,V432
44
TRIODE
9014C
V406,V416,V421,V422,V423,V424,V426,V427,V434,V4
35
45
TRIODE
9015C
V425
46
TRIODE
KB688O
V410,V420
TRIODE
KB688Y
V410,V420
47
TRIODE
KD718O
V409,V419
TRIODE
KD718Y
V409,V419
48
IC
CD4052BCN DIP
N401
49
RELAY
JH4237-024-2H DC24V
Y401,Y402
50
PCB
4217
£ -
3
51
TERMINAL
SOCKET
AV6-8.4-3B
XC2
52
TERMINAL
SOCKET
AV4-8.4-3B
XC1
53
SOCKET
3 PIN 2.5mm
XS3,XS4
54
SOCKET
6 PIN 2.5mm
XS5
55
SOCKET FOR
EXTERNAL
CORDS
WP6-1B
XL1
56
POLE SOCKET
WP4-10A
XC3
57
CONNECTION
CORDS
¦ µ
0.6 SHAPED 7.5mm
W29,W32,W35,W36,W39,W48,W54,W58,W13
58
CONNECTION
CORDS
¦ µ
0.6 SHAPED 10mm
W10~W12,W15,W19~W21,W27,W31,W33,W34,
W37,W43,W44,W47,W51,W53,W55
59
CONNECTION
CORDS
¦ µ
0.6 SHAPED 12.5mm
W14,W16,W49,W50,W56
60
CONNECTION
CORDS
¦ µ
0.6 SHAPED 15mm
W5,W7,W17,W18,W22,W23~W26,W28,W30,W45,W46
,
W40,W41,W52
61
CONNECTION
CORDS
¦ µ
0.6 SHAPED 20mm
W38,W42,W57
62
FUSE TUBE
T6.3AL 250V
FL401,FL402
63
LARGE
RADIATOR
204×80×61 AB217
CONNECT TO THE MAIN AMP BOARD
64
FUSE HOLDER
0 FL401,FL402
65
SMALL CHIP
AB207
FIX THE TRIODES V406 AND V416
66
TAPPING SCREW PB 3×12H COLOR ZINC
2 FOR SMALL CHIP AND LARGE RADIATOR
67
TAPPING SCREW PWT 3×8×8 COLOR ZINC
2 FOR PCB/RADIATOR
68
MACHINE
SCREW
PWM 3×16×8 COLOR ZINC
4 FOR POWER TUBE / LARGE RADIATOR
69
SCREW NUT
M3
POWER TUBE SCREW
70
SCREW SPACER
¦ µ
3×7.2×0.5
POWER TUBE SCREW
71
SPRING SPACER
¦ µ
3
POWER TUBE SCREW
72
MICA SPACER
24×20×0.1
4 FOR POWER TUBE / LARGE RADIATOR
