Kenwood KAC-929, Service Manual

Page: 3 / 13

KAC-929
3
CIRCUIT DESCRIPTION
-20
-20 -10 0 +10
-10
0
+10
(dB)
(dB)
OUTPUT
LEVEL
INPUT LEVEL
Fig.1
(A)
(B)
(C)
-20
-20
1.1dB
2.1dB
3.2dB
5.3dB
6.5dB
0.7dB
0.15W
-30
-30
-10 -5 -7 -15 -25 0
0
150W
15W
1.5W
-10
(dB)
(dB)
OUTPUT
LEVEL
INPUT LEVEL
Fig.2
200mV
63mV 20mV 6.3mV
(4
Ω
)
0dB=24.5V (4
Ω
150W)
R2 20K
GAIN
VARIABLE
R1 10K
RECTIFIER
R3 20K
R4 30K
THD TRIM R3 INVERTER IN
RECT CAP
VREF
OUTPUT
1.8V
RECT IN
G IN
Fig.3
[Expander Circuit]
The expander circuit has been designed to expand
the range of audio.
Specifically, it inputs a signal with variation over 10
dB and outputs a signal with variation over 20 dB.
In other words, the expander circuit can make loud
sound louder and small sound smaller.
Its characteristic is as shown in Figure 1, which
shows its characteristic (B) in comparison with the
characteristic of an ordinary amp (A).
(A) Characteristic of ordinary amp
(B) Characteristic of expander
(C) Characteristic of expander amp used in the set
The point in incorporating an expander circuit in this
set is to make the audio more powerful, with punch in
it.
The expander amp used in the set outputs similar
audio to ordinary amp when the input level is low,
while it can provide powerful audio with punch when
the input level is above a certain level.
Figure 2 shows the characteristics of the expander
amp used in this set.
It shows that the effect described above is applied in
the same way all over the bandwidth
Appendix
IC4 block diagram is as shown in Figure 3.