Akai AM-2650

ST-MONO SW &
VCO STOP LOOP FILTER
on} OSC RC, NETWORK
LOOP FILTER
pf
W
nm] DETECTOR INPUT
SWITCH FILTER SWITCH FILTER
ST LAMP &
19KHz MONITOR
vco PHASE LOCK
vexxz | |_| oerecror
PILOT
PRESENCE
DETECTOR
STEREO
nes SWITCH
LAMP DRIVER
ST-MONO, SW
VCO STOP SW
76KHz TO 38KHz TO
38KHz ISKHz
DIVIDER DIVIDER
38KHz TO
ISKHz
DIVIDER
me |
PRE AMP NF AMP
BUFFER
AMPLIF
| BUFFER
AMPLIFIER
STEREO
DEMODULATOR B
Vec
PRE AMP OUTPUT | ~
OUTPUT
PRE AMP INPUT '|®
L ch. DEMODULATOR
This 38 kHz sub carrier is supplied to the multiplex
decoder together with the sub channel of the
composite stereo signal. At the multiplex decoder,
left and right channel audio signals are separated in
order as shown in Fig. 16.
The 38 kHz sub carrier composited with the sub
channel signal of which the carrier part was removed
when sub channel signal and sub carrier passed R1,
R2 produces the regular AM wave. Then, because this
envelop is detected by mutually reverse polarity
connected diodes D1 and D2, L—R signal is emitted
at point@and R—L signal at point®.
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Fig. 17 wPC1173C Block Diagram
Also, because the main channel signal (L+R) is
supplied to R3, R4 center point, @®)point voltage is
added and subtracted and becomes
(L+R) + (L—R) = 2L (left channel)
(L+R) + (R—L) = 2R (right channel)
The level of the main channel signal (L+R) can be
adjusted by means of the variable resistor VR (VR1)
for optimum separation.
However, please refer to Fig. 17 for the Block
Diagram of PLL IC uPC1173C used in the model
AT-2650.