JBL JSR-400, Service Manual

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Dolby Pro-Logic Ò A/V Receiver JSR-400
2) DOLBY PRO-LOGIC CIRCUIT
Dolby Pro-Logic is a sound effect system for movies developed by the Dolby Laboratories Licensing Corp. IC10 (NJW1102) is
a Dolby Pro-Logic decoder IC. When an audio signal recorded using the Dolby Pro-Logic system is sent to this IC, the left,
right, center and surround components are separated. The surround signal component is delayed by the delay IC11
(NJU9702). Fig. 3 shows the configuration of the Dolby decoder.
With Dolby Pro-Logic, three center modes depend on the use of a center speaker as follows.
NORMAL:
Bass frequencies are sent only to the Left and Right Front channels. Select this mode when the
Center Speaker is smaller than the left and Right speakers.
WIDE:
Bass frequencies are sent to the Left, Center and Right speakers. Select this mode when the
Center speaker is approximately the same size as the Left and Right speakers.
PHANTOM: Center channel information is sent to the Left and Right speakers. Select this mode when you do
not have a center channel speaker.
3) STEREO CIRCUIT
In 3-stereo mode, surround sound is sent to front Left channel and front Right channel and no surround sound is sent to
surround channel.
L-ch
L-ch
R-ch
R-ch
C-ch
C-ch
Input
Auto-
balance
Control
X1
X1
Audio
Signal
Audio
Signal
IC10
AMP
AMP
C
S
C
S
electric
vol.
Center/
Operating
Mode
Control
Adaptive
Matrix
By-Pass Line
L
R
C
S
S
S
V
LR
V
CS
IC11
NJU9702
Time
Delay
7knz
LPF
Modified
Dolby B NR
Fig. 3
Flow of signals within the system
in the Dolby Pro-Logic mode
Adaptive
Matrix
Center/
Operating
Mode
Channel
L-ch
L-ch
R-ch
R-ch
C-ch
L
R
C
C
electric
vol.
Input
Autobalance
Control
IC10 NJW1102
X1
X1
Audio
Signal
Audio
Signal
Fig. 4
Flow of signal within the system in the 3-stereo mode