Dolby Laboratories SDU4 - Manual (Page 13)

2-6
SDU4 OUTPUTS—CENTER LOUDSPEAKER SWITCH SET TO “NO”
Mode Left Right Surround
Mono .707 (Lt & Rt) .707 (Lt & Rt) —
Stereo Lt Rt —
Dolby Surround L + .707 (C) R + .707 (C) S
Wake-Up Mode Selection
The SDU4 can be set to default to any operating mode when power is first
turned on. This is set using the internal jumpers J1/J2/J3. See Figure 2.5. The
factory setting is Dolby Surround.
External Master Level Control Switch
An external master level control may be added by connecting an external 100K
linear potentiometer between pins 11, 12, and 1 on J503. (All three connections
are required.) The external level control must be engaged by switching the
internal switch S303 to the “remote” position. See Figure 2.6. The factory
setting is “local.”
(REAR VIEW) MOUNTING SCREW
CONNECTOR
DC GND
WIPER
TOP
TO PIN 1
J503
1 13
TO PIN 12
TO PIN 11
OR EQUIVALENT
BELDEN 8771
100K LINEAR TAPER
FADER POTENTIOMETER
CUSTOMER SUPPLIED REMOTE
F3710A0C
Figure 2.6 External fader connected to J503
Surround Delay Setting
Delay setting
2
Figure 2.7 Cat. No. 150 delay adjustment
The Cat. No.150 decoder module has a single adjustment for setting the
surround delay. The delay can be adjusted in 10ms steps. It is helpful to
understand its purpose. The delay to the surround channel is used to reduce
the audibility of crosstalk by offsetting it in time behind the arrival of the main
signal coming from the front loudspeakers. This is particularly important with
dialog information, where crosstalk would be particularly bothersome when
heard coming from the rear. By delaying the surround channel so that common
crosstalk information arrives at the listener about 15-20 ms after the main front
signal, the audibility of the crosstalk signal is substantially reduced.
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