Dolby
®
Model CP650 Installation Manual
Front-Panel and Alignment Overview
3-8
3.3
Power Supply Voltage Test Points
Six test points are located behind the front-panel for measuring power supply
voltages. They can be accessed by removing the front panel. See Section 9.3.1 for the
voltage test ranges.
Main power supply DC test points:
+15 V, –15 V, +5 V
Bypass (“B”) power supply DC test points:
+14 V, –14 V, +5 V
Sw
+5VB
--14VB
+5V
--15V
+14VB
+15V
Rs
MIC MUX
Figure 3–6
Power Supply Voltage Test Points
(A portion of the front subpanel, with front panel removed, is shown in this figure.)
3.4
Aligning the B-Chain and A-Chain
The B-chain is made up of system components from the main fader through to the
loudspeakers. In the CP650, B-chain adjustments include speaker equalization, level
settings, surround speaker delay settings, and mute fading time. If your CP650 is
equipped with an optional Cat. No.791 Crossover Card, additional steps are required
such as setting crossover points, filter types, and crossover slopes to select.
It is not practical for the entire cinema industry to standardize to a single make and
model of loudspeaker. The different acoustical characteristics of individual theatres
require individual speaker solutions. Therefore, electronic equalization of individual
loudspeaker systems is used to achieve consistent results in a broad spectrum of
environments, and with a broad range of speakers.
Accurate equalization requires the use of standardized acoustic measurement
procedures.
The CP650’s built-in pink-noise generator provides a continuous random noise signal
that covers the total bandwidth. This signal is used to measure and adjust the response
of the loudspeakers. The use of random noise eliminates the problems inherent with
the use of test tones (standing wave patterns in the theatres) and enables the frequency
response of the entire system to be observed. Each channel can be measured and
adjusted independent of the other channels.
A multi-microphone setup with multiplexer is placed in the auditorium to receive the
pink noise reproduced by the loudspeaker. The output of the selected microphone is
fed to a real-time analyzer (RTA) circuit built into the CP650 (or to your separate
