Dolby Laboratories CP65 - Manual (Page 79)

C-1
APPENDIX C
CP65M (MONO) INSTRUCTIONS
1. Operation
The CP65 can be configured for mono-only operation. Systems so equipped are shipped with
only the center channel Cat. No. 64 house equalization module and without the Cat. No. 150
surround decoder module and Cat. No. 241 or 441 surround equalizer and optical bass
extension board. A Cat. No. 327A mono board replaces the Cat. No. 150 module. The Cat.
No. 443 control board should have diode D56 in the INC (Inhibit Center) row removed.
When the system is so configured, optical and non-sync sources will be summed and sent to
the center channel via the fader or faders and house equalization. When using non-sync
inputs the left, right, and center LEDs on the Cat. No. 242 will light although signal will only
be present at the center channel output. Magnetic and auxiliary center channel inputs can be
selected by choosing the appropriate format using the front panel controls.
Mono films should be played using format 01 Mono. However, with the CP65M, Dolby Stereo
films can be screened with the noise reduction and wider frequency response usually only
available in Dolby Stereo theatres. Simply select format 04 Dolby Stereo A-type. This turns
on the noise reduction circuitry and disables the mono filter. Although the sound will be
monophonic, the quality of reproduction will be improved. If your CP65M is fitted with Cat.
No. 300 or 350 modules, you can play Dolby Stereo SR prints best by selecting format 05
Dolby Stereo SR.
Follow the level adjustment procedures in the installation and alignment manual. Adjust only
the center channel.
2. Cat. No. 327A Circuit Description
The Cat. No. 327A mono board accepts four inputs: optical Lt and Rt from the Cat. No. 222
or Cat. Nos. 350/300 at both 300 and 500 mV levels. All inputs are combined and fed to the
output, which appears at the same pin as the center output of a Cat. No. 150.
The Cat. No. 327A may be replaced by a Cat. No. 327 but this will require re-adjustment of
levels. Follow the level adjustment procedures in the installation and alignment manual.
Adjust only the center channel.
A signal present LED is provided at the output of the Cat. No. 327A. It will come on at about
15 dB below Dolby level, which is the same threshold as the other signal present lights in the
system.