MODEL CP45 CINEMA PROCESSOR Users' Manual
USERS' MANUAL FOR MODEL CP45 CINEMA PROCESSOR Dolby Laboratories Inc U.S.A. 100 Potrero Avenue, San Francisco, CA 94103 Tel: 415-558-0200; Fax: 415-863-1373 U.K. Wootton Bassett, Wiltshire SN4 8QJ, England Tel: 01793-842100; Fax: 01793-842101 Dolby is a registered trademark of Dolby Laboratories Licensing Corporation. ©1995 Dolby Laboratories ISSUE 1 S95/10750 Dolby Part No.
TABLE OF CONTENTS INTRODUCTION SECTION 1 OPERATING INSTRUCTIONS ............................................................................................ 1-1 A. NORMAL OPERATION 1. Initial Power-Up .................................................................................................. 1-1 2. Format Selection .................................................................................................. 1-1 3. Local (Front-Panel) Fader .......................................................
APPENDIX C CP45 MODULE DESCRIPTIONS ........................................................................................ C-1 APPENDIX D ABOUT DOLBY FILM SOUND FORMATS ..................................................................... D-1 1. How Dolby Noise Reduction Works.............................................................. D-1 2. About Dolby SR .................................................................................................. D-1 3.
i INTRODUCTION WHY A CINEMA PROCESSOR? Originally, stereo sound on motion picture film was possible only by means of magnetic striping, which was introduced in the 1950s. Although capable of very good sound, this was such a costly approach that by the 1970s relatively few films were being released with stereo soundtracks. Then in 1975 Dolby Laboratories introduced the stereo optical soundtrack originally known as Dolby Stereo.
ii About The Dolby CP45 Once installed, the Dolby CP45 Cinema Processor becomes the heart of your theatre sound system. All sound sources are connected to the CP45, which processes their signals appropriately and feeds them to the power amplifiers. The Dolby Model CP45 provides the high performance for which all processors manufactured by Dolby Laboratories are known in a new cost-effective, integrated design.
iii • Section 3, Troubleshooting, will help you track down problems in the sound system without test equipment. It consists of a troubleshooting chart and procedures to follow during a show, between shows, and after closing. • The Appendices contain valuable background information which will help you to get the most out of the Model CP45 and your theatre sound system.
1-1 SECTION 1 OPERATING INSTRUCTIONS A. NORMAL OPERATION 1. Initial Power-Up Each time the CP45 is connected to power, it automatically sets itself to the format it was in when power was removed unless the power has been removed for more than a week.
Normal fader setting. FORMAT 01 FORMAT 04 For mono optical soundtracks. For Dolby Stereo SR For Dolby Stereo soundtracks except those marked SR or SR•D. soundtracks. FORMAT 05 FRONT PANEL FADER Controls the auditorium level when selected. The control should be set at or near 7 for normal operation.
1-3 • 64 Mic: for public address announcements in the theatre. The film soundtrack format numbers used on the CP45 front panel often appear on the film can and leader. If these numbers are not supplied and you are not sure if a print is mono or stereo optical, see Appendix A for a means to distinguish mono from stereo optical soundtracks. If you are playing an early Dolby Stereo release and it is marked as format 03 “Dolby Stereo without surround,” select format 04 Dolby Atype. 3.
1-4 • Fade out the intermission music with the local front panel fader. • Move to the remote location and see that the fader there is at 7. • Select the film format. • Start the projector. • After the film leader has passed through the gate, select the remote fader and trim the level slowly if necessary. Following the above procedure should prevent the audience from hearing annoying thumps and leader crackle at the beginning of the show. B.
1-5 be sure that the projector is not selected. If you are playing an optical film print, be sure that there are no signals present from any of the other sound sources. • Even when a stereo print is playing, a summed mono signal is fed to all the screen speakers. Thus, you can switch to the bypass mode to keep the show going if one of the power amplifiers or speakers fail.
1-6 WARNING The CP45 was adjusted initially by a specially-trained engineer so that your theatre would have the same standard playback characteristics as the dubbing theatres in which all Dolby encoded films are mixed. This results in the most accurate reproduction possible. Never attempt to adjust any controls within the CP45 except those specified in this manual. All other controls are for use by a trained engineer when the CP45 is first installed or repaired.
2-1 SECTION 2 MAINTENANCE AND ADJUSTMENTS The installation of the Dolby CP45 in your theatre indicates a commitment to providing a high-quality presentation to your audiences. However, the presence of even the very best equipment does not in itself guarantee the best results. A number of routine maintenance and adjustment procedures, requiring no special test equipment or technical knowledge, are necessary to realize the full potential of the sound system on a dayto-day basis.
2-2 X Figure 2 Never touch the solar cell B. PRINT CLEANLINESS A high fidelity Dolby Stereo theatre system is like a high-quality home stereo system: it can sound only as good as the program material played through it. A good theatre system will reproduce pops, crackles, and other unwanted noises from worn and dirty film prints. If you receive a poor print from your distributor, there is little you can do except, if possible, arrange for its replacement.
2-3 The adjustment procedure is as follows: 1. Clean the soundhead optics (see part A above). 2. Select format 01 Mono. Format 01 Mono 3. Thread the loop of Dolby Cat. No. 69T test film on the projector and play the Dolby Level tone (with its characteristic warble). Be sure that the emulsion side of the film faces towards the projector exciter lamp. The film must run in the direction of the printed arrow. 4. Open the front panel of the CP45 using a screwdriver. 5. Locate the Cat. No. 510 card and Cat.
2-4 6. Turn the projector on. 7. As the test loop is played, watch the LEDs on the Cat. No. 222A/ SR. Correct Dolby Level is indicated when the two center green LEDs for each channel are equally bright. If necessary, adjust the Left and/or Right gain controls (mounted on the front edge of the Cat. No. 510) for the projector in use so that the pair of green LEDs is equally lit.
3-1 SECTION 3 TROUBLESHOOTING Your theatre sound system consists of a number of critical audio components in addition to the Dolby CP45. Thus, the first step when something goes wrong with the sound is to find the source of the problem. The troubleshooting chart starting on page 3-6 can be helpful. If the troubleshooting chart is not sufficient for finding and solving the problem right away, the procedures in the following paragraphs should be helpful.
3-2 • If you know why power was lost and is now back, (there is one or more LEDs alight in the pushbuttons) check that the format is appropriate and switch the CP45 out of bypass. The unit will stay in bypass for about 5 seconds then revert to the format on the front panel. • If you don’t know why power was lost keep the unit in bypass until you can find the reason. • Be sure that the correct projector and format are selected.
3-3 CP45 transformers, the bypass transformer wires must have come unscrewed from the back panel connections or, (this is very unlikely) the transformer has failed internally. • If you have a spare Cat. No. 514 optical preamp module, switch off the power amps and processor and replace the Cat. No.514 in the CP45 with the spare. Switch the power amps back on and check if sound is restored. • If replacing the Cat. No.514 does not restore sound in the bypass mode, the bypass circuitry within the Cat. No.
3-4 • If the indications are that the fault is in the CP45, perform the checks below after you have turned off the power amps to prevent loud thumps in the theatre. • With the CP45 still in bypass, check the screw terminals at the back of the unit where the two power transformers connect, if any of the screws is loose, re-tighten and check all the other terminal block screws for tightness. • Locate the four red LEDs at the front edge of the Cat. No.
D. TROUBLESHOOTING PROCEDURES Trouble Probable Cause Recommended Action No sound output. No power to CP45 No LEDs lit. CP45 does not respond to commands. No LEDS on the front panel are lit. Front panel board ribbon cable is unplugged. Power LED's on front edge of the main board are on. There is sound. Check that the power blocks are firmly plugged into a live mains outlet of the proper line voltage. No LEDS on the front panel are lit.
D. TROUBLESHOOTING PROCEDURES (cont'd) Trouble Probable Cause There is hum in the output. (You Malfunctioning exciter lamp or lamp power can detect hum coming from the supply. booth speaker at normal listening level.) Stray light striking the stereo solar cells. Recommended Action Cover the solar cells with a business card or other opaque object. Do NOT touch the cells and do NOT disturb the position of the cell bracket! If the hum disappears, the problem is in the exciter lamp.
D. TROUBLESHOOTING PROCEDURES (cont'd) Trouble All channels fail when playing a movie and Bypass does NOT bring the sound back. Probable Cause Recommended Action Check that the exciter lamp is on and that the lamp power supply is operating. If not, fade up background music and transfer the reel to the alternative projector and continue the show there until the exciter lamp can be replaced. Call service engineer. Projector selection wire/switch is faulty.
D. TROUBLESHOOTING PROCEDURES (cont'd) Trouble One channel fails. Probable Cause Defective power amplifier or wiring for that channel. Recommended Action Place the CP45 in bypass. All three screen speakers should become active. If not, there is a fault in the power amplifier or wiring for the missing channel. Check if the amplifier concerned is on and check for blown fuses.
D. TROUBLESHOOTING PROCEDURES (cont'd) Trouble The sound from one channel is distorted (you can detect the distortion at the booth monitor at normal listening level). Probable Cause Recommended Action Check if amplifier is on and if its fuse(s) is ok. Defective speaker for that channel. (Booth sound is OK but sound in the auditorium is bad). Check speaker. Malfunctioning card in CP45.
D. TROUBLESHOOTING PROCEDURES (cont'd) Trouble Probable Cause Recommended Action The A-chain has become misaligned. Call service engineer. You can hear pops and thumps during projector changeover. If your projector changeover relay power is DC, a diode should be soldered across the winding of the relay to prevent noise from the relay winding from leaking into the audio wiring. This diode may be missing or defective. If possible, check that the diode is installed across the relay winding.
D. TROUBLESHOOTING PROCEDURES (cont'd) Trouble You hear an echo in a small theatre. The sound level in bypass is higher or lower than the normal sound level. There is distortion when you play non-sync sound, but sound from the film is not distorted. Probable Cause Recommended Action Call service engineer. Adjust with the front panel fader since other parts of the system may be malfunctioning. Call service engineer. The non-sync source is introducing distortion.
D. TROUBLESHOOTING PROCEDURES (cont'd) Trouble Projector changeover command does not change to sound output of the selected projector and the front panel LEDs do not light according to the projector selected. The sound output of the CP45 is at a medium level, regardless of the setting of the fader control. Probable Cause Recommended Action Defective changeover relay or switch. If possible, check that the relay or switch contacts actually open and close as the changeover command is issued several times.
D. TROUBLESHOOTING PROCEDURES (cont'd) Trouble You cannot change from local to remote fader operation. Probable Cause The remote control is not plugged in. The CP45 will only select Mono or Missing or unplugged CAT222A/SR module. the non-sync/aux formats. If either Dolby Stereo format is selected, the LED does not stay on when the button is released. The CP45 will select formats but The unit is in bypass (bypass LED on front the sound does not change panel flashing). between them.
A-1 a APPENDIX A HOW TO TELL A STEREO OPTICAL PRINT FROM A MONO PRINT A Dolby encoded optical print should be identified as such on both the film can and leader. However, with handling the identification may be lost. If you are not sure if you have a stereo print, play a reel and find a section with music and/ or effects only (on dialogue or narration, stereo soundtracks look much the same as mono soundtracks).
B-1 APPENDIX B DOLBY TEST AND DEMONSTRATION FILMS Several test and demonstration films produced by Dolby Laboratories are available from your equipment supplier. For proper system maintenance, the Cat. No. 69T test film is required and the Cat. No. 251 Jiffy Test Film is strongly recommended. The Cat. No. 69T test film should be formed into endless loops for ease of use. The eight-minute color short “listen . . .” (Cat. No.
B-2 Cat. No. 69T Dolby Tone Test Film JIFFY TEST FILM Cat. No. 251 SR•D—A subjective film for testing theatre sound RECORDED IN Running Time: 6 minutes Picture format: 1.85:1 widescreen or 2.35:1 anamorphic Sound formats: 10 05 digital analog SR Dolby Laboratories Inc. • 100 Potrero Avenue San Francisco, CA 94103-4813 Telephone 415-558-0200 • Facsimile 415-863-1373 Dolby, the Double-D symbol and Dolby Stereo are trademarks of Dolby Laboratories Licensing Corporation S94/10117 Cat. No.
B-3 Cat. No. 351 Stereo Demonstration Film: “listen . . .” “listen . . .”, an eight-minute Dolby Stereo demonstration film for public exhibition, has been professionally produced to demonstrate the commitment of the theatre to providing its audiences with the best in both sound and picture. It is intended for screening prior to a feature and is a fast-paced, entertaining short which shows off a quality projection system to its best advantage.
GND MATRIX MIC LEVEL OUT CENTER SURR SUB OUTPUT LEVEL RIGHT NS1 INPUT LEVEL LEFT PROJ POWER SCREEN SELECT INPUT MODE LOSS B AC A DC RIGHT XOVER FREQ 500 HZ IN L C R L C R 800 HZ LEFT CROSSOVER OUTPUTS 2 3456 SURROUND DELAY LEFT 0 1 2 3 4 5 6 7 0 mS 10 mS 20 mS 30 mS 40 mS 50 mS 60 mS 70 mS CENTER 8 9 A B C D E F 80 mS 90 mS 100 mS 110 mS 120 mS 130 mS 140 mS 150 mS RIGHT HF HF HF LEVEL TRIM LEVEL TRIM LEVEL TRIM 789 Cat. No.
C-1 APPENDIX C CP45 MODULE DESCRIPTIONS Cat. No. 510/514 Input/Output Card The Cat. No. 510 is the input and output part of the CP45. It has two stereo inputs for optical soundtracks, one mono microphone input, and six outputs for the front screen speakers. The card is normally fitted with a Cat. No. 514 optical preamplifier card which converts the solar cell signals from the projectors into voltages which are handled by the Cat. No. 510.
C-2 The card also contains the controls for selecting the format of the film to be shown or for selecting background music etc. Cat. No. 515 Stereo Surround Card The Cat. No. 515 is a small board that is mounted on the Cat. No. 511 main board when stereo surround operation is desired. Cat. No. 222 Module This module provides two channels of Dolby A-type noise reduction for the soundtracks. Cat. No.
D-1 APPENDIX D ABOUT DOLBY FILM SOUND FORMATS The application of Dolby A-type noise reduction to film soundtracks, as explained in Appendix G, “Cinema Sound and the Evolution of Dolby Stereo,” had a major impact on cinema sound recording and reproduction. The later application of DolbySR has had still further impact.
D-2 enable the soundtrack to carry louder sounds with lower distortion and fewer signal losses. The result is a dramatic improvement in soundtrack dynamic range, that is, the volume range between residual film grain noise and the loudest sounds that can be recorded accurately.
D-3 3. Why Adjusting Dolby Level Is Important The accurate reproduction of Dolby soundtracks requires that the decoders in the theatre act as precise mirror images of the encoders used when the tracks were recorded. This precision is ensured in two ways. First, Dolby system circuits are manufactured to very close tolerances.
D-4 Dolby B-type was the first Dolby system developed for consumer applications, and is in use today in hundreds of millions of cassette recorders and other products (a modified version of B-type noise reduction is also used to encode the surround channel on Dolby Stereo and Dolby Stereo SR release prints). Dolby C-type was later developed to provide more noise reduction than Dolby B-type, and is provided along with B-type in many of today’s high-performance consumer products.
E-1 APPENDIX E HOW FOUR CHANNELS ARE DERIVED FROM DOLBY STEREO OPTICAL PRINTS The 35-mm Dolby Stereo optical format calls for the recording in the studio and the reproduction in the theatre of four separate sound channels, — left, center, right, and surround — and yet a Dolby Stereo optical print has only two soundtracks.
E-2 recorded on both the left and the right tracks. And the surround information is also split between the two channels, but is recorded with a distinct phase shift to distinguish it from the left, center, and right information. In the theatre, when the signals from the two tracks on a Dolby Stereo print reach the CP45 processor, its 2:4 decoder constantly compares the two signals. Those signal elements which differ primarily in amplitude are assigned to the left and right speakers.
F-1 APPENDIX F OPTICAL BASS EXTENSION Dolby Laboratories developed the optical bass extension (OBE) circuitry for use with subwoofers — special bass loudspeaker units designed to provide the very low-frequency bass performance lacking in most conventional theatre speaker systems. (If your theatre is not equipped with subwoofers, consult your theatre equipment supplier for further information on how to take full advantage of optical bass extension.
G-1 APPENDIX G THE EVOLUTION OF DOLBY FILM SOUND Thanks to such developments as multichannel sound, the motion picture viewing experience today is more exciting and involving than ever before. And what the audience hears today is very much the result of a continuing effort to improve film sound originally undertaken by Dolby Laboratories more than twenty years ago. Indeed, the evolution of motion picture sound over the past two decades is, in great part, that of Dolby film sound technologies.
G-2 This caused a dilemma for soundtrack recordists. Should the tracks be recorded to take advantage of the improved speakers, or should they be prepared to sound best on the many older installations already in place? Given that it was impractical to release two versions of a given title, the only alternative was to tailor soundtracks to the older speakers. The result was to ignore the improved high-frequency response of the newer, better units.
G-3 Many theaters were equipped for magnetic sound in the 1950s, even though the playback equipment was expensive. Many films were issued with magnetic soundtracks, although magnetic prints were, and remain, much more expensive than optical sound prints (35 mm magnetic prints cost at least double their optical equivalents, and today’s 70 mm magnetic prints cost up to fourteen times as much). By the 1970s, however, the film industry declined overall, with fewer films and fewer theaters.
G-4 An important advantage of the Dolby optical format is that the soundtracks are printed simultaneously with the picture, just like mono prints. Thus a four-channel stereo release print costs no more to make than a mono print (although it is more expensive to record and mix in stereo than in mono).
G-5 analog track on the same 35 mm prints. This Dolby Digital format is yet another significant step forward in film sound, providing independent left, center, right, left surround, and right surround channels, plus a sixth channel for bass effects. In addition to multiple channels, the Dolby Digital track provides extraordinary dynamic capability, wide frequency, range low distortion, and relative immunity to wear and tear.
G-6 Making Films Sound Better Dolby format release prints and the equipment which reproduces them are only links in a chain that extends from the original location, through the dubbing theater, to the laboratory, and finally into the theater. Developments like Dolby SR and Dolby Digital ensure that the soundtrack itself remains one of the strongest links.