Dolby Laboratories DA20 User Manual

MODEL DA20
DIGITAL FILM
SOUND PROCESSOR
Users' Manual

Issue 4 Part No. 91342

USERS' MANUAL

FOR

MODEL DA20 DIGITAL

FILM SOUND PROCESSOR

Dolby Laboratories Incorporated

U.S.A. 100 Potrero Avenue, San Francisco, CA 94103

Tel: [phone]; Fax: [phone]

U.K. Wootton Bassett, Wilshire SN4 8QJ, England

Tel: [phone]; Fax: [phone]

www.dolby.com

WARRANTY INFORMATION—U.S.A.: warranty on the product covered by this manual is subject to the limitations and disclaimers set forth
in the warranty disclaimer originally shipped with the product and also printed on the back of the invoice.

All requests for repairs or information should include the unit serial number to ensure rapid service.

Note: This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC
Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a
commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in
accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a
residential area is likely to cause harmful interference in which case the user will be required to correct the interference at his own
expense.

Digital decoding covered by the following U.S. patents: 4,790,016, 4,914,701, 4,799,260 4,941,177, 5,109,417, 5,142,656, 5,230,038, 5,274,740,
5,297,236, 5,357,594, 5,463,424, 5,583,962, 5,608,805, and other worldwide patents granted and pending.

Dolby is a registered trademark of Dolby Laboratories.

©1997 Dolby Laboratories

ISSUE 4

S97/10410/11548

Dolby Part No. 91342

i

TABLE OF CONTENTS

INTRODUCTION

About this manual........................................................................................................................................ ii

About the Dolby DA20 and the Dolby Stereo Digital Format............................................................... ii

SECTION 1 OPERATING INSTRUCTIONS

1.1 How to Identify Sound Tracks on Prints ................................................................................. 1-1

1.2 Film Threading ............................................................................................................................ 1-2

1.3 Displays ........................................................................................................................................ 1-2

1.4 Format Control and Auto Digital Modes ................................................................................ 1-4

1.5 Single Projector Installations ..................................................................................................... 1-8

1.6 Two Projector Changeover Operation ..................................................................................... 1-8

1.7 Operation With an Automation System .................................................................................. 1-8

SECTION 2 MAINTENANCE AND ADJUSTMENTS

2.1 Digital Soundhead Maintenance .............................................................................................. 2-1

2.2 Print Cleanliness ......................................................................................................................... 2-2

2.3 Adjustments................................................................................................................................. 2-2

SECTION 3 UNIT SERVICING/IN CASE OF DIFFICULTY

APPENDIX A DA20 CIRCUIT BOARD LOCATIONS

INTRODUCTION

Thank you for purchasing the Dolby Model DA20 Digital Film Sound Processor. It
combines the high performance for which all processors manufactured by Dolby
Laboratories are well known with the latest digital technology to decode the Dolby
Digital print format.

About this manual

This User’s Manual has been prepared specifically to help theater personnel get the most
from the Model DA20 and Cat. No.700 Digital Soundhead after proper installation.
Installation should be attempted only by qualified personnel. Installation and alignment
instructions are provided in a separate manual. We suggest that you keep this manual
readily available for quick reference.

The manual is organized as follows:

• Section 1, Operating Instructions, covers the basic control and indicator functions of
the DA20, and is all you need to get the show started.

• Section 2, Maintenance and Adjustments, contains tips for maintaining the DA20 and
the Cat. No.700 Soundhead in your theater system.

• Section 3, Troubleshooting, will help you track down problems in the digital sound
system without test equipment. It consists of procedures to follow to isolate and fix
simple problems.

• Appendix A contains circuit board location information.

For the sake of clarity, boldface type is used for all specific references to DA20 controls
and indicators and their labels, such as Digital Signal Level, and CP Status. CP refers to
Cinema Processor. In addition, indicator lights on the DA20 are referred to in the text as
LEDs (Light-Emitting Diodes).

About the Dolby DA20 and the Dolby Stereo Digital Format

The Dolby Model DA20 enables Dolby models CP45, CP55, CP65, CP200 and CP500
Cinema Processors to play the Dolby digital soundtrack format.

The Digital Film Sound System consists of a Cat. No.700 Digital Soundhead with cables
and the Model DA20 Digital Film Sound Processor. An additional Cat. No.700 Digital
Soundhead may be added for use in two projector changeover systems. The soundhead is
a mechanical assembly which provides a stable film path, and uses a CCD array to scan
digital data from a digital print. The DA20 decodes the scanned digital soundtrack into
six channels of high quality audio.

Among the features of the DA20 are:

• Automatic format selection between a Dolby digital track and the conventional analog
SR track.

• Display of digital signal level.

ii

• Adjustable time delay for mounting the Cat. No.700 Digital Soundhead up to 135
frames in advance of the analog soundhead.

• Adjustable surround delay to match theater size.

• Simple interface to the Dolby Cinema Processors.

• Comprehensive Cinema Processor status display.

• Automatic switching to analog soundtrack in the event of damaged or missing digital
data.

The DA20 includes interface cables to mate with the required Cinema Processor type.

Dolby Digital prints have conventional SR analog and digital tracks which enables low­cost 35mm optical prints to deliver the volume range, fidelity and discreteness previously
associated only with 70mm releases. The Dolby Digital format utilizes an innovative
digital encode/decode process, Dolby AC-3. The process translates five full range (20-20
kHz) channels plus a subwoofer audio channel and auxiliary data channel into a series of
data blocks, printed between the perforations of standard 35mm film. On playback, the
data blocks are scanned by an optical pickup head, and transformed back into full
professional quality digital audio. Release prints in the Dolby Digital format also contain
standard SR encoded Dolby Stereo analog tracks, resulting in single inventory prints and
unprecedented quality and reliability in film audio presentation.

This manual describes the operation of the DA20 when equipped with a Cat. No. 611A
Cinema Processor Interface card. The Cat. No. 611A has features that were not available
on the original Cat. No. 611. In particular, the automatic selection of Format 10 (Dolby
Digital), Format 05 assertions after a power failure, and other improvements are now
incorporated. Thus, the manual sections that describe the operation of auto digital and
power failure format assertion are not applicable to those units which are equipped with
the original Cat. No. 611 card.

To determine if a Cat. No. 611A is installed in your unit, look through the CP Status
opening on the DA20 front panel. If your unit is equipped with a Cat. No. 611A, you will
see “CAT. NO. 611A” printed on the PC board just inside the window immediately below
the “Analog” LED. Behind the text you will also see a cross hatched pattern printed on
the board. These two markings indicate that your unit is equipped with a Cat. No. 611A.
Your installer can provide details.

If your unit is not equipped with a Cat. No. 611A, the switch positions for Auto Digital
Disabled modes are not available and the CP Type is selected using positions 1 through 3
depending on which cinema processor is attached. See manual Section 1.4

iii

1-1

SECTION 1

OPERATING INSTRUCTIONS

1.1 How to Identify Sound Tracks on Prints

1.2 Film Threading

1.3 Displays

1.4 Format Control

1.5 Single Projector Installations

1.6 Two Projector Changeover Operation

1.7 Operation With An Automation System

1.1 How to Identify Sound Tracks on Prints

A Dolby Digital film print or a stereo optical print (A-Type or SR), or a mono 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 analog 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). Examine the soundtracks
closely; on music and effects, the two soundtracks will appear to be different on a stereo
print; on a mono print they are identical. If you specified a stereo print and received a
mono print in error, be sure to check with your local exchange or the film distributor.

a

a

a

a

a

a

a

a

a

a

a

a

Digital Print

The digital data blocks are
clearly visible between
perforations next to the
analog track. The analog
track is Dolby SR encoded.

Analog Dolby Stereo
Print

Clear differences
between channels will
be seen in some places
along the track.

Mono Print

Both tracks are the
same.

Figure 1.1 Film Sound Tracks

There is no way to tell by visual inspection if a stereo print has been encoded with a
surround channel or whether it is Dolby A-type or SR encoded. However, all but a few
early Dolby Stereo releases do have a surround channel. The majority of prints are now
Dolby SR encoded. If you are in doubt, play the print in format 04 Dolby A-type until
you have a chance to listen to the track and compare playback quality in formats 04 and

05.