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Model SDU4
Surround Decoder
User's Manual
Issue 2 Part No. 91413
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User's Manual Model SDU4 Surround Decoder Dolby Laboratories Incorporated U.S.A. 100 Potrero Avenue, San Francisco, CA 94103-4813 Tel: 415-558-0200; Fax: 415-863-1373; Web: www.dolby.com U.K. Wootton Bassett, Wiltshire SN4 8QJ Tel: (44) 1793-842100; Fax: (44) 1793-842101 : Equipment manufactured by Dolby Laboratories is warranted against defects in materials and DISCLAIMER OF WARRANTIES workmanship for a period of one year from the date of purchase. All warranties, conditions or other
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i TABLE OF CONTENTS SECTION 1–INTRODUCTION ............................................................................................. 1-1 1.1 The SDU4 ......................................................................................................................... 1-1 1.2 Specifications .................................................................................................................. 1-2 1.3 Regulatory Notices ..........................................................
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1-1 SECTION 1 INTRODUCTION 1.1 The SDU4 The Dolby SDU4 is designed for reference monitoring of Dolby encoded film formats or Dolby Surround program material in broadcast, audio-for- video, and music recording applications. The unit contains a reference 2:4 matrix decoder, like that used in the Dolby monitoring equipment found in film production centers. The 2:4 decoder takes a two-track matrix encoded signal as its input and generates four output signals (Left, Center, Right and Surround). Th
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1-2 Center Speaker In/Out: 1.2 Specifications Selected by an internal switch. Used to match either theater-style systems with three front Layout: channels or smaller systems with two front Rack-mount unit incorporating a loudspeakers. The latter mode routes professional surround decoder module, spatially decoded signals from the surround interface circuitry, and power supply. decoder as follows: left decoder output to Left main output; right decoder output to Signal Connections: (on rear panel
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1-3 1.3 Regulatory Notices UL Troubleshooting must be performed by trained technicians. Do not attempt to service the unit unless you are qualified to do so. WARNING: Check that the units have been set to the correct supply voltage and that the correct fuses have been installed. To reduce the risk of fire, replace the fuses only with the same type and rating. Do not use a ground- lifting adaptor and never cut the ground pin on the three-prong power plug. UK Connections for United Kingdom: WA
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1-4 IEC NOTICES IMPORTANT SAFETY NOTICE This unit complies with the safety standard IEC65. To ensure safe operation and to guard against potential shock hazard or risk of fire, the following must be observed: • Ensure the voltage selector is set to the correct mains voltage for your supply. • Ensure fuses fitted are the correct rating and type as marked on the unit. GB • The unit must be earthed by connecting to a correctly wired and earthed power outlet. • The power cord supplied with this un
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2-1 SECTION 2 INSTALLATION AND CALIBRATION 2.1 Monitor Setup Front Loudspeaker Arrangement The SDU4 is designed for monitoring rooms with either two or three front loudspeakers. The choice between using either two or three front loudspeakers depends upon the distance between the Left and Right speakers, (how large the stereo image is) and how the primary listening area is arranged relative to the front sound image. In most cases, three front loudspeakers are recommended with the center loudspe
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2-2 Surround Loudspeakers The surround loudspeakers are used to distribute a single channel of sound in a diffuse field behind the viewer. The number of loudspeakers needed, therefore, depends upon the size of the area to be covered. In smaller rooms, such as those used for video production and home surround installations, two loudspeakers generally provide sufficient coverage. Equalization The monitor system used with the SDU4 should have its electro-acoustical frequency response adjusted to
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2-3 2.2.2 Multi-Voltage SDU4 SPARE FUSE (UPPER) OCTAGONAL PEG OPEN THE DOOR ROUND PEG VOLTAGE SELECTOR WHEEL FUSE ACTIVE FUSE CARRIER (LOWER) A2F4037 FUSE Figure 2.3 Fuse compartment, multi-voltage unit Open the fuse compartment door in the AC mains input connector with a small flat blade screwdriver (see Figure 2.3), and check that the fuse has the correct rating. If necessary, rotate the selector drum until it displays the correct voltage for the installation. (The drum may also be removed
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2-4 2.3.1 External Facilities Connector (J503) J503 FEMALE D-CONNECTOR 13 CHASSIS GROUND 25 12 REMOTE FADER WIPER 24 11 REMOTE FADER TOP +24V 23 RIGHT TOTAL MONITOR 10 22 9 LEFT TOTAL MONITOR 21 8 DOLBY SURROUND 20 +15V 7 STEREO 19 -15V 6 MONO 18 DC GROUND LEFT MONITOR 5 17 4 CENTER MONITOR 16 3 RIGHT MONITOR 15 2 SURROUND MONITOR 14 1 DC GROUND Figure 2.4 J503 connections Connector J503 provides fixed level (500mV for Dolby level) monitoring points for Lt and Rt and for L,C,R and S signals, an
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2-5 controls are on the right-hand module, Cat. No. 344, as shown in Figure 2.5. Figure 2.5 Cat. No. 344 Center Speaker Switch Switch S301 allows the SDU4 to be installed in monitoring rooms that have either two loudspeakers (labeled “center speaker, no”) or three loudspeakers (“yes”). The factory setting is “yes.” While decoding Dolby Surround with the internal switch in the “yes position, the decoder’s Center output signal is sent to the center loudspeaker, as normal. With the internal switc
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2 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
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2-7 The delay setting can be estimated by using the following method: 1. Estimate the distance between the primary listening location and the nearest surround loudspeaker, in feet. If the metric system is used, convert the distance from meters to feet by multiplying by three (3). 2. Estimate the distance from the primary listening location to the front center loudspeaker, in feet. If the metric system is used, multiply the distance by three (3) to convert distance from meters to feet. 3. Subtr
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2-8 The SDU4 contains two four element LED calibration indicators for setting of input level. The two input level potentiometers are set so that reference tone from the signal source, representing the studio’s operating level, is equal to the SDU4’s internal operating level. Any level between –8 dBr and +8 dBr can be set to correspond with the internal operating level. This is indicated by the two green LEDs being equally illuminated. (0dBr = 0.775V rms.) 2.6 Output Level Setting The SDU4 cont
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2-9 PINK NOISE AUTO OFF MANUAL CSCS LCRS NOISE SEQUENCE OUTPUT L C R S Figure 2.9 Pink-noise calibrate functions Output Level Adjustments Output potentiometers are provided so that the decoder output level can be matched to the monitor system. Typically, the SDU4 output level is set using the internal pink noise source. The front panel master level control is set to the “ ” mark (2 o’clock). Then the SDU4 output trims, (or alternatively, the level controls on the power amplifiers) are set
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3-1 SECTION 3 OPERATION 3.1 Operating Modes and Applications The SDU4 has three modes of normal operation: Mono, Stereo and Dolby Surround. Mono The mono mode combines the Lt and Rt input signals into a single channel and routes it to the Center loudspeaker, if the internal switch S301 is in the "yes" position. If the internal switch is in the "no" position, the mono sum of Lt and Rt is sent to the Left and Right loudspeakers at a reduced level, thereby creating a correct phantom center image. S
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3-2 The matrix format used on Dolby soundtracks is compatible with both monophonic and conventional stereo playback. Many home viewers have purchased Dolby Surround decoding equipment for use during playback of prerecorded videotape or videodisk program material. These consumer grade decoders are being manufactured by the many companies who are licensed by Dolby Laboratories. Viewers are finding that the Dolby Surround decoders are also capable of effectively decoding broadcasts of Dolby films a
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3-3 center channel information. This, in effect, will cause the mono-compatible elements of the mix to appear to always come from the center of the picture. On the other hand, the incompatible elements (those that would cancel if the two input channels were summed) would be reproduced around and behind the listener. This spatial effect is useful as it instantly alerts sound mixers to compatibility problems should inappropriate elements, such as on-screen effects, or dialogue, suddenly appear in
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4-1 SECTION 4 BLOCK DIAGRAM MONITOR POINTS J503 LT RT 21 23 CAT.NO.344 J503 CAT. 150 5 LEFT TOTAL 4 3 L J501 Z K LEVEL 2 VAR. L INPUT TRIM 22 AMP LEFT ATTEN. 3 10 E P501 LT 1 V OUTPUT 2 VCA 18 AMP 3 AUTO 4 1 1 = CHASSIS PINK 5 2 LEVEL C OFF NOISE METERS 2 = HI J LEVEL GEN (LEDS) C TRIM 3 = LO CENTER MANUAL CENTER 4 = CHASSIS SPKR SW P502 U 2 OUTPUT LOOP VCA AMP 17 SWITCH 3 1 RIGHT TOTAL 7 3 J502 5 6 1 RT R Y 2 VAR. H LEVEL INPUT R 21 AMP TRIM ATTEN. 3 RIGHT 1 4 S P503 1 MONO SURR T 2 OUTPUT 14 1
