Section 3 Operation
.........................................................................................................................................3-1
8685 FRONT PANEL .........................................................................................................3-1
INTRODUCTION TO PROCESSING..........................................................................................3-4
Some Audio Processing Concepts.................................................................................... 3-4
Distortion in Processing ................................................................................................... 3-4
Loudness and Distortion .................................................................................................. 3-4
Processing for Low Bit Rate Codecs................................................................................. 3-5
Speech/Music Detector..................................................................................................... 3-6
Sound-for-Picture Applications: Controlling Dynamic Range..............................3-6
Optimod 8685 in Audio-Only Applications: From Bach to Rock..........................3-7
ABOUT THE 8685’S SIGNAL PROCESSING FEATURES ..............................................................3-8
Simultaneous Stereo (2.0) and Surround (5.1 or 7.1) Processing .........................3-8
Signal Flow...............................................................................................................3-9
Input Conditioning........................................................................................................... 3-9
Two-Band Gated AGC ...................................................................................................... 3-9
Equalization....................................................................................................................3-10
Multiband Compressor/Limiter...................................................................................... 3-11
LFE Processing................................................................................................................. 3-13
Low-IM Look-Ahead Limiter .......................................................................................... 3-13
Loudness Control............................................................................................................ 3-14
Input/output Delay......................................................................................................... 3-16
CUSTOMIZING THE 8685’S SOUND ...................................................................................3-16
Basic Modify...........................................................................................................3-17
Intermediate Modify .............................................................................................3-18
Advanced Modify ..................................................................................................3-18
Setting Preset Loudness Correctly for Dolby Digital Transmission ....................3-19
Gain Reduction Metering .....................................................................................3-20
To Create or Save a Preset ....................................................................................3-20
ABOUT THE PROCESSING STRUCTURES ...............................................................................3-21
FACTORY PROGRAMMING PRESETS ...................................................................................3-24
To import a 2.0 preset from the 8685’s front panel: .................................................... 3-25
To import a 2.0 preset from PC Remote:....................................................................... 3-25
Sound-for-Picture Presets......................................................................................3-26
Table 3-1: Factory Programming Presets (Sound-for-picture)...................................... 3-27
Protection and Studio AGC Presets ......................................................................3-30
Table 3-2: Pass-Through, Protection and AGC Presets.................................................. 3-31
Radio-Style Presets ................................................................................................3-32
Table 3-3: Radio-Style Presets ........................................................................................ 3-33
EQUALIZER CONTROLS ....................................................................................................3-36
Table 3-4: Five-Band Equalizer Controls........................................................................ 3-38
AGC CONTROLS ............................................................................................................3-41
Table 3-5: AGC Controls................................................................................................. 3-42
Advanced AGC Controls........................................................................................3-43
AGC Controls Exclusive to 2.0 Processing:..................................................................... 3-45
DISTORTION CONTROL ....................................................................................................3-46
Table 3-6: Distortion Control Adjustments ................................................................... 3-46
THE TWO-BAND STRUCTURE ...........................................................................................3-48
Customizing the Settings ......................................................................................3-49
The Two-Band Structure’s Full and Advanced Setup Controls ...........................3-49
Table 3-7: Two-Band Controls ....................................................................................... 3-50
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