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OPTIMOD-FM 8200 OPERATION
3-1
Section 3
Operation
page contents
3-3 8200 Controls and Meters
3-5 Introduction to Processing
3-7 Customizing the 8200's Sound
3-9 About the Processing Structures
3-9 Factory Programming Presets
3-15 The Protection Limiter Structure
3-21 The Two-Band Structures
3-31 The Multi-Band Structure
3-41 8200 Screen Displays
3-45 RECALL PRESET Screen
3-49 MODIFY Screens
3-59 AUTOMATION Screens
3-63 SYSTEM SETUP Screens
Caution
The installation and servicing instructions in this manual are for
use by qualified personnel only. To avoid electric shock do not
perform any servicing other than that contained in the Operating
Instructions unless you are qualified to do so. Refer all servicing
to qualified service personnel.
3-2
TEST
SWITCH
OPERATION
ARROW
KEYS
POWER
LED
STEREO SCREEN ESC HELP SOFT KEY CONTROL KNOB
ENCODER CONTRAST BUTTON BUTTON BUTTONS
CONTROLS CONTROL
OPTIMOD-FM 8200
OPTIMOD-FM 8200 OPERATION
3-3
pagecontents
8200 Controls and Meters
Arrow Keys (, , , ) are used for moving around screen to select a function to be
changed.
Control Knob is used for changing the setting that is selected by the arrow keys.
Screen Display provides all metering information, labels the five soft-key buttons, provides
control setting information.
Screen CONTRAST adjusts the optimum viewing angle of the screen display.
Five Soft Key Buttons provide access to all 8200 functions and controls. The functions of
the buttons change with each screen, according to the labels at the bottom of each screen
ESC Button provides an escape from current screen, returns user to the next previous
screen, and repeated ESC commands will always return you to the IDLE G/R screen.
HELP Button provides HELP information for the current screen and provides detailed help
for all of the buttons on that screen (by pushing HELP button, then the screen button).
POWER LED lights when the unit is powered. (It monitors the unregulated +12V DC bus.)
Stereo Encoder Screwdriver-Adjustable Controls
Orban supplies a special green-handled flat-blade screwdriver (Xcelite
R3323) to adjust the stereo encoder controls. Note that the Orban tweaker
tool supplied with the analog OPTIMODs cannot be used with the 8200.
Test Switch (OPERATE -- SUB TO MAIN -- MAIN TO SUB) sets the stereo encoder
to operate normally, or to produce pure L-R or L+R signals for system testing.
COMPOSITE LEVEL 1 sets the output level of Composite Output 1.
COMPOSITE LEVEL 2 sets the output level of Composite Output 2.
SEPARATION adjusts the level of the L+R signal, enabling you to optimize the separation
through the entire transmission system. (See step 4 on page 4-11.)
PILOT LEVEL adjusts the level of the 19kHz stereo pilot tone. See the note on page 4-14
about accessing and using the pilot meter.
3-4 OPERATION OPTIMOD-FM 8200
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OPTIMOD-FM 8200 OPERATION
3-5
Introduction to Processing
Some Audio Processing Concepts
Loudness is increased by reducing the peak-to-average ratio of the audio. If peaks are
reduced, the average level can be increased within the permitted modulation limits. The
effectiveness with which this can be accomplished without introducing objectionable side
effects (such as clipping distortion) is the single best measure of audio processing effective-
ness.
Compression reduces the difference in level between the soft and loud sounds to make more
efficient use of permitted peak level limits, resulting in a subjective increase in the loudness
of soft sounds. It cannot make loud sounds seem louder. Compression reduces dynamic
range relatively slowly in a manner similar to riding the gain: limiting and clipping, on the
other hand, reduce the short-term peak-to-average ratio of the audio.
Limiting increases audio density. Increasing density can make loud sounds seem louder, but
can also result in an unattractive busier, flatter, or denser sound. It is important to be aware
of the many negative subjective side effects of excessive density when setting controls that
affect the density of the processed sound.
Clipping sharp peaks does not produce any audible side effects when done moderately.
Excessive clipping will be perceived as audible distortion.
Distortion in Processing
In a competently-designed processor, distortion occurs only when the processor is clipping
peaks to prevent the audio from exceeding the peak modulation limits of the transmission
channel. The less clipping that occurs, the less likely that the listener will hear distortion.
However, to reduce clipping, you must decrease the drive level to the clipper, which causes
the average level (and thus, the loudness) to decrease proportionally.
The FM pre-emphasis curve introduces further complications. Pre-emphasis boosts the
treble at 6dB/octave starting at 2.1kHz (for 75