2200 Manual Section 3 Operacion
2200 Manual Section 3 Operacion
2200 Manual Section 3 Operacion
3-1
Section 3
Operation
page contents
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 OPERATION OPTIMOD-FM 2200
page
OPTIMOD-FM 2200 OPERATION
3-3
2200 Controls and Meters
Contrast Button adjusts the optimum viewing angle of the screen display. Press this
button to cycle through four contrast settings for the screen display.
Four Soft Key Buttons provide access to all 2200 functions and controls. The
functions of the buttons change with each screen according to the labels at the bottom
of each screen. Push a button:
To select options (always identified on the screen by all-capital-letter
words surrounded by left and right vertical bars), press the button directly
below the option.
To change a parameter setting (always identified by lower-case letters or
numerals), hold down the button directly below the parameter setting, turn
the control knob to scroll through choices, and release the button to set the
parameter.
Escape Button returns the user to the previous screen; pressing this button repeatedly
will always return you to main screen, which shows the on-air preset name.
Recall Preset Button brings up a screen that displays the current on-air preset and next
preset (which can be changed by turning the control knob). To put a different preset
on-air, turn the control knob to find the preset desired, then press the RECALL NEXT
soft key.
When the button’s yellow LED is lit, the Recall Preset screen is displayed.
3-4 OPERATION OPTIMOD-FM 2200
Modify Processing Button brings up a screen to modify parameters for the current
on-air preset. For Two-Band presets: LESS-MORE, EQ and FULL CONTROL. For the
Protection preset, DRIVE and 30HzHPF.
When the button’s yellow LED is lit, the Modify Processing screen (or one
of its submenus) is displayed.
System Setup Button brings up a screen to modify system settings (such as I/O
levels). There are four System Setup submenus: I/O CALIB, STEREO ENCODER, RE-
MOTE INTERFACE, TEST.
When the button’s yellow LED is lit, the System Setup screen (or one of
its submenus) is displayed.
HF Limiting LEDs light when the high-frequency content of audio is being limited
by the very fast high-frequency limiters. These LEDs indicate when greater than 0.5dB
HF limiting is occurring.
Gated LED indicates gate activity, lighting when the input audio falls below the
threshold set by the gate threshold control (Modify Processing screen GATE THRS
control). When this happens, the compressor’s recovery time is drastically slowed to
prevent noise rush-up during low-level passages.
Composite Meter is a 10-segment bargraph showing the stereo encoder’s composite
output level before the composite level controls.
Function Button selects which of three functions are displayed in the Function
meters: Enhance, L/R Input or L/R Output.
Function LEDs indicate which function is currently displayed by the Function meters:
Enhance, L/R Input or L/R Output. Press the Function button to toggle between the
three functions.
Function Meter indicates level of Enhance, L/R Channel Input or Output, as selected
with Function button. The meters operate over a −27dB to 0dB range. Input meters are
referenced to clip level. Output meters are referenced to 100% modulation level. HF
Enhance meter shows the active amount of enhancement activity. Since the HF
Enhancement is program-dependent, it will vary with source material and the HF
parameter. Note: HF Enhance is displayed only on the left-hand meter, below “HF.”
Stereo Encoder Screwdriver-Adjustable Controls
Orban supplies a special green-handled flat-blade screwdriver (Xcelite
R3323) to adjust the stereo encoder controls.
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 75µs countries) or 3.2kHz (for 50µs countries).
This reduces the headroom available at high frequencies, and makes it difficult to achieve a
bright sound. This is because bright sound requires considerable high-frequency power to
appear at the output of the receiver’s de-emphasis filter, and thus requires a very large
amount of high-frequency power to be transmitted so that a sufficient amount will survive
the de-emphasis process.
Without very artful processing, the pre-emphasis will radically increase the level of the
peaks and force you to decrease the average level proportionally. Orban’s high-frequency
limiting and distortion-canceling clipping systems greatly ease this trade-off, but cannot
entirely eliminate it. Therefore, you can only increase brightness by reducing average
modulation (loudness) — unless you accept the increased distortion caused by driving the
final clippers harder.
3-6 OPERATION OPTIMOD-FM 2200
In the 2200, a processing structure is a program that operates as a complete audio processing
system. Only one processing structure can be active at a time.
There are two processing structures in the 2200:
Two-Band
Protection/Limiting
Unlike an analog system, where creating a complete processing system involves physically
wiring its various components together, the 2200 realizes all of its processing structures as
a series of high-speed mathematical computations made by Digital Signal Processing (DSP)
integrated circuit chips. So the 2200 can be changed from one structure to another by loading
new software from high-speed semiconductor memory within the 2200.
Factory Presets are our “recommended settings” for various program formats. These presets
were designed by our experienced engineers as good starting points for the program format.
In many cases, the sound of the factory preset will suit your needs without the need for
further adjustment.
There are eight factory presets:
Classical-Protect
2B General Purpose
Talk
Music-Light
Music-Medium
Music-Heavy
Music+Bass Medium
Music+Bass Heavy
Classical-Protect produces a very clean, open sound that is ideal for
stations whose success depends on attracting and holding audiences for
very long periods of time. It uses the Protection/Limiting structure. All
other presets use the Two-Band structure.
2B General Purpose provides an average amount of processing;
Talk provides processing for Talk format stations that primarily feature
news, call-in shows, interviews, and other voice material. TALK keeps the
levels of announcers and guests consistent, and keeps a proper balance
between voice and commercials.
Music-Light produces a very open, unprocessed sound. This is a sound
that is easily listenable for many hours without fatiguing listeners.
3-8 OPERATION OPTIMOD-FM 2200
Start with one of these presets. Spend some time listening critically to your on-air sound.
Listen to a wide range of program material typical of your format, and listen on several types
of radios (not just on your studio monitors). Then, if you wish, customize your sound using
LESS-MORE, EQ and FULL CONTROL.
To recall a preset:
Press Recall Preset Button. Turn the control knob to scroll through preset
list and stop when you find a desired preset. Press RECALL NEXT soft
key button.
It is normal for the audio to mute for about a second when switching
between a preset based on the Two-Band structure and a preset based on
the Protection/Limiting structure. This gives the 2200 time to download the
appropriate code to its DSP chips.
OPTIMOD-FM 2200 OPERATION
3-9
Customizing the 2200’s Two-Band Sound
The subjective setup controls on the 2200 give you the flexibility to customize your station’s
sound. But, as with any audio processing system, proper adjustment of these controls
consists of balancing the trade-offs between loudness, density, brightness, and audible
distortion.
When you start with one of our Two-Band factory presets, there are three levels of subjective
adjustment available to you to let you customize the factory preset to your requirements:
LESS-MORE
EQ
FULL CONTROL.
LESS-MORE
After selecting a factory preset, LESS-MORE is the next level of adjustment.
As you go from less to more, the air sound will become louder, but (as with any processor)
processing artifacts will increase. The single LESS-MORE control changes many different
processing controls at the same time.
Many users will never need to go beyond the LESS-MORE level of control, because the
combinations of subjective setup control settings produced by this control have been
optimized by Orban’s audio processing experts on the basis of years of experience designing
audio processing, and upon hundred of hours of listening tests.
To adjust Less-More:
Press Modify Processing Button, then press LESS-MORE soft key button.
Hold the LESS-MORE button down while turning the control knob to
change LESS-MORE setting. When you find a setting you like, release the
LESS-MORE button.
EQ
After LESS-MORE, EQ is the next level of adjustment. It gives you equalization control
independent of the LESS-MORE control. EQ provides a 30Hz High-Pass Filter, Low Bass
(boost) control and HF Enhancement. We give a detailed description of the EQ controls on
page 3-11 (Two-Band Processing Control Details.)
To adjust EQ control
Press the Modify Processing Button, then press the EQ soft key button.
From the EQ display, hold down the soft key button for the EQ control you
want to change, turn the control knob to scroll through choices and release
the button when you find a desired setting.
3-10 OPERATION OPTIMOD-FM 2200
FULL CONTROL
With FULL CONTROL you can modify any subjective processing control to create a sound
exactly to your taste. Use LESS-MORE to get as close as possible to your desired sound. Then
use FULL CONTROL to make small changes to get the sound you want.
30HzHPF (30Hz High Pass Filter) control determines if the 30Hz high-pass filter prior to
the AGC is in or out of the signal path.
The 30Hz high-pass filter has an 18dB/octave slope, is down 0.5dB at 30Hz, and is located
before the gain-riding AGC. It can be switched in or out-of-circuit by the 30HzHPF control.
This filter eliminates modulation-wasting subsonic energy from acoustic and turntable
rumble, and removes most of the energy from pops caused by breath blasts into micro-
phones. It prevents any such subsonic energy from modulating the audio processor’s AGC
and compressor control signals (which could cause unpleasant distortion), and prevents the
automatic frequency control loops in FM exciters from introducing modulation distortion
into the audio or even becoming entirely unlocked.
The cutoff frequency of this filter is so low that the only common musical instruments
producing lower fundamental frequencies are the pipe organ and synthesizer. The bass
energy in most pop music occurs above 40Hz. We recommend operating the system with
the 30HzHPF control set in.
LOW BASS (Low Bass Boost) control is an equalization control designed to add punch
and slam to rock and urban music. It provides a shelving boost from 0dB to +12dB in 1dB
steps. The equalizer operates at 110Hz and below.
Because the Two-Band Structure often increases the brightness of program material when
the HF ENHANCE control is used, some bass boost is usually desirable to keep the sound
spectrally well-balanced. Adjustment of bass equalization must be determined by individual
taste and by the requirements of your format. Be sure to listen on a wide variety of radios
— it is possible to create severe distortion on poor-quality speakers by over-equalizing the
bass. Be careful!
3-12 OPERATION OPTIMOD-FM 2200
OPTIMOD-FM 2200 OPERATION
3-13
The moderate-slope (12dB/octave) shelving boost achieves a bass boost that is audible on
smaller radios, but which can sound boomy on high-quality receivers. There are no easy
choices here; you must choose the amount of boost you want by identifying your target
audience and the receivers they are most likely to be using. In general, we recommend a +1
to +4dB boost for most formats.
HF ENHANCE (HF Enhancement) control sets the amount of high frequency energy
added to program material. This enhancement is dynamically determined by the program
material: Continuous analysis of program material intelligently and automatically deter-
mines the amount of equalization necessary at each moment to achieve detailed, defined
program material that is never shrill or over-sibilant.
On mixed program material, HF ENHANCE usually produces the best sound if adjusted in the
0 to 5 range; the detail and definition of the program material is improved, yet the material
does not sound excessively shrill. Always use your ears and judge how the processing
affects the material.
Generally, if the material is very bright to begin with, you will hear little effect; if the
program material is dull, you will hear very significant brightening. HF Enhancement works
seamlessly with program material that contains previously enhanced tracks, like CD-quality
music, because the 2200’s enhancement detects that such material already has considerable
HF power and reduces its enhancement accordingly.
AGC (Automatic Gain Control) on/off control activates or defeats the slow AGC prior to
the two-band compressor. If you are using an external compressor before the 2200 to protect
an STL (like the Orban 8200ST OPTIMOD-Studio), set the AGC on the 2200 to off.
AGC DRIVE control adjusts signal level going into the slow AGC, and therefore deter-
mines the amount of gain reduction in the AGC. This also adjusts the “idle gain” — the
3-14 OPERATION OPTIMOD-FM 2200
amount of gain reduction in the AGC section when the structure is gated. (It gates whenever
the input level to the structure is below the threshold of gating.)
The total amount of gain reduction in the Two-Band Structure is the sum of the gain
reduction in the AGC and the gain reduction in the two-band compressor. The total gain
reduction determines how much the loudness of quiet passages will be increased (and,
therefore, how consistent overall loudness will be). Total gain reduction is determined by
the setting of the AGC DRIVE control, by the level at which the console VU meter or PPM is
peaked, and by the setting of the 2B DRIVE compressor control, discussed directly below.
The range of the AGC DRIVE control is -10dB to +25dB.
REL TIME (Release Time) control determines how fast the two-band compressor
releases (and therefore how fast loudness increases) when the level of the program material
decreases.
It can be adjusted from 1dB/Second (slow) to 20dB/Second (fast). Settings toward
20dB/Second result in a more consistently loud sound on the air, while settings toward
1dB/Second allow a wider variation of dynamic range. The actual release time of the
compressor is determined by both the setting of the REL TIME control and the dynamics and
level of the program material. In general, you should use faster release times for mass-appeal
pop or rock formats oriented toward younger audiences, and slower release times for more
conservative, adult-oriented formats (particularly if women are an important part of your
target audience).
The action of the REL TIME control has been optimized for resolution and
adjustability. But its setting is critical to sound quality — listen carefully
as you adjust it. There is a point beyond which increasing density (with
faster settings of the REL TIME control) will no longer yield more loudness,
and will simply degrade the punch and definition of the sound.
When the REL TIME control is set between 8 and 1dB/Second (the slowest
settings), the amount of gain reduction is surprisingly non-critical. Since
gating prevents noise from being brought up during short pauses, and
pumping does not occur at high levels of gain reduction, the primary
danger of using large amounts of gain reduction is that the level of quiet
passages in input material with wide dynamic range may eventually be
increased unnaturally. Therefore, when you operate the REL TIME control
between 8 and 1dB/Second, it may be wise to defeat the gain-riding AGC
and to permit the two-band compressor to perform all of the gain-riding.
This will prevent excessive reduction of dynamic range, and will produce
the most natural sound achievable from the Two-Band Structure.
With faster REL TIME control settings (above 8dB/Second), the sound will
change substantially with the amount of gain reduction in the two-band
compressor. This means that you should activate the gain-riding AGC to
ensure that the two-band compressor is always being driven at the level that
produces the amount of gain reduction desired. Decide on the basis of
listening tests how much gain reduction gives you the density you want
without creating a feeling of over-compression and fatigue.
Release in the two-band compressor automatically becomes faster as more
gain reduction is applied (up to about 10dB). This makes the program
progressively denser, creating a sense of increasing loudness even though
peaks are not actually increasing. If the gain-riding AGC is defeated (with
the AGC control), you can use this characteristic to preserve some feeling
of dynamic range. Once 10dB of gain reduction is exceeded, full loudness
OPTIMOD-FM 2200 OPERATION
3-15
is achieved — no further increase in short-term density occurs as more gain
reduction is applied. This avoids the unnatural, fatiguing sound often
produced by processors at high gain reduction levels, and makes OPTI-
MOD-FM remarkably resistant to operator gain-riding errors.
2B DRIVE control adjusts signal level going into the two-band compressor, and therefore
controls the dynamic range of the output audio by determining the amount of gain reduction
in the two-band compressor. Depending on the setting of the REL TIME control (see above),
the resulting sound texture can be open and transparent (low settings of 2B DRIVE), solid
and dense (high settings of 2B DRIVE), or somewhere in between.
Regardless of the release time setting, we feel that the optimal amount of gain reduction in
the two-band compressor for popular music and talk formats is 10-15dB. If less gain
reduction is used, loudness can be lost.
For classical formats, operating with 0-10dB of gain reduction (with the
gain-riding AGC defeated), maintains a sense of dynamic range while still
controlling levels effectively. Because OPTIMOD-FM’s density gently
increases between 0 and 10dB of compression, 10dB of compression
sounds very natural, even on classical music.
BASS COUPL (Bass Coupling) control is used to set the balance between bass and the
rest of the frequency spectrum.
The two-band compressor processes audio in a Master Band for all audio above approxi-
mately 200Hz, and a Bass Band for audio below approximately 200Hz. The BASS COUPL
control determines how closely the on-air balance of material below 200Hz matches that of
the program material above 200Hz.
Settings toward 100% (wideband) make the output sound most like the input. Because
setting the BASS COUPL control at 100% will sometimes cause bass loss, the most accurate
frequency balance will often be obtained with this control between 70% and 90%. The
optimal setting depends on the amount of gain reduction applied. Adjust the BASS COUPL
control until the Bass and Master Gain Reduction meters track as closely as possible.
With the Two-Band’s REL TIME control set to 2dB/Second, setting the BASS
COUPL control toward 0% (independent) will produce a sound that is very
open, natural, and non-fatiguing, even with large amounts of gain reduc-
tion. Such settings will provide a bass boost on some program material that
lacks bass.
With fast release times, settings of the BASS COUPL toward 100% (wide-
band) do not sound good. Instead, set the BASS COUPL control toward 0%
(independent). This combination of fast release and independent operation
of the bands provides the maximum loudness and density on small radios
achievable by the 2200. But such processing may fatigue listeners with
high-quality receivers, and also requires you to activate the AGC to control
the average drive level into the two-band compressor, preventing uncon-
trolled build-up of program density.
HF LIMIT control determines how the processor avoids high-frequency overloads due to
the pre-emphasis curve. When set toward − 4.0dB (soft), the highs are controlled mostly by
limiting (a form of dynamic filtering), which tends to soften highs — this could improve the
sound of marginally distorted program material. When set toward + 2.0dB (hard), the highs
are controlled mostly by clipping, which could potentially distort highs.
3-16 OPERATION OPTIMOD-FM 2200
Control of highs by limiting tends to slightly dull the sound. Control of highs by clipping
doesn’t reduce brightness, but the resulting sound can tend towards grittiness and smearing.
Because the OPTIMOD-FM distortion-canceling clipper does not produce
significant distortion at low frequencies, the HF LIMIT control will have a
different effect on clipping distortion than you might expect. Outright
break-up (principally sibilance splatter) will not occur — you must listen
to the upper midrange and the highs to hear the effect of the clipper.
Program material containing highly equalized hi-hat cymbals will clearly
demonstrate the effect of adjusting the control.
When the CLIPPING control is set to 0.0dB or below and the REL TIME
control is set slower than 8dB/Second, it is possible to set the HF LIMIT
control to + 2.0dB without producing objectionable distortion (provided
that the program material is very clean). If the CLIPPING control is set
above 0.0 and/or faster release times are used (such that greater level and
density is produced), it is usually necessary to readjust the HF LIMIT control
closer to − 2.0dB (soft) to avoid objectionable distortion. Fortunately, the
high-frequency limiter knows that greater density and level have been
produced when these other controls are set this way, and most of the
necessary increases in high-frequency limiting will occur automatically. In
fact, you will clearly hear a loss of highs when you adjust any control to
produce greater loudness and density — this is an automatic response to
the loudness/brightness/distortion trade-off inherent to all broadcast proc-
essing.
We recommend that you examine the factory settings used by the “LESS-
MORE” curves (adjust LESS-MORE to a given setting, then enter FULL
CONTROL to look at the settings). This will help you learn about the
trade-offs.
CLIPPING control adjusts signal level going into the distortion-canceling clippers and
therefore determines the amount of peak limiting done by clipping. Range is − 4.0dB to
+2.0dB. This control and the FINAL CLIP control govern the trade-off between loudness and
distortion.
OPTIMOD-FM controls fast peaks by distortion-canceled clipping. The CLIPPING control
adjusts the level of the audio driving the distortion-canceled clippers, and therefore adjusts
the peak-to-average ratio. The loudness/distortion trade-off is primarily determined by the
CLIPPING control.
Turning up the CLIPPING control drives the distortion-canceled clippers harder, reducing the
peak-to-average ratio, and increasing the loudness on the air. When the amount of clipping
is increased, the audible distortion caused by clipping is increased. Lower settings reduce
loudness, of course, but result in a cleaner sound and better high-frequency response.
In our opinion, when the REL TIME control is set between 1 and 8dB/Sec-
ond, the best setting for the CLIPPING control is between −1.0 and 0.0. If
the program material is clean, this setting produces an output that sounds
undistorted even on high-quality receivers.
If you use faster settings of the REL TIME control, or if program material
is not always clean, use lower settings of the CLIPPING control. Ulti-
mately, your ears must judge how much distortion is acceptable. But
audition difficult program material like live voice and piano before you
make your final decision.
OPTIMOD-FM 2200 OPERATION
3-17
If you are optimizing for live voice, you will probably want to reduce the
setting to the −3 to −4 range to eliminate any audible clipping.
FINAL CLIP (Drive) control determines the level driving the final clipper that performs
protection peak limiting. This clipper follows the distortion-canceling clipper system, and
is not itself distortion-canceling.
The effect of adjusting this control is very critical — changes of 0.1dB
make clearly audible differences in the amount of distortion produced by
the processing. In most cases, we recommend that the user not adjust this
control and use the factory preset settings instead; the control has only been
made available for experienced, sophisticated users who need to achieve
the absolute maximum on-air loudness and who are willing to take the time
necessary to listen to many different kinds of program material to verify
that nothing falls apart after the clipper drive has been increased. The effect
of adjusting this control is very similar to the effect of changing the amount
of clipping in a composite clipper, except that in the 2200 (unlike a
composite clipper), the SCA region of the baseband spectrum is always
perfectly protected from interference.
3-18 OPERATION OPTIMOD-FM 2200
OPTIMOD-FM 2200 OPERATION
3-19
Customizing The Protection Limiter Structure
Sound
The Protection Limiter Structure is designed for stations wanting the highest possible
fidelity to the source, such as a station broadcasting concert music at night when its audience
is likely to listen in a concentrated and critical way. While the Protection Limiter Structure
can readily reduce the dynamic range, it is designed to do so without increasing program
density, loudness, or the consistency of sound from different sources. Its primary function
is to protect the transmitter from over-deviation while preserving the spectral and textured
quality of the source material.
There are virtually no user controls — the parameters of the structure have been chosen to
make it audibly undetectable.