Shrill, Harsh Sound; Excessive Sibilance; Gain Pumping When High Frequency Energy Is Present; System Receiving Optimod-Pc's Aes Digital Output Will Not Lock; System Will Not Pass Line-Up Tones At Full Output Level/100% Modulation - Orban Optimod-PC 1101 Operating Manual

2-40
INSTALLATION

Shrill, harsh sound; excessive sibilance

Gain pumping when high frequency energy is present

System receiving OPTIMOD-PC's AES digital output will not lock

System will not pass line-up tones at full output level/100% modulation

General dissatisfaction with subjective sound quality

Excessively high settings of the HF G
caused by excessively high settings of the B5 T
Threshold) control. In the latter case, you are first likely to notice the problem as
harsh sibilance on voice.
This will occur with most OPTIMOD-PC factory presets when OPTIMOD-PC's preem-
phasis is set to 50 µs or 75µs. [See step 5 on page 2-23.] The gain pumping happens
because the preemphasis creates a large high frequency boost before the look-
ahead limiter, so the look-ahead limiter must produce large amounts of gain reduc-
tion to control peak levels.
To correct this problem, turn down the F
pumping is no longer audible (see Processing for Low Bitrate Codecs on page 3-5). It
may also be helpful to adjust band 5 so that it produces some high frequency limit-
ing. (The AGC+75 LIMITER factory preset illustrates this technique; see page 3-18.)
US
Then save your work as a User Preset.
Be sure that OPTIMOD-PC's output sample rate is set to match the sample rate that
the driven system expects. Be sure that OPTIMOD-PC's digital output format control
is set to match the standard expected by the driven system (either AES3 or SPDIF).
(See step 4 on page 2-22.)
This is normal in O
PERATE
by comparison to program material. The processing thus automatically reduces their
peak level to bring their average level close to that of program material, promoting
a more consistent and well-balanced sound quality.
To pass line-up tones transparently, recall OPTIMOD-PC's P
sary, adjust its gain and save your edited preset as a User Preset.
These tones should be injected into the transmitter after OPTIMOD-PC, or
OPTIMOD-PC should be temporarily switched to P
Alternatively, you can you can bypass OPTIMOD-PC's processing of the tones by
patching OPTIMOD-PC's digital output into one of its digital inputs. This leaves you
with one analog or one digital input into which you can connect the unprocessed
audio. Use the remaining unused input to receive the output of the tone generator.
Use the Direct mixer to mix the tone generator and processed signal as desired. In
OPTIMOD-PC's Output Levels tab (in the I/O mixer), assign to the Direct Mixer the
OPTIMOD-PC output driving your target system.
This scenario is particularly practical if the final output of the system is a
WAVE stream. Otherwise, the only remaining available output is the ana-
log output. Of course, you can reverse the scenario by using the
OPTIMOD-PC analog output and input for the loop-through connection,
in which case the final mixed output could be the digital output.
OPTIMOD-PC is a complex processor that can be adjusted for many different tastes.
For most users, the factory presets, as augmented by the gamut offered by the L
control for each preset, are sufficient to find a satisfactory "sound." However,
M
ORE
control can cause this problem. It can also be
AIN
L
INAL IMIT
mode. Sine waves have a very low peak-to-average ratio
ORBAN MODEL 1101
(Band 5 Compression
HRESHOLD
D control (page 3-40) until the
RIVE
preset. If neces-
ROTECT
to pass the tones.
ROTECT
-
ESS