Orban OPTIMOD-FM 8600Si, Operating Manual

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OPTIMOD-FM DIGITAL OPERATION
3-65
Ordinarily, the gating on the AGC and multiband limiter will prevent objectionable
build-up of noise and you will want to use the single-ended noise reduction only on
unusually noisy program material. Modern commercial recordings will almost never
need it. We expect that its main use will be in talk-oriented programming, including
sports.
Please note that it is impossible to design such a system to handle all program mate-
rial without audible side effects. You will get best results if you set the
MB D
OWN
E
XPANDER control of the noise reduction system to complement the program mate-
rial you are processing. The
MB D
OWN
E
XPANDER should be set higher when the input
is noisy and lower when the input is relatively quiet. The best way to adjust the
MB
D
OWN
E
XPANDER control is to start with the control set very high. Reduce the control
setting while watching the gain reduction meters. Eventually, you will see the gain
increase in sync with the program. Go further until you begin to hear noise modula-
tion—a puffing or breathing sound (the input noise) in sync with the input program
material. Set the
MB D
OWN
E
XPANDER control higher until you can no longer hear the
noise modulation. This is the best setting.
Obviously, the correct setting will be different for a sporting event than for classical
music. It may be wise to define several presets with different settings of the
MB
D
OWN
E
XPANDER control and to recall the preset that complements the program ma-
terial of the moment.
Note also that it is virtually impossible to achieve undetectable dynamic noise reduc-
tion of program material that is extremely noisy to begin with, because the program
never masks the noise. It is probably wiser to defeat the dynamic noise reduction
with this sort of material (traffic reports from helicopters and the like) to avoid ob-
jectionable side effects. You must let your ears guide you.
Band 5 is particularly critical for noise reduction because much of the Downward Ex-
pander’s utility lies in hiss reduction. Hiss has most of its energy in band 5, while pro-
gram material typically has less energy in this band, so the
B5 D
OWN
E
XPANDER
D
ELTA
T
HRESHOLD control’s setting is critical to removing hiss while minimizing removal of
desired program energy.
Starting in V2.0, the Downward Expander’s dynamic frequency response is no longer
constrained to being strictly lowpass—Band 5 is now uncoupled from the lower
bands, so the band 5 downward expander can produce less gain reduction than oth-
er bands. This can help prevent loss of desired high frequency material in the pro-
gram.
Band 3 > 4 Coupling control determines the extent to which the gain of band 4
and 5 (centered at 3.7 kHz) is determined by and follows the gain of band 3 (cen-
tered at 1 kHz). Set towards 100% (fully coupled) it reduces the amount of dynamic
upper midrange boost, preventing unnatural upper midrange boost in light pop and
instrumental formats.
Band 4 > 5 Coupling control extent to which the gain of band 5 (6.2 kHz and
above) is determined by and follows the gain of band 4.