Orban OPTIMOD 6300, Руководство по эксплуатации

Страница: 202 / 255

5-2
TROUBLESHOOTING ORBAN MODEL 6300
Verify that the source material at the 6300's audio inputs is clean. Heavy processing
can exaggerate even slightly distorted material, pushing it over the edge into unac-
ceptability.
The subjective adjustments available to the user have enough range to cause audi-
ble distortion at their extreme settings. Advancing the
F
INAL
L
IMT
control too far will
invariably cause distortion. Setting the L
ESS
-M
ORE
control beyond “9” can cause au-
dible distortion of some program material with all but the Classical and Protect pre-
sets.
If you are using analog inputs, the peak input level must not 27 dBu or the
6300's A/D converter will clip and distort.
Unlike earlier digital Optimods, there is no input peak clipping level ad-
justment for the A/D converter. Instead, we have provided adequate
headroom for virtually any facility. This is possible because the A/D con-
verter in the 6300 has higher dynamic range than older designs. Without
compromising the 6300’s noise level, we could thus eliminate a control
that was frequently misadjusted.
If you are using an external processor ahead of the 6300, be sure it is not clipping or
otherwise causing problems.
Audible Noise
(See also “RFI, Hums, Clicks, or Buzzes” on page 5-1.)
Excessive compression will always exaggerate noise in the source material. The 6300
has two systems that fight this problem. The
silence gate freezes the gain of the
AGC and compressor systems whenever the input noise drops below a level set by
the threshold control for the processing section in question, preventing noise below
this level from being further increased.
There are two independent silence gate circuits in the 6300. The first affects the AGC
and the second affects the Multiband Compressor. Each has its own threshold con-
trol. (See
M
B
G
ATE
on page 3-50.)
In sound for picture, the setting of the
G
ATE
T
HRESHOLD
control is quite critical if you
want the processing to be undetectable to the audience. If this control is set too
low, then the 6300 will pump up quiet sounds such as ambiance and underscoring to
unnaturally high levels. Refer to Section 3 of this manual for a further discussion.
In the 5-band Structure, dynamic single-ended noise reduction (see D
WNEXP
T
HR
on
page 3-52) can be used to reduce the level of the noise below the level at which it
appears at the input.
If you are using the 6300's analog input, the overall noise performance of the sys-
tem is usually limited by the overload-to-noise ratio of the analog-to-digital con-
verter used by the 6300 to digitize the input. (This ratio is better than 108 dB.) It is
important to drive the 6300 with professional levels (more than 0 dBu reference
level) to achieve adequately low noise. (Clipping occurs at +27 dBu.)