Orban OPTIMOD 8400 - Shrill, Harsh Sound; Dull Sound; System Will Not Pass Line-Up Tones at 100% Modulation; System Will Not Pass Emergency Alert System (“EAS” USA Standard) Tones at the Legally Required Modulation Level

5-6
TROUBLESHOOTING Orban Model 8400
Shrill, Harsh Sound
If you are using the Multi-Band structure, this problem can be caused by excessive HF
boost in the HF Equalizer and HF Enhancer. It could also be caused by an excessively
high setting of the
BAND 4 THRESH control, or by excessively high settings of the
BAND 4 MIX and BAND 5 MIX controls (located in Intermediate and Advanced Modify).
If you are driving an external stereo encoder with built-in pre-emphasis, you must set the
8400’s output to
FLAT in the System Setup/Output screen to prevent double pre-
emphasis, which will cause very shrill sound (and very poor peak modulation control).
You will always achieve better peak control by defeating the pre-emphasis
and input filters of an external stereo encoder, permitting the 8400 to per-
form these functions without overshoot. Section 1 of this manual contains a
detailed explanation of these, and other, system design considerations.
Dull Sound
If you are using the Two-Band structure, dull-sounding source material will sound dull
on the air. The Multi-Band structure will automatically re-equalize such dull-sounding
program material to make its spectral balance more consistent with other program mate-
rial.
If the 8400’s output is set to
FLAT in System Setup/Output, there will be no pre-emphasis
unless it is supplied somewhere else in the system. This will cause very dull sound.
System Will Not Pass Line-Up Tones at 100% Modulation
This is normal. Sine waves have a very low peak-to-average ratio by comparison to pro-
gram material. The processing thus automatically reduces their peak level to bring their
average level closer to program material, promoting a more consistent and well-balanced
sound quality.
The 8400 can generate test tones itself. The 8400 can also be put into Bypass mode (lo-
cally or by remote control) to enable it to pass externally generated tones at any desired
level. See page 3-??.
System Will Not Pass Emergency Alert System (“EAS” USA Standard)
Tones at the Legally Required Modulation Level
See “System Will Not Pass Line-Up Tones at 100% Modulation” (directly above) for an
explanation. These tones should be injected into the transmitter after the 8400, or the
8400 should be temporarily switched to
bypass to pass the tones.