Section 5 Troubleshooting; Problems And Potential Solutions; Rfi, Hum, Clicks, Or Buzzes; Poor Peak Modulation Control - Orban OPTIMOD 6300 Operating Manual

OPTIMOD 6300 DIGITAL
Section 5
Troubleshooting

Problems and Potential Solutions

Always verify that the problem is not the source material being fed to the 6300, or
in other parts of the system.

RFI, Hum, Clicks, or Buzzes

For good RFI resistance, always use balanced inputs and outputs.
Review the information on grounding on page 2-7. The 6300 has been designed
with very substantial RFI suppression on its analog and digital input and output
ports, and on the AC line input. It will usually operate adjacent to high-powered
transmitters without difficulty. In the most unusual circumstances, it may be neces-
sary to reposition the unit to reduce RF interference, and/or to reposition its input
and output cables to reduce RF pickup on their shields.
The AES/EBU inputs and output are transformer-coupled and have very good resis-
tance to RFI. If you have RFI problems and are using analog connections on either
the input or output, using digital connections will almost certainly eliminate the RFI.

Poor Peak Modulation Control

The 6300 ordinarily controls peak modulation to an accuracy of ±1% when operated
with 48 or 96 kHz output sample rate. As explained in Section 1, output sample rate
conversion will slightly compromise this control because the peak control occurs
with reference to individual sample values at 192 kHz. The converted samples no
longer have the same peak values as the 192 kHz samples; some values can be
slightly higher. However, the overshoot of the converted signal never exceeds 0.5dB
and is therefore not a significant problem.
Using the analog output will cause similar amounts of overshoot because the sam-
ples in the transmitter are not synchronous with the peak-controlled samples in the
6300. Further, analog connections can cause analog-domain overshoot if the connec-
tion is not phase linear and has a –3dB low-frequency cutoff of greater than 0.15Hz.
A lossy codec (like Dolby AC3) will always introduce some peak overshoot. You can
compensate for this without compromising the 6300's loudness control calibration
by turning down the 100% O
Diagram of Dialnorm Control on page 1-2.
L
UTPUT EVEL control. See Figure 1-1: Simplified Block
TROUBLESHOOTING
5-1