Orban OPTIMOD-PC 1100, Руководство по эксплуатации

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OPTIMOD-PC INSTALLATION
2-39
I get clicks in the 1100’s WAVE output.
Wrap-around glitches can occur at the peaks of OPTIMOD-PC’s processed output
when you are recording or streaming it via the Windows WAVE mechanism at sam-
ple rates other than 48 kHz and OPTIMOD-PC’s WAVE output level is set to 0 dBfs.
We believe that overshoots in the computer’s WAVE sample rate converter cause
this; it is not caused by OPTIMOD-PC’s DSP. To prevent such glitches, set the 1100’s
WAVE output level lower than –0.5 dBfs for 44.1 kHz recording/streaming and lower
than –1.0 dBfs for 32 kHz recording/streaming.
The 1100’s hardware outputs do not have this issue.
I am running Windows 2003 and I cannot get audio to pass through OPTIMOD-PC’s
WAVE inputs and outputs.
See Enabling the Windows 2003 Server Audio Service on page 2-36.
Meters on Optimod-PC Control Application freeze temporarily but audio continues
to be processed normally.
This is by design. The software thread controlling the meters is given lower than
“normal” priority in Windows to prevent the meters from interrupting important
threads that maintain audio continuity through the Windows WAVE mechanism.
RFI, hum, clicks, or buzzes
A grounding problem is likely. Review the information on grounding on page 2-18.
OPTIMOD-PC has been designed with substantial RFI suppression on its analog and
digital input and output ports. It will usually operate adjacent to high-powered
transmitters without difficulty. In the most unusual circumstances, it may be neces-
sary to reposition the host computer to reduce RF interference, and/or to reposition
OPTIMOD-PC’s input and output cables to reduce RF pickup on their shields.
The AES3 inputs and output are transformer-coupled and have good resistance to
RFI. If you have RFI problems and are using analog connections on either the input
or output, using digital connections will probably eliminate the RFI.
Poor peak level control
OPTIMOD-PC audio processing ordinarily controls its output peak levels to an accu-
racy of ±2% when operated with 48 kHz output sample rate. As explained in the
note on page 1-24, output sample rate conversion will slightly compromise this con-
trol because the peak control occurs with reference to individual sample values at 48
kHz. The converted samples no longer have the same peak values as the 48 kHz
samples, and some values can be slightly higher. However, the overshoot of the con-
verted signal almost 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 or encoder are not synchronous with the peak-controlled
samples in OPTIMOD-PC. Further, analog connections can cause analog-domain
overshoot if the connection is not phase linear and has a low-frequency cutoff of
greater than 0.15Hz (at –3dB).
Audible distortion
Make sure that the problem can be observed on more than one sound system and at
several locations.