OPTIMOD-PC INTRODUCTION
1-15
Analog Left/Right Input/Output
The left and right analog inputs are on XLR-type female connectors on the umbilical
cable. Input impedance is greater than 10k
Ω
; balanced and floating. Inputs can ac-
commodate up to +20dBu (0dBu = 0.775Vrms).
The left and right analog outputs are on XLR-type male connectors on the umbilical
cable. Output impedance is 50
Ω
, balanced and floating.
The outputs are intended for monitoring. They can drive 600
Ω
or higher imped-
ances. However, they are AC-coupled with a –3dB frequency of approximately 1 Hz,
which is higher than the 0.15 Hz recommended by Orban to avoid low-frequency
overshoots (“bounce”) caused by phase shifts. Therefore, when you are using the
audio processing for peak control, such control will be noticeably poorer at the ana-
log outputs than at the AES3 or WAVE outputs, both of which exhibit very tight
peak control. Consequently, you should always use OPTIMOD-PC’s AES3 or WAVE
outputs to drive your transmission chain.
For a more detailed diagram of the “Processor” block, see
Figure 3-2: Simplified
OPTIMOD-PC Digital Signal Processing Diagram
on page 3-9.
The Orban I/O Mixer
The I/O Mixer mixes and routes audio to and from the OPTIMOD-PC card.
(See
Figure 1-4: OPTIMOD-PC Signal Flow and I/O
on page 1-13, and
Figure 1-5: Typi-
cal I/O mixer
on page 1-16.) You can open the Optimod PC Mixer from the Tools
menu in the Orban Control application.
Within the Optimod PC Mixer, there are two mixers, each of which receives the same
four inputs:
•
The stereo analog input on the DB-25 connector
•
Digital 1 Input(AES3) on the DB-25 connector
•
Digital 2 Input (AES3) on the DB-25 connector
•
The WAVE Out from the computer operating system’s internal mixing and rout-
ing
The first “Processor Mixer” sends its output to the audio processing DSP on the
OPTIMOD-PC card.
The second “Direct Mixer” sends its output directly to the output routing switcher.
There are three outputs, each of which can receive the following four possible
sources:
•
The
Direct WAVE
bitstream
received from the computer.
