Grass Valley NV5128 v.2.5 - Manual (Page 35)

NV5128 Multi-Format Router • User’s Guide 25
2. Introduction
Active Cards
Figure 2-19 shows the signal path through the SRC.
Figure 2-19. Signal Flow through SRC Card
Analog Audio
Incoming and outgoing analog audio signals are received or distributed through four DB25 connec-
tors, housed on a backplane. (See
Backplanes on page 13.)
The analog audio input card and output card feature DIP switches and a jumper that allow gain and
mute detection to be set. (See
Analog Audio Switches on page 69.) In addition, using a separate
DIP switch set, the operating level of the card can be set to match the operating level of the facility.
By matching the incoming signal level, there is less degradation of the signal when it is converted
to digital for internal routing in the router. For information on setting analog input card levels, see
Analog Audio Switches on page 69.
Input Card
The analog audio input card ( EM0585 ) receives up to 16 stereo signals (32 mono channels) through
passive backplane I/O connectors. Inputs are forwarded to an analog-to-digital (A/D) converter.
The A/D converter accepts two analog signals, either left and right channels of a stereo pair or two
mono channels. The A/D converter is rate locked to the systems clock on the control card, convert-
ing the signals to a sample rate of 48
kHz and into AES compatible bit streams containing the sam-
pled data. The audio data is set to a common sample point, which is important for proper phase
alignment of audio signals. The resulting synchronous AES signals are sent to the motherboard.
Output
The analog audio output card (EM0586) receives 128 stereo inputs from the motherboard. The sig-
nals are then sent to a crosspoint array of 128 inputs x 16 outputs (256 inputs x 32 outputs mono)
for switching and then on to a digital-to-analog (D/A) converter which converts the signal from
digital format to analog. From the D/A converters, the analog signals have low-pass filtering and
gain correction applied and then forwarded to output cable drivers and backplane I/O connectors
for distribution.
I/O
Connectors (up to 16)
AES
Rec’r
Input Card
Transformer
Coupled
Motherboard
I/O
Connectors (up to 16)
Control Card
SRC
Timing
Control and
AES3
Encoder
Reference Clock Signal
Channel Status Bits
Note The analog audio output card is designed to function in a voltage-matched system
driving high impedance loads. The output drivers are not designed to drive 600
Ω
loads continuously and may overheat if used in a 600 Ω environment.