Grass Valley 8920ADT - Manual (Page 17)

8920ADT Instruction Manual 11
Configuration
Input Level Adjustments
The maximum signal level of the analog input must be set for full-scale
digital outputs (0 dBFS) on the left and right channels. Fine and coarse gain
controls are tied together so that the gain changes in a continuous fashion
with the paddle switch.
To adjust input levels, use the paddle switch (SW 3) on the front of the
module and set the Control rotary switch (SW 1) to the position given in
Table 6 on page 10 to adjust both channels together, or the left and right
channels individually.
Set the Mode Rotary Switch at the front of the module to the Default posi-
tion marked 0 as shown at left. The Default position will put each channel
output into a normal mode with no phase inversion, channel swapping or
summing.
To correctly adjust the 8920ADT for your digital application, determine
your maximum signal level (MSL). This is the level above which digital
clipping occurs. This module has been set up at the factory with a
maximum signal level default value of +24 dBu = 0 dBFS.
Note The paddle switch changes input levels by increments of approximately
0.1 dB when held momentarily. Holding the switch up or down for about 1
second activates a continuous change mode that ramps the change rate from
about 0.1 dB per second to 0.6 dB per second. The yellow CONF LED will
flash slow (0.1 dB rate) or fast (0.6 dB rate) to indicate the change rate.
There are three ways to adjust the paddle switch for the proper level:
■ Apply the maximum signal level for your device to the analog input
and monitor the AES output with a meter that indicates digital level in
dBFS. Adjust the paddle switch for each channel until the meter indi-
cates 0.0 dBFS.
Note Because the paddle switches have a resolution of 0.1 dB, you may not be able
reach 0.0 dBFS exactly. Use the closest negative setting possible.
■ Apply an input audio level that is -20 dB below the maximum level,
(+4 dBu for the default, +24 dBu -20 dB = +4 dBu) and adjust the AES
output as indicated on a digital audio meter to -20 dBFS.
Note If you have no meters calibrated in dBFS you can use the tone output position
to compare with the output level. Tone output is position E on the Function
Switch and outputs a 1 kHz tone at -20 dBFS. Note the internal tone level indi-
cation while monitoring the AES output and switch back to 0 or F position on
the Function Switch, then adjust the gain paddle switch to the same level as the
internal tone level.
012
34
5
67
89AB
C
D
EF
Default
Position