GRASS VALLEY 8920ADC -, Instruction Manual

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8920ADC Instruction Manual 15
Configuration
There are three ways to adjust the onboard gain toggle switches to the
proper level:
• Apply the maximum level to the input (e24 dBu) and monitor
the AES output with a meter that indicates digital level in dBFS and
adjust the toggle switch for each channel until the meter indicates
0.0 dBFS.
Because the toggle 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 audio level that is -20 dB below the maximum level, (+4 dBu
for the example, +24 dBu -20 dB = +4 dBu) and adjust the AES output
as indicated on a digital audio meter to -20 dBFS.
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 indication while monitoring the AES output and
switch back to 0 or F position on the Function Switch, then adjust the
gain toggle switch to the same level as the internal tone level.
• Apply the maximum level to the input (e24 dBu) and adjust
the gain toggle switch for each channel until the clip LED comes on.
This is -0.5 dBFS, and by tapping the toggle switch four more times you
will be within 0.15 dB (worst case) of the correct gain setting.
CAUTION Using a maximum level that is larger than the high end of the range setting
jumper will result in a clipped waveform and high distortion. Use the next
higher jumper setting that includes the maximum level and readjust the gain
following the instructions above.