6800/7000 Series - Audio and Video Multi/Demultiplexing Products Installation and Operation Manual
17
Operation
Chapter 2: ADC-6880 Analog to AES/EBU Digital Audio Converter
Operation
Analog Audio Input
The ADC-6880 has two balanced audio input channels that are typically
used for stereo audio inputs (left and right). The audio input stage
processes the analog audio signal prior to its conversion to a digital
signal. In order to accommodate various nominal analog audio levels,
each input channel has a selectable attenuator that allows the full-scale
digital output level (0 dBFS) to correspond to the user’s maximum audio
signal level. The attenuator can be set in 2 dB increments from +16 dBu
to +30 dBu. The factory default setting is +28 dBu.
Gain can be adjusted on each channel over a ± 2 dB range. The gain
adjustments are set at the factory from a high-precision audio test
reference signal such that the full-scale digital output level (0 dBFS)
corresponds precisely with the calibrated selectable attenuator positions
of +16 dBu to +30 dBu (described above). The gain can be adjusted by
the user to match specific level requirements for full-scale digital audio
signal levels.
In addition to performing audio-level attenuation, the analog input stage
allows the analog audio inputs to be AC- or DC-coupled. The factory
default is AC-coupled, and this is the recommended mode of operation.
If the ADC-6880 is set to DC-coupled, any DC signal present on the
analog audio input signals will be a source of error in the A-to-D
conversion. The analog input stage rejects common mode signals that
may be present on the audio input signals and provides over-voltage
protection for the A-to-D converter.
See
“Configuration”, on page 19 for detailed information on attenuation/
gain setting and AC/DC-coupled selection.
