Redbox User Handbook No 1
5
DIGIT
AL A
UDIO C
ONVERTERS - RB
-ADD
A
Status Select Switches
These switches are used to determine the status or content of the digital signals.
The type of information encoded in the channel status bits of a digital audio signal can be
professional or consumer and is determined by switch 1.
If de-emphasis is selected (switch 2) the RB-ADDA will decode 50/15µs emphasis when
indicated by certain channel status bits in the incoming digital audio data.
The sample size for the analog to digital conversion can be set to 24, 20 or 16 bits (switch 3
& 4). When the signal is truncated from 24 bits, a psycho-acoustic filter is applied to maintain
optimum signal quality. These settings are summarised by the table in Fig 1-5, which is also
shown on the top panel of the unit.
Status
Bits
1
ON Professional
16
20
24
1
OFF Consumer
3
OFF
OFF
ON
2
ON De-emphasis On
4
OFF
ON
ON
2
OFF De-emphasis Off
Fig 1-5: RB-ADDA Status Select Switches
Digital Select Buttons
These buttons are used to switch the digital connection between the AES/EBU XLR
connector (button out) and the S/PDIF phono connector (button in) for the digital input and
the digital output.
Analogue Select Button
This button is used to switch the Analogue input between the balanced XLR connector
(button out) and the unbalanced phono connector (button in).
Frequency and Sync Mode Rotary Switch
This rotary switch is used to select the Synchronisation Mode and to select the frequency
of the digital output when using the on-board clock generator. There are 4 modes of
operation: - Master Mode, Auto Sync Mode, Auto Lock Sync Mode & Slave Mode.
In
Master Sync Mode
, switch positions 0 – 5, the digital output sample rate is simply set by,
and locked to, the internal on-board clock generator. No sync signal is used or required.
In
Auto Sync Mode
, switch positions 6– B, the digital output sample rate follows the digital
input. When the digital input signal is not present the output sample rate will be set by,
and locked to, the internal on-board clock generator at a frequency determined by the
switch position.
In
Auto-Lock Sync Mode
, switch position C, No output will be generated until lock is
achieved with a digital input signal. The digital output sample rate now follows the digital
input. If the digital input signal is removed then the output sample rate will be set by, and
locked to, the internal on-board clock generator at the closest frequency available to the
previous digital input.
DIGITAL AUDIO CONVERTERS
1