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Rear Panel Controls
Status Select Switches
These switches are used to determine the status or content of the digital output 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. However at frame rates higher
than 48kHz, consumer mode is not available, so professional mode is used and this switch
will be ignored.
The sample size for the analogue to digital conversion can be set to 24, 20 or 16 bits
(switches 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 below and also on the
top panel of the unit.
Status
1
ON
Professional
1
OFF Consumer
2
ON
Dual Mono
2
OFF Mono
Fig 6-6: RB-DMA2 Status Select Switches.
Output Routing
This uses switch 2 of the STATUS dipswitch block. When switch 2 is "ON", the audio signal
from Mic input 1 is copied to both channels of the digital output signal (channel B = channel
A) and Mic input 2 is ignored (Dual mono mode). When "OFF", the Mic input 1 signal is on
channel A only of the digital output signal and channel B contains the Mic input 2 signal
(Mono mode).
Note: This does not affect the routing of the analogue outputs.
Phantom Power & LF Filter
For each channel there are independent switches to provide phantom power at +48V to the
connected microphones. With phantom power selected, a voltage of +48V is applied to pins
2 and 3 of the XLR connector to power the microphone, supplied through 6k8
resistors giving a current of 14mA. Phantom power is used when the switches are
towards the arrows.
The LF filter switches provide control for a high pass filter with low frequency roll off at
125Hz. The roll-off filters are switched "in" when the switches are in the down position
(towards the arrows).
Redbox User Handbook No 3
MICROPHONE AMPLIFIERS
Bits
16
20
3
OFF
ON
4
OFF
OFF
& LI MI TE R S
24
ON
ON
6
39
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