Handbook

Table Of Contents
Redbox User Handbook No 3
39
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 lter is applied
to maintain optimum signal quality. These settings are summarised below and also on the
top panel of the unit.
Status Bits
1 ON Professional 16 20 24
1 OFF Consumer 3 OFF ON ON
2 ON Dual Mono 4 OFF OFF ON
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 aect 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 lter switches provide control for a high pass lter with low frequency roll o at
125Hz. The roll-o lters are switched “in when the switches are in the down position
(towards the arrows).
MICROP HONE AMPLIF IERS
& LIMITERS
MICROPHONE AMPLIFIERS & LIMITERS - RB-DMA2
6