Manual

Chapter 8 - RB-DMA2 Dual Digital Microphone Amplifier
Redbox User Handbook 8-1
8. RB-DMA2 Dual Digital Microphone
Amplifier
Fig 8-1: RB-DMA2 Front Panel
8.1. Introduction
The RB-DMA2 consists of two independent low-noise microphone pre-amplifiers for
converting microphone level signals to digital AES/EBU, or S/PDIF, and analogue line
level outputs. The RB-DMA2 can be used as a front end for digital mixing desks or
routers, which do not have microphone inputs. The analogue outputs can be used for
routing to talkback systems.
The microphone inputs are XLR-3 type and are electronically balanced. The input gain
for each input can be adjusted individually by coarse and fine gain controls on the
front panel and each input has a level indicator. Additionally the fine gain control knob
can be disabled by internal jumpers. A switch on the rear panel allows input 1 to be
routed to both left and right digital outputs, or as input 1 to left output and input 2 to
right output respectively.
For each channel there are independent switches to control a high pass filter (low
frequency roll-off at 125Hz) and to provide phantom power at +48V to the connected
microphones. It also has AES/EBU, S/PDIF and Word Clock sync inputs.
The unit operates in four modes:
Master Mode - In this mode the unit receives a microphone-input
signal, which is digitised and formatted for digital serial
transmission (IEC958). The necessary clock signals are generated
internally from an on board master clock at a selectable rate
(32kHz, 44.1kHz, 48kHz, 64kHz, 88.2kHz or 96kHz).
Slave Mode - In this mode the unit automatically detects the presence of a digital
audio sync signal, if present at the digital input or word clock input, and synchronises
the digital output to it. If no sync is present, no output will be generated.
Auto Mode - Here the unit synchronises to the digital audio sync signal if present at
the digital input and uses the internal master clock only if no sync input signal is
detected. In this case, the internal master clock is used at the selected sample rate.
RB-DMA2
DIGITAL MICROPH ONE AMPLIFIER
LEVEL 1
LEVEL 2
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