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RB-ADDA Combined A/D and D/A Converter
Introduction
Fig 1-1: RB-ADDA Front Panel
Using 24 bit, 96kHz capable devices, the RB-ADDA A/D and D/A Converter is a 1U rack-
mount which produces an AES/EBU or S/PDIF level digital audio output from a balanced XLR
or unbalanced phono stereo audio input. The unit also produces a stereo balanced XLR or
unbalanced phono output from an incoming AES/EBU or S/PDIF digital input signal.
The unit operates in four modes:
Master Mode - In this mode the unit receives an analogue audio 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, 88.1kHz 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, 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.
Auto Lock Mode - This operates like the auto mode. The difference is that if the sync input
signal is lost, the unit will revert to an internal master clock rate as near as possible to the
last sync signal received.
When operating in sync modes, the front panel power LED flashes whenever the unit is not
synchronised to the incoming digital signal, or when the unit is being calibrated. The RB-
ADDA should be calibrated once it has been powered up for more than 10 minutes.
The analogue inputs have left and right level controls using pre-set potentiometers and
DIP switches allowing a signal range from +9dBu to +27dBu. The analogue outputs have
an output level control, allowing full-scale settings selectable from +12dBu, +18dBu or
+24dBu. There are factory-set internal level controls for the analogue outputs allowing gain
adjustment of ±1dB.
There are buttons to select either the AES/EBU or S/PDIF input or output for the D/A and
A/D sections respectively. The output bit depth can be selected from 16, 20 or 24 bits.
Inputs of a different bit depth to the output are dithered using a psychoacoustic noise filter.
Redbox User Handbook No 1
DIGITAL AUD I O CO N VE RTE R S
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Summary of Contents for Sonifex RB-ADDA
- Page 1 Introduction Fig 1-1: RB-ADDA Front Panel Using 24 bit, 96kHz capable devices, the RB-ADDA A/D and D/A Converter is a 1U rack- mount which produces an AES/EBU or S/PDIF level digital audio output from a balanced XLR or unbalanced phono stereo audio input. The unit also produces a stereo balanced XLR or unbalanced phono output from an incoming AES/EBU or S/PDIF digital input signal.
- Page 2 The channel status bits can be set to either Professional or Consumer Mode. System Block Diagram Fig 1-2: RB-ADDA System Block Diagram Front Panel Indicators The LED on the front panel is normally red to indicate that power is present on the unit.
- Page 3 DIGITAL AUD I O CO N VE RTE R S RB-ADDA Inputs XLR Analogue Inputs (Left and Right) The XLR 3 pin sockets used for the left and right channel inputs are electronically balanced and have an impedance of greater than 10kΩ bridging. Each XLR has the following connections: Pin 1: Screen.
- Page 4 The full-scale dB settings can be set for signals of +12, +18, +24 dBu to give full-scale digits in the digital domain. Analogue (A/D) Switch 1 Switch 2 Input Full Scale Setting (dBu) Analogue (D/A) Switch 3 Switch 4 Output Full Scale Setting (dBu) Fig 1-4: RB-ADDA Full Scale dB Settings Redbox User Handbook No 1...
- Page 5 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.
- Page 6 Fig 1-6: RB-ADDA Frequency and Sync Rotary Switch Test/Calibration Mode For optimum performance of the RB-ADDA, the unit should be calibrated when it has been powered up for approximately 10-15 minutes. The circuitry and chipsets contained in the unit will warm up during this time and the performance will deteriorate unless calibrated (the noise floor and dynamic range will be 1-2dB down on their best).
- Page 7 DIGITAL AUD I O CO N VE RTE R S Technical Specifications RB-ADDA A/D Connections Analogue Inputs: 2 x XLR 3 pin (balanced) (L & R) 2 x RCA phono (unbalanced) (L & R) Digital Outputs: 1 x AES/EBU XLR 3 pin plug...
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