Sonifex RB-ADDA A/D and D/A Converter

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Product Information

Sonifex RB-ADDA A/D and D/A Converter

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.

It 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, 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, 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 except that if no sync input signal is detected, it will use the internal master clock to sync to the sample rate which was last clocked to.

When operating in sync modes, the front panel power LED flashes whenever the unit is not synchronised to the incoming digital signal.

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 RCA phono inputs have a further 10dBu gain incorporated to give a total gain range of -1dBu to +17dBu for full-scale digits.

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.

For the digital output, there is a switch available to define the content of the channel status bits embedded within the digital audio stream.

The channel status bits will be forced to Professional Mode for sample rates above 48kHz as they are not supported by the Consumer Mode. For sample rates of 32kHz, 44.1kHz and 48kHz, the status bits can be forced to either Professional or Consumer Mode. 


  • Rack mounted
  • Maximum Input Level +27dBu balanced inputs, +17dBu unbalanced inputs
  • Input Impedance >10kohms unbalanced, >20kohms bridging unbalanced
  • Dynamic Range >110dB
  • Gain Range Adjustable input gain of +/-3dB on 12dBu, 18dBu or 24dBu, ref FSD
  • Distortion and Noise >96dB THD + N at 1kHz
  • A/D Connections
  • Analogue Inputs 2 x XLR 3 pin (balanced)
  • 2 x RCA phono (unbalanced)
  • Digital Outputs 1 x AES/EBU XLR 3 pin male
  • 1 x S/PDIF RCA phono
  • Mains Input Filtered IEC, switchable 110-120V, or 220-240V, fused, 10W max
  • Analogue to Digital Conversion
  • D/A Audio Specification
  • Maximum Output Level +24dBu balanced inputs, +14dBu unbalanced inputs
  • Output Impedance 100dB
  • Gain Range Selectable 12dBu, 18dBu or 24dBu output level, ref FSD
  • D/A Connections
  • Digital Inputs 1 x AES/EBU XLR 3 pin female
  • 1 x S/PDIF RCA phono
  • Analogue Outputs 2 x XLR 3 pin male (balanced)
  • 2 x RCA phono (unbalanced)

Operational Controls

  • Analogue Input Select XLR or phono, via push-switch
  • Digital Output Select AES/EBU or S/PDIF, via push-switch
  • Digital Input Select AES/EBU or S/PDIF, via push-switch
  • De-emphasis On/Off DIP switch
  • Input Level Adjust DIP switch and preset pots
  • Bit Depth 16, 20 or 24 bits via DIP switch
  • Modes & Frequencies 16 way rotary DIP switch
  • Channel Status Bits Forced to consumer mode or professional mode, via DIP switch
  • Output Level Adjust DIP switch

Physical Specification

  • Weight Nett: 1.6kg
  • Gross: 2.2kg
  • Dimensions Raw: 48cm (W) x 10.8cm (D) x 4.2cm (H) (1U)
  • Boxed: 53cm (W) x 20.5cm (D) x 6cm (H)