Sonifex RB-ADDA User Handbook Manual

Redbox User Handbook No 1

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DIGITAL AUDIO CONVERTERS

1 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 rack­mount 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 dierence 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 ashes whenever the unit is not
synchronised to the incoming digital signal, or when the unit is being calibrated. The RB­ADDA 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 dierent bit depth to the output are dithered using a psychoacoustic noise lter.

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For the digital output, there is a switch available to dene the content of the channel status
bits embedded within the digital audio stream. 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.
However, it also has a secondary role to indicate the status of the digital inputs

Fast ashing between red and amber – indicates a loss of digital input signal or that the unit
is being calibrated.

Rear Panel Connections and Operation

RCA Phono

Inputs

RCA Phono

Outputs

AES/EBU

Input

S/PDIF
Input &
Output

Frequency & Synch

Mode Rotary Switch

DIGITAL AUDIO CONVERTERS - RB-ADDA

XLR Analogue

Inputs

Fig 1-3: RB-ADDA Rear Panel

XLR Analogue

Outputs

Digital Select

Button

AES/EBU

Output

Digital Select

Status Select

Switches

Button

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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.
Pin 2: Phase.
Pin 3: Non-phase.

RCA Phono Inputs (Left and Right)

The two left and right RCA inputs are unbalanced and have an impedance of greater
than 20kΩ.

Input Level Adjustment

The input gain can be individually adjusted for left and right channels by dipswitches and
through pre-set potentiometers accessible on the rear panel. For full scale dB settings refer
to Fig 1-4.

Individual preset pots give a further ± 3dBu to give a total gain range of +9dBu to +27dBu
for full-scale digits. The consumer input on the phono connector has a further 10dbU gain
incorporated to give a total gain range of -1dBu to +17dBu for full-scale digits.

AES/EBU Inputs

The digital input XLR 3 pin socket has an impedance of 110 Ω. It has the following
connections:
Pin 1: Screen
Pin 2: Phase
Pin 3: Non-phase

The signals on this connector should meet the IEC 60968 specication

S/PDIF Inputs

The S/PDIF digital phono inputs have an impedance of 75Ω.

RB-ADDA Outputs

Analogue Outputs (Left and Right)

The XLR 3 pin output plug connectors are electronically balanced with an output
impedance of less than 50Ω. They have the following connections:
Pin 1: Screen.
Pin 2: Phase.
Pin 3: Non-phase.

RCA Phono Outputs (Left and Right)

These RCA (phono) outputs are unbalanced and have an output impedance of less
than 75Ω.

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Output Level Adjustment

The output gain can be individually adjusted for left and right channels through the rear
panel by dipswitches. Each output gain can be set for a signal of full-scale digits in the
digital domain to give +12, +18 or +24dBu output on the XLR connectors (see Fig 1-4).
The consumer output on the phono connector has a further 10dbU attenuation
incorporated.

AES/EBU Output

The digital output XLR 3 pin socket has an impedance of 110Ω. It has the following
connections:
Pin 1: Screen
Pin 2: Phase
Pin 3: Non-phase

The signals on this connector will comply with the IEC 60968 specication

S/PDIF Output

The digital output S/PDIF phono output has an impedance of 75Ω.

Rear Panel Controls

Full Scale dB Settings

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)
Input Full Scale

Setting (dBu)

+12 OFF OFF

+18 ON OFF

+24 ON ON

Analogue (D/A)

Output Full Scale

DIGITAL AUDIO CONVERTERS - RB-ADDA

Setting (dBu)

+12 OFF OFF

+18 ON OFF

+24 ON ON

Fig 1-4: RB-ADDA Full Scale dB Settings

Switch 1 Switch 2

Switch 3 Switch 4

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Status Select Switches

These switches are used to determine the status or content of the digital 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.

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.

The sample size for the analog to digital conversion can be set to 24, 20 or 16 bits (switch 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 by the table in Fig 1-5, which is also
shown on the top panel of the unit.

Status Bits

1 ON Professional 16 20 24

1 OFF Consumer 3 OFF OFF ON

2 ON De-emphasis On 4 OFF ON ON

2 OFF De-emphasis O

Fig 1-5: RB-ADDA Status Select Switches

Digital Select Buttons

These buttons are used to switch the digital connection between the AES/EBU XLR
connector (button out) and the S/PDIF phono connector (button in) for the digital input and
the digital output.

Analogue Select Button

This button is used to switch the Analogue input between the balanced XLR connector
(button out) and the unbalanced phono connector (button in).

Frequency and Sync Mode Rotary Switch

This rotary switch is used to select the Synchronisation Mode and to select the frequency
of the digital output when using the on-board clock generator. There are 4 modes of
operation: - Master Mode, Auto Sync Mode, Auto Lock Sync Mode & Slave Mode.

In Master Sync Mode, switch positions 0 – 5, the digital output sample rate is simply set by,
and locked to, the internal on-board clock generator. No sync signal is used or required.

In Auto Sync Mode, switch positions 6– B, the digital output sample rate follows the digital
input. When the digital input signal is not present the output sample rate will be set by,
and locked to, the internal on-board clock generator at a frequency determined by the
switch position.

In Auto-Lock Sync Mode, switch position C, No output will be generated until lock is
achieved with a digital input signal. The digital output sample rate now follows the digital
input. If the digital input signal is removed then the output sample rate will be set by, and
locked to, the internal on-board clock generator at the closest frequency available to the
previous digital input.

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In Slave Sync Mode, switch position D, the digital output sample rate follows the digital
input. When the digital input signal is not present the digital output is turned o.

The following table, also printed on the top of the unit, summarises the above settings
and shows the sample rate generated by the internal clock generator in master and auto
sync modes.

Frequencies and Sync Modes

Rotary
Switch

Number

Mode Sample

Frequency

(kHz)

0 Master 32

1 Master 44.1

2 Master 48

3 Master 64

4 Master 88.2

5 Master 96

6 Auto 32

7 Auto 44.1

8 Auto 48

9 Auto 64

A Auto 88.2

B Auto 96

C Auto Lock -

D Slave -

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

DIGITAL AUDIO CONVERTERS - RB-ADDA

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 oor and dynamic range will be 1-2dB down on their best). The calibration cycle
calibrates the gain and the zero reference of the A/D converter.

To calibrate the RB-ADDA, set the rotary FREQUENCIES AND SYNC MODES switch to position
“F”. The power LED on the front panel will ash quickly for 2 – 3 seconds and will illuminate
fully when the unit is calibrated. Once calibration is complete, reset the rotary switch to the
position that you require.

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VERTERS

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Technical Specications 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

1 x S/PDIF RCA phono socket

A/D Audio Specication

Maximum Input Level: +27dBu (balanced inputs)

Maximum Input Level: +17dBu (unbalanced inputs)

Input Impedance: >10kΩ bridging (balanced inputs)

Input Impedance: >20kΩ (unbalanced inputs)

Input Levels: Switchable +24dBu/+18dBu/+12dBu for FSD

Gain Range: Adjustable 3dB loss to 3dB gain (L and R adjust)

Signal to Noise: Better than –109dbFS (RMS A-weighted at 24bit)

Dynamic Range: >110dB

Distortion and Noise: >96dB THD + N at 1kHz

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) (L & R)

2 x RCA phono (unbalanced) (L & R)

D/A Audio Specication

Max Output Level: +24dBu (balanced outputs)

Max Output Level: +14dBu (unbalanced outputs)

Output Impedance: <50Ω (balanced outputs)

Output Impedance: <75Ω (unbalanced outputs)

Dynamic Range: >100dB

Gain Range: Selectable 12dBu, 18dBu or 24dBu output level, ref FSD

Other Connections

Mains Input: Filtered IEC, 110-120V, or 220-240V switchable, 10W max

Fuse Rating: Anti-surge fuse 100mA 20 x 5mm (230VAC)

Anti-surge fuse 250mA 20 x 5mm (115VAC)

Operational Controls

Analogue Input Select: XLR or phono, via push-switch

Bit Depth: 16, 20 or 24 bits via DIP switch

Digital Output Select: AES/EBU or S/PDIF, via push-switch

Modes & Frequencies: 16 way rotary DIP switch

Digital Input Select: AES/EBU or S/PDIF, via push-switch

Channel Status Bits: Set to consumer or professional mode via DIP switch

Equipment Type

RB-ADDA

Physical Specications

Dimensions (Raw) 48cm (W) x 10.8cm (D) x 4.2cm (H) (1U)
19” (W ) x 4.3” (D) x 1.7” (H) (1U)

Dimensions (Boxed) 58.5cm (W) x 22.5cm (D) x 7cm (H)
23” (W ) x 8.9” (D) x 2.8” (H)

Weight Nett: 1.6kg Gross: 2.2kg Nett: 3.5lbs Gross: 4.8lbs

Combined A/D and D/A converter

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DIGITAL AUDIO CONVERTERS - RB-ADDA