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DIGITA L AUDIO CONVERTERS
4 RB-DAC1 Digital to Analogue Converter
Introduction
Fig 4-1: RB-DAC1 Front Panel
Using 24 bit, 96kHz capable devices, the RB-DAC1 Digital to Analogue Converter is a 1U
rack-mount which produces a stereo balanced XLR or unbalanced phono output from an
incoming AES/EBU or S/PDIF digital input signal. There is also a headphone output for
monitoring purposes.
The analogue outputs have an output level control, allowing full-scale settings selectable
from +12dBu, +18dBu or +24dBu. De-emphasis on the output can be enabled via
dipswitch.
There is a button to select either the AES/EBU or S/PDIF input for the D/A converter, which is
located on the rear panel.
When operating, the front panel power LED flashes whenever the unit is not synchronised
to the incoming digital signal.
System Block Diagram
Fig 4-2: RB-DAC1 System Block Diagram
L
L
R
R
AES/EBU
S/PDIF
Digital
Input
Volume Control
Stereo
Headphone
Output
Professional
Output
Consumer
Output
Digital Source
Selector
AES
Receiver
DAC
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Front Panel Indicators & Controls
Fig 4-3: RB-DAC1 Front Panel
Sync & Power Indicator
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 :
Flashing between red and amber – indicates a loss of a valid digital input signal.
Headphone Output
The output available on the front panel through a ¼” stereo jack socket, is designed to drive
150 mW into 32Ω to 600Ω professional headphones.
Volume Control
The headphone output has its own volume control, which is independent of the level
adjustment for the main outputs, and has a maximum output level of +12dBu.
Rear Panel Connections and Operation
Fig 4-4: RB-DAC1 Rear Panel
Sync & Power
Indicator
Headphone
Output
Volume
Control
AES/EBU
Input
Analogue
Outputs (L&R)
RCA Phono
Outputs (L&R)
Full Scale
Digits and
De-emphasis
Switches
Digital Select
Button
S/PDIF
Input
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RB-DAC1 Inputs
AES/EBU Input
The digital input 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 should meet the IEC 60968 specification
S/PDIF Input
The S/PDIF digital phono input has an impedance of 75Ω.
RB-DAC1 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.
Rear Panel Controls
Full Scale dB Settings
Switch Number +12 +18 +24
1 OFF ON ON
2 OFF OFF ON
Emphasis Settings
3 ON De-emphasis On
3 OFF De-emphasis Off
4 Reserved
Fig 4-5: RB-DAC1 Full Scale Digits and De-emphasis Settings Switches
Output Level Adjustment
The output gain can be adjusted by dipswitches on the rear panel. The 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. The consumer output on the phono connector has a further 8½dBu
attenuation incorporated.
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De-emphasis Switch
If de-emphasis is selected (switch 3) the RB-DAC1 will decode 50/15µs emphasis when
indicated by certain channel status bits in the incoming digital audio data.
Digital Select Button
This button is used to switch the digital input from the AES/EBU XLR connector (button out)
to the S/PDIF phono connector (button in).
Technical Specifications RB-DAC1
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)
Headphone Output: 1 x ¼” (6.35mm) A/B gauge 3-pole stereo jack socket
Mains Input: Filtered IEC, 110-120V, or 220-240V switchable,
fused 10W max
Audio Specification
Max Output Level: +24dBu (balanced outputs)
+14dBu (unbalanced outputs)
+12dBu (headphone outputs)
Output Impedance: <50Ω (balanced outputs)
<75Ω (unbalanced outputs)
Dynamic Range: >100dB
Noise & Distortion: <0.01% THD + N @1kHz
Sample Freq Range: 30kHz – 100kHz
Gain Range: Selectable 12dBu, 18dBu or 24dBu output level, ref. FSD
Headphones: Drives 150 mW into 32Ω to 600Ω headphones
Max Output Level: +12dBu
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Operational Controls
Digital Input Select: AES/EBU or S/PDIF, via push-switch
Gain Select: Selectable 12dBu, 18dBu or 24dBu output level,
ref. FSD
De-emphasis On/Off: Dipswitch
Equipment Type
RB-DAC1 Digital to Analogue Converter
Physical Specifications
Dimensions (Raw) 48cm (W) x 10.8cm (D) x 4.2cm (H) (1U)
Dimensions (Boxed) 53cm (W) x 20.5cm (D) x 6cm (H)
Weight Nett: 1.4kg Gross: 2.0kg
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