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.

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1 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 Digital AES/EBU S/PDIF Digital Source Selector AES Receiver DAC Volume Control Stereo Headphone L Professional R L Consumer R 4 Fig 4-2: RB-DAC1 System Block Diagram Redbox User Handbook No 1 25

2 4 DIGITAL AUDIO CONVERTERS Front Panel Indicators & Controls Sync & Power Indicator Headphone Volume Control 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 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 Analogue s (L&R) AES/EBU S/PDIF RCA Phono s (L&R) Fig 4-4: RB-DAC1 Rear Panel Full Scale Digits and De-emphasis Switches Digital Select Button 26 Redbox User Handbook No 1

3 4 RB-DAC1 s AES/EBU 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 specification S/PDIF The S/PDIF digital phono input has an impedance of 75Ω. RB-DAC1 s Analogue s (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 s (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 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 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. Redbox User Handbook No 1 27

4 4 DIGITAL AUDIO CONVERTERS 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 s: 1 x AES/EBU XLR 3 pin female 1 x S/PDIF RCA phono Analogue s: 2 x XLR 3 pin male (balanced) (L & R) Headphone : Mains : Audio Specification Max Level: Impedance: Dynamic Range: Noise & Distortion: 2 x RCA phono (unbalanced) (L & R) 1 x ¼ (6.35mm) A/B gauge 3-pole stereo jack socket Filtered IEC, V, or V switchable, fused 10W max +24dBu (balanced outputs) +14dBu (unbalanced outputs) +12dBu (headphone outputs) <50Ω (balanced outputs) <75Ω (unbalanced outputs) >100dB <0.01% THD + Sample Freq Range: Gain Range: Headphones: Max Level: 30kHz 100kHz Selectable 12dBu, 18dBu or 24dBu output level, ref. FSD Drives 150 mw into 32Ω to 600Ω headphones +12dBu 28 Redbox User Handbook No 1

5 Operational Controls Digital Select: Gain Select: De-emphasis On/Off: Equipment Type RB-DAC1 Physical Specifications Dimensions (Raw) Dimensions (Boxed) AES/EBU or S/PDIF, via push-switch Selectable 12dBu, 18dBu or 24dBu output level, ref. FSD Dipswitch Digital to Analogue Converter 48cm (W) x 10.8cm (D) x 4.2cm (H) (1U) 53cm (W) x 20.5cm (D) x 6cm (H) Weight Nett: 1.4kg Gross: 2.0kg 4 Redbox User Handbook No 1 29