February 25, 2020
February 25, 2020
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Using a front panel button, you can select which channel needs to be delayed. There is also an ‘ALL’ option which allows the selected delay to be applied to all channels. Then using another front panel button you can select the length of one frame of delay and the multiple of frames to delay by.

The connectivity is incredibly flexible, allowing three different types of connection to each input and output including AES/EBU, S/PDIF and TOSLink. All three different types of output can be used simultaneously. There is a monitor socket on the front panel which allows you to listen to each mono channel, by front panel selection. Pairs of channels can be monitored (1 & 2 or 3 & 4) using a rear panel stereo option. There is also an option to attenuate the monitor by 12dB selectable by rear panel DIPswitch. Audio presence is detected and displayed for each channel around the INPUTS 1 & 2 and INPUTS 3 & 4 buttons.

The flexibility continues with many audio synchronization options. The digital audio output can be synchronized to either input, an additional AES/EBU reference input, a TTL wordclock BNC input or an analogue/SDI video feed if used with an additional RB-SYA or RB-SYD board. Also the output can be synchronized to an on-board master clock, with a selectable frame rate. There are warning indicators on the front panel for loss of lock on both inputs and for the selected external synchronization. Selectable synchronization modes are as follows:

Master Mode

In this mode 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.

Auto Sync Mode

In this mode the digital output sample rate follows the selected sync input. When the sync signal is not present the output sample rate will be set by, and locked to, the internal on-board clock generator at the selected output frequency.

Auto Lock Mode

In this mode no output will be generated until lock is achieved with a sync signal. The digital output sample rate now follows the sync input. If the sync 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 sync input.

Slave Mode

In this mode the digital output sample rate follows the sync input. When the sync signal is not present the digital output is turned off.

A powerful feature of the RB-DD4 is that by using the Sonifex SCi serial software, the unit can be programmed for different delay durations, levels and switching functions so that you can program the unit for your specific application. A rear panel DIPswitch configures the unit to be controlled serially. Contact Sonifex for further information if you have a particular requirement that isn’t catered for by the RB-DD4 as standard.

The RB-DD4 has been designed to have a passive signal path through the main input, so if power to the unit fails, signal inputs 1 & 2 are routed to outputs 1 & 2 and signal inputs 3 & 4 are routed to outputs 3 & 4. This is essential for applications such as installation at transmitter sites, where a power failure to the unit should not prevent the audio input signal from being output to the transmitter. Please note that this is not true for the TOSLink outputs which are muted.

system diagram

RB-DD4 Block Diagram

See larger image >

SCi logoThis product has settings that can be adjusted using the Sonifex SCi (Serial Control Interface) software. To download a copy of the SCi software, please use this link >

SCi Screens

Sci image - RB-DD4

Status Screen.

Sci image - RB-DD4

Unit Set-up Screen.

Sci image - RB-DD4

Miscellaneous Screen.

Technical Specification For RB-DD4

Audio Specification

Dynamic Range:>138dB
Distortion and Noise:<-137dB THD + N at 1kHz, ref 0dB FS
Input & Output Impedances:110Ω ±20% AES/EBU balanced I/O
75Ω ±5% S/PDIF unbalanced I/O
75Ω ±5% TOSlink unbalanced I/O
50Ω BNC TTL word clock input
Signal Level:Balanced: 3V/10V peak to peak min/max
Unbalanced: Min 0.5V±20% peak to peak
Sample Frequencies:32, 44.1, 48, 88.2, 96,176.4 or 192kHz
Bit Depth:Up to and including 24 bit
Max Delay:8 secs per mono channel at 32kHz 1.33 secs per mono channel at 192kHz
Frame Rates (Front Panel):23.98fps, 24fps, 25fps, 29.97fps, 30fps, 50fps, 59.94fps, 60fps
Frame Rates (SCi Software):525/29.97, 625/25, 720/60p,720/59.94p, 720/50p, 720/30p, 720/29.97p, 720/25p, 720/24p, 720/23.98p, 1035/60i, 1035/59.94i, 1080/60i, 1080/59.94i, 1080/50i, 1080/30p, 1080/29.97p, 1080/25p, 1080/24p, 1080/23.98p, 1080/30pSF, 1080/29.97pSF, 1080/25pSF, 1080/24pSF, 1080/23.98pSF, 1080/60p, 1080/59.94p, 1080/50p
Delay Settable:1 to 19 frames (front panel controls)
Frames, lines, fields, milliseconds and
samples up to total delay time (SCi

Front Panel Operational Controls & Indicators

Digital Input Select:AES/EBU, S/PDIF or TOSlink optical via INPUT 1 & 2 or INPUT 3 & 4 push-buttons
Delay Control:Delay time selection system via front panel push button
Monitor Select Control:Headphone monitor channel select
Indicators:Input presence indicators via
bicolour LEDS around each push button

Rear Panel Operational Controls

Master Select:32, 44.1, 48, 88.2, 96,176.4 or 192kHz Frequency via rear panel DIPswitches
Sync Source Select:INPUTS 1&2, INPUTS 3&4, AES Sync, Word Clock, Video Sync via rear panel DIPswitches
Sync Mode Select:Master, Auto Sync, Auto Lock, Slave via rear panel DIPswitches
Stereo Features:Stereo monitor outputs via rear panel DIPswitches
Monitor Attenuation:12dB Monitor attenuation via rear panel DIPswitches
Serial Mode:Enter serial control mode via rear panel DIPswitches
Boot Mode:Boot up base code or firmware via rear panel DIPswitches


Digital Inputs:2 x AES/EBU XLR 3 pin female
2 x S/PDIF RCA phono
2 x TOSLink optical input
Digital Outputs:2 x AES/EBU XLR 3 pin plug
2 x S/PDIF RCA phono socket
2 x TOSLink optical output
Sync Inputs:1 x AES/EBU XLR 3 pin female
1 x Word Clock BNC
1 x Video Input (optional)
Remote I/O Port:15 way D-type plug
Serial Port:RS232, RJ45 socket
Mains Input:Universal filtered IEC, continuously rated 85-264VAC@47- 63Hz, max 10W
Fuse Rating:Anti-surge fuse 1A 20 x 5mm

Equipment Type

RB-DD4:4 channel digital audio delay

Physical Specifications

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):59cm (W) x 27.5cm (D) x 11cm (H)
23.2” (W) x 10.8” (D) x 4.3” (H)
Weight:Nett: 1.4kg Gross: 2.0kg
Nett: 3.1lb Gross: 4.4lb


RB-SYA:Analogue video sync board (NTSC, PAL & SECAM)
RB-SYD:Digital video sync board (SD-SDI & HD-SDI)
RB-RK3:1U Rear panel rack kit for large Redboxes
* Note that this product is deeper than standard Redboxes.


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