Sonifex RB-DSD1 Digital Silence Detection Unit (1U)

Sonifex RB-DSD1 Digital Silence Detection Unit (1U)

Although it has AES/EBU, S/PDIF, and TOSlink inputs and outputs in place of analogue inputs and outputs, the RB-DSD1 digital silent detection unit functions similarly to the Sonifex RB-SD1 analogue quiet detection unit. The device, which is meant to switch between inputs in case of audio loss, is perfect for use at transmitter locations or following a studio's master output in case a master source fails. It can also be used for simultaneous broadcasting.

The RB-DSD1 features two digital stereo audio inputs that can be selected from AES/EBU balanced XLRs, S/PDIF unbalanced phonos, or TOSlink unbalanced optical inputs via push buttons on the front panel. Each input has a sample rate converter, allowing sources with various sample rates to be used and independently defining the output sample rate. Every input has a remote failure alert and can be configured by the user to be either the primary or secondary source. Both sources are watched for malfunctions. The primary (green) and auxiliary (red) pushbuttons' colors designate which input is whose, and a blinking LED denotes a loss of synchronization.

When the primary source falls below a pre-established threshold for a pre-established duration, the device will automatically transition to the backup signal. Using front panel DIP switches, the silence detect level can be adjusted in 3dBfs increments between -39dBfs and -84dBfs. Another DIP switch block on the front panel can be used to change the silence interval in steps of two seconds, from 0 to 252 seconds. To stop anybody from tampering with the settings, a thin cover panel can be bolted in place to hide the DIP switches.

To enable the distribution of the specified input to numerous outputs, there are two stereo outputs. Each output can be used as a simultaneous balanced XLR for AES/EBU, an unbalanced phono for S/PDIF, or an unbalanced optical output for TOSlink. The output sample rates are selectable via rear panel DIP switches from one of 32kHz, 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz or 192kHz.

The unit has TTL wordclock BNC and AES/EBU XLR synchronising inputs as standard and optionally, the RB-SYA and RB-SYD synchronisation boards can be fitted to synchronise the unit to analogue or digital video signals. A front panel DIP switch block is used to decide whether the unit is synchronised to Input 1, Input 2, the AES/EBU sync input, the wordclock sync input or an optional video sync board. A front panel SYNC button selects the synchronisation mode of the unit and the button flashes whenever the unit is not synchronised to an incoming sync signal. Selectable sync 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.

The unit can operate in 2 modes - automatic or manual, selectable using a rear panel DIP switch. In both modes it will automatically switch over to the auxiliary source on detecting silence. When the main signal is again detected it will either return to the main signal automatically or manually depending on the mode chosen. In manual mode, the front panel RESTORE button is used to return to the main signal.

The RB-DSD1 has a number of remote operational features. Remote outputs provide separate relay contact closures for failure of the main and auxiliary inputs. You can also remotely select between auto and manual mode (with tally output), action the signal RESTORE, set the silence detection delay to be 2mins 5 seconds and define which input is the main input (with tally output). You can remotely start and stop another piece of equipment on alarm failure and there is an option to set the remote start output as either momentary or latched.

The unit can be configured to alarm when either the left or right channel of the main input source fails, or if the whole stereo signal fails. Additionally, if one channel of a stereo signal is lost, you can define whether to mute the lost channel, or whether to mix the remaining channel to the lost side, effectively creating a mono signal. If the main source synchronization is lost, you can define whether the unit switches to the auxiliary input immediately, or whether to treat the signal as silence to be detected and then switched based on the unit’s silence detection settings.

Front panel LED indicators by the MAIN and AUX buttons show individual left and right program and alarm conditions for both the main and auxiliary inputs. A powerful feature of the RB-DSD1 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 front panel DIP switch configures the unit to be controlled serially and a front panel LED indicates serial operation. Contact Sonifex for further information if you have a particular requirement that isn’t catered for by the RB-DSD1 as standard.

The RB-DSD1 has been designed to have a passive signal path through the main input, so if power to the unit fails, signal input 1 is routed to output 1, and signal input 2 is routed to output 2. 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.