The RB-DMX4 can mix four mono channels of audio into up to four mono outputs, alternatively, two stereo inputs into two stereo outputs can be configured by the matrix switching. There are three different types of connection to each input and output, AES/EBU, S/PDIF and TOSLink. All three different types of output can be used simultaneously. Sample-rate converters on each input provide for sources of different sample-rates to be mixed while the output sample-rate is defined independently. The digital audio output can be synchronised to either input, an AES/EBU reference input, a TTL word-clock BNC input or an analogue/SDI video feed if used with optional boards. The output can also be synchronised to an on-board master clock, with a selectable frame-rate. In the case of power failure AES and S/PDIF signal inputs are routed to outputs, essential for environments such as transmitter sites.
In the synchronisation 'Master' mode the 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 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. In 'Auto Lock' mode no output will be generated until lock is achieved with a sync signal. The output sample-rate then 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. In 'Slave' mode the output sample-rate follows the sync input. When the sync signal is not present the digital output is turned off. Using the Sonifex SCi serial software, the unit can be programmed to apply different mixing functions or gain levels for specific applications.
The front panel, with the familiar Redbox red-anodised finish, has three momentary switches each with an arc of LED indicators. The first switch selects which source is used for each of channels one and two; three LEDs above the button illustrate which source AES, S/PDIF or Optical, is selected, the button itself is illuminated when the input is locked, two bicolour LEDs, show input presence and give an indication of the input level. The second switch provides the same functionality for channels three and four. The final switch selects which channel is fed to the adjacent headphone socket with level control. The four LEDs also indicate the presence of an output signal. Four rotary trimmers are accessible through the panel to set input gain. Removing a cover-plate reveals four miniature switch banks, one for each output, each having four switches corresponding to the four inputs. By adjusting the switches, and combination of inputs may be mixed to any output.
The rear panel has two groups of connectors, one for inputs one for outputs. Each has two sets of: An XLR connector for balanced AES/EBU digital connections, an RCA (phono) connector for S/PDIF and a Toslink optical connector. One set is for channels one and two, the second for channels three and four. An XLR provides an input for AES/EBU sync and a BNC for word-clock. The aperture for the BNC connector of optional video sync boards is capped. The serial port and 'remotes' connectors are 9-pin and 15-pin D-sub types, respectively. Power is connected by an IEC inlet. A DIP switch provides the following settings: The sample rate the output is set to in 'Master' mode; the input used as the source of synchronisation; the synchronisation mode, Master, Auto sync, Auto lock or Slave; whether the headphone operates in stereo (listening to either inputs one and two as a pair or three and four as a pair) or they operate in mono, with ones channel sent to both earphones; headphone attenuation for low impedance headphones; remote control by RS232, defeating DIP-switch control.
Distortion and Noise: Better than -137dB THD + N at 1kHz, ref 0dB FS.
Sample frequencies: 32, 44.1, 48, 88.2, 96,176.4 or 192kHz. Bit-depth: Up to and including 24-bit.
Power source: 85-264V AC, 47- 63Hz, 10W maximum. Dimensions: 480 x 108 x 42 (w x d x h) mm, 1U rack-mounting. Weight: 1.4kg.
Included accessories: Manual, AC power cable.
Optional accessories: RB-RK3 Rear rack panel kit. Video sync boards, see below.
Video Sync Boards
These mount inside the case, with a BNC connector protruding through a pre-punched aperture. They can be used to synchronise the outputs to a 48kHz sample rate.
The RB-SYA analogue sync board will accept a composite signal of NTSC (525), PAL (625) & SECAM (625) signals covered by SMPTE-170-M (NTSC) and ITU-R BT.470-6 (PAL and SECAM).
The RB-SYD digital video sync board will accept 270Mbps SD-SDI and HD-SDI signals covered by SMPTE-259-M-C (SD) and SMPTE-292M (HD).