Technology

Networking

The NEXUS STAR system is networked using RFOC fibre-optic interface boards and duplex fibre-optic cables alone. This approach allows various application-specific network set-ups to be implemented, for example, a star-topology network, optionally with parallel and redundant fibre-optic lines between NEXUS Base Devices.
A maximum of 16 RFOC boards can be installed into a NEXUS STAR, with each board providing a maximum of four ports.
The NEXUS audio network is a single entity: All inputs, outputs, and processing channels can be accessed and operated from anywhere on the routing system.

Optical Lines

The optical lines between Base Devices are always duplex, transferring 128 audio channels plus control and sync information bi-directionally.
Fibre-optic cables are convenient in mobile applications, too: Despite their immense transmission capacity, they are thin and light-weight. The galvanic separation established by optical lines avoids groundloops and confers increased electrical safety. Fibre-optic cables can span several thousand meters without signal loss and are insusceptible to electromagnetic and electrostatic interference. Therefore, new cables can be run in existing cable channels with no requirement for shielding.

System Size

A NEXUS audio network including a NEXUS STAR allows for bi-directionally interconnecting a maximum of 31 NEXUS Base Devices. (This corresponds to 4,096 inputs and 4,096 outputs.) Thus, a NEXUS network allows the creation of systems covering all possible applications – from simple format converters in a studio to networked broadcasting complexes and even exhibition-centre overall networks.
The optimum network structure and the number of parallel and redundant fibre-optic connections are determined during the planning process. For example, the network structure depends on the physical position of the Base Devices and on the required routing capacity.
Even with large-scale routing systems, total interconnectivity of overall-system inputs and outputs (the so-called »non-blocking« or »unlimited simultaneousness«) can be achieved using a reasonable number of NEXUS Base Devices and fibre-optic connections.

Signal Distribution

On NEXUS STAR, inputs are routed to outputs using the RCX active routing matrix. The matrix centrally manages all audio channels of the interface boards (up to 16) installed into NEXUS STAR. It provides 256 input and 256 outputs to each interface board, resulting in a total capacity of 4,096 routing paths. The signals are routed dynamically between Base Devices over optical lines. Multiple parallel lines between Base Devices increase the routing capacity accordingly (by 128 channels per cable) or can be used as redundant lines.

Synchronisation

In accordance with the NEXUS philosophy, NEXUS STAR operates fully in sync. This allows for a constant and short delay of all routed signals: the latency is just 6 samples. This figure makes NEXUS STAR perfectly suitable for time-critical applications where minimum latency is a must (e.g. live broadcasting).
The incoming sync clock is processed on the RCX controller board to ensure a low-jitter Base Device clock. This clock signal is made available at the wordclock output of the STAR router for use as a studio master clock or synchronizing external recorders.
Separate wordclock distribution is no longer required. Thus, significantly simplifying installation of distributed systems and mobile operation.

Sample Rates

The NEXUS STAR routing system operates with the standard sample rates of 44.1 or 48 as well as 88.2 and 96 KHz. The NEXUS network sample rate is selected in the graphical control program running on a control computer.

Sync Sources

The following sync sources on NEXUS STAR and the NEXUS Base Devices can be used for synchronizing the NEXUS network:

• Any wordclock input
• Any digital input
• The internal clock generator
• Any optical input
• The optional RSYNC board (video, WCLK, AES/EBU)
• MADI (RMF) if available

The clock signal of an external source is processed on the NEXUS STAR RCX controller board or the XCPU controller board of any connected Base Device and is then distributed on the NEXUS network as a low-jitter clock.

Generator

The clock generator integrated on the control boards is based on a precision quartz crystal oscillator and can be used as a master clock for the entire studio. The standard version provides a frequency accuracy of better than ±10 ppm, thus meeting the requirements of AES-11, grade 2.

Auto Sync Search

At sync-source failure, NEXUS STAR and the NEXUS network will automatically select another clock source. The change occurs smoothly and without interruption. If no legitimate sync source is found (for example, because inappropriate sample rates are used), the system will switch to the internal clock generator of NEXUS STAR or a Base Device.
A freely configurable priority list determines the order of up to eight sync sources considered for auto sync search.

Hot Swap

All NEXUS STAR boards apart from the RCX boards, can be replaced while the system is in use. This allows for immediate servicing without shutdowns. Inadvertent installation of boards into unsuitable slots will not cause any damage. Failed, inappropriately installed, or missing boards are displayed on the user interface.

Power Supply

NEXUS STAR is a highly energy-efficient system. Even when fully populated, it requires a mere 160 W. Switch-mode, wide-range power supply units are mounted onto the router back panel. Operation with redundant supply units and automatic supply takeover is a standard feature; for this purpose, up to four power supplies can be connected to the router backplane. When a power supply fails, changeover is performed automatically and seamlessly.
While no NEXUS Base Device uses forced ventilation, attention must be paid to ensuring NEXUS STAR has sufficient air supply and circulation due to the high component density. In thermally critical areas, air-conditioning should be seriously considered.