Components

DSP for Noise Shaping and Dithering

The 24-bit NEXUS audio signal can be output to external downstream units with 16-bit or 20-bit resolution. To maintain optimum audio quality, the resolution is converted by the internal DSP using a dithering algorithm. This efficiently minimises the inevitable signal inaccuracies and deterioratiion of S/N ratio and THD&N.
In addition, a selectively engaged noise-shaping function moves the noise energy up to frequency ranges less perceivable to the human ear. The noise reduction achieved in the range below 1 kHz is approximately 15 dB and about 10 dB in the critical range around 3 kHz. Noise-shaping is computed on the integrated DSP using a 5th-order algorithm.
The signal processor implemented on the board also allows for phase inversion, gain, and output limiting. The respective parameters can be set using the service software.

Free Sample Rates Supported

The XET board is equipped with sample-rate converters to handle external appliances not in sync with the system clock or using different sample rates. For this purpose, the board includes a precision clock generator for the standard rates (32, 44.1, and 48 kHz). In addition, double or fourfold of the selected rate can be selected individually for each output. The optional XOSC generator module allows a free system-independent clock rate to be configured. The XOSC board supports a variety of system-specific clock rates.
The board also provides an input for external wordclock signals, which the sample-rate converters can synchronise to.
This input can also be used for synchronisation to a neighbouring XER AES/EBU input board independently of the system clock. Using flexible circuit boards this even allows for cascading multiple boards.
To achieve identical latencies and signal phases at the various outputs, the board’s sample-rate converters can be synchronised to each other; this is reasonable, for example, when connecting multitrack recorders fed via AES/EBU inputs. When using the same rates, the converters are auto-synchronised.
They can be enabled separately for each stereo pair using the control software.

Ancillary Information

AES/EBU ancillary data is transparently forwarded on the NEXUS system or can be regenerated. The channel status can be set to either professional or consumer format.

Test Tone Generator

For test purposes, the board features a generator capable of producing sine signals as well as low-amplitude noise.
 

XEOX - Adaptor for AES/EBU-LWC Converter

The benefits of transmitting AES/EBU signals via fibre-optic lines – such as large spanning distances of up to 2,000 meters, insusceptibility against EMI, and full galvanic isolation of transmitter and receiver – are made available by the optoXLer optical converter by Connex. The optoXLer converts differential AES/EBU signals to optical signals and vice versa. This method allows for bit rates of up to 10 Mbps.
The electronic converter components are incorporated in a modified XLR connector and are plugged directly into the XLR port. The optoXLer is available as a transmitter or receiver equipped with male or female XLR-3 terminals respectively.
Connectivity to fibre-optic lines is provided within the XLR adaptor using a F-SMA standard connector.
The optional XEOX module allows for using optoXLers with NEXUS XET boards. The module is just plugged onto a terminal strip on one of the participating boards.