Optocore in Athens 2004

Many of you have read numerous articles about the design of the audio system and production specifications for the Olympic Games in Athens 2004. It was indeed a massive international event and the sound systems that played critical roles during both the opening and closing ceremonies have been discussed and dissected at length in various publications both here and abroad.

One thing which stood out amongst all the talk and charts was (Olympic Games Audio Designer) Scott Willsallen’s glowing report on the Optocore Digital Audio Transport Systems, the DD32 and X6, used to deliver the processed loudspeaker feeds to the amplifiers, and to collect the field of play inputs and return them to front-of-house, with Scott praising the system as “faultless”. He also commented that Optocore’s Production Manager, Mark Wesler, came over from Germany for a couple of weeks and had nothing to do, as the Optocore gear simply worked flawlessly–high praise for this high-quality product.

The games, held from the 13th to 29th of August 2004, were one of the most important and biggest media spectacles ever held in the world. 72,000 spectators in the stadium and 4 billion people on the television watched the Opening Ceremony, with live performances from Icelandic singer Björk, DJ Tiesto and hundreds of actors, performers and athletes.

Optocore powered the Opening and Closing Ceremonies with 26 devices bound in two redundant rings. Both rings, one in the stadium roof, the other on the field play, were connected with over 4 kilometres of fibre optic cables. “With a job this important you need to have a very stable system” says Scott Willsallen, “redundancy is absolutely necessary, and Optocore offers it on three levels”.

Optocore runs redundant fibre optic rings, auto-switching redundant power supplies. Each unit is a clock master, which means if one ring of the network fails it never affects another’s unit sync. “Others aren’t quite there yet, but Optocore is. Optocore rocks!” says Scott.

For those wondering about Optocore, it is available in Australia, and it is beginning to gain itself a reputation here, based on its international use at big events (yes, the Olympics has helped) across Europe and the USA. Details of Optocore DD32 and X6 products, as used during Athens Olympic Games by Scott and his team, are as follows.

OPTOCORE DD32:

The Optocore DD32 is devised for the transmission of a maximum amount of digital data via optical fibre, occupying only 1U of 19" rack space. Connections are of the widely available, SubD25 and SubD9 type allowing the preparation of various, inexpensive, hard patching adapters catering for the diversity of each users connecting system. A significant amount of auxiliary ports are provided for various useful tasks. The unit is equipped with a dual 1Gbps full-bandwidth optical interface and dual power supply with automatic switchover.

PRINCIPAL PORTS:

The unit provides 32 digital ports of the RS422 hardware standard, allowing the transmission of 32 DMX/RS422 or 64 AES3 digital audio channels (32 stereo channels). The 32 ports are grouped together to four-channel input or output groups defined by software adjustment. LEDs indicate the status of each channel (busy), the status of the four-channel groups (input or output) and also display the used sample frequency.

AUXILIARY PORTS:

Four additional RS485 digital ports are provided. These may be "downgraded" by means of software to be either inputs or outputs of the RS422 standard. An RS232 channel is available on the front panel. N.B. a data stream inputted via PC/RS232 or PC/USB, may be outputted to one of the RS485 ports of the same unit or via the fibre, to any RS485 port in a system of several units.

VIDEO PORTS:

A video in- and output are incorporated for the transmission of 10MHz-bandwidth composite video signals

WORD CLOCK:

A word clock output provides the necessary signal to synchronise external devices to the Optocore system.

REMOTE ACCESS and UPGRADING:

A USB-port is available for the remote controlling of the units via PC. Additionally the RS232 channel may be adjusted by software to be used as a remote access input, or for the connection of a planned "hand-held" device, enabling the performance of set-up changes on location. Due to the units' FPGA (field programmable gate array) based concept for the internal logic circuits, upgrading of the hardware can easily be implemented via the unit’s remote access ports.

THE FRONT-PANEL:

Incorporates the same unique section on the right hand side of all modules. This comprises seven status LEDs and a three character, LCD-display for ID purposes. An RS232 and a USB connector complement this section. To the left of this section, LED groups show the status of each principal port and the status of the eight 4-channel groups (in-/output) as well as the sample frequency.

THE REAR-PANEL: Situated on the rear-panel are the connections for the internal power supplies (85...275VAC), principal, auxiliary and video ports, the word clock output and the optical in- and outputs.

INTER CONNECTION:

The optical interfaces are of the SC-type. For more rugged applications an expanded beam connector mounted on a 1U panel can be connected. Each of the four female SubD25 connectors supplies eight RS422 principal ports. The two female SubD9 connectors supply the four RS485 and the RS232 auxiliary ports. The USB port is equipped with a USB-device-connector. Video input and output as well as the word clock output use BNC connectors.

DATA DELAYS:

Data streams transmitted through similar channels all appear at the outputs at the same time. The processing of previously converted audio signals requires between 0 and a complete sample period for synchronisation purposes. Transmission delay is negligible (< 100ns), so that maximum delay sums to only 41.6 / 20.8m s @ 48 / 96kHz sample rate, whereas the minimum delay is 20.8 / 10.4m s.

USE in the OPTOCORE LX4 System:

As an alternative to the Optocore LX4B which incorporates DA converters, the DD32 unit may be used to supply digital audio signals from/to the LX4A. In this case one SubD25 principal port will service the return channel inputs whilst the remaining three service the Mic/Line outputs.

• Dual 1Gbps full-bandwidth optical interface.
• Dual power supply with automatic switch-over.
• 32 principal ports with a data transfer rate of up to 30Mbps. May be used as 64 AES digital audio channels with a sample rate of up to 192kHz or as 32 DMX or RS422 channels.
• Input or output configuration in groups of four. AES or RS422 in groups of eight.
• 4 auxiliary RS485 ports with a data transfer rate of up to 10Mbps.
• 1 RS232 port (transfer rate up to 115200 Baud).
• 1 USB port.
• 1 composite video input, 1 composite video output featuring converter-resolution of 10-bits and bandwidth of 10MHz @ 27MHz sample frequency.
• 1 word clock output.
• Full remote access to processing parameters.
• Upgradeable internal logic.
• Configurable as LX4-D unit for Optocore LX4 application.
• Comprehensive status control via LED banks.

SUPPORTING YAMAHA DEVICES:

Due to the lack of an industry standard the pin connections of the units SubD25s are wired according to the Yamaha MY8-AES plug-in-cards each of which carry four inputs and four outputs. However, the flexibility of the system should be noted in that the DD32s principal ports may subsequently be determined as either in- or outputs. Should either an eight input AD824 AD-converter or an eight output DA824 DA-converter be connected to the Optocore, four channels of the MY8-card (inputs with the AD824 and outputs with the DA824) cannot be used. Thanks to the flexibility of the Optocore ports, each of its SubD25 ports may serve either two AD824 or two DA824 devices or one AD824 and one DA824, always handling 16 digital audio channels, depending on the correct SubD25 (split) cable. "Daisy-chaining" necessary to control a decentralised system of YAMAHA devices, is easily implemented using the auxiliary ports of the Optocore units in the RS422 mode, linking the isolated parts of the chain at the various locations via the fibre.

RS485 TRANSMISSION:

In comparison to the half-duplex, RS485 bus standard, the Optocore optical digital network system is a full-duplex system as are the RS422 and RS232 bus standards. Full-duplex transmission utilises two data buses, one send and one return, whereas a half-duplex transmission uses a common bus for all components of a system. A full-duplex system cannot totally fulfill this crucial condition. However, the Optocore system is able to emulate the function of RS485 half-duplex transmissions.

AES3 STANDARD, RS422:

The AES3 recommended hardware practice is based on the RS422 standard, but prescribes 110W ± 20% output impedance of drivers and the same value for the termination impedance of receivers. This leads one to expect an optimum transmission performance through a balanced cable with a nominal characteristic impedance of 110W. The RS422/RS485 standards recommend 120W termination impedance at the beginning and also at the end of a data bus and apart from these use low impedance drivers directly to the bus. The unit’s standard version RS422 principal ports as well as the RS485 auxiliary ports are all terminated with 120W, which meet the recommendation for AES3 receivers but not for drivers. No performance restrictions have been experienced with short and medium length cables in the field.

If necessary the unit may be assembled as a "real" AES3 I/O unit during the production process. In this case however, inputs and outputs are "fixed" at the connectors and can no longer be rearranged by software adjustment. Hardware and software arrangement are totally dependant on the hardware assembly.

OPTOCORE X-6 SERIES:

The 16 audio channel CONVERTER UNITS of the X6-series have been developed as inserts to the optical fibre network system via a DIGITAL I/O UNIT DD32. By this means, up to four converter modules can be served by one DD32, summing to at least 64 analog in- or outputs. The devices may also be used as high-quality AD and DA converter units for non-Optocore applications.

Three different versions are available:

1. 16IN: 16-mic/line input,
2. 16OUT: 16-line output,
3. 8 / 8: 8-mic/line input – 8-line output.

High integration density achieved with SMD production ensures smallest possible enclosure dimensions. With regards to audio transmission quality, the components and circuitry meet the highest of demands. The conception of the X6-series has been developed in close collaboration with professional users from the fields of broadcast, live sound and studio.

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