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MTV Networks’ Mobile Unit 8

MTV Networks managers and engineers knew they had a tough challenge in front of them. With the 22nd Annual Stellar Awards gospel show set for Saturday,

MTV Networks managers and engineers knew they had a tough challenge in front of them. With the 22nd Annual Stellar Awards gospel show set for Saturday, January 13, 2007, at the historic Grand Ole Opry House in Nashville, the mobile audio truck scheduled to record the broadcast was driven tag-team style back to its Nashville base only a few weeks before engineers were to complete a technical refurbishment of the truck in time for this prestigious awards show.

From its base in Nashville, and as a frequent traveler to production locations throughout the United States, this 48-foot truck has been at the audio heart of hundreds of broadcast concerts and television music shows spanning the past 10 years. The Neve Capricorn console at its center — the first all-digital, large-format audio console and a remarkable piece of technology for its time — was beginning to show the stress of constant travel. Therefore a decision was made one year earlier to replace the console, upgrade the video monitors to HD and move toward 96kHz recording.

Greg Lankford, EIC for Mobile Unit 8, describes the project as a unique experience: “We used as much MTVN staff as possible to meet the engineering deadline of January 8. Stan ‘Quack’ Dacus, audio mixer at MTVN, was even tasked to cut and haul cables — everyone got involved. The challenge was not just to finish the refurbishment and upgrade on time, but also to be on location on January 10 for the rig and technical rehearsals. So there was very little margin for error.” The planning stage took three months, with Lankford and MTVN project manager/audio mixer Marc Repp hammering out the details. Using as much of the existing infrastructure as the new specification allowed not only saved money, it also saved time.

“We decided to use the existing analog patch fields,” says Repp. “In the initial construction of the truck in 1996, we had configured the patch fields to terminate in DL connectors, which then mated to DLs feeding to and from the Neve console and other outboard equipment. It was then a simple matter, wherever possible, to build new DLs to feed the new console, a 56-fader Lawo mc266. The Lawo digital console proved to be a familiar operating surface — similar to the Capricorn in many ways, but with the added bonus of being able to give us lots of DSP paths at 96 kHz and a massive 512 DSP paths at 48 kHz.

“This truck is now only one of a very few that can handle such a large amount of inputs and track sends,” Repp adds. “I can now change the whole soundstage smoothly and at speed, so for multiple band shows, this is ideal. And what’s more, the sound of this board is outstanding.” With space saved, it was also possible to physically change things around. The existing pair of Pro Tools HD systems, for example, could now be moved to the back of the truck. Each was connected to the console I/O interface via separate AES cards. This one-to-one input connectivity was preferred to a MADI style of distribution, minimizing connections to additional conversion racks and providing a further level of redundancy. A third AES card handles another 64 tracks, if required.

At work in Mobile Unit 8 are, from left, Marc Repp and Stan “Quack” Dacus (at console, respectively) and Greg Lankford at the Pro Tools rigs

Photo: David Vespie

“With the new console, we have a lot more redundancy than we ever had before,” says Lankford. “We decided to continue this into other systems, especially in the blackburst and word clock synchronization system, as well as throughout the fiber-connected I/Os. We are extremely conscious to make sure everything is held in sync to prevent any chance of signal glitching due to synchronization issues, and to protect not only against equipment failure, but also to minimize connector-cabling problems due to on-the-road mechanical vibration or through connector oxidation.”

Mobile Unit 8 uses two Apogee Big Ben master digital clocks, each fitted with Apogee’s X-Video card, which has a connection for a video reference input and three video reference outputs, in addition to the existing six word clock outputs gen-locked to the incoming video. The video-reference inputs to each of the Big Ben units are fed from a separate video isolation DA, whose inputs receive the external reference from the video production truck or any other video-reference source. A video-reference output from each of the two X-Video cards then connects to a changeover switch, whose output is connected to a pair of video DAs to distribute gen-locked blackburst to other equipment. In addition to this arrangement, a word clock output from each of the two master clock units connects to a Rosendahl Nanoclock word clock server, which provides up to 12 word clock outputs. These outputs are then used to distribute word clock throughout the truck.

To check for the presence of the external reference source into the truck, Lankford used an additional output from each of the two video isolation DAs at the front of the master clock units to feed an audible alarm and signaling rack. This custom unit checks for the absence of the video-reference signal into the two master digital clocks: If one of the input references is lost, an audible alarm will inform the crew. The changeover switch feeding the reference blackburst into the pair of video blackburst DAs is manually switched to receive the output of the second master clock unit. “I know we could have done this many different ways,” says Lankford, “but the method we finally chose is simple and cost-effective.”

A second, smaller Lawo control surface provides added redundancy; in the future, this surface will be used as a separate stand-alone mixer. “We all felt that putting as much redundancy as possible into the truck would be the best investment we could make,” says Repp.

Claire Hall is a freelance marketing consultant and broadcast engineer.