Audio Engineering Society

Chicago Section

Meeting Review, January 2004

9/24/03 Meeting Highlights
by Tom Miller

On September 24, Tim Wright led a tour of the Clear Channel Communications studios.�

Clear Channel Communications owns 7 AM and FM radio stations in the Chicago area.� They started consolidating of all of the stations into one central studio complex in November of 2002, by moving in one or two stations each month.� A new station that will operate in the expanded band AM band is still being completed at this time.� Facilities are located on the 27th floor, with additional offices on the 28th floor for a total of 100K Square Feet.

The studios are built around a Pod configuration.� Each pod has 4 rooms, and supports one radio station.� Each pod has an identical set of equipment, down to the last microphone.� In theory, any studio can go on air for any station.

The facilities take full advantage of the flexibility of digital audio.� All audio is converted to digital at an early point in the signal chain.� All audio is controlled in the studios using a combination of touch screens and mixing control surfaces.� No audio actually runs through any of the control surfaces.� Each mixer is fully programmable, and can be quickly configured to match the needs of any of the stations.�

The tour started in the Technical Operations Center, which houses nearly all of the audio equipment for the stations.� Here the audio is routed, mixed, and distributed by a highly programmable router.� All of the program material is stored as MP2 files on computer file servers.� Few compact discs were seen in the facility, as most songs are obtained from headquarters through a wide area network.� The music is played directly from the file servers to the digital router.� The bulk of the equipment in the operations center had the appearance of rack-mounted personal computers.

The majority of the plant is connected using AES digital on 110 Ohm balanced cable.� The high volume traffic of the router is carried on fiber optic cables using time division multiplexing.� When asked why they chose 110 Ohm cable when video studios often use coax for their digital audio, Tim explained that there two reasons.� First, radio traditionally is used to using balanced wiring while video studios are more comfortable with coax.� Secondly, the 110 Ohm cables can be used either as digital or as analog wiring.

Tim explained the many backup systems in place to guarantee non-stop operation.� If any digital system were to fail, others could automatically take its place.� If all of the digital systems were to fail, the engineer can manually switch in simple analog systems.

After explaining how the equipment worked in the operations center, the group was given a tour of the individual pods.� The tour group gathered in the new studio just being finished, where Tim conducted a question and answer session to augment the topics discussed throughout the tour.

The Chicago Section would like to thank Mr. Wright for a very informative presentation.

�