Planning the Digital Facility

January 1, 2001

The move to a digital facility involves a mix of traditional ideas and innovative methods.

A facility sync generator is a necessity for most installations unless the purchased system provides its own digital sync timing source, which some do.

Throw out the patch bays, and cut all the copper wire! Now may not be time for that—or is it? The days of planning a facility based around a lot of copper wire, punch blocks, patch bays, and intense labor may be over for many engineers. Planning a facility using the latest digital advances provides many advantages. The use of CAT5 or fiber cable with digital audio and control signals meets the requirements for flexibility and functionality in today's progressive broadcast facilities. The use of LAN and WAN network technologies are the logical choice for operators who need to share audio and data among multiple stations in various markets. Using digital technology within the facility environment can dramatically improve efficiency of production. Stations can now effectively and efficiently operate in a live, live-assist, or automated mode as well as integrate the tasks of scheduling, billing, news capture, and audio delivery using digital technology.

Talk shows can be simplified by using one of the many digital phone systems now available. This is an important area for those designing facilities for talk radio formats. Within some systems, 12 callers or more can be routed to two digital hybrids. High-quality audio can now be transmitted over a normal POTS line by using digital codecs.

The use of digital technology for voice tracking can save time and money. A typical four hour show can usually be voice tracked within 30 to 60 minutes. Digital technology can provide seamless integration with traffic and music systems as well as news capturing and text management for talent. Digital automation systems effectively and efficiently provide programming to many audiences throughout the country. WANcasting enables you to transfer large amounts of digital data over a wide area. Digital systems can provide enhanced system security via the issuance of multi-level user passwords. User interfaces are becoming increasingly friendly.

Digital combines the best features and technology into a facility. The digital technology has become a rapidly emerging science that is in the process of evolving broadcast industry requirements. With so many possibilities, new facility plans can begin in a very different way.

A new approach

Every facility designer must seek an easy and orderly transition to digital with the goal of implementing proven solutions for audio and data delivery to satellite links, multiple transmitters, multiple stream webcasting, and other destinations. The selection of network architecture, hardware, and application software is critical to the success of any broadcast facility. Digital technology provides for a new perspective on networking audio for broadcast and a new design paradigm for the facilities planner.

A few popular digital audio mixing console (control surface) manufacturers, either on their own or in cooperation with a router manufacturer, offer facility-wide audio, logic, and associated programming routing functions via control integrated into the console or adjacent PC. It is now possible to connect any source, regardless of location and audio type, to any console input via router controls integrated into the console, thus eliminating the need for analog patchbays and digital audio distribution amplifiers.

The router provides a central point for all input and output wiring. Think of the router as an electronic patch bay with capabilities ranging from 32in/32out up to 256in/256out or more. An LCD display contained within each console input module displays the source of choice. Some manufacturers integrate system-wide logic command and control to or from any device connected anywhere in the system in a logic follow source/destination configuration within their router control. GPI units, in some cases, can be located anywhere within the facility, and a common GPI unit can be shared by multiple channels. Individual channel settings for all audio settings and logic commands can be saved and recalled in an instant, including mix-minus set ups.

As an added bonus to our pending digital future, program-associated data, such as that which may be used in digital radio, as well as the program-associated data used for webcasting, can also follow the router assignments in some consoles. Routing functions may be automated via logic command salvos or time-of-day commands.

More and more console inputs are now capable of audio format conversion, both on the inputs and outputs, thus eliminating the expense of external format converters and the artifacts caused by over-sampling of audio. Other console manufacturers use a daughter board on each console input to convert from analog to digital. Look for automatic sample rate sampling and conversion in the consoles as well, which eliminates the need for somewhat expensive sample-rate converters. Some digital signal processing (DSP) console input modules are capable of dynamics control such as equalization, gating, limiting, ducking, compression, and expansion, thus eliminating the requirement for external processing units. A large number of mix-minus sends are also available on a few digital consoles.

The use of flatscreen monitors is becoming more popular due to their smaller overall size. Some digital audio console manufacturers now offer flatscreen integration with their console designs. Fully redundant system power supplies, as well as a redundant digital audio sync source with selectable clock rates, should be considered standard equipment in an all-digital facility.

Getting connected

ATM technology can be used for connectivity in some larger facilities, or between multiple facilities throughout the country. However, the most popular methods of connecting networked control surfaces together is the use of a CAT5/RJ-45 LAN, via fiber using RS-422, RS-232, Ethernet, or other proprietary technologies. The audio media is typically transmitted over the fiber channel while the control circuits are transmitted via the CAT5/RJ-45 LAN. The use of CAT5 and fiber cable eliminates the need for a lot of audio and control wire, which greatly minimizes documentation requirements. Shielding, line loss, and ground loop problems can also be eliminated when using digital technology.

Some fiber-based systems that use 62.5×125 standard fiber with ST connectors can be interconnected at distances of 10,000 feet or greater, making it an ideal transmission medium for group-owned multiple stations located within a common city. Fiber cable is also highly tolerant to heat and insensitive to electromagnetic and electrostatic fields. Further cost savings may be realized via the use of CAT5 or fiber cable because of their reduced conduit requirement, greatly reduced costs for analog termination hardware (such as audio connectors and punch blocks), and lower labor costs due to increased installation efficiency. Future rooms can easily be added to a LAN-based system using CAT5 or fiber cable by simply installing the required number of cables from the existing system to the new room. Be sure to use AES-3 cable for all digital audio paths to and from digital sources and destinations. Be sure to test each cable, end to end, and keep the test data for future reference as needed.

A facility sync generator is a necessity for most installations unless the purchased system provides its own digital sync timing source, which some do. The proper use of the sync generator will eliminate audible pops and clicks from mixing unsynchronized digital sources. It will also eliminate timing errors from daisy chaining word clock signals through equipment, and it will lock multiple digital sources to one accurate and stable clock.

User-friendly software will ensure ease of operation in all types of broadcast environments. Back-up of all software is very important. Some digital audio equipment manufacturers now offer sophisticated software that continuously monitors their operating system and displays fault messages on the screen in the event of a malfunction. Remember, the easier the software is to use, the greater ease you will have in training station personnel on its use.

Handling digital

Digital audio meters and processors are also an area for consideration when designing an all-digital facility. The meters need to indicate digital domain metering via full-scale digital peak plus VU and/or PPM for overall best accuracy. Digital audio processors, such as those used for STL pre-processing, SCA processing, satellite uplink audio, and Internet feeds, need to have AES-3 input and outputs with, preferably, no internal conversions. An STL system with an AES input and output is also highly desirable, as is an FM exciter with an AES digital input.

Other considerations for a facility design include proper power management. UPS units of the proper size and type should be used, along with power line conditioning procedures that will assure a pure, clean, and balanced power source. Always be sure to plan for expansion of power distribution to facilitate future equipment installations. Proper ventilation and air filtration should also be a high priority in any facility, especially one with digital equipment. And, don't overlook those often forgotten areas of acoustics and ergonomics when designing your facility.

New design, installation, and troubleshooting paradigms are now necessary in most engineering departments for the support of high-speed networks such as those found in an all-digital facility. Redundancy, connectivity, and low-fault tolerances are all of importance within a well-designed facility. New methods of network termination and the proper use of the necessary tools need to be learned. Engineers need to take the time necessary to be properly trained in design, installation, and maintenance of networking technologies and equipment. Test equipment capable of high-speed measurements now has become more of a necessity rather than a luxury. Be sure to include funding for training and equipment within your project budget. A network systems integrator, in lieu of in-house support, may also become a portion of your project budget.

Digital is here to stay. Digital audio, when properly created and handled, provides a bright and resonant sound. With satellite radio and terrestrial digital radio very near, it is now time for facility designers to think outside of the box by designing a facility that will provide a digital audio media platform that includes facility-wide audio, logic, and program associated data management to and from multiple locations. The greatly increased efficiency of an all-digital networked facility will lead to savings in day-to-day operation. A quality, all-digital facility can be implemented at a cost similar to that of a high-end analog installation. For an easy-to-use and totally flexible facility capable of storing audio, integrating plant-wide control, and increasing operator productivity, digital is the answer.

Ron Bartlebaugh is director of engineering for the WKSU stations, Kent, OH, and president of Audio and Broadcast Specialists, Akron, OH.

How are you planning for digital?

You can see how other facilities are planning for digital in Radio's Facility Showcase features and online in the Studio Spotlight.

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