To the other end

Turning attention to the opposite end of the spoke, Wheatstone offers, in addition to the Bridge, a satellite router frame that is a scaled-down version of the Bridge. It lives in a studio. This unit holds the I/O cards that are studio-specific; audio peripherals such as CD players, DAWs and monitor amps get their audio inputs and outputs from this device. It will also work in conjunction with a control surface located in the studio. Connections from the satellite to other Bridges are formed via fiber or CAT-5 cable. Once that connection is made, all the peripherals become part of the network.

In the Studer 5000 router system, studio-specific peripherals are first connected to an I/O frame such as the D19M series. Individual I/O cards (such as four-input 24-bit A/D converters, four-output 24-bit D/A converters, dual-input AES or dual output AES) are plugged into this satellite frame, and are then added to the audio network by way of an MADI connection back to the 5000 router core.

SAS offers the Riolink — a device it calls an extension cord for the 32KD. This device is installed in a studio and serves as the audio and control I/O for the room. The Riolink is actually connected between the SAS control surface (known as the Rubicon) and the 32KD itself. The Riogrande, a new offering from SAS, works in conjunction with the Riolink and can change the Riolink in to a small 32 × 32 mixer in the event of a loss of the 32KD. Connectivity between the Riolink and the 32KD is formed with CAT-5 cable and RJ-45 connectors.

While multiple cable runs may still be necessary with an audio network, the number of cross-connects and distribution points are reduced.

Logitek's approach to the studio-specific I/O is to use another audio engine; all of its power and features are thus available locally. One audio engine in a studio, plus the corresponding control surface, provides the user with the normal console functions plus complete access to the audio network.

Klotz uses a similar approach for the studio I/O. For example, a Vadis 212 frame would be placed in a studio, then connected to a control surface, making up (as far as the user was concerned) a console and at the same time adding all that studio's equipment to the audio network.

The Harris Vistamax system has a unique approach to the studio I/O aspect of the audio network. A Vistamax frame can be located in a studio, providing the appropriate I/O and functionality therein. Alternatively, one of Harris' digital consoles can also serve as a node, or peer, in the network. This provides scalability and allows the system to be integrated with legacy equipment.

Axia's approach to the audio network is to have all the spokes communicate with one another via Ethernet by way of a network switch that is effectively the hub of the spoke and hub topology. Axia offers function-specific 1RU devices it calls nodes that perform functions such as microphone amplification; analog I/O; AES digital I/O; router X-Y control; and finally control I/O. These nodes live in studios or other locations as needed. These nodes, in conjunction with the Studio Engine, the Smartsurface and the Ethernet switch, make up the audio network Axia-style.

AEQ's system uses satellite BC2000 frames linked to other frames in the system for local studio I/O. In conjunction with the modular DM/D10 control surface, the console functions are completely handled, while all sources/destinations become integrated into the audio network.

The explosion of computer networking over the last 10 years has had an effect on the methodology and technology of radio station construction. The appropriate concepts, physical layer materials and devices have been borrowed from the computer network and modified and used completely in others to make up what is now known as the audio network. It's time to take what you have learned about computer networking and apply it to audio, especially if there is a studio build or upgrade on your horizon.

Resource Guide

Manufacturers of audio networking systems

Doug Irwin is the chief engineer of WKTU-FM, New York City.