Great ideas in studio design

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Axia makes 1RU devices refered to as nodes as part of its product line. The node is a device that converts a protocol we are more familiar with, whether it is analog audio, AES3, GPIO, or even microphone level audio, into the IP protocol used over Ethernet and other network types. The pair of Axia AES3 nodes, for example, can be used to send and receive eight separate AES data streams between each other over a 100baseT Ethernet connection.

The Cumulus Youngstown engineers built a network out of HP Procurve Ethernet switches trunked together — one at each site — making use of fiber optic cables in the physical layer. The same old buried conduits were used. Problem solved — lightning damage has been eliminated.

The exclusive mix

Sometimes I find myself pining for the simplicity of yesteryear in radio — until I remember cart machines. Then I come to my senses. One thing about the old days though is that stations were often stand-alones, and when remote broadcasts were done, the talent typically listened off-air right at the remote site. There simply was no appreciable delay when using phone lines or RPU.

Along with all the great possibilities ISDN codecs brought to remote broadcasts in the early 1990s came the minor issue of the coding/decoding delay. To get around that, stations started using sending a mix-minus feed to the remote site, so the talent would hear everything but themselves delayed. That problem was solved.

Then the consolidation period started, with multiple stations located increasingly under one roof. One of the obvious benefits was the sharing of resources such as ISDN codecs.

And so another problem was generated: if you planned on sharing ISDN codecs among the stations, how would you generate separate mix-minus feeds, and more importantly, how would you switch them into the appropriate ISDN codecs?

When the station was a stand-alone, it was easy: You generated a mix-minus right on the console, and fed that bus to your codec. When multiple stations came under one roof, typically you made the mix-minus in the same way, and perhaps you used a patch bay or some other type of electro-mechanical switcher to change the mix-minus going outbound.

Once routers became more common in facilities, the patch bay or electro-mechanical means was typically replaced with the router's functionality. Therein lies a problem though; the router can give you too much control. If station WXYZ is doing a remote with ISDN codec 1 (for example) it's very easy for someone to accidentally change the mix-minus feed to accommodate another station in the group. WXYZ's mix-minus suddenly disappears or becomes station WUVW's during the middle of a remote! Unfortunately I've seen it happen. More than once.

Sierra Automated Systems 32KD digital audio routing switcher

Sierra Automated Systems 32KD digital audio routing switcher

Fortunately, modern console/router systems have a way to handle this problem. Clear Channel recently installed a Sierra Automated Systems 32KD audio routing system, so I know its method around this very real problem: dynamic mix minus. I know that Wheatstone, Logitek, Klotz and others offer it as well.

At our new Clear Channel facility in New York, we have five stations, 29 studios, and a collection of 16 different codecs (ISDN, POTS and IP types). Friday afternoon holds the biggest potential for errors in the mix-minus assignments, since we are doing remote broadcasts, taking traffic feeds from a remote location as well as remote talent via ISDN for production/imaging purposes. The 32KD is programmed to allow certain studios access to certain codecs; when the control surface in the studio is told to take that codec feed (in other words, the channel on the control surface that corresponds to that feed is turned on) a mix-minus feed is automatically made of a particular bus on that control surface (typically the one we all call off-line mix) and routed to the send input of the codec. Other studios that have been programmed to have access to that same codec can listen to the return audio, but as long as the studio using that codec has the channel turned on, all other potential-use studios are locked out from changing the mix-minus being sent. This prevents errors on the fly. This methodology has prevented the errors ever since.

The radio station of today shares much in common with the radio station of yesteryear; it's the way we accomplish what we need to that has changed. Sometimes by looking at the way something used to be accomplished we gain a little more insight in to the way things are done now. I hope the ways in which these “old” problems were solved with new technology inspire you to come up with some clever solutions of your own.

Irwin is chief engineer of WKTU, New York.

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