Many broadcast stations around the country are a hybrid mix of analog and digital audio signals. Popular audio/video matrix house routers offer not only the ability to route signals through matrices, but will accept analog, digital, and embedded audio. In addition, these routers can provide A/D-D/A conversion.
This “parallel” operation can save broadcasters many thousands of dollars in audio conversion equipment. However, the process can be complex. When multicasting to a mix of analog and digital outputs, the opportunity for errors increases.
Just a few years ago, the idea that audio might not follow video through a house router would seem remote. Each source would get a real world checkout many times a day. In today’s modern studio, this regular check may not be so frequent. For instance, although the video may remain SDI, some destinations may require AES audio while others require analog audio. Perhaps you have a secondary broadcast channel that is digital only, and you need to route a purely digital signal into it. If a single cable has been incorrectly connected, or possibly moved, your AES source may not match your analog audio source.
There are more than a few stations that still use house router monitoring amps fed by analog audio instead of AES to verify audio parameters. During this transitional period, it may be a good idea to occasionally verify that both digital and analog audio does indeed follow video through your routing system.
