Transporting the Signal: Digital vs. Analog

January 27, 2015 by Chris Jackson

In the past, audio signals were analog one-way, single-purpose and point-to-point, requiring single wires for each, commonly resulting in large confusing masses of cables.

Today, digital technology transports the audio on standard data networks.

Some Advantages Are:

  1. Digital audio signal is not as susceptible to radio frequency interference (RFI) or electromagnetic interference (EMI) as analog audio signal.
  2. There is no degradation of signal on long cable runs.
  3. The cable installation cost is considerably less.

One of the first of these technologies was developed in 1996 called CobraNet. CobraNet data is organized into channels and bundles. A typical CobraNet signal can contain up to four bundles of audio traveling in each direction, for a total of eight bundles per device. Each bundle houses up to 8 channels of 48 kHz, 20-bit audio, for a total capacity of 64 channels.

CobraNet Disadvantages Include:

  1. Latency, or network transmission delays. This may not be a problem in applications such as a convention center, but it can be for a live performance venue or in a church.
  2. Hardware cost. CobraNet encode/decode equipment can be costly. Since a single network cable only carries 64 channels, the dollars saved in cabling using CobraNet may be offset by encode/decode interfaces.

Developed in 2006, Dante is a newer digital audio transport protocol. Dante offers uncompressed 1024channels of audio, 512 in each direction, at 192 kHz at 24 bits using standard IEEE protocols. Although it still requires proprietary encoding and decoding equipment, Dante has lower latency.

Now video has been added. In 2004, the IEEE 802.1 standards committee developed Audio Video Bridging or AVB. It was developed to transport precisely synchronized audio and video over a network. This new protocol can be adopted by equipment manufactures providing synchronized, low latency streaming through standard ethernet networks. One advantage to AVB is lower cost hardware. Since a standard DSP box, typically used on an audio install, can be ordered with an AVB or simple network port, hardware cost is minimal.

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