What is MADI?
By Rob Masters
(The Audio Pros Resident Tech Guru)
Over the past few years, more and more people are beginning to hear about and take advantage of the MADI (Multichannel Audio Digital Interface) format. Gone are the days of prohibitive pricing and limited real world solutions – MADI has gone mainstream.
Born in 1989, MADI was an extension of the Audio Engineering Society’s AES3 (also known as AES/EBU) standard transmission format. While AES/EBU is limited to 2 channels, because it is a balanced bi-phase signal, the first incarnation of MADI could handle 56. Simply put, 28 bi-phase signals in series. |
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MADI multimode fibre optic cable |
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ALVA MADI Drum |
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Since its inception, MADI has evolved from its initial form to support 64 channels up to a sampling rate of 48kHz, 32 channels at 96kHz and 16 channels at 192kHz. Not only this, but it can now be carried on generic multimode optical fibre, of 50 or 62.5 µm diameter (see below), as well as 75W coaxial cable. Unlike ADAT, MADI over optical fibre uses a frequency of light outside of the visible spectrum.
Why use MADI? Outside of the obvious benefits of being able to carry up to 64 audio channels, there are a number of other reasons why MADI is an increasingly popular format: |
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Very long cable runs are possible. MADI can run up to 100m over coaxial cable and up to 2000m (!) over optical cable, making it possible to transmit audio around large venues and recording locations. |
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The fibre optic cable used is of the same variety as generic computer network cable making it very cost effective. Much cheaper than lots of expensive copper cabling. |
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With more and more people moving to higher sampling rates, MADI has become a cost effective and simple way to handle multiple channels at 96kHz and 192kHz. For example, 16 channels at 192 kHz down 1 thin optical cable is a very elegant solution. |
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It is also possible to transmit control data, such as MIDI and RS-232, within the available user bits of the MADI stream without encroaching upon the 64 audio channels. This means, for example, you can fully control all settings of a microphone preamp mounted in the roof of a theatre from any location, up to 2km away, within the venue! |
Initially conceived to distribute bulk volumes of audio around large complexes, MADI is now commonly seen throughout studio, broadcast and live environments. It has evolved over many years to become a flexible and powerful solution for professional audio applications.
Need more information? Call 01923 693770 or email info@audiopros.eu |
