MADI: Theory

MADI is the Pro Audio Industry standard for multichannel audio. The MADI standard was defined by the AES (Audio Engineering Society). Many factors have influenced the increasing importance of MADI in pro audio production systems. These include an overall growth in the use of digital audio equipment, and the ever increasing demand for greater numbers of audio channels in large productions. Surround sound production has also raised the requirements of multi-Channel applications. MADI is an attractive and convenient interface technology, as it provides the simplest method of transmitting 'sample accurate' audio channels over long distances. The balance between operating distances, installation costs and overall maintenance is exemplary.

Technically, MADI keeps all AES/EBU 24-bit signals in serial, while allowing the sample rate to still vary by +/-12.5%. Time Division Multiplexing is used to fit all audio channels into a single cable. MADI can also be used to transmit high sample rate audio signals. The MADI format is capable of transmitting up to 64 audio channels (at standard sample rates of 44.1 or 48 kHz) on a standard 75 Ohms coaxial cable or an optical fibre cable. The 64-Channel mode was introduced officially in 2001. It allows for a maximum sample rate of 48 kHz + ca. 1%, corresponding to 32 channels at 24-bit / 96 kHz. MADI is unidirectional, providing a 'point-to-point' interface between a source and a destination. The MADI format is fully specified in the AES-10 standard document.

MADI signals can be transmitted by two cable types:

• Coaxial, max. 100 m (75 Ohms, BNC)
• Optical fibre glass, max. 2000 m (62.5/125 µ, standard network technology)

MADI: Practice

The MADI standard is the perfect solution for the transmission of multiple audio channels.

Multi-pair snakes for different applications in live, studio and installation have been an audio-standard for years and still are. The more channels are needed the more a snake becomes invaluable. The use of a snake, especially in mobile applications or on the road, does not become more reliable as the time goes by, because it will get hoisted, coiled and often stomped on by the crowd. If even one channel in a snake fails you are faced with the following problems: Where is the fault? - Is it the cable or the connector? - Can we fix it? - Do we have to swap to another unused or even used channel? Under stress conditions there often might not be any time to analyse the fault and to even to fix it. In most cases a faulty snake becomes obsolete and has to be replaced completely. Even if money does not matter – problems occurring on a 64-Channel snake can hardly be controlled.

On the contrary MADI: A thin cable transmits up to 64 audio channels, lossless - up to 2000 meters!

Please study our MADI setup examples.

Redundancy: RME MADI devices have the SM-I (Safe Mode Input) feature to switch automatically between the optical and coaxial port if one of the cables or connections are disconnected by mistake, or are the signals become distorted.

RME MADI products come with optical and coaxial MADI connectors. The coax MADI cable allows transmission distances of up to 100 meters. The MADI fibre cable connection allows transmission distances of up to 2000 meters. The cables used are standard in high-speed computer network technology. There are many applications where long distance audio transmission is required: multi-room production facilities, outside broadcast venues, live venues etc. The optical interface is much more interesting due to its complete galvanical isolation.

For numerous users the optical interface is a mystery, because very few have ever dealt with huge cabinets full of professional network technology. Therefore, here are some explanations regarding ‘MADI optical’: The cables have an internal fibre of only 50 or 62.5 µm diameter and a coating of 125 µm. The plugs used are an industry standard, called SC. The cables are available as a duplex variant (2 cables being glued together) or as a simplex variant (1 cable). The transmission uses the multi-mode technique, which supports cable lengths of up to almost 2000 meters. By the way, due to the wave-length of the light being used (1300 nm), the optical signal is invisible to the human eye. Road-proven MADI optical cables with cable drums are also available. Ask your Premium Line Dealer for the Audio AG / Alva Cableware program.

MADI is being used: as a multi-Channel link between mixing consoles, DAWs or multi-track recorders or other digital outboard gear, as a transmission format in large scale digital audio routing systems, to transmit digitised microphone and line signals from a stage box to a theatre or studio mixing console. With RME MADI products and the RME ADI series front-end devices, you can combine different audio standards such as AES/EBU, ADAT and TDIF into one MADI audio system. Any MADI installation will remain an open system, easily expandable to any size on demand, using RME devices or products from any other major pro audio brand.

Costs

A flexible analog multichannel connection includes different components:

Multicore cable - circuit connectors - breakout box - stagebox - signal splitter.

Such a system is usually very expensive. A RME MADI system for 64 audio channels in a simple case includes two 19" devices (e.g. ADI-648) and a fibre glass connection cable - not more.

The cost for such a MADI system include extensive audio signal processing options:

Routing - splitting - merging - MIDI in MADI - remote control of all devices - redundancy

Economical Benefits: Integrating MADI solutions into an audio network not only increases more than just reliability. The setup and cabling is simple, too. Routings are remote controllable without any physical switching or swapping of connections. Patchbays become more and more obsolete in the overall system. Especially when dealing with different acts, performances or shows, MADI simplifies and speeds up any configuration changes. MADI saves time and therefore saves costs. In older buildings, expanding existing cable networks (for more or bigger multi-snakes) can be a major cost factor, or even physically impossible. The low maintenance associated with a MADI installation, compared to analog solutions, saves money and raises reliability.

MADI Suppliers

The MADI standard is supported by many Pro Audio manufacturers

The list of supporting manufacturers reads like a "Who's Who" of the high-end audio industry: Euphonix, Merging, Lawo, YAMAHA/Audio Service (MADI cards for YAMAHA digital desks), Stagetec, Studer, DiGiCo/Soundtracs, Fairlight, GENEX, Otari, Publison, Soundscape, Jünger, Sony, Cadac, Calrec, Axon, AMS/Neve, Stagetec and others.