Multichannel Audio Digital Interface, or MADI, is an industry-standard electronic communications protocol that defines the data format and electrical characteristics of an interface carrying multiple channels of digital audio. The AES standard for MADI is currently documented in AES10-2003. The MADI standard includes a bit-level description and has features in common with the two-channel format of AES3. Serial digital transmission over coaxial cable or fibre-optic lines of 28, 56, or 64 channels is supported, with sampling rates of up to 96 kHz and resolution of up to 24 bits per channel.
MADI links use a transmission format that is similar to the FDDI networking technology (ISO 9314), which was popular in the mid-90's for backbone links between LAN segments. Since MADI is most often transmitted on copper links via 75 ohm coaxial cables, it is more closely related to the FDDI specification for copper-based links, called CDDI.
The original specification (AES10-1991) defined the MADI link as a 56 channel transport for the purpose of linking large-format mixing consoles to digital multi-track recording devices. Large broadcast studios adopted it for use routing multi-channel audio throughout their facilities as well. The latest specification, called AES10-2003, adds a 64 channel capability as well as support for "double-rate" sampling at 96 kHz by removing vari-speed operation.
MADI is widely used in the audio industry, especially in the professional sector. Its advantages over other audio digital interface protocols and standards such as AES/EBU (AES3), ADAT, TDIF and S/PDIF are first support of a greater number of channels per line and second the use of coaxial and optical fibre media that enable the transmission of audio signals over 100 meters and up to 3000 meters. Some main providers of interfaces and computer cards for MADI are:
- Euphonix 
- Solid State Logic 
- RME 
- Fairlight 
- Sydec Audio 
- Lawo 
- Merging Technologies 
- Harrison Consoles.