Like the master section E2 and S, the AT Master Section is designed for the stereo versions of the 5MT Mixing Consoles. It is compatible with the other stereo master sections E2 and S and combines all the master amplifiers for the main stereo master MIX and the cue- and aux sends, the monitor controller, and the talkback and playback system. The AT section offers a rich feature set. Many processing sections in the mix master chain make it possible to use a console with AT master block for mastering as well. In addition, the Master Extention module can be installed alternatively to the master module MST-AT. This module is a stereo processing device that includes two stereo master compressor with side EQ, 3 band fully parametric mastering equalizer, niveau filter, wide range phase shifter, M/S direction mixer with 'add center' function, a harmonics generator that can add 2nd and 3rd harmonic distortion and a dynamic EQ section.

The partitioning of the functions and the connection scheme makes the modules of the Master Section S interchangeable with the E2 and the AT master modules. It is not only possible to exchange the entire master block but a single module. Each single module of the E2, S and AT master section is compatible to the corresponding modules of the other master sections. Modules of different master blocks can be combined in any desired way. It is possible to arrange a kind of custom configured master block, just by putting together a set of a talkback module, a master module, a monitor controller and 2 or three monitor modules.

The functions of the Master Section S are distributed amoung 5 modules: