With the Avid MTRX 8 AES 3 Module you can add eight line AES3 inputs and outputs (16 channels), with built-in sample rate conversion.
Pro Tools | MTRX is fully modular, enabling you to customise it with up to eight analogue and/or digital audio I/O option cards to create a 64-channel interface for Pro Tools | HD. You can install a maximum of six AD and/or DA cards to support up to 48 analogue channels. Or design an all-digital box - or any combination between. Just start with the Pro Tools | MTRX base unit and go from there.