AAX - Avid Audio Extensions are used in the Pro Tools digital audio workstation for Microsoft Windows and OS X developed and manufactured by Avid Technology. Pro Tools can run as standalone software, or operate using a range of external A / D converters and internal PCI or PCIe audio cards with onboard DSP. There are currently two main versions: 11 (build 11.3.1) and 10 (build 10.3.10). Two other releases have also been announced, known as 12 and First, a free version of the DAW. For more on AAX click here.