Hi,
The dual EVM setup is a 2 C6670 EVMs + an AMC break-out card: https://estore.ti.com/CI2EVMBOC--P2685.aspx. When connecting 2 EVMs for AIF2 traffic, you need to ensure a common source clock for both EVMs, and a common 10ms frame sync pulse to trigger AIF2 timers on both EVMs at the same time.
Best Rgds/Seb.