There is a known issue when using Symphony I/O or Symphony I/O MkII in Pro Tools HD mode with a Pro Tools HD Native card or HD Native Thunderbolt. The routing will be incorrect and/or audio will not show up where expected when you connect 2 Symphony I/Os (MkI or MkII) and the 1st unit only has one I/O module installed. This only occurs with HD Native– not with HDX or the older Core/Accel/Process HD cards.

 

Solution:

Make sure the 1st unit connected to the HD Native card or HD Native Thunderbolt on Port 1 has 2 I/O modules installed if you have 2 units connected.