There is a known issue with the input routing in ProTools HD if you install a 2×6 module in the primary slot of a Symphony I/O MkII and any other I/O module in the secondary slot and use it in ProTools HD mode.

 

Solution:

If you are using a 2×6 module in combination with another I/O module in a Symphony I/O MkII in ProTools HD mode, make sure you install the 2×6 module in the secondary slot and the other module in the primary slot.

 

Supported 2×6 configurations for Symphony I/O MkII in ProTools HD mode:

Primary: 2×6
Secondary: none

Primary: 8×8 (any old or MkII 8×8)
Secondary: 2×6

Primary: 16×16 Analog In/Out (original or MkII)
Secondary: 2×6

 

2×6 configurations not supported for Symphony I/O MkII in ProTools HD mode:

Primary: 2×6
Secondary: 2×6

Primary: 2×6
Secondary: 8×8 (any old or MkII 8×8)

Primary: 2×6
Secondary: 16×16 Analog In/Out (original or MkII)

Note: the older 16 Analog In/Digital Out and 16 Digital In/Analog Out modules are not supported in Symphony I/O MkII regardless of what mode you’re using the unit in.