If you are experiencing a buzzing noise that changes tone with buffer size in Pro Tools this is probably due to a mismatch in the buffer size reported by the driver and the H/W buffer size in Pro Tools. This can be resolved by making sure that the 'Minimise Additional I/O Latency'
option is unchecked
in the Pro Tools Setup > Playback Engine options.
This is shown correctly in the diagram below:
If you continue to experience problems, please contact Focusrite Technical Support