[hirundos]

Thanks for your response, Darryl!

I believe that "Focusrite Thunderbolt" always has to be selected as the playback engine when using it, otherwise you won't hear anything coming out. Sessions sometimes default to the Aggregate I/O when I open them and the interface is connected, and I know this because I won't be able to hear anything when playing back and have to go in an manually change the playback engine. Though I can run a test to see if this is indeed totally the case.

90% of the time I am using PT I am doing editing and not using an interface (and monitoring through headphone out on my laptop). Should I still delete the aggregate I/O? And if so, how? I haven't bothered to look up what it is, but I'm usually using it by default when just editing, but maybe I don't have to.

When referring to I/O buffer size, do you mean the H/W buffer? I currently have it set to the highest setting at 1024 samples.

I had the person who was doing the recording do all of the "recording best practices" on my computer: turn off wifi, no other programs running, do not allow disks to go to sleep, etc.

Stuff like this is maddening because it's so intermittent. Focusrite gave me some test to do, but just because I run it without any noise doesn't mean it won't come back.

Thanks again!