I am new to this but how do you record audio on an external source and maintain sync? The one time I did it the audio drifted after a few minutes until it was off by a few seconds after twenty minutes of recording. What settings do I need to be aware of on my audio recorder to make sure it is the same speed as the camera?
Apple Certified Master Pro FCS 2
For sync you rely on crystal sync accuracy. Almost all modern digital recording devices from cameras to audio recorders have highly accurate onboard crystals that set an accurate speed, sufficient for sync over many hours.
Your issue is most likely the fact that FCP stamps a frame rate on imported audio which has been causing the avalanche of sync drift threads here on this forum for the past few years. Thankfully Matt Lyons wrote and excellent tutorial on why this happens, how to fix it via XML and also how to correctly import audio BEFORE syncing. Please search for Matt Lyons tutorials.
This is the second sound sync thread today btw, so this really is becoming the most common issue with FCP. I hope the FCPX developers are following trends and taking notes. Feel free everyone to contact Apple with your bug report