HI Everyone,
I too experienced the dreaded latency issue on stage on the first date of a 6 month tour of a high profile artist. 3 resets during the show got me through, but it eroded my confidence in mainstage completely. Please remember, I'm no computer whiz, and I probably have the technical details wrong on some things.
Here's my check list of things that I changed, that have now stopped the issue from recurring. I can't narrow it down to one specific thing I did (to be certain I went back to my apogee Duet which i had been using before the tour) but if you want to keep using mainstage, these are my list of options To try:
1) replace all your cables, even if they are new. It seems simple but long USB cable runs, and short ones can cause issues and even new cables may cause the little glitch that sets off the latency. Maybe there's a loose wire that when shorts causes the clock to destabilise. Sometimes we buy a new interface and use the same cables.
2. If you have a retina screen, run it in low resolution mode (right click on get info in the MainStage application and check low-res mode). This will reduce your CPU usage if you don't have a dedicated graphics card (13" Mbp particularly).
3. Save each patch and layout for your shows and open them in an empty concert. Rebuild your show in the latest version. Maybe there is something residual triggering here.
4. I turn off I/O safety buffer; experiment with this one. This maxed my CPU when it was on, and I have a reasonably fast Mac. lowering your CPU usage is more likely to reduce crashes not the latency issue, but hey, try it anyway.
5. Does your interface have an alternate mains power supply? Don't rely on the USB slot to provide constant power. Possibly the introduction of latency occurs during a brief moment of power loss or energy change modes in the computer, so bring that mains power supply, and you know the power will be constant. I actually think this is the biggest possibility of the source of the problems.
6. plug your interface into the powered slot! Don't go through a USB hub, because the data can bottleneck if you have too many devices on that one hub. My approach is that the interface goes into one slot on the laptop, and the hub goes into the other. The powered external hub receives all of your instruments and midi devices etc. the interface is therefore running independently. And make sure the USB slot on your Mac where the audio is going in is the powered hub. They are not all the same.
7.Make sure the screensaver isn't kicking in. I disable the lock screen completely when performing, so that the screensaver or lock screen isn't attempting to kick in, and then being over-ridden by Mainstage's own setting.
8. Oh, if you're using a hub, make sure it's externally powered.
9. I found the latency setting and samples in audio preferences had no effect on the overall introduction of 1s of latency issue, but just at resetting the audio When You're on stage and you are in a hurry to restart.
10. That didn't work? Throw your computer aggressively at an audience member during a show. It won't fix the latency, but you won't have a gig anymore, so in a way the need to use mainstage problem is fixed.
good luck.
