First, I apologize if this is too vague a question for this group -- I'm perplexed and I don't have much data to work with. I think it's probably impossible to solve, given the limited data, but I just wanted to see if anyone had any ideas. Also if there's something I should watch out for if it happens again, so that I can have better data to track down any issue.
I have a studio setup with modular synthesizers running into an RME UFX II which is also connected to a pair of Yamaha HS 8 studio monitors. I record using Logic Pro X on a somewhat old MacBook Pro (running the latest system). The electrical lines were checked when I moved in, all are correctly grounded. Power is run through a Furman power conditioner before it reaches the equipment.
I was playing back in Logic something I had just recorded and listening to it through the studio monitors. Suddenly there was a really loud POP through the studio monitors and the playback sound cut out. I can't remember whether the UFX II showed anything on its LED interface -- I was kind of shocked and trying to shut things down -- but it seemed to me that it still had a couple of bars lit.
I quickly lowered the volume on the UFX II, in case there were any more pops (there weren't) and stopped Logic playback. I tried playing Logic again, but no sound came out. I quit Logic and started it back up and everything worked normally. I shut down the entire system and then started it up again (I didn't reboot the Mac, though) and all seems fine.
I know this is a long shot, but where would I start looking to try to determine what happened? Hopefully it's nothing with the UFX II -- it's only about a year old, so no idea why there would be a problem. The Mac has about 7 GB worth of free space, which I know is very little. Perhaps it's something with Logic? I believe I have the buffers set to 512MB, for whatever that's worth.
I've been using this setup for a year or so with no issues. I did have another issue earlier today: when I started everything up, I couldn't get any playback sound from Logic through the monitors: just a lot of scratchy sounds. I had only 200MB of free disc space on the Mac, so figured that might be the issue. I rebooted the Mac and cleared off about 7GB of space and it worked fine, until the events described above.
Also, FWIW, I know this kind of popping is bad for the monitors -- nothing I can do about it now. But I suppose I'd notice it if it had done any damage, right?
Thanks for any info!
Edit: one thing I thought of, when I cleared off disco space, I erased some caches and application support files from my /Library, but nothing to do with Logic as far as I know.