I've heard of people having all kinds of problems with Yosemite if they update from a previous version of OS X as opposed to doing a clean install and then re-installing your software. The update route can break all sorts of things. It might be necessary to do this (a clean install) to get things working properly again. Make sure to back up anything you don't want to lose first if you go this route. I did do a clean install of Yosemite and am experiencing no problems whatsoever. I have Logic Pro 9 and Logic Pro X running flawlessly on both a MacBook Pro with Retina display and a MacBook Air. Hopefully, you can find another fix to your problem but, if not, a clean install should get everything working again. There is all sorts of info on the web about how to do this...it's pretty painless. Good luck!!

Hi Tim, Glad to hear it was such a simple fix...sure saved you a lot of trouble. I hadn't thought about updating the drivers as the interface I use doesn't require one on a Mac. I have a Focusrite 2i4 USB interface which is recognized by Apple Core Audio when you plug it in. As I mentioned, I did do a clean install with Yosemite and have experienced no problems of any kind. After taking a bit of time to get used to its new look and behaviour, I really like it now. Anyway, happy recording and good luck with your projects. Best regards. Ivan

I should think it would run just fine. I run it on a MacBook Air with only an i5, 1.4 gHz processor with no problems whatsoever and the Mac Mini you described is higher spec'd so you should be good to go. You'll need to upgrade to the latest version of Yosemite though if you want to run the most recent update to Logic Pro X.