@ benitom25:
The behaviour you describe when playing an audio file from the finder seems to be a bug in Mavericks. In the Metric Halo mailing list (the company that makes the MIO audio interfaces) one of the developers wrote the following:
In addition, on Mac OS X 10.9 (Mavericks), Metric Halo is aware of the following issues:
The Finder and QuickTime Player in Mac OS 10.9 play mono files as silence when playing to a MIO. You can work around this by using other apps to play this kind of content. We believe that this is a bug in Mac OS X and have reported it to Apple.
QuickTime Player and Safari in Mac OS 10.9 play stereo files and HTML5 audio with sputtering dropouts when playing to a MIO. You can work around this by using other apps to play this kind of content (e.g. Chrome or FireFox). We believe that this is a bug in Mac OS X and have reported it to Apple.
As these issues currently appear to be bugs in Mac OS X, we do not know when they will be resolved.
Let’s hope that Apple will fix these bugs.