Audio Playback Issues

Hi chaps,

I just purchased iReal for my Mac and the audio playbacks terrible through my audio interface but perfect through the built-in speakers. I'm running OSX 10.9.5 and the interface is a Lexicon Alpha. My first thought was that the interface is playing up, but I run everything else through it (so I can be on cans and not annoy the neighbours/family!) and this is the only program which isn't working properly.

Any help would be greatly appreciated, thanks! :)