Sound glitching

Hi all,

I've posted this before but no responses and it's really starting to frustrate me now.

When playing audio through my iMac (New 2011 27 i7) the audio keeps cutting out intermittently for short second bursts. This is happening both through the internal speakers and when i'm running a line out through the headphone out to speakers.

When i attempted to record this 'glitch' it doesn't show any error, instead a perfect waveform.

I've recreated an audio sample to let you hear what i mean as it's difficult to describe.
Audio Glitch - Soundcloud

Please please please if anyone knows what this could be i'd appreciate it as it's really doing my head in.

 

Thanks for the quick reply.

I've just added a new device (Aggregate Device) and changed this to be the default built-in output. It's still giving me the same issue unfortunately.