I recently picked up a Fireface UC and I'm experiencing pops and crackles when using Logic Pro X on my mid-2010 MacBook Pro. After experiencing this initially in High Sierra, I did a clean install of Sierra (10.12.6), but the problem persists. I've tried changing buffer size, sample rate etc with no luck. It also seems to be affecting audio playback from YouTube. However, when monitoring my hardware synthesisers directly through TotalMix, the pops and cracks are not present. I have latest drivers and firmware installed.

Any help or advice would be much appreciated. Thanks!