Recording has crackles

Hi,

I have 2x PIONEER CDJ2000-nexus's and a PIONEER DJM900-nexus (mixer). The DJM900 has a USB output which you can plug directly into a Mac and record your mix, using Audacity.

I previously had a Windows 8.1 laptop which recording crackles and pops during my recording. My friend came around with his MacBook Pro and plugged into the same setup and recorded with Audacity successfully, no crackles, no pops. We have since done quite a few recordings without problems.

So I decided to buy a MacBook Pro myself. However when I record on my MacBook Pro (same setup, same drivers, same applications) I get the crackles and pops. I am really frustrated with this. I have since tested on a friends MacBook Air and that worked perfectly.

To save you some time in asking me to do certain tests I'll list what I've done:

Restarted Mac

Deleted Driver and App

Installed latest Driver and App

Changed every setting known to man in Audacity

Completely wiped my Mac (this evening) and gone from a fresh install of OS X.

I did start playing with the Pioneer hardware and USB cables but since successfully recording on 2 different Macs I've ruled the hardware out.

What is wrong with my Mac? 😟

Any help appreciated. Thanks.