I have recently bought a Fireface 800 from USA. Well, it's cutting and crackling audio. Even on Analog 1-8 Bandwidth. My system is:
Model Identifier:    iMac12,2
Processor Name:    Intel Core i5
Processor Speed:    3.1 GHz
Number of Processors:    1
Total Number of Cores:    4
L2 Cache (per Core):    256 KB
L3 Cache:    6 MB
Memory:    16 GB
Can really somebody help me please.  I also have a Tascam DM 4800 console. And wotk with LPX 10.4.1.
Thanks a lot guys..