ARC 100.2/ GOT A PROBLEM

Well, I am a newbie for ARC AMP. Actually, I just upgrade my system to ARC LS16+100.2. Here is the problem, when I turn the AMP on, there have a subtle "bo" noise come out from speaker and right after ten more second another one.
It is really annoy. I am wondering if this is normal for such HI-END component. My CLASSE CA-100 never have such issue anyway.
Thanks