Tube pre-amp pop

my guess would be a DC coupling capacitor has gone bad in the AR pre

You means dc leaking? Would it will damage all my other new components. It is a brand new pre-amp and I thought AR is a good products. Any SP16 owner outhere? Called AR two hours ago, left a message but no response yet.

It does sound as if you have a capacitor leaking dc. Leonard at ARC would be the person to contact. I don't see anyway to fix it w/o sending back to ARC.
It shouldn't damage your other equipment, if the pop is at a low level as you say. If it is a leaking cap, the pop can get louder though, at which point it is possible that it could harm your speakers or amplifier. Get it fixed now.
If it's brand new, just have your dealer replace it, or send it to ARC, it should be covered under warranty.

The Bryston and Rotel are solid state, correct? From my experiences, tube equipment sounds much better, but is more prone to issues like this than solid state equipment.
This is not normal ARC operation though.

Thanks, jmcgrogan. I went to my dealer and tried on both of his SP16. They both are quite, no pops no boops from speakers. You are right that this is not normal. Bought the ARC about a month ago but did not received my Bryston amp untill last week. Just hooked them up couple days ago, very small pop at first and I did not sweat it. Today, the BOOPS sound is louder right beteen the speakers. Will put ARC service at test if the can exchange for another unit. My dealer will let me know and I will post follow-up about ARC customer service. Regards.