Turn on popping noise.

I just picked up a Creek 4330 integrated.When the amp is
turned on (volume turned down),there is a very noticeable
popping sound that comes out of both speakers.Is this normal
or cause for concern?
How loud is it? A subdued popping is quite normal (more of a low frequency thump). A pop that makes you wince and check the speaker cones are still attached to the cabinets would probably indicate an amp problem. My densen amp produces a little pop when turned on, but nothing worrying.
That model Creek did have a turn on popping sound that will make your speakers jump a bit, nothing that will damage it, but still sonically noticeable. Many integrated manufacturers favor that thumping feature as it is something that they cannot rid when designing amplifiers without protection circuit. It is said that protection circuits that will prevent that sort of sound will degrade the quality of sound.
Other amplifiers that did this are:
Audio Refinement Complete
Sheaburn integrated (used to be distributed in the US, I think the dealer pulled the plug.)
Creek 4330 model....The other Creeks do not seem to have this.
Densen, as the other Goner says.

and some more.

I had the AR complete and it annoyed the crap out of me. I got rid of two of them, because of that fact and also because the second one, became almost a sort of lemon.