slackernaut

Hey kids. I just recently got a Spider IV 150 combo used at geetar center and it's been really fun so far, but, something has come up. It seems there's an echo that I can't figure out how to get rid of no matter if the delays and reverbs are completely off. Is this "normal" or has my used amp been dropped on its head?!. It's there with every amp model, not real prominent, but enough so that it makes this kind of annoying slapback tick/click sound, especially when doing clean, palm muted picking with some reverb. Anyone ever notice this or hear of this? Thanks in advance.