Everytime I change the input on my receiver, the sub makes a loud BOOM... Is the sub blown, or the amp on the sub fried?

Have you used this receiver with another sub before? It could actually be your receiver and not the sub. Do you have another sub you can try?

Your receiver should mute its output when it's switching. If it doesn't, the switching transient can create a noise in your sub and/or speakers.

Yeah.... what Mojo said. The problem is that your receiver is sending something out when you switch inputs... It's not the subs' fault!

That's what my first thought was, but I actually tried another receiver, same outcome. I don't have another sub or sub cable to test with.

I was about to say you can be sure it's not the cable, but who knows? is it a piece of bare wire fashioned from a coat hanger or something?

I have exactly the same problem with my system. My EP-500 makes the same pulse noise each time my receiver detects a new surround mode (changing channels on my STB, DVD layer changes, etc.). Just out of interest are you using a Onkyo receiver (mine is a 5 yr old TX-DS696)? I believe Onkyo has a problem with their muting during mode changes and this causes the problem. I had this receiver hooked up to an old Sound Dynamics sub for years and never had this problem which is strange.

Axiom suggested a ground problem from my cable provider may be at fault but I have tried removing my cable connection from the system with no joy. My sub behaves perfectly once I'm thru the menus, etc. on a DVD, until it gets to the layer change.

This is not a cable problem - I've tried several different cables with the same problem each time.

Did you ever get find a solution for this problem?

That's a common occurence caused by voltage in the line when you switch inputs. I've experience that with all my subs. Some receivers or processors however avoid the pulse. Depends on the unit not the sub.

FYI, I don't have such a problem with my Denon.

No problem with Onkyo 805 (but this is a new line).

No such noises with my Denon 3608 either.

NO such problem with my Yamaha RX-V659