Troubleshooting Amp/Preamp

I was disconnecting an Ipod from a cable running to my home-gym system(NAD preamp/Carver amp)--should have switched off stem first! There was a loud low-pitched hum. Now, I'm getting no sound out of the system. No sound from cd/phono/ipod. The Carver amp has a fuse but it seems intact in the wire within is intact (it also contains a small spring and a metal sheath around part of the wire)

Any ideas? Do you think it's likely the amp or the preamp?

I recommend replacing the fuse even if it looks good. It's going to be the cheapest solution. More than likely, there's also a fuse in the preamp. You should check that too.
Do you think it's likely the amp or the preamp?
If it's not obvious where the problem exists, you'll have to do some basic troubleshooting. Can you pull out the amp and replace it with the one in your other system? If it's not the amp, switch out the preamp. That should help isolate the problem.