It probably is being caused by the amp being enabled by the blue "power on" indicator line from the empeg. Some amps can draw a lot of current from this line; the empeg, consequently, draws more also - then pop goes the fuse on the main power line to the empeg.

Solution: fit a relay to the amp and use the blue power enable line to turn on the relay.

Are you also connecting the blue wire to a powered antenna? If so, same rule applies.

Read the FAQ on installation issues.