Lesson learnt: If something tripped, shutdown, don't try it again right away. Always check, investigate, or/and wait for the unit to have a chance to settle, cool down.
In this case it looked like the Denon's protection circuit did work the first time and shutdown the unit time before it blew, but then you did it again too soon and the protection circuit did not react fast enough to protect the already cooked, or overheated, weakened some parts (to a point..).
At work, I lost count how many times electricians blew something up (e.g. motors) because right after it tripped on overload or short and their typical reflex action was to do a "reset", be it resetting a thermal overload, instantaneous over current device or circuit breakers. The odd time they would do it right by troubleshooting with a multi-meter. Lots of people do the same with fuses, always turn things on right after replacing the fuse, without trying to figure out why it blew in the first place. Sometimes, they end up blowing all the spare fuses even if lucky enough the device manage to survive but still stuck because they would run out of fuses when they eventually found and eliminated the root cause.
