Why did my amp just crash and burn ?

I’m sure you new interconnects were not faulty but you could check with a volts meter to make sure signal wire is not crossed with return. If there was a problem or defect with interconnect it could caused amp to shut down.
 

I would think there would be more than one fuse for the amp other than just the one on the IEC inlet. Maybe one on each rail. I don’t know your amp so may not be the case. Good luck finding the problem.

I’ve been in your shoes, I crossed speaker cables on a McCormack rev a DNA 1and it blew the fuses on the rail. Not a good feeling, luckily got it up and running. Hang in there you will have it playing music again soon one way or another, YBA makes very nice musical gear.

Sorry,  thought you new cables were interconnects not speaker wire, should have read more thoroughly 

@erik_squires 

No music playing at the time . Can you elaborate on "DC on the the amp outputs"?

@larryi Has it right I was going to post the same thing your spades touched together you should be fine once you get a new fuse in there.

Does the YBA have rail fuses?

These would be inside the chassis.

B