Why did my amp just crash and burn ?

Glad you got the amp working again. If an amp has to be opened up to replace B+ fuses be careful. Even with amp unplugged and off, the power supply capacitors can still store dangerous energy. Most power amps drain this energy. Saw a friend loose part of a screwdriver tip when it shorted a giant capacitor. It is also bad to rapidly cycle amps on off on. 

Weirdest thing I encountered was a friend tripping over a speaker wire. As expected it blew the amp fuse. It also blew the fuse in the Linn Sondek LP12 turntable. Took a while to find that.

Thanks,

aldnorab 

My Naim and Teddy Pardo gear provides additional fuses onboard. I recently upgraded my Supernait 3 and Teddy Pardo TeddyCap SE with Synergistic Research Purple fuses. They are excellent! Check out the thread below. 

Is there an actual risk as to safety on switching interconnects for example with a dac in standby and a line stage thats always powered?

Sounds like a short. 

I don't ever use spades becasue they can short when twisted.

Jerry

Some Amplifiers only accept spade connectors.  Mark Levinson for example.