Just had my first tube go on me after two years of tube rolling. Red flashing followed by a load of loud crackling. It was a GU50 to, such a strong looking tube. Like a daft bugger I tried it once more after removing and replacing it but same results again. Luckily having replaced the GU50 with a spare all seems to be fine both with Euforia and my precious HD800's. Still sounds marvelous.
I'm happy your Euforia and HD800 survived. I had an EL39 fail on me in December. No loud popping, but a brief crackling before the channel cut out. I know the chances of a tube taking out a driver as it dies is low, but that did scare me!