So I powered up my PRRI a few minutes ago to check things before tonight's gig. I got weird thundering and sputtering. I looked in back, and one of my power tubes was doing some cool purple arcing and flashing, much like in this video: So I replaced it with a spare EV I had sitting around, and all seems to be well. Full disclosure: the amp is only a few months old, but I did accidentally leave it on all night (volume only at 2) earlier this week. So my questions: 1. Is it good for tonight? 2. Is there a bias thing I need to do eventually? 3. Should I just replace both? 4. Is there a way to buy them pre-biased/matched? 5. What's a good power tube upgrade I can do (if I need to be replacing them anyway)? Thanks muchos!