Of an Ultra Double 550+. Or however its labeled.
My 550 blew out a few weeks ago, which Frank narrowed down to a defective tube frying a signal MOSFET.
I took the opportunity to upgrade the thing from a plain old 550 since Frank already had it in the shop.
I can't wait to receive the unit back, although since I'm stuck in England for the time being, I won't have time to hear it for about a month. I'm sure it will be great though, I could tell the difference between my double 240 and the plain 550, and I'll love to have all that extra power back.