Here's a quote from a customer from
www.eurotubes.com:
Hang on... I have been torturing the JJ 6V6's in my 66 Bassman head now for several weeks at 460 plate volts biased at 22mA per tube and they sound GREAT! Jamona told me that they would run at up to 500 plate volts so I decided to give them a thrashing and they are holding up just fine. I also have a pair in a friends Hot Rod Deluxe at 445 plate volts and 24mA per tube and this is a gig amp for him so it will be a good test. So far the JJ 6V6's make a surprising amount of power and tend to breakup a little earlier with a mid and upper end crunch that is VERY cool! I'll keep you all posted on how they do over the long run but so far I'm very impressed! This should be a nice option for players looking for a little earlier breakup and that classic 6V6 crunch in bigger amps.