FWIW, the dealer initially said you could also run 6L6's in the One, so I tried it out. Initially I had no problem 'til one day I left the amp on continuously for 12 hours. I was out of the room for the last 6 hours. I came in and the sound was 'dark' and the sound stage was closed in. Highs were rolled off and the sound generally muffled. It wasn't subtle. Short story - I turned off the amp and turned it back on about 30 minutes later. The problem was gone. I assumed that the auto bias curcuit was the problem (and I still think that is so). You will note that no where in the manufacturer's literature does it say that you can use 6L6's, only EL34's, whereas in the Two it includes 6L6's and KT88's. Obviously there are more changes in the two amps than the simple ones that mentioned in the vendors descriptions. I reverted to EL34's. Anyway, thats my experience.
What experiments have you made with the small tubes - fertile ground there for tonal changes.
What experiments have you made with the small tubes - fertile ground there for tonal changes.