I'll be honest, when I first got the amp off a friend of a friend, I was a bit disappointed. There was this "brash/harsh" sound to the upper midrange, that bugged the shit out of me. I was ready to off it, but decided to try an RFT in V1 for the halibut. It changed the character of the midrange for me, which leads me to believe there was something wrong with the preamp tube. Since then, I couldn't imagine getting rid of it. I'm running EL34L that came in it stock, but I love 6CA7, so would be very open to trying it.