I just took out a Tung Sol RI from V1 in my amp cause it had a fizzy distortion when using high gain(which I like), and put a JJ in place of it. I'm now finding that the JJ sounds too trebly with the highs and doesn't really have a nice distortion character. Do you think it will improve with a few hours of use ? I do still have the original Sovtek preamp tubes and an extra Mullard RI 12ax7, so I may do some swapping to find something I really like. When I swap preamp tubes around do I need to turn the entire amp off or can I simply put it on standby ?