I believe that the Pro-Tube II has the ability to blend the clean and overdrive channels.There is also a switch to cut power down to 1/3 of the amp's rated 55 watts rms.It also has a push/pull shift pot on the overdrive channel's Gain Contour control.Other than those features,I believe that the circuit is basically the same.I hope that helps.
Ed
Thanks for the info-- sounds like a sweet amp. I'm going to have to try one out if I can ever find one.