To me it sounds like C is the brightest of the three, while B is the dullest. The input impedance might be making a difference, since the Type 10 is rated to 10MOhm, the FFUFX to 800kOhm and the Axe-FX II has a variable input impedance (1MOhm max). However 99.9% of tube amplifiers has a 1MOhm...