Orange VT-MKII-EXP-A Valve Tester Mark II Expansion Module AOranges Valve Tester Mark II accommodates an assortment of different tube designs, from bog standard preamp tubes to lesser known power tubes and beyond. However, as any of tube amp techs will be quick to tell you, guitar history is full of countless variations of valve varieties. Luckily, Orange offers a robust range of expansion modules for the Orange Valve Tester Mark II, allowing you to quickly check their health with a comprehensive set of tests