Mesa Boogie Mark V 90W Tube HeadThe MARK V is really a collection of amplifiers. There are far too many circuits and sounds to think of it as merely an amp. It is also a living history of our company. From the groundbreaking MARK I that introduced the world to high gain with it's cascading pre amp, to the Mark II the world's first high gain Dual Mode Channel Switching amplifier and it's later siblings that introduced Simul Class power. From the MARK III that ushered in the era of 3