A stack, in the world of guitars, consists of an amplifier head and two speaker cabinets that are stacked on one another. This arrangement is most likely where the name “stack” came from. The speaker cabinets within a stack usually contain four twelve inch speakers in a square arrangement and the head is typically around 100watts.When these components are all on top of each other they form quite a large and intimidating wall of musical amplification that is desired by many guitarists.
One of the most famous makers of stacks is Marshall Amplification; however, almost all amplifier manufacturers produce a stack in one form or another.