A combo is a ‘combination’ of the preamp/power amp and all controls with the speaker contained in one unit, hence the name ‘combo’. This makes things much more convenient and easier to transport compared to the other amp type which is called a ‘Stack’. The stack system requires a ‘Head’ which houses the preamp/power amp and all other controls. This is connected with speaker cables to a wooden speaker cabinet, otherwise known as a ’cab’. There are two types of ‘stack’ a half ‘stack’ which has one speaker cab and a full ‘stack’ which has two ‘cab’s’. Two of the most common cabinet sizes are 2×4’s which have 2 speakers that are 12” and 4×4 which have 4 speakers that are 12”.