A full stack refers to a guitar amplifier made of a head and two cabinets. The amp head is the part that contains all of the actual amplifier components. However, very few amp heads contain any speakers. The amp head only serves to amplify the signal, but it rarely produces any actual sound. A guitar cabinet only contains the speakers used by a guitar amp. The number of speakers can vary, but a full stack amp almost always has two cabinets with four speakers each.
Turn off the amp head. You do not want to connect or disconnect anything while the amp head still has power. The motion of plugging or unplugging a jack on the amp can cause popping noises, which can damage the speakers.
Connect the “L” output jack on back of the amp with the input jack on the back of either speaker cabinet with an instrument cable. It does not matter which cabinet is connected to this jack. A guitar produces a mono signal, so both cabinets produce the same sound regardless of which output jack is used.
Connect the “R” output jack on the back of the amp to the input jack of the other cabinet with an instrument cable.
Flip the switch on the back of the amp to the same impedance setting marked on the back of the cabinets next to the input port. This step only needs to be performed if your amp head has an impedance switch.
Connect the input port on the front of the amp head to the output jack on the guitar using an instrument cable.
Turn the volume control on the amp head to the lowest setting. Turning on an amp can cause popping sounds to occur that can damage the speakers. In addition, you can potentially damage your hearing if the amp is set too high when you turn it on. Turning down the volume control and turning it back up slowly prevents both issues from occurring.
Turn on the amp head.
The impedance of the amp head and cabinets must match or you risk damaging the speakers. Some amps can vary the impedance to match different cabinets. However, you need to get matching impedance cabinets for amp heads that do not have this capability.