Many people do not know the difference between head, cabinet, stack and combo amps. Here is a brief discussion of the differences between these amps.
Electric guitars need to be amplified in order to hear them louder than a simple acoustic guitar. An amplifier is exactly that, a machine designed to increase the volume of the guitar. This machine is comprised of two main components, namely the amplifier and speakers. More information is available about pre-amps, power amps and rack units but they are not discussed here.
The head amplifier is one that stands alone without any speakers attached. It is named head because it normally sits at the head of the speaker it is attached to. This amplifier will not produce any sound unless attached to a speaker. The lack of speaker does not make it any less of an amplifier; it just will not create any sound. These kinds of amps will need to be connected to a speaker in order to have any practical use.
The cabinet amplifier that only has speakers. Playing through this will have as little sound as playing into only a head amplifier. There is nothing to amplify the guitar’s signal and so will be useless on its own. These speaker cabinets are available in various combinations. A four by twelve cabinet normally has four twelve inch speakers, one that is two by ten will have two ten inch speakers. There are more combinations of sizes and speaker number and variants that are available. The twelve inch speakers are most widely used, but some people like to use the ten inch speakers for a different sound.
A Stack is a head and a set of guitar amplifier cabinets connected and ready to use. Although bulky, heavy, and loud, musicians prefer stacks for gigs, especially if they play large venues and stadiums on a regular basis.
Half stack guitar amplifiers: Smaller heads connected to a single 4×12 cabinet containing four 12-inch speakers are known as a half stack. Working musicians use this configuration to get the volume they need when they don’t want to wrestle with the bulk of a full stack.
Full stack guitar amplifiers: Many guitarists dream of owning a full stack. It’s usually a 100-watt head connected to two 4×12 cabinets, but the wattage can vary. The stack gets its name from the way the cabinets are stacked vertically. Suitable for all but the most cavernous stadiums, full stacks offer impressive volume. Wear protective earphones or headphones when you play guitar through a full stack at higher volumes.
Finally, a combo amp is just what it sounds like, a unit that has both the amplifier and speakers. Different units will have a different combination of speakers and amplifier. It is this unit that is normally called an amp by guitar players. This is typically the type of amplifier used in guitar practice. This is the most common form of amplifier used by players of any skill level.