Guitar Amps, Combos and Speaker Cabinets

Combo, head or cabinet: what the box actually contains

A combo puts the amplifier and speaker in one cabinet and works as soon as you plug in. A head is only the amplifier and needs a separate speaker cabinet, while a cabinet holds only speakers. Cabinets are described by speaker count and size, so 1x8 is a single 8-inch speaker and 4x12 is four 12-inch speakers. Check the head's output impedance, in ohms, against the cabinet's rating before connecting; a mismatch can damage the amplifier.

Tube or solid state, and how many watts you need

Solid-state amplifiers are lighter, steadier and need little upkeep, which suits practice and travel. Tube amplifiers respond more dynamically when pushed and need their valves replaced eventually. Watts are not a straight loudness scale: a 20 W amplifier is plenty for home practice, while a rehearsal with a drummer calls for far more headroom. Also look at channels, built-in reverb or chorus, a headphone output and, on acoustic guitar amplifiers, a separate microphone input.

Questions about Guitar Amps, Combos and Speaker Cabinets

How do I match a head to a speaker cabinet?

Compare the impedance, commonly 4, 8 or 16 ohms. The amplifier head must be set or built for the load the cabinet presents, otherwise it can overheat or be damaged. Match the two numbers printed on the labels.

Can I switch on a head without a speaker connected?

No. Running an amplifier head with no speaker load can damage it, tube models especially. Always connect a suitable cabinet with a proper speaker cable, not an instrument cable, before powering up.

How loud is a 20 watt guitar amplifier?

Loud enough for a bedroom, and workable in a small practice room. Loudness also depends on speaker efficiency, so two amplifiers with the same wattage can sound different. More power than you need gives headroom, and you can always turn it down.