Recently I helped a friend of mine buy his first tube amp. Not a “hybrid” amp, with just a preamp tube, mind you, but an actual tube amp. I thought a nice series of blogs on the topic was in order. We’ll tackle a few different aspects of tube amps, and my goal by the end of this series is that you would have all the info you need on tube amps to make an informed choice if you are shopping for a new amp.

What is a tube amp?
“Tube amp” is just a way to describe an amplifier that uses vacuum tubes to amplify the source signal. Sometimes they are also called “valve amplifiers.” A vacuum tube is a glass “tube” that amplifies the signal, versus a circuit which is what amplifies the sound in a “solid state” amplifier.

The typical guitarist’s amp setup in all kinds of heavier rock music (like punk, emo, and hardcore) is the “half stack,” which refers to a “head,” which is the actual amp, and a “cab,” which is the speaker cabinet, in the case of a half stack, it is generally a speaker cabinet with four 12″ speakers.

An EL34 power tube

The “head” or the actual amplifier, if a tube amp, is usually 100W, though there are many other wattages available. 100W is fairly standard among touring punk, emo, and hardcore bands. All tube amps have two stages of amplification, the “preamp” section and the “power amp” section. The preamp section uses small glass tubes called (of course) “preamp tubes” which are about 2.5″ long. The power amp section uses “power tubes” which are about 4″ long and fatter.

Generally a 100W tube amp has 4-5 power tubes and 4-6 preamp tubes, while a 50W tube amp, by comparison, will have 2 power tubes and maybe 3-4 preamp tubes. As you can see, the more power, the more tubes required.

In the next installment of “tube amps in a nutshell” we will look at historically popular tube amps and why.