For guitarists, the amplifier is an instrument all by itself, because it tends to color the original sound of the guitar, rather than just reproduce a louder signal. Because of this, amplifiers have a great deal to do with the sound of your guitar. Amps fall into two categories: tube and solid state. There are two dominant amp manufacturers: Fender and Marshall.

Tube Amps

Tube amps are the most common amplifiers in use. They're called “tube amps” because they use vacuum tube technology to generate power and distortion. Tube amps fall into two categories: American and British. The American amps, made by Fender, have a long tradition of being “clean” amps, because they produce a clean and loud signal without much distortion. Their sound is legendary, and as a result, vintage Fender amps command serious prices when sold. In the old days, distortion was seen as a bad thing and amp manufacturers went out of their way to prevent it. As time progressed, distortion became a permanent part of rock guitar sound, although it was discovered more or less by accident. The Fender Twin is one of the most famous amp designs and embodies the American sound: strident and clean. You could turn these amps up very loud without any sound deterioration or unwanted distortion (yes, there was a time when distortion was bad!).

Marshall Amplifiers, manufactured in England, differ greatly from their Fender counterparts. The amps, while clean at low volumes, tend to distort greatly when turned up. The louder they're played, the more distorted they become. This is one of the reasons that rock and roll music was always so loud—players had to crank their amps all the way up to get the desired tone. Marshall Amps became famous for their distorted sound and became the alternative to the Fender sound. Fender amps did distort slightly when turned all the way up, but not to the extent that Marshalls did.

As time progressed, other amp manufacturers began to enter the amp market basing their designs on pre-existing Marshall and Fender designs. Mesa Boogie began their amplifier line by modifying old Fender Princeton amps and adding more gain and power to them. Mesa Boogie became successful with their first amp, the Mark I, and is now a legend in the amplifier world. Some of the other big names in amps are: Crate, Vox, Carvin, Ampeg, Peavey, and Matchless.

Solid State

Tubes were replaced by smaller and more durable integrated circuits in the 1960s. One of the main drawbacks to tube amps is that tubes wear out over time, and most amps don't sound good unless cranked to 10. Solid state amps don't use tubes, and they're smaller and lighter than tube amps. The majority of amps, especially in the beginners market, are solid state. Solid state amps are more durable and dependable than tube amps, and over their lifetime require little or no service, but they've long been criticized for lacking some of the warmth of tube amps. However, some players are fond of the sound that solid state amps make and make them part of their sound. Either way you slice it, it's a matter of personal taste. In the low end of the amp market, you won't find many tube amps under $500, or many solid state amps over $500.

Combos vs. Stacks

Many amps come as all-in-one units, called “combo amps,” because they combine the speaker and the amp into one unit. Larger amps are available with separate heads and speakers that you can combine. Of course, you've all seen those impressive eight-foot-tall full stacks at the music store. While stack amps look great, and are great for your ego, they tend to be very bulky and hard to transport. The only advantage they have is sheer volume, because they're built to play much louder than the combo amps are. In reality, you'll never need to play that loud. Most venues have P.A. systems, so you'll be able to mike your amp through the house system. This will allow you to play at a comfortable volume level onstage, while the soundman takes care of the rest. For most players, combo amps are easier to deal with because they are smaller and lighter.

How Loud?

How loud do you need to be? Most amps are rated in watts, and for most professional players, 50 watts is plenty, but 100 watts is preferred. But the watt rating can be deceiving because different amps have different volumes. You can tell a lot from the speaker size. Most amps with smaller speakers are not suitable for loud playing. You should look for a ten-inch speaker, at the minimum. However, on bigger amps you'll find twelve-inch speakers are more common.

Digital Amps

Technology has changed our lives, and for guitar players it has changed our sound. One of the drawbacks of solid-state amps is that they sound sterile compared to their tube counterparts. Digital modeling, via computers, has enabled amp designers to model the way a tube reacts in computer software. This technology has grown tremendously in the last few years. It seems that everyone is getting on the bandwagon, although the pioneer in this field is Line6.

Digital amps allow you to choose what you want to hear. You can change from a Fender twin, to a Marshall plexi with the touch of a button. Most digital amps include many different amps modeled after the legendary amps of rock and roll. As the technology keeps improving, the quality of the sounds also keeps improving. You can fool even the most ardent tube purist! Many players prefer digital amps and view them as the “Swiss army knives” of amplifiers.

For many players, this digital technology has allowed them to use only one amp, when in the past they would tour with many different amps for different tones. These digital amps also include built-in effects like reverb, delay, chorus, and many other standard effects. Many companies make digital amps, most notably Fender, Line6, Crate, Digitech, and Johnson.