Making It Loud: Amplifiers

21 Nov 2014

Amplifiers boost a signal electronically so it can be heard over a larger area.  There were many experiments with such technology in the early 20th century, especially after the introduction of radio and talkie motion pictures. 

The guitar amplifier was born at the same time as the electric guitar.  Obviously, an electric guitar would be useless without a device that would boost its volume to a point where it could be heard.  The first guitar amplifier company was Electro String (1931), co-founded by George Beauchamp, George Rickenbacker and Harry Watson, co-developers of the first electric guitar.  By 1941, they were selling four models out of a shop in Los Angeles.  Their maximum output was about 10 watts.

Leo Fender, who specialized in repairing Electro String amplifiers, began building his own units in 1949.  His Super Amp had an output of 50 watts and used 12-inch speakers.  The Fender Twin Reverb became a much in-demand classic.

Other manufacturers entered the arena in the 1950s.  Vox, a British company, produced the AC30, which became a favourite of the Beatles, Jimi Hendrix and Jeff Beck.  As musicians demanded louder and more durable amplifiers, companies such as Marshall, Hi-Watt, Laney, Ampeg, Peavey and many others began to produce units more suited to the needs of rock and roll.

There are three main components to a guitar amplifier:  the pre-amp, the power amplifier and the speaker.  The pre-amp’s job is to boost the signal of the guitar high enough so it can actually drive the power amplifier.  The speaker turns the electrical energy of the guitar signal into kinetic energy which is manifested as sound.

Guitar amplifiers can come as all-in-one units or can be separated into a head (the amplifier and its controls) and one or more cabinets (the housing for the speakers).

While many musicians still prefer the warm sound of vacuum tube powered amplifiers, solid-state amps have proved much more reliable, lighter, more durable and less inexpensive.  Guitarists debate endlessly over the relative merits of both.

Many amplifiers have signature sounds coveted by musicians of different genres.  Traditional amps provide a warm, clean sound.  Hi-gain amps are popular with those who like a very overdriven (distorted) sound.  Amps used for hard rock often come with distortion effects, filters and other controls.  Bass guitars require their own version of amplifiers capable of driving deep notes with extra power and dissipating the heat that’s generated.

In some cases, a guitarist will use a DI (direct input) box to plug a guitar or bass directly into the microphone input of a mixing or recording console.  The DI box balances the signal of the guitar so it will not cause noise, distortion or damage to the console.

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