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Amplification: Turn Up the Music

Without amplification, a Stratocaster is just a quiet guitar with a tail. Read on to learn what puts the power into an amplifier.

When you pluck a guitar string, you produce a sound wave. Especially if that guitar is electric, that sound wave isn’t very loud, which is to say that its amplitude is small—if you charted it on paper, its peaks wouldn’t be high enough to challenge an adventurous stick figure. To make them larger, the amplifier must turn the sound wave into an electrical signal powerful enough to move the amp speaker’s cones and produce a new, louder sound wave.

An amplifier gets power from a wall outlet (or, if it’s a tiny practice amp, a battery), which it stores in capacitors and transformers inside its power supply; you might think of them as a city’s water tanks. When you play a note on the guitar, it kicks off a circuit that tells the transformers exactly how to release that stored power—sort of like turning on a faucet, but with all the pitches of the sonic spectrum in place of hot and cold.

Going with the Flow

Seen this way, it’s not surprising that an analog amplifier is sometimes called a “valve” amp. The analog part means that the waveform created by the transistors is just a blown-up version of the incoming sound wave; in other words, it’s analogous. This mirroring happens via the valves, glass tubes that are vacuum-sealed so electrons can flow unimpeded through space from a heated metal element toward a highly positively-charged plate. This flow creates a powerful current that can be modulated by the input signal and by the amp’s settings.

Tube amps are still preferred by many guitarists today for their distinctly warmer sound and their more-harmonious distortion. The circuitry of digital amps—which tend to be lighter, cheaper, and more power-efficient—translates the initial sound wave into a discrete series of on/off pulses, which are then converted back into a sound wave after being amplified. At most volumes, a digital amp produces a clear, neutral sound. But when pushed to their limits, digital amps will end up clipping part of the sound waves, creating harsher bursts of noise that may summon mean bats.