Heavy Metal And Hard Rock Amplifiers

Guitar amplifiers that are designed for the purpose of playing heavier music like Metal or Hard Rock, tend to deliver a more aggressive drive or intensity to the guitar sound, utilizing distortion effects, tone filters, and preamplification boost controls.
Many of the more expensive and high-end models use tube amplifiers, but there are many other models that make use of transistor amplifiers, as well as others that combine both types into one, such as a tube preamplifier with a transistor power amplifier.
Guitar amplifiers of the type just mentioned, such as Marshall amplifiers, are put to good use in a number of heavier, louder genres of rock music. Some of these genres would be hardcore punk, hard rock, and of course heavy metal. These kinds of amplifiers are available in a broad range of formats that range from the smaller combo amplifiers (great for practice and rehearsals) all the way to the heavy "heads" that are designed for use with separate speaker cabinets, and is also referred to as a "stack".
Back in the late 60′s and into the early 70′s, public address systems were used at many rock concerts for the vocals, and as a result, early heavy metal and rock-blues type bands would often times use a "stack" of 4×12″ Marshall speaker cabinets on stage so they could get that nice loud electric guitar sound.
Through the years many famous musicians began adding more and more amplifiers to the stage to create walls of over 20 guitar amplifiers. However, once into the 80′s and 90′s, the majority of sound at live concerts was being produced by the sound reinforcement system rather than onstage guitar amplifiers. Most of the cabinets were not being connected to an amplifier, but instead the walls of speaker cabinets were used simply for aesthetic reasons.
Guitar amplifiers for the heavier genres of music usually use valve amplifiers also. Valve amplifiers contain a "warmer" tone than the transistor amplifiers, especially when overdriven. As apposed to suddenly clipping off the signal at cut-off and saturation levels, the signal can be rounded off more smoothly. Also, vacuum tubes will exhibit different harmonic effects than transistors will.
Companies such as Marshall prefer to use 12″ speakers in a closed-back cabinet in contrast to "tweed"-style amplifiers that tend to use speakers set in an open-backed cabinet. These guitar amplifiers usually let users switch between "clean" and distorted tones (or a "crunch" tone for the rhythm guitar, and "lead" tone) by means of a foot-operated switch.