Guitar Amplifier - Types

Types

As said, guitar amplifiers are manufactured in two main forms. The "combination" (or "combo") amplifier contains the amplifier head and guitar speakers in a single unit which is typically housed in a rectangular wooden box. The amplifier head or "amp head" contains the electronic circuitry constituting the preamp, built-in effects processing, and the power amplifier. Combo amps have at least one 1/4" phone connector input jack where the patch cord from the electric guitar can be plugged in. Other jacks may also be provided, such as an additional input jack, "send" and "return" jacks to create an effects loop (for connecting electronic effects such as compression, reverb, etc.), an extension speaker jack (for connecting an additional speaker cabinet). Some smaller practice amps have stereo RCA jacks for connecting a CD player, portable media player or other sound source and a 1/4" headphone jack so that the player can practice without disturbing neighbors or family members.

Some amplifiers have a line out jack for connecting the amplifier's signal to a PA system or recording console or to connect the amplifier to another guitar amp. Players use the line out to connect one guitar amplifier to another amplifier in order to create different tone colors or sound effects. However, in most styles of rock and blues guitar the line out is not used to connect the guitar amp to a PA system or recording console because the tonal coloration and overdrive from the amplifier and speaker is considered an important part of the amplifier's sound.

In the "amp head" form, the amplifier head is separate from the speakers, and joined to them by speaker cables. The separate amplifier is called an amplifier head, and is commonly placed on top of one or more loudspeaker enclosures. A separate amplifier head placed atop a guitar speaker enclosure or guitar speaker cabinet forms an amplifier "stack" or "amp stack". Amp heads may also have the different types of input and output jacks listed above in the combo section. In addition to a 1/4" input jack, acoustic guitar amplifiers typically have an additional input jack for a microphone, which is easily identified because it will use a three-pin XLR connector. Phantom power is not often provided on general-use amps, restricting the choice of microphones for use with these inputs. However, for high-end acoustic amplifiers, phantom power is often provided, so that musicians can use condenser microphones.

Amplifiers used with electric guitars may be solid-state, which are lighter in weight and less expensive than tube amplifiers. Most guitarists, particularly in the genres of blues and rock, prefer the sound of vacuum tube amplifiers despite their higher cost, heavier weight, the need to periodically replace tubes and need to re-bias the output tubes (every year or two with moderate use). Some companies design amplifiers that require no biasing as long as properly rated tubes are used. Some modern amplifiers use a mixture of tube and solid-state technologies.

Since the advent of microprocessors and digital signal processing, "modeling amps" have been developed in the late 1990s, these can simulate the sounds of a variety of well-known tube amplifiers without needing to use vacuum tubes. Amplifiers with processors and software emulate the sound of a classic amp well, but from the player's point of view the response of these amplifiers may not feel the same as the digital modeling does not accurately model all aspects of a tube amplifier.

A wide range of instrument amplifiers is available, some for general purposes and others designed for specific instruments or particular sounds. These include:

• "Traditional" guitar amplifiers, with a clean, warm sound, a sharp treble roll-off at 5 kHz or less and bass roll-off at 60–100 Hz, and often built-in reverb and tremolo (sometimes incorrectly called 'vibrato') units. These amplifiers, such as the Fender "Tweed"-style amps, are often used by traditional rock, blues, and country musicians. Traditional amps have more recently become popular with musicians in indie and alternative bands
• Hard rock-style guitar amplifiers, which often include preamplification controls, tone filters, and distortion effects that provide the amplifier's characteristic tone. Users of these amplifiers use the amplifier's tone to add "drive", intensity, and "edge" to their guitar sound. Amplifiers of this type, such as Marshall amplifiers, are used in a range of genres, including hard rock, metal (though they are often boosted with a pedal for more gain), and punk.
• Hi-gain guitar amplifiers, are an increasingly popular type of amplifier, built for high amounts of preamp gain, to give a very overdriven sound. In case of tube amps, 4 preamplifier tubes (8 stages, 2 stages per tube) is common (compared to 1 tube in most traditional style amps), but amplifiers with as many as 8 preamp tubes are available. These extra tubes allow for more gain, and thus a more distorted sound. These amplifiers are almost always in class AB.
• Bass amplifiers, with extended bass response and tone controls optimized for bass guitars (or more rarely, for upright bass). Higher-end bass amplifiers sometimes include compressor or limiter features, which help to keep the amplifier from distorting at high volume levels, and an XLR DI output for patching the bass signal directly into a mixing board. Bass amplifiers are often provided with external metal heat sinks or fans to help keep the amplifier cool.
• Acoustic amplifiers, similar in many ways to keyboard amplifiers but designed specifically to produce a "clean," transparent, "acoustic" sound when used with acoustic instruments with built-in transducer pickups and/or microphones.