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123-561: The Marshall JTM45 amplifier is the first guitar amplifier produced by the British company Marshall . It was initially produced in 1963, and has been ranked among the most desirable of the company's amplifiers. Notable musicians who have used this amplifier include David Gilmour , The Rolling Stones , and Jimi Hendrix , among others. Prototyping of the JTM45 began in 1962, after London musical instrument retailer Jim Marshall decided to create

246-866: A balanced output from the preamp section to a PA system or recording input. Instrument amplifiers are available in a wide range of price, quality, and performance levels. Some are designed for beginners, such as small, low-wattage practice amps , which typically have a single 8" speaker and about 10 watts, or smaller combo amps with relatively low wattage (15 to 20 watts) and a single 10" speaker. Mid- to large-size combo amps with 30 to 50 watts and one 12" speaker or four 10" speakers are best for high-volume situations, such as band rehearsals and onstage performances. For large venues, such as outdoor music festivals , guitarists may use one or more 100 watts (or several hundred watts) heads with one or more 8x10” cabinets. Vacuum tubes (called valves in British English) were by far

369-517: A drum machine ), send and return jacks to create an effects loop, a line out jack, and an extension speaker jack. Practice amps sometimes have a 1/4" headphone jack, or stereo RCA or mini jacks for connecting a CD player , portable media player or other sound sources. Some guitar amps have an XLR input so that a microphone can be plugged in for singing. Guitar amps that include a mic input are in effect small, portable PA systems . Some amps, typically bass amps, have an XLR connector to provide

492-427: A graph of the equalizer's response plotted versus frequency. The number of frequency channels may be matched to the requirements of the intended application. A car audio equalizer might have a total of five to ten frequency bands. An equalizer for professional live sound reinforcement typically has some 25 to 31 bands, for more precise control of feedback problems and equalization of room modes . Such an equalizer

615-492: A speaker cabinet —a head on top of one cabinet is commonly called a half stack , a head atop two cabinets a full-stack . The cabinet that the head sits on often has an angled top in front, while the lower cabinet of a full stack has a straight front. The first version of the Marshall stack was an amp head on an 8×12 cabinet, meaning a single speaker cabinet containing eight 12" guitar speakers. After six of these cabinets were made,

738-404: A 100-watt amplifier is only just noticeably louder than a 50-watt amplifier. Such generalizations are also subject to the human ear's tendency to behave as a natural compressor at high volumes. Power attenuation can be used with either low-power or high-power amplifiers, resulting in variable-power amplifiers. A high-power amplifier with power attenuation can produce power-tube distortion through

861-422: A capacitor and resistor. Second-order filters are capable of resonance (or anti-resonance) around a particular frequency. The response of a second-order filter is specified not only by its frequency but also its Q ; a higher Q corresponds to a sharper response (smaller bandwidth) around a particular center frequency. For instance, the red response in the accompanying image cuts frequencies around 100 Hz with

984-613: A carrying handle, and many combo amplifiers and cabinets have metal or plastic-reinforced corners to protect the amp during transportation. Control knobs and buttons are typically on the front of the cabinet or chassis, though in some cases, the knobs are on a recessed panel at the back of the top of the amplifier. The most basic amps only have a few knobs, which typically control volume, bass, and treble. More expensive amps may have several knobs that control pre-amp volume (or gain), distortion or overdrive, volume, bass, mid and treble, and reverb. Some older amps (and their re-issued versions) have

1107-812: A combination ("combo") amplifier that includes an amplifier and one or more speakers in a single cabinet, and a standalone amplifier (often called a head or amp head ), which passes the amplified signal via a speaker cable to one or more external speaker cabinets . A wide range of speaker configurations are available in guitar cabinets—from cabinets with a single speaker (e.g., 1×10" or 1×12") or multiple speakers (e.g., 2×10", 4×10" or 8x10"). Guitar amplifiers vary widely in price and quality. Many music equipment companies import small, low-powered practice amplifiers for students and beginners that sell for less than $ 50. Other companies produce expensive custom-made amplifiers for professional musicians, which can cost hundreds or even thousands of dollars (USD). Most combo amplifiers have

1230-404: A combination of first-order responses and second-order responses (implemented as so-called biquad sections). These can be described according to their so-called pole and zero frequencies, which are complex numbers in the case of second-order responses. A first-order filter can alter the response of frequencies above and below a point. In the transition region the filter response will have

1353-473: A computer running tone-shaping software. Using a modeling amp or a multi-effects pedal used with line level output, a guitarist can plug in the guitar into a flat response mic input or into a keyboard amplifier . Acoustic amplifiers are intended for acoustic guitars and other acoustic instruments, especially for the way these instruments are used in relatively quiet genres such as folk and bluegrass . They are similar to keyboard amplifiers, in that they have

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1476-701: A cut above the rest. Today, many non-British companies such as Behringer and Mackie advertise British EQ on their equipment. A British style EQ seeks to replicate the qualities of the expensive British mixing consoles. Filtering audio frequencies dates back at least to acoustic telegraphy and multiplexing in general. Audio electronic equipment evolved to incorporate filtering elements as consoles in radio stations began to be used for recording as much as broadcast. Early filters included basic bass and treble controls featuring fixed frequency centers, and fixed levels of cut or boost. These filters worked over broad frequency ranges. Variable equalization in audio reproduction

1599-441: A first-order response and provide an adjustable boost or cut to frequencies above or below a certain point. A high shelf or treble control will have a frequency response | H ( f )| whose square is given by: where f p and f z are called the pole and zero frequencies, respectively. Turning down the treble control increases f z and decreases f p so that frequencies higher than f p are attenuated. Turning up

1722-429: A fixed center frequency and Q factor , but an adjustable level. The user can raise or lower each slider in order to visually approximate a graph of the intended frequency response. Equalization in the context of audio reproduction is not used strictly to compensate for the deficiency of equipment and transmission channels. A high-pass filter modifies a signal by eliminating only lower frequencies. An example of this

1845-551: A guitar amplifier and other guitar equipment. Electric guitars and basses have a volume control on the instrument that attenuates the signal from selected pickups. There may be two volume controls on an electric guitar or bass, wired in parallel to mix the signal levels from the neck and bridge pickups. Rolling back the guitar's volume control also changes the pickup's equalization or frequency response, which can provide pre-distortion equalization. The simplest guitar amplifiers, such as some vintage amps and modern practice amps, have only

1968-431: A higher Q than the blue response which boosts frequencies around 1000 Hz. Higher Q's correspond to resonant behaviour in which the half-power or −3 dB bandwidth, BW , is given by: where F 0 is the resonant frequency of the second-order filter. BW is the bandwidth expressed in the same frequency unit that F 0 is. Low Q filter responses (where Q < 1 ⁄ 2 ) are not said to be resonant and

2091-474: A home computer or laptop. Line 6 is generally credited with bringing modeling amplification to the market. Modeling amplifiers and stompbox pedals, rackmount units, and software that models specific amplifiers, speakers cabinets, and microphones can provide a large number of sounds and tones. Players can get a reasonable facsimile of the sound of tube amplifiers, vintage combo amplifiers, and huge 8x10” speaker stacks without bringing all that heavy equipment to

2214-470: A knob that controls a vibrato or tremolo effect. The 1/4" input jack is typically mounted on the front of the amplifier. In the simplest, least expensive amplifiers, this 1/4" jack is the only jack on the amplifier. More expensive amplifiers may have a patch bay for multiple inputs and outputs, such as a pre-amp out (for sending to another guitar amplifier), a second low gain input, to use with active basses, an in jack to create an effects loop (when used with

2337-720: A live performance was in September 1963, when the amplifier was tested at the Ealing Club , a short distance from the original Marshall shops. By the mid-1960s, the JTM45 had become so popular that it began to supplant the ubiquitous Vox amplifiers, including the Vox AC50, even though the Vox amplifier was equally powerful to the Marshall amplifier. In late 1965, Marshall introduced its now standard script lettering, in white. By early 1966 it began calling

2460-524: A low-pass filter is used in the signal chain before a subwoofer to ensure that only deep bass frequencies reach the subwoofer. While high-pass and low-pass filters are useful for removing unwanted signal above or below a set frequency, shelving filters can be used to reduce or increase signals above or below a set frequency. Shelving filters are used as common tone controls (bass and treble) found in consumer audio equipment such as home stereos, and on guitar amplifiers and bass amplifiers . These implement

2583-432: A microphone, either for the guitar amp to be used for singing (in effect as a mini- PA system ), or, for acoustic guitar, to mix a mic signal with a pickup signal. The vast majority of guitar amps can only be powered by AC mains power (plugging into a wall outlet); however, a small number of practice amps are designed for buskers also have battery power so they can be used for street performances. A combo amp contains

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2706-416: A microphone, it is further reamplified; this recirculation of sound can lead to "howling", requiring the sound technician to reduce the gain for that microphone, perhaps sacrificing the contribution of a singer's voice, for instance. Even at a slightly reduced gain, the feedback will still cause an unpleasant resonant sound around the frequency at which it would howl. But because the feedback is troublesome at

2829-498: A mix, creating the impression that some sounds in a mono or stereo mix are farther away or closer than others. Equalization is also commonly used to give tracks with similar frequency components complementary spectral contours, known as mirrored equalization . Selected components of parts that would otherwise compete, such as bass guitar and kick drum, are boosted in one part and cut in the other, and vice versa, so that they both stand out. Equalizers can correct problems posed by

2952-421: A modified negative feedback circuit , which affected the harmonics produced by the amplifier. As Bran later said, "The JTM also had different harmonic content, and this was due to the large amount of feedback that Dudley Craven had given it." Early versions used 6L6 or US 5881 valves (a version of the 6L6) in the output stage; later models used KT66 (from 1964), EL34 (from 1966), or KT88 (from 1967; in

3075-479: A more limited range, since their purpose is not to eliminate any frequencies but only to achieve a greater balance when, for instance, the treble is lacking and the sound is not crisp. Since the range of possible responses from shelving filters is so limited, some audio engineers considered shelving controls inadequate for equalization tasks. On some bass amps and DI boxes , the units provide both low and high shelving controls and additional equalization controls. In

3198-422: A narrow range of frequencies. In addition to specifying the center frequency F 0 and the Q, the specification of the filter's zeros determines how much that frequency band will be boosted (or cut). Thus a parametric equalizer section will have three controls for its center frequency F 0 , bandwidth or Q, and the amount of boost or cut usually expressed in dB . The range of second-order filter functions

3321-400: A new amplifier in response to local guitarists ' desire for an alternative to imported American Fender amplifiers. Marshall sought the advice of his shop repairman Ken Bran, who recommended electronics " whiz kid " Dudley Craven as the chief circuit designer. Marshall then arranged for Pete Townshend and Ritchie Blackmore demo prototypes to be constructed by Bran and Craven, settling on

3444-408: A particular frequency, it is possible to cut the gain only around that frequency while preserving the gain at most other frequencies. This can best be done using a parametric equalizer tuned to that very frequency with its amplitude control sharply reduced. By adjusting the equalizer for a narrow bandwidth (high Q), most other frequency components will not be affected. The extreme case when the signal at

3567-525: A particular guitarist's sound, recording engineers and PA system techs typically put a microphone in front of the guitar speaker, rather than only use the guitar amp's pre-amp out signal. A sound engineer or music producer may send the DI out signal from the pickups to a separate track at the same time, so they can re-amp the signal later. In contrast, it is fairly common to use a DI box with electric bass . Distortion sound or "texture" from guitar amplifiers

3690-518: A range of listening volumes but with a decrease in high-power distortion. Other technologies, such as dual rectifiers and the sag circuit —which should not be confused with attenuation—allow high-power amplifiers to produce low power volume while preserving high power distortion. Speaker efficiency is also a major factor affecting a tube amplifier's maximum volume. For bass instruments, higher-power amplifiers are needed to reproduce low-frequency sounds. While an electric guitarist would be able to play at

3813-496: A regular wall socket "quickly became popular with musicians"; indeed, "... Leon McAuliffe (with Bob Wills ) still used a carbon mic and a portable PA as late as 1935." During the late 1920s to mid-1930s, small portable PA systems and guitar combo amplifiers were fairly similar. These early amps had a "single volume control and one or two input jacks, field coil speakers" and thin wooden cabinets; remarkably, these early amps did not have tone controls or even an on-off switch. In 1928,

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3936-629: A relatively flat frequency response with minimal coloration. To produce this relatively clean sound, these amplifiers often have powerful amplifiers (providing up to 800 watts RMS), to provide additional Headroom and prevent unwanted distortion. Since an 800-watt amplifier built with standard Class AB technology is heavy, some acoustic amplifier manufacturers use lightweight Class D amplifiers , which are also called switching amplifiers. Acoustic amplifiers produce an uncolored, acoustic sound when used with acoustic instruments with built-in transducers, pickups or microphones. The amplifiers often come with

4059-406: A room's acoustics , as an auditorium will generally have an uneven frequency response especially due to standing waves and acoustic dampening . For instance, the frequency response of a room may be analyzed using a spectrum analyzer and a pink noise generator. Then a graphic equalizer can be easily adjusted to compensate for the room's acoustics. Such compensation can also be applied to tweak

4182-544: A sharper or more "brilliant" sound, or can be used to cut such high frequencies when they have been overemphasized in the program material or simply to accommodate a listener's preference. A "rumble filter" is a high-pass (low cut) filter with a cutoff typically in the 20 to 40 Hz range; this is the low frequency end of human hearing . "Rumble" is a type of low-frequency noise produced in record players and turntables, particularly older or low quality models. The rumble filter prevents this noise from being amplified and sent to

4305-414: A similar combo amp that added metal corner protectors to keep the corners in good condition during transportation. In 1933, Dobro released an electric guitar and amp package. The combo amp had two 8" Lansing speakers and a five- tube chassis. Dobro made a two speaker combo amp that was on the market over 12 years before Fender launched its two-speaker Dual Professional/Super combo amp. In 1933, Audio-Vox

4428-428: A simple mixer, so that the signals from a pickup and a condenser microphone can be blended. Since the early 2000s, it has become increasingly common for acoustic amplifiers to provide a range of digital effects, such as reverb and compression . As well, these amplifiers often contain feedback -suppressing devices, such as notch filters or parametric equalizers . An amplifier stack consists of an amplifier head atop

4551-521: A single volume control. Most have two volume controls: a first volume control called "preamplifier" or "gain" and a master volume control. The preamp or gain control works differently on different guitar amp designs. On an amp designed for acoustic guitar , turning up the preamp knob pre-amplifies the signal—but even at its maximum setting, the preamp control is unlikely to produce much overdrive . However, with amps designed for electric guitarists playing blues , hard rock and heavy metal music , turning up

4674-415: A slightly more raw, open and edgy sound." The relationship between power output in watts and perceived volume is not immediately obvious. The human ear perceives a 5-watt amplifier as half as loud as a 50-watt amplifier (a tenfold increase in power), and a half-watt amplifier is a quarter as loud as a 50-watt amp. Doubling the output power of an amplifier results in a just noticeable increase in volume, so

4797-463: A slope of up to 6  dB per octave . The bass and treble controls in a hi-fi system are each a first-order filter in which the balance of frequencies above and below a point are varied using a single knob. A special case of first-order filters is a first-order high-pass or low-pass filter in which the 6 dB per octave cut of low or high frequencies extends indefinitely. These are the simplest of all filters to implement individually, requiring only

4920-616: A small club with a 50-watt amplifier, a bass player performing in the same venue would probably need an amplifier with 200 or more watts. Distortion is a feature available on many guitar amplifiers that is not typically found on keyboard or bass guitar amplifiers. Tube guitar amplifiers can produce distortion through pre-distortion equalization, preamp tube distortion, post-distortion EQ, power-tube distortion, tube rectifier compression, output transformer distortion, guitar speaker distortion, and guitar speaker and cabinet frequency response. Because many factors beyond preamp distortion contribute to

5043-541: A smooth Marshall sound with a warm bass response due to the EL34/KT66 valves. Guitar amplifier Guitar amplifiers can also modify an instrument's tone by emphasizing or de-emphasizing certain frequencies, using equalizer controls, which function the same way as the bass and treble knobs on a home stereo, and by adding electronic effects ; distortion (also called overdrive) and reverb are commonly available as built-in features. The input of modern guitar amplifiers

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5166-411: A switch labeled high cut or described as a hiss filter (hiss being high-frequency noise ). In the phonograph era, many stereos would include a switch to introduce a high-pass (low cut) filter, often called a rumble filter , to eliminate infrasonic frequencies. High and low-pass filters are used in audio crossovers to direct energy to the speaker drivers capable of reproducing it. For instance,

5289-485: A tube power amp fed by a solid-state pre-amp circuit, as in most of the original MusicMan amplifiers. Alternatively, a tube preamplifier can feed a solid-state output stage, as in models from Kustom , Hartke, SWR , and Vox . This approach dispenses with the need for an output transformer and easily achieves modern power levels. Microprocessor technology allows the use of digital onboard effects in guitar amps to create numerous different sounds and tones that simulate

5412-427: A tunable EQ for a new recording console. Bob Meushaw, a friend of Massenburg, built the equalizer. According to Massenburg, "Four people could possibly lay claim to the modern concept: Bob Meushaw, Burgess Macneal, Daniel Flickinger, and myself… Our (Bob’s, Burgess’ and my) sweep-tunable EQ was borne, more or less, out of an idea that Burgess and I had around 1966 or 1967 for an EQ… three controls adjusting, independently,

5535-632: A wider frequency range and need a full-range speaker system. Much more amplifier power is required to reproduce low-frequency sound, especially at high volume. Reproducing low frequencies also requires a suitable woofer or subwoofer speaker and enclosure , with bass cabinets often being larger than a cabinet for mid-range or high-range sounds. As well, the open-back cabinets used on many electric guitar amps, while effective for electric guitar, do not have good bass reproduction. Woofer enclosures must be larger and more sturdily built than cabinets for mid-range or high-frequency ( tweeter ) speakers. As such, in

5658-487: Is a 1/4" jack , which is fed a signal from an electro-magnetic pickup (from an electric guitar) or a piezoelectric pickup (usually from an acoustic guitar) using a patch cord , or a wireless transmitter. For electric guitar players, their choice of amp and the settings they use on the amplifier are a key part of their signature tone or sound. Some guitar players are longtime users of a specific amp brand or model. Guitarists may also use external effects pedals to alter

5781-675: Is a preamplifier . It amplifies the audio signal to a level that can drive the power stage. The preamplifier also changes the tone of the signal; high preamp settings add overdrive . The power amplifier produces a high current signal to drive a loudspeaker and produce sound. Various types of tone stages may affect the guitar signal: Tone stages may also provide electronic effects—such as equalization , compression, distortion, chorus , or reverb . Amplifiers may use vacuum tubes (called valves in Britain), solid-state (transistor) devices, or both. The two common guitar amplifier configurations are

5904-453: Is a filter, an electronic circuit or device, that passes higher frequencies well but attenuates lower-frequency components. A low-pass filter passes low-frequency components of signals while attenuating higher frequencies. In audio applications these high-pass and low-pass filters are frequently termed low cut and high cut , respectively, to emphasize their effect on the original signal. For instance, sometimes audio equipment will include

6027-403: Is a low-cut or rumble filter , which is used to remove infrasonic energy from a program that may consume undue amplifier power and cause excessive diaphragm excursions in (or even damage to) loudspeakers. A low-pass filter only modifies the audio signal by removing high frequencies. An example of this is a high-cut or hiss filter , which is used to remove annoying white noise at the expense of

6150-425: Is called a 1/3-octave equalizer (spoken informally as " third-octave EQ") because the center frequencies of its filters are spaced one third of an octave apart, three filters to an octave. Equalizers with half as many filters per octave are common where less precise control is required—this design is called a 2/3-octave equalizer. Parametric equalizers are multi-band variable equalizers that allow users to control

6273-730: Is called an equalizer . Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments. Graphic and parametric equalizers have much more flexibility in tailoring the frequency content of an audio signal. Broadcast and recording studios use sophisticated equalizers capable of much more detailed adjustments, such as eliminating unwanted sounds or making certain instruments or voices more prominent. Because of this ability, they can be aptly described as "frequency-specific volume knobs." Equalizers are used in recording and radio studios , production control rooms , and live sound reinforcement and in instrument amplifiers , such as guitar amplifiers , to correct or adjust

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6396-421: Is further shaped or processed through the frequency response and distortion factors in the microphones (their response, placement, and multi-microphone comb filtering effects), microphone preamps, mixer channel equalization, and compression. Additionally, the basic sound produced by the guitar amplifier can be changed and shaped by adding distortion and/or equalization effect pedals before the amp's input jack, in

6519-512: Is important because any analog filter function can be decomposed into a (usually small) number of these (plus, perhaps, simpler first-order responses). These are implemented directly by each section of a parametric equalizer where they are explicitly adjusted. And each element of a graphic equalizer based on a filter bank includes one such element whose Q is not adjustable by the user. In sound recording , equalization may be used to adjust frequency responses for practical or aesthetic reasons, where

6642-432: Is introduced by the radio is then also de-emphasized at the higher frequencies (where it is most noticeable) along with the pre-emphasized program, making the noise less audible. Tape recorders used the same approach to reduce " tape hiss " while maintaining fidelity. On the other hand, in the production of vinyl records , a filter is used to reduce the amplitude of low frequencies which otherwise produce large amplitudes on

6765-573: Is more common for bass amplifiers than for electric guitar cabinets), two 10" speakers, four 10" speakers, four 12" speakers, or eight 10" speakers. Less commonly, guitar cabinets may contain different sizes of speakers in the same cabinet. Cabinets with eight 10" speakers are large and heavy, and they are often equipped with wheels and a towel bar -style handle for transport. Some cabinets use mixed speaker types, such as one 15" speaker and two 10" speakers. Combo guitar amplifier cabinets and guitar speaker cabinets use several different designs, including

6888-441: Is not the same company as Stromberg Electro Instruments) introduced a guitar amp with "high output" and a "string driven magnetic pickup". Electro set out the standard template for combo amps: a wooden cabinet with the electronic amplifier mounted inside, and convenient carrying handles to facilitate transporting the cabinet. In 1933, Vivi-Tone amp set-ups were used for live performances and radio shows. In 1934, Rickenbacker launched

7011-579: Is now broadly used to describe the application of such filters regardless of intent. This broad definition, therefore, includes all linear filters at the disposal of a listener or engineer. A British EQ or British style equalizer is one with similar properties to those on mixing consoles made in the UK by companies such as Amek, Neve and Soundcraft from the 1950s through to the 1970s. Later on, as other manufacturers started to market their products, these British companies began touting their equalizers as being

7134-554: The cleaner sound of solid-state amplifiers. Only a few solid-state amps have enduring attraction, such as the Roland Jazz Chorus . Solid-state amplifiers vary in output power, functionality, size, price, and sound quality in a wide range, from practice amplifiers to combos suitable for gigging to professional models intended for session musicians who do studio recording work . A hybrid amplifier involves one of two combinations of tube and solid-state amplification. It may have

7257-408: The cutoff frequencies . A low shelf , such as the bass control on most hi-fi equipment, is adjusted to affect the gain of lower frequencies while having no effect well above its cutoff frequency. A high shelf , such as a treble control, adjusts the gain of higher frequencies only. These are broad adjustments designed more to increase the listener's satisfaction than to provide actual equalization in

7380-446: The cutoff frequency . For instance, a second-order low-pass notch filter section only reduces (rather than eliminates) very high frequencies, but has a steep response falling to zero at a specific frequency (the so-called notch frequency ). Such a filter might be ideal, for instance, in completely removing the 19 kHz FM stereo subcarrier pilot signal while helping to cut even higher frequency subcarrier components remaining from

7503-416: The graphic equalizer , the input signal is sent to a bank of filters . Each filter passes the portion of the signal present in its own frequency range or band . The amplitude passed by each filter is adjusted using a slide control to boost or cut frequency components passed by that filter. The vertical position of each slider thus indicates the gain applied to that frequency band, so that the sliders resemble

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7626-475: The impedance of the system. Two 8 ohm speakers wired in parallel have 4-ohm impedance. Guitarists who connect multiple cabinets to an amplifier must consider the amp's minimum impedance. Parallel vs. series also affects tone and sound. Speakers wired in parallel slightly dampen[s] and restrain[s] them, giving what some describe as tighter response and smoother breakup . Some describe speakers wired in series (usually no more than two) as sounding "...looser, giving

7749-434: The preamplifier , equalization filters, power amp , guitar speakers , and cabinet design. The FRFR approach assumes the tone is shaped by sound processors in the signal chain before the amplifier and speaker stage, so it strives to not add further coloration or dedicated combo-style amplifiers with a broad frequency range. Such processors can be traditional guitar effects, a modeling amplifier (without power amplifier), or

7872-419: The timbre of individual instruments and voices by adjusting their frequency content and to fit individual instruments within the overall frequency spectrum of the mix . The concept of equalization was first applied in correcting the frequency response of telephone lines using passive filters ; this was prior to the invention of electronic amplification. Initially, equalization was used to compensate for

7995-429: The "gain" knob is equivalent to the distortion control on a distortion pedal and similarly may have a side-effect of changing the proportion of bass and treble sent to the next stage. Equalization (audio) Equalization , or simply EQ , in sound recording and reproduction is the process of adjusting the volume of different frequency bands within an audio signal . The circuit or equipment used to achieve this

8118-481: The 1930s and 1940s craze for Western Swing and Hawaiian music , which extensively used amplified lap steel guitars . In fact, the very first recording of an electrically amplified string instrument was the September 1933 recordings of Milton Brown and his Musical Brownies, featuring steel guitarist Bob Dunn In the 1920s, the earliest combo amplifiers had no tone controls. The first tone controls were simple, mainly providing treble adjustment. The limited controls,

8241-623: The 1930s and beyond. The first amplifiers and speakers could only be powered with large batteries, which made them heavy and hard to carry around. When engineers developed the first AC mains -powered amplifiers, they were soon used to make musical instruments louder. Engineers invented the first loud, powerful amplifier and speaker systems for public address systems and movie theaters . These PA systems and movie theatre sound systems were very large and very expensive, and so they could not be used by most touring musicians. After 1927, smaller, portable AC mains-powered PA systems that could be plugged into

8364-672: The 1950s, when Ampeg introduced bass amplifier and speaker systems, bass guitarists began to use them. Similarly, Hammond organ players used a specialized keyboard combo amplifier, the Leslie speaker cabinet, which contains a woofer for the low frequencies and a horn for the high frequencies. The Leslie horns rotate and a baffle around the woofer rotates as well, producing a rich tremolo and chorus effect . Typically, guitar amplifiers have two amplifying circuit stages, and frequently have tone-shaping electric circuits, which usually include at least bass and treble controls, which function similarly to

8487-424: The 200W Major), and ECC83 ( 12AX7 ) valves in the pre-amplification stage. The amplifier was also available in the bass format (although this model lacked a "bright" capacitor) and an additional PA version (which lacked a "mixer" capacitor). Because of its power, Marshall decided early on to build it as a "head," with a separate 4×12" cabinet with Celestion speakers. The first-ever use of this JTM 45 model in

8610-528: The JTM 45 did not receive serial numbers until 1964–1965 when backplates began to be applied. However, at random some of the early amplifiers had serial numbers stamped into the chassis on their reverse side. For all of its differences when compared with the Bassman , the sound of the JTM45 is still described as "like a tweed Fender", and is favored for blues and rock rather than for hard rock and metal. The JTM 45 delivers

8733-514: The Stromberg-Voisinet firm marketed an electric stringed instrument and amplifier package. There are no records as to how many—if any—of the amps were ever built and sold, beyond marketing materials. Stromberg-Voisinet still launched a new idea: a portable electric instrument amp with a speaker, all in a transportable wooden cabinet. In 1929, Vega electrics launched a portable banjo amplifier. In 1932, Electro String Instruments and amplifier (this

8856-406: The above formula for bandwidth does not apply. It is also possible to define the Q of a band-pass function as: where N is the bandwidth in octaves. The reverse mapping is: A second-order filter response with Q of less than 1/2 can be decomposed into two first-order filter functions, a low-cut and a high-cut (or boost). Of more interest are resonant filter functions which can boost (or cut)

8979-530: The amplifier and one or more speakers in a single cabinet. In a head and speaker cabinet configuration, the amplifier and speaker each have their own cabinet. The amplifier (head) may drive one or more speaker cabinets. In the 1920s, guitarists played through public address amplifiers, but by the 1940s this was uncommon. Besides instrument inputs and speaker outputs (typically via 1/4" jacks), an amp may have other inputs and outputs. These can include an auxiliary input jack (sometimes with its own level control, for

9102-448: The amplifiers "JTM 50". Some 100 early models had red lettering, and are especially sought after by collectors. Other cosmetic changes included a gradual change to different knobs. The JTM 45 became the basis for many subsequent Marshall amplifiers, most notably the Marshall 1962 combo (later referred to as the "Bluesbreaker" due to its use by Eric Clapton with John Mayall's Bluesbreakers ). Production of this model ceased in 1966, but it

9225-598: The amps and electrified or electric guitars that had been made from 1928 through the end of 1934. The first electric instrument amplifiers were not intended for electric guitars, but were portable PA systems . These appeared in the early 1930s when the introduction of electrolytic capacitors and rectifier tubes enabled economical built-in power supplies that could plug into wall sockets. Previously, amplifiers required heavy multiple battery packs . People used these amplifiers to amplify acoustic guitar , but electronic amplification of guitar first became widely popular in

9348-472: The baffle material (the wood panel that holds the speaker), and the way the baffle attaches to the cabinet all affect tone. When two or more speakers are used in the same cabinet, or when two cabinets are used together, the speakers can be wired in parallel or in series, or in a combination of the two (e.g., two 2x10" cabinets, with the two speakers wired in series, can be connected together in parallel). Whether speakers are wired in parallel or in series affects

9471-481: The cabinet arrangement was changed to an amp head on two 4×12 (four 12" speakers) cabinets to make the cabinets more transportable. Some touring metal and rock bands have used a large array of guitar speaker cabinets for their impressive appearance. Some of these arrangements include only the fronts of speaker cabinets mounted on a large frame. There are many varieties of speaker combinations used in guitar speaker cabinets, including one 12" speaker, one 15" speaker (this

9594-470: The center frequency selected. In a semi-parametric equalizer the bandwidth is preset by the designer. In a quasi-parametric equalizer, the user is given limited switchable options for bandwidth. A graphic equalizer also implements second-order filter functions in a more user-friendly manner but with somewhat less flexibility. This equipment is based on a bank of filters covering the audio spectrum in up to 31 frequency bands . Each second-order filter has

9717-423: The channel or recording process. At the end of the channel or when the recording is played, a complementary filter is inserted which precisely compensates for the original filter and recovers the original waveform. For instance, FM broadcasting uses a pre-emphasis filter to boost the high frequencies before transmission, and every receiver includes a matching de-emphasis filter to restore it. The white noise that

9840-518: The circuit topology that would come to dominate audio equalization until the present day, as well as the theoretical underpinnings of the elegant circuit. Instead of slide potentiometers working on individual bands of frequency, or rotary switches, Flickinger's circuit allowed arbitrary selection of frequency and cut or boost level in three overlapping bands over the entire audio spectrum. Six knobs on his early EQs would control these sweepable filters. Up to six switches were incorporated to select shelving on

9963-435: The crispness of the program material. A first-order low-pass or high-pass filter has a standard response curve that reduces the unwanted frequencies well above or below the cutoff frequency with a slope of 6 dB per octave. A second-order filter will reduce those frequencies with a slope of 12 dB per octave and moreover may be designed with a higher Q or finite zeros in order to effect an even steeper response around

10086-437: The dominant active electronic components in most instrument amplifier applications until the 1970s when solid-state semiconductors ( transistors ) started taking over. Transistor amplifiers are less expensive to build and maintain, reduce the weight and heat of an amplifier, and tend to be more reliable and more shock-resistant. Tubes are fragile and they must be replaced and maintained periodically. As well, serious problems with

10209-563: The early loudspeakers , and the low amplifier power (typically 15 watts or less before the mid-1950s) gave poor high treble and bass output. Some models also provided effects such as an electronic tremolo unit. In confusion over nomenclature, Fender labeled early amplifier tremolo as vibrato and called the vibrato arm of the Stratocaster guitar a tremolo bar (see vibrato unit , electric guitar , and tremolo ). Some later amplifier models included an onboard spring reverb effect, one of

10332-405: The effects loop just before the tube power amp, or after the power tubes. Power-tube distortion is required for amp sounds in some genres. In a standard master-volume guitar amp, as the amp's final or master volume is increased beyond the full power of the amplifier, power-tube distortion is produced. The "power soak" approach places the attenuation between the power tubes and the guitar speaker. In

10455-407: The end result typically is unequal volume levels for the different frequencies. For example, equalization is used to modify an instrument's sound or make certain instruments and sounds more prominent. A recording engineer may use an equalizer to make some high-pitches in a vocal part louder while making low-pitches in a drum part quieter. Equalization is commonly used to increase the depth of

10578-461: The equivalent controls on a home hi-fi system. More expensive amplifiers typically have more controls for other frequency ranges, such as one or two midrange controls and a presence control for high frequencies. Some guitar amplifiers have a graphic equalizer , which uses vertical faders to control multiple frequency bands. Some more expensive bass amps have a parametric equalizer , which enables precise control of tone. The first amplifier stage

10701-466: The filter's center frequency is completely eliminated is known as a notch filter . An equalizer can be used to correct or modify the frequency response of a loudspeaker system rather than designing the speaker itself to have the desired response. For instance, the Bose 901 speaker system does not use separate larger and smaller drivers to cover the bass and treble frequencies. Instead it uses nine drivers all of

10824-416: The first 100-watt guitar amplifier. He pushed the limits of electric amplification technology, helping to develop new equipment that was capable of producing "thick, clearly defined tones" at "previously undreamed-of volumes." Distortion became more popular from the mid-1960s, when The Kinks guitarist Dave Davies produced distortion effects by connecting the already distorted output of one amplifier into

10947-536: The first being the Ampeg Reverberocket amp. In the 1950s, several guitarists experimented with producing distortion by deliberately overdriving amplifiers. These included Goree Carter , Joe Hill Louis , Elmore James , Ike Turner , Willie Johnson , Pat Hare , Guitar Slim , Chuck Berry , Johnny Burnette , and Link Wray . In the early 1960s, surf rock guitarist Dick Dale worked closely with Fender to produce custom made amplifiers, including

11070-420: The form of variable bass and treble controls, and switches to apply low-cut or high-cut filters for elimination of low-frequency rumble and high-frequency hiss respectively. Graphic equalizers and other equipment developed for improving fidelity have since been used by recording engineers to modify frequency responses for aesthetic reasons. Hence in the field of audio electronics the term equalization

11193-406: The frequency response in recording, reproduction, and live sound reinforcement systems . Sound engineers correct the frequency response of a sound system so that the frequency balance of the music as heard through speakers better matches the original performance picked up by a microphone . Audio amplifiers have long had filters or controls to modify their frequency response. These are most often in

11316-473: The high and low bands, and bypassing for any unused band for the purest signal path. Similar designs appeared soon thereafter from George Massenburg (in 1972) and Burgess McNeal from ITI corp. In May 1972 Massenburg used the term parametric equalization in a paper presented at the 42nd convention of the Audio Engineering Society . Most channel equalization on mixing consoles made from 1971 to

11439-410: The inclusion of the leading factor simply indicates that the response at frequencies much higher than f z or f p is unity and that only bass frequencies are affected. A high shelving control in which f z is set to infinity, or a low shelving response in which f z is set to zero, implements a first-order low-pass or high-pass filter, respectively. However, the usual tone controls have

11562-475: The input of another. Later, most guitar amps were provided with preamplifier distortion controls, and fuzz boxes and other effects units were engineered to safely and reliably produce these sounds. Overdrive and distortion have become integral parts of many styles of electric guitar playing, ranging from blues rock to heavy metal and hardcore punk . Guitar combo amplifiers were at first used with bass guitars and electric pianos , but these instruments produce

11685-400: The loudspeakers. Some cassette decks have a switchable "subsonic filter" feature that does the same thing for recordings. A crossover network is a system of filters designed to direct electrical energy separately to the woofer and tweeter of a 2-way speaker system (and also to the mid-range speaker of a 3-way system). This is most often built into the speaker enclosure and hidden from

11808-412: The manufacturer. Tone controls (usually designated "bass" and "treble") are simple shelving filters included in most hi-fi equipment for gross adjustment of the frequency balance. The bass control may be used, for instance, to increase the drum and bass parts at a dance party, or to reduce annoying bass sounds when listening to a person speaking. The treble control might be used to give the percussion

11931-524: The open back cabinet, the closed back cabinet (a sealed box), and, less commonly, bass reflex designs, which use a closed back with a vent or port cut into the cabinet. With guitar amps, most open back amp cabinets are not fully open; part of the back is enclosed with panels. Combo guitar amp cabinets and standalone speaker cabinets are often made of plywood . Some are made of MDF or particle board —especially in low-budget models. Cabinet size and depth, material types, assembly methods, type and thickness of

12054-593: The parameters for each of three bands for a recording console… I wrote and delivered the AES paper on Parametrics at the Los Angeles show in 1972… It’s the first mention of 'Parametric' associated with sweep-tunable EQ." Daniel N. Flickinger introduced the first parametric equalizer in early 1971. His design leveraged a high-performance op-amp of his own design, the 535 series to achieve filtering circuits that were before impossible. Flickinger's patent from early in 1971 showed

12177-513: The parametric equalizer is the semi-parametric equalizer, which is also known as a sweepable filter. It allows users to control the amplitude and frequency, but uses a pre-set bandwidth of the center frequency. In some cases, semi-parametric equalizers allow the user to select between a wide and a narrow preset bandwidth. The responses of linear filters are mathematically described in terms of their transfer function or, in layman's terms, frequency response . A transfer function can be decomposed as

12300-402: The pre-amp out jack), an external speaker output (for powering an additional speaker cabinet ), and stereo RCA jacks or a 1/8" jack, for connecting a CD player or MP3 player so that a player can practice along with recorded music. Some amps have a 1/4" jack for connecting a pedal to turn the amp's onboard overdrive and reverb on and off or to switch between channels. Some amps have an XLR jack for

12423-481: The preamp or gain knob usually produces overdrive distortion. Some electric guitar amps have three controls in the volume section: pre-amplifier, distortion, and master control. Turning up the preamp and distortion knobs in varying combinations can create a range of overdrive tones, from a gentle, warm growling overdrive suitable for a traditional blues show or a rockabilly band to the extreme distortion used in hardcore punk and death metal . On some electric guitar amps,

12546-428: The present day rely upon the designs of Flickinger, Massenburg and McNeal in either semi or fully-parametric topology. In the late 1990s and in the 2000s, parametric equalizers became increasingly available as digital signal processing (DSP) equipment, usually in the form of plug-ins for various digital audio workstations. Standalone outboard gear versions of DSP parametric equalizers were also quickly introduced after

12669-442: The re-amped or "dummy load" approach, the tube power amp drives a mostly resistive dummy load while an additional low power amp drives the guitar speaker. In the isolation box approach, the guitar amplifier is used with a guitar speaker in a separate cabinet. A soundproofed isolation cabinet , isolation box, isolation booth, or isolation room can be used. A variety of labels are used for level attenuation potentiometers (knobs) in

12792-452: The response of microphones , instrument pickups , loudspeakers , and hall acoustics . Equalization may also be used to eliminate or reduce unwanted sounds (e.g., low-frequency hum coming from a guitar amplifier), make certain instruments or voices more (or less) prominent, enhance particular aspects of an instrument's tone, or combat feedback (howling) in a public address system. Equalizers are also used in music production to adjust

12915-411: The same four-inch diameter, more akin to what one would find in a table radio. However, this speaker system is sold with an active equalizer. That equalizer must be inserted into the amplifier system so that the amplified signal that is finally sent to the speakers has its response increased at the frequencies where the response of these drivers falls off, and vice versa, producing the response intended by

13038-602: The sixth prototype as the production model. This model was dubbed the "JTM45" – for Jim and his son Terry Marshall, and 45 for the RMS-rated wattage – the amplifier mimicked the circuitry of the Fender Bassman but had an all-aluminum chassis, and a 12AX7 valve as the first in the chain (while the Bassman had a 12AY7 ). In addition, it featured Celestion speakers with a closed cabinet (rather than open-backed Jensen speakers), and

13161-439: The software versions. Although the range of equalization functions is governed by the theory of linear filters , the adjustment of those functions and the flexibility with which they can be adjusted varies according to the topology of the circuitry and controls presented to the user. Shelving controls are usually simple first-order filter functions that alter the relative gains between frequencies much higher and much lower than

13284-425: The sound of a range of tube amplifiers and different sized speaker cabinets, all using the same amplifier and speaker. These are known as modeling amplifiers , and can be programmed with simulated characteristic tones of different existing amplifier models (and speaker cabinets—even microphone type or placement), or dialed in to the user's taste. Many amps of this type are also programmable by way of USB connection to

13407-418: The sound of their tone before the signal reaches the amplifier. In the 1920s, it was very hard for a musician playing a pickup-equipped guitar to find an amplifier and speaker to make their instrument louder as the only speakers that could be bought were "radio horns of limited frequency range and low acoustic output". The cone speaker, widely used in 2000s-era amp cabinets, was not widely offered for sale until

13530-402: The sound quality of a recording studio in addition to its use in live sound reinforcement systems and even home hi-fi systems. During live events where signals from microphones are amplified and sent to speaker systems, equalization is not only used to "flatten" the frequency response but may also be useful in eliminating feedback . When the sound produced by the speakers is picked up by

13653-419: The stereo demultiplexer . In addition to adjusting the relative amplitude of frequency bands, an audio equalizer usually alters the relative phases of those frequencies. While the human ear is not as sensitive to the phase of audio frequencies, music professionals may favor certain equalizers because of how they affect the timbre of the musical content by way of audible phase artifacts. A high-pass filter

13776-468: The strict sense of the term. A parametric equalizer has one or more sections each of which implements a second-order filter function. This involves three adjustments: selection of the center frequency (in Hz ), adjustment of the Q which determines the sharpness of the bandwidth , and the level or gain control which determines how much those frequencies are boosted or cut relative to frequencies much above or below

13899-401: The string vibration, a potentially dangerous approach that did not become popular. In 1934 Dobro released a guitar amp with a vacuum tube rectifier and two power tubes. By 1935, Dobro and National began selling combo amps for Hawaiian guitar. In 1934, Gibson had developed prototype combo amps, but never released them. By 1935, Electro/Rickenbacher had sold more amps and electric guitars than all

14022-402: The studio or stage. The use of full range, flat response (FRFR) amplification systems by electric guitarists has received an extra impetus from modeling amplifiers. Before widespread availability of modeling, guitarists did not commonly plug electric guitars straight into PA systems or powered speakers because most genres relied on the tonal coloration of a regular guitar amplifier setup—from

14145-520: The three primary parameters: amplitude , center frequency and bandwidth . The amplitude of each band can be controlled, and the center frequency can be shifted, and the bandwidth (which is inversely related to " Q ") can be widened or narrowed. Parametric equalizers are capable of making much more precise adjustments to the sound than other equalizers, and are commonly used in sound recording and live sound reinforcement . Parametric equalizers are also sold as standalone outboard gear units. A variant of

14268-448: The treble control increases f p and decreases f z so that frequencies higher than f z are boosted. Setting the treble control at the center sets f z  = f p so that | H ( f )|  = 1 and the circuit has no effect. At most, the slope of the filter response in the transition region will be 6 dB per octave. Similarly the response of a low shelf or bass control can be represented as: In this case,

14391-704: The tubes can render an amplifier inoperable until the issue is resolved. While tube-based circuitry is technologically outdated, tube amps remain popular since many guitarists prefer their sound. Tube enthusiasts believe that tube amps produce a warmer sound and a more natural "overdrive" sound. Most inexpensive and mid-priced guitar amplifiers are based on transistor or semiconductor (solid-state) circuits, which are cheaper to produce and more reliable, and usually much lighter than tube amplifiers. Solid-state amps are less fragile than tube amps. High-end solid-state amplifiers are less common, since many professional guitarists favor vacuum tubes. Some jazz guitarists favor

14514-405: The uneven frequency response of an electric system by applying a filter having the opposite response, thus restoring the fidelity of the transmission . A plot of the system's net frequency response would be a flat line, as its response at any frequency would be equal to its response at any other frequency. Hence the term equalization . Later the concept was applied in audio engineering to adjust

14637-448: The user. However, in bi-amplification , these filters operate on the low level audio signals, sending the low-frequency and high-frequency signal components to separate amplifiers, which connect to the woofers and tweeters, respectively. Equalization is used in a reciprocal manner in certain communication channels and recording technologies. The original music is passed through a particular filter to alter its frequency balance, followed by

14760-508: Was first used by John Volkman working at RCA in the 1920s. That system was used to equalize a motion picture theater sound playback system. The Langevin Model EQ-251A was the first equalizer to use slide controls. It featured two passive equalization sections, a bass shelving filter, and a pass band filter. Each filter had switchable frequencies and used a 15-position slide switch to adjust cut or boost. The first true graphic equalizer

14883-538: Was founded by Paul Tutmarc , the inventor of the first electric bass (Tutmarc's instrument did not achieve market success until Leo Fender 's launched the Precision Bass ). In 1933, Vega sold a pickup and amplifier set for musicians to use with existing guitars. In that same year, the Los Angeles-based Volu-Tone company also sold a pickup/amplifier set. Volu-Tone used high voltage current to sense

15006-428: Was reissued in 1989, albeit with a modern printed circuit board and 6L6 output valves. In 2014 Marshall reissued a "handwired" 30 W amplifier based on the JTM45, the 2245THW, whose circuitry is identical to the 1962 combo circuit; it is a "fine high-end piece" according to Vintage Guitar , listed at $ 4,800. The first JTM45s did not have the standard Marshall numbers that later amplifiers had; models that derived from

15129-559: Was the type 7080 developed by Art Davis 's Cinema Engineering . It featured 6 bands with a boost or cut range of 8  dB . It used a slide switch to adjust each band in 1 dB steps. Davis's second graphic equalizer was the Altec Lansing Model 9062A EQ. In 1967 Davis developed the first 1/3 octave variable notch filter set, the Altec-Lansing "Acousta-Voice" system. In 1966, Burgess Macneal and George Massenburg envisioned

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