I created and wrote the following encyclopedia articles:
http://wikibooks.org/wiki/Guitar/Tone_and_volume - textbook page
I also contributed significantly to these encyclopedia articles:
The below is older and less developed than my latest versions at Wikipedia. Some articles aren't shown below. Wikipedia has full historical archives shown who wrote what.
I wrote the following at Wikipedia in August 2006. There might be a few sentences started by others, but I did a heavy rewrite and major expansion; nearly all of these paragraphs I wrote from scratch off the top of my head.
– Michael Hoffman, BSEE, Amptone.com
An electric guitar has a volume control and tone control. The volume control almost always has a side-effect on equalization as you turn it down, affecting the pre-distortion equalization (EQ). The tone control reduces the amount of treble, affecting the pre-distortion EQ and thus the distortion voicing.
For increased control of the pre-distortion EQ, place an equalizer pedal in-between the guitar and the first distortion stage such as a distortion pedal or the guitar amp's built-in preamp. Switch between all the pickup settings, in conjunction with changing the distortion settings and EQ settings, to use the full range of basic sounds or "tones" the amp can produce.
The preamp Gain control on the distortion channel of the amp, or the Distortion control on a distortion pedal, sometimes has a side-effect of changing the equalization and thus the distortion voicing. In that case, you can use a lower distortion setting combined with a higher volume setting prior to the distortion stages, to dial-in a different distortion voicing with the same amount of distortion.
The tone stack on a standard tube amp is in-between the preamp distortion and the power-tube distortion. Thus the tone stack acts as the final part of shaping the preamp distortion voicing and also shapes the power-tube distortion voicing, together with the Master Volume control, which affects the amount of power-tube distortion voicing. For maximum power-tube distortion, set the tone controls and Master Volume to maximum, which is equivalent to bypassing them entirely.
When setting the preamp distortion, learn all the ways to adjust the equalization before the preamp distortion, including the guitar's volume and tone controls, a wah pedal, an equalization pedal, and any other volume or tone controls prior to the distortion stage. These affect the distortion voicing. More treble causes the treble to predominate in the complex clipping, resulting in a glassy liquid breakup tone; more bass prior to a distortion stage causes a dry, crusty breakup tone.
The same principles hold for controlling the power-tube distortion voicing. Learn all the ways to affect the equalization and level prior to the tube power amp, but after the preamp distortion.
To get power-tube distortion quietly or independently of volume level, use a power attenuator or an amplifier that has a built-in power attenuator, or a built-in power-supply based power attenuation (Power Scaling, Power Dampening, a Sag circuit, or a Variac).
It is possible to further voice the power-tube distortion by placing a dummy load (usually a power attenuator set entirely to use its built-in dummy load), an equalizer, and then a solid-state power amp between the power tubes and the guitar speaker.
A guitar speaker is a complex dynamic filter and transducer. Line-level cabinet simulators attempt to simulate this complex dynamic sound.
In the recording studio, the amp head and speaker cabinet are typically separated and the miked speaker cabinet is placed with microphones in a soundproofed isolation booth or in the live room. Either location is a soundproofed room separate from the control room where the mic signals return and the full-range monitor speakers reside for listening to the resulting power-tube distortion sound or loud quasi-clean amp sound at a controlled volume. In a home studio, the guitar speaker is sometimes placed in an isolation box with microphones.
Place one or two microphones near the guitar speaker. If you use two microphones, this causes some complex comb filtering; be prepared to swing the mixer's equalization for the two channels around very freely, because the effects of comb filtering are unpredictable. If you use a single microphone, setting the mixer's equalization is more straightforward.
The first version of the
A variety of labels are used for level attenuation potentiometers in a guitar amplifier and other guitar equipment, including Level, Gain, Volume, Distortion, Fuzz, Blend, Wattage, or Power Scale.
A guitar has a control labelled Volume, to attenuate whichever pickup is selected. There may be two volume controls 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, thus affecting distortion voicing, serving as pre-distortion equalization.
A distortion pedal has a Volume and a Distortion control; Volume essentially is a potentiometer at the output jack of the distortion pedal. Distortion essentially controls the driver amplitude prior to the clipping stages, so it affects the amount of clipping much more than it affects the output level at the output jack. However, some Distortion controls also change the amount of bass or treble, serving as an equalization side-effect in addition to an overall level change. Thus some Distortion controls also affect the pre-distortion equalization and thus the distortion voicing in the pedal's gain stages.
A standard guitar amp is a "master-volume" amp, meaning that it has a Gain control and a Master Volume control. The Gain control is exactly 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; it may affect the pre-distortion equalization and thus the preamp distortion voicing.
The amplifier's tone stack is a set of passive Bass, Midrange, and Treble controls, which reduce the level of only the bass frequencies, only the midrange frequencies, or only the treble frequencies. When the amplifier's Master Volume is set to maximum and yet even more power-tube distortion is desired, these tone controls can be set to maximum, which almost amounts to bypassing the tone stack attenuation entirely.
The amplifier's Master Volume restricts the amount of signal permitted through to the driver stage and tube power amp. This will affect the sound level produced by the guitar speaker, unless a power attenuator is placed in-between the tube power amp and the guitar speakers and set to some degree of attenuation.
When using a power attenuator, the Master Volume is no longer acting as the master volume control; instead, the power attenuator's Attenuation control takes over the role of controlling the wattage sent to the speaker, and the amplifier's Master Volume control is converted into purely a controller for the amount of power-tube distortion, independently of listening volume. An equivalent setup is power-supply based power attenuation, which is controlled by a knob on the tube power amp, labelled as Wattage, Power, Scale, Power Scale, or Power Dampening.
[[Distortion]] factors are a key distinguishing aspect of guitar amplifiers, requiring distinctive special treatment of guitar amplifiers compared to general instrument amplifiers. No other musical instrument is primarily oriented around distortion textures, as is the electric guitar as used in Rock music. All-tube guitar amps produce desirable distortion textures through the following frequency-response and distortion stages: pre-distortion EQ, 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.
Distortion texture from guitar amps is further shaped or post-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 dramatically changed and shaped by adding distortion-related and equalization-related [[Effects_pedal|effects pedals]], placed before the amp's input jack, in the amp's effects loop just before the tube power amp, or after the power tubes by using suitable connections.
Obtaining power-tube distortion at the desired volume is a major part of getting many of the desired guitar amp sounds. In a standard master-volume guitar amp, as the amp's final or master volume is increased, more power tube distortion is produced. This is slow-onset distortion; a tube (or valve) power amp rated at 50 watts produces 50 clean watts or, when pushed harder, twice as many distorted watts.
To make the amount of power-tube distortion independent from the volume heard at the guitar speaker, the main approaches are power-soak based [[Attenuator_(electronics)|power attenuation]], power-supply based power attenuation, a re-amped dummy load, and speaker isolation. The power soak approach places the attenuation between the power tubes and the guitar speaker; it pushes the power tubes to full power and then drains away the unwanted excess power by sending it to a mostly resistive dummy load and allowing only a portion through to the guitar speaker. Power soak products include the Rockman Power Soak, the THD Hot Plate, and the Marshall Power Brake.
The power-supply approach places the attenuation in the power supply and power amp; it runs the power tubes at a lower bias voltage and lets the full resulting power through to the guitar speaker. This prevents wearing-out the tubes or blowing the output transformer, and obviates purchasing and transporting a separate, bulky power attenuator. Power supply attenuation circuits include London Power's Power Scaling, Maven Peal's Sag circuit, and Mojave's Power Dampening circuit.
In the re-amped dummyload approach, the tube power amp drives a mostly resistive dummy load rather than a guitar speaker. The dummy load is typically the internal dummy load inside a power attenuator, with the load selector switched all the way to internal load rather than a mix of internal load and guitar speaker. A line-level signal is tapped from the dummy load, optional signal processing is applied such as EQ and reverb, and then the signal is sent through the final amplifier, typically solid-state run only in the linear region, which finally drives a guitar speaker. The guitar speaker contributes complex physical transducer dynamics at a quiet listening level controlled by the final amp, or even more complex dynamics if the speaker is pushed hard, into distortion.
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. The guitar speaker and microphones are placed inside a soundproofed space separate from the control room or listening area, such as in a double-walled isolation room in a different floor of a house. A speaker cable runs from the tube guitar amplifier in the control room out to the miked guitar speaker cabinet out in the separate isolated area. The microphone cables then run back from the isolated area back into the control room. This is the professional recording studio approach to obtaining power-tube distortion independently of the listening volume.
A guitar [[Effects pedal|effects pedal]] is connected into a signal chain using two 2-conductor instrument cables with [[Jack_plug|1/4" jack plugs]] (or "phone plugs"). The Input jack is usually on the right side, and Output on the left; thus the signal path for a chain of pedals is usually right-to-left. Some effects pedals have [[stereophonic sound|stereo]] out via two [[mono]] out signals, and a few have stereo input jacks as well as stereo output jacks. Several pedals can be linked together in a [[chain]]. An effects chain can be placed between the guitar and the guitar [[Instrument_amplifier|amplifier's]] preamp section, within the guitar amplifier's effects loop, after a guitar amplifier's Direct Inject line-level tap jack, after a dummy load attached to the guitar amplifier's output jack, or at the mixing board to process the miked guitar-speaker signal.
When a pedal is off or inactive, the signal coming in to the pedal is shunted onto a bypass, so that the "dry" or unaffected signal can go on to other effects down the chain, and thus any combination of effects on a chain can be created without having to reconnect boxes during a performance. True Bypass amounts to an isolated wire passing straight through the effects pedal, as opposed to buffered bypass, which can cause loss of treble, depending on the circuit.
The instrument signal can be routed through the stomp boxes in any combination, but to shape and preserve the clarity of the basic distortion tone, it is most common to put wah and overdrive pedals at the start of the chain; pedals which alter the pitch or color of the tone in the middle; and boxes which modify the resonance, such as flanging, delay (echo) and reverb units at the end. EQ, auto-wah, phaser, and vibe effects fit naturally at any position without introducing intermodulation distortion, while the emphatically time-based effects can sound unnatural and chaotic if placed early in the chain. Effects pedals can be used together with other [[effects unit]]s and a guitar amplifier's built-in effects.
Some guitar amplifiers have built-in effects such as Reverb and Tremolo and a switching pedal that turns the effects on or off. Channel switching between clean and distorted channels of a guitar amplifier's built-in preamp is also done with a switching pedal.
Equalizer/EQ - Adjusts the frequency response in a number of different bands of EQ. A graphic EQ provides slider controls, one for each frequency region; each of these bands has a fixed width (Q) and a fixed center-frequency. The slider changes only the level of the band. The tone controls on guitars, guitar amps, and most stompboxes are similarly fixed-Q and fixed-frequency, but unlike a graphic EQ, are rotation controls rather than sliders. Most parametric EQ pedals (such as the  Boss PN-2 and GE-2 pedals) provide semi-parametric EQ: in addition to level control, each band provides either a center frequency or Q width control. Parametric EQs have rotating controls rather than sliders.
Placing an EQ pedal before a distortion pedal and another EQ pedal after the distortion pedal provides maximum control over the preamp distortion voicing; an equivalent approach is to place an EQ pedal before an amp's built-in preamp distortion and use the amp's tone controls which are after the preamp distortion. An EQ pedal or amp's tone controls placed after preamp distortion is post-distortion EQ, which finishes shaping the preamp distortion and also sets up the power-tube distortion voicing. Eddie Van Halen thus places a 6-band MXR EQ pedal before the Marshall amplifier head (pre-distortion EQ), and the guitarist Slash by places a 7-band BOSS EQ pedal before his Marshall amp. This technique is similar to placing a Wah pedal before the amp's preamp distortion and leaving the Wah pedal positioned part-way down (pre-distortion EQ), along with adjusting the amp's tone controls (post-distortion EQ). Equalization-related effects pedals include Wah, Auto-Wah, and Phase Shifter. Most EQ pedals also have an overall Level control distinct from the frequency-specific controls, thus enabling an EQ pedal to act as a configurable level-boost pedal. Some EQ pedals include: MXR 10-band EQ, BOSS 7-band EQ.
Auto-Wah - A Wah stompbox without a rocker pedal. An auto-wah, also called more technically an envelope filter, uses the level of the guitar signal to control the wah filter position, so that as a note is played, it automatically starts with the sound of a wah pedal pulled back, and then quickly changes to the sound of a wah pedal pushed forward, or the reverse movement depending on the settings. Controls include wah pedal direction and input level sensitivity. This is an EQ-related effect and can be placed before preamp distortion or before power-tube distortion with natural sounding results. Auto-Wah pedals include: Electro-Harmonix Q-Tron
Vibe - This device produces the sound of a rotating speaker, which is a synchronized combination of volume oscillation, frequency-specific volume oscillation, vibrato (pitch wavering), and phase shifting and chorusing in relation to a non-rotating speaker. The modulation speed can be ramped up or down, with separate speeds for the bass and treble drivers on a 2-driver rotating speaker. This effect is simultaneously a volume-oriented effect, an equalization-oriented effect, and a time-based effect. Some Vibe pedals include: Dunlop Univibe
A switcher/mixer pedal enables running two effects or two effects chains in parallel, or switching between the two effects with a single stomp, or mixing the dry guitar signal with an effected signal. This is useful to make overly processed, "brick-wall processing" effects more mild and natural sounding. A wah can be mixed with dry guitar to make it more mild and full-bandwidth, with less volume swing. A compressor can be mixed with dry guitar to preserve the natural attack of the dry signal as well as the sustain of the compressor. Two overdrive pedals can be blended together. A gimmicky-sounding phaser that is too strong can be mixed with dry guitar to make it more subtle and musical. Some examples include: BOSS LS-2 Line Switcher
Several devices are similar to effects pedals but packaged and hooked-up distinctively, including [[Attenuator_(electronics)|power attenuators]] (the THD Hot Plate), power-tube pedals (ZVex' Nano Head, Stephenson's Stage Hog, or Damage Control's Demonizer), a string feedback pedal with headstock transducer (Sustainiac's Model C), a handheld string driver (the EBow), and talk boxes (the Heil Talk Box, Danelectro's Free Speech).
(added subheads at wiki)
In the world of [[guitar]] music and guitar [[amplifier|amplification]], distortion is actively sought, evaluated, and appreciatively discussed in its endless flavors. In many types of music, distortion is applied to [[guitars]] and other instruments, particularly within [[Rock and roll|Rock]] and [[heavy metal (music)|Metal]]. Guitar distortion can provide a sustaining tone for playing solos or leads, or a rough, crunchy tone suitable for [[rhythm]] guitar.
The central point of reference for dialing-in Rock distortion sounds is not a clean signal, but rather, a tube power amp that is running on the edge of audible distortion, so that as the guitar strings are plucked harder, the amount of distortion and the resulting volume both increase, and lighter plucking cleans-up the sound. Special effects are then dialed-in to complement and preserve that baseline foundation of edge-of-breakup.
Guitar amp modelling is about various guitar-specific distortion qualities, rather than pure amplification or special effects. Amp modelling is about reproducing several popular varieties of distortion that serve as common points of reference. Guitar distortion is produced by using effects pedals in conjunction with a guitar amplifier, and thus bridges the two subjects, while also including guitar pickup selection and windings, guitar volume, and how the guitar is played.
Rock guitar distortion is obtained and shaped throughout the standard signal processing chain, including multiple stages of [[preamplifier|preamp]] distortion, power tube distortion, power transformer distortion, and guitar speaker distortion. Much of the distortion character or voicing is controlled by the frequency response curve before and after each distortion stage; this dependency of distortion voicing on frequency response can be heard in the effect that a Wah pedal has on the subsequent distortion stage, or by using an EQ pedal to extremely favor the bass or treble components of the guitar pickup signal prior to the first distortion stage. Similarly, a guitar amp's tone controls shape a different power-tube distortion voicing if the tone controls are set to extremely emphasize the bass or treble.
Power-tube distortion can be produced in a dedicated rackmount tube power amp. A modular rackmount setup often involves a rackmount preamp, a rackmount tube power amp, and a rackmount unit containing a dummy load and guitar speaker cabinet simulator filter (Palmer's PDI-03). A similar alternative is to use a rackmount dummy load (without a cabinet simulation filter), followed by additional line-level rackmount signal processing, and then use a rackmount solid-state amplifier to re-amplify the signal to drive a guitar speaker.
Some effects pedals internally produce power-tube distortion, including an optional dummy load for use as a power-tube distortion pedal. Such effects units use a preamp tube such as the 12AX7 in a power-tube circuit configuration (as in the Stephenson's Stage Hog), or use a conventional power tube, such as the EL84 (as in the H&K Crunch Master compact tabletop unit).
Preamp distortion can be produced entirely within a [[stomp box|distortion pedal]], floor preamp/processor, or rackmount [[signal processor|preamp/processor]] designed for guitar. Or, a non-distorting level booster such as an equalizer pedal can be used to push the guitar amp's preamp stages into distortion. Similarly, a floor guitar preamp/processor or an outboard rackmount guitar preamp/processor with built-in preamp distortion can be the sole origin of the preamp distortion.
During the 1960s to early 1970s, distortion was primarily created by overdriving the power tubes. During the 1980s and 1990s, the Master Volume feature was standard on almost all guitar amplifiers, enabling conveniently generating high distortion levels in the guitar amp's preamp section while blocking most of the resulting signal from going to the power tubes, keeping well within the linear region of the power tubes and thus keeping the sound level down to the desired level. A wide selection of distortion and overdrive pedals became available then, including preamp-tube based distortion boxes, so distortion was popularly created by preamp distortion.
Preamp tube distortion can't produce all the classic tube distortion sounds; it sounds relatively buzzy, thin, fizzy, and dynamically flattened. Power-tube distortion is becoming available at lower volumes by using [[Attenuator_(electronics)|power attenuators]], power-supply-based power attenuation, built-in attenuation in tube guitar amps down to the milliwatt level, lower-wattage tube amps (such as a quarter-watt or less), speaker isolation boxes, and low-efficiency guitar speakers.
Amp modelling, typically using [[Digital signal processing|digital signal processing]], produces refined flavors of distortion that attempt to emulate the combined sounds of preamp, power-tube, and speaker distortion in famous guitar amplifiers. This digital signal processing to produce a wide range of famous distortion sounds can be in the form of realtime software running on a [[computer]], or it can live in hardware such as a compact pedal, oversize pedal, rackmount processor, desktop or floor processor, or in a guitar amp head, including a tube amp.
Distortion, equalization, or other pedals can change the sound that is emitted from the amplifier.
In the 1970s, as effects pedals proliferated, their sounds were combined with power-tube distortion at lower, more controlled volumes by using power attenuators such as Tom Scholz' Power Soak as well as re-amplified dummy loads such as Eddie Van Halen's use of a variac, power resistor, post-power-tube effects, and a final solid-state amp driving the guitar speakers. A variac is one approach to power-supply based power attenuation, to make the sound of power-tube distortion more practically available.
A line-level attenuator in the preamp or a power attenuator after the power amplifier uses electrical resistance to reduce the amplitude of the signal that reaches the speaker, reducing the volume of the output. A line-level attenuator has lower power handling, such as a 1/2-watt potentiometer. A power attenuator has higher power handling, such as 10 or 50 watts.
In audio electronics, attenuators are used as a dummy load by sending all of the power to the resistor and none to the speaker, in order to silence or reduce the output volume of an audio amplifier (for example, a guitar amplifier). Silencing an amplifier is useful for biasing the positive and negative signal crossover, for running bench tests such as measuring the amplifier's maximum output wattage, and for adding line-level effects between a guitar amplifier and a guitar speaker.
With guitar amplifiers, power-tube distortion is one of the main purposes of guitar amplifiers, and power attenuators are frequently used essentially for signal processing, as a means of obtaining power-tube distortion at a controlled volume level. A power attenuator is similar to a guitar effects pedal: it provides a useful way of getting a guitar amp to produce distortion for use in musical performance.
Whether set to full dummy load or only partial attenuation, a guitar-amp power attenuator typically offers a line-level output jack to enable recording the distortion-processed signal directly or reamplifying the distortion-processed signal through a larger or smaller amplifier for more or less volume, independently of how much power is being output by the first guitar amplifier's power amp section.
A power attenuator or dummy load is either purely resistive, or mostly resistive and partly reactive. The original guitar-amp power attenuator, the Altair Attenuator, was purely resistive, using a toaster coil with an electrically insignificant number of windings. Other models, such as the Marshall Power Brake, add some electrical inductance or capacitance to the electrical load (including fans, light bulbs and coils). There is debate about whether reactive attenuators do a better job of preserving a guitar amplifier's tone.
Use of an attenuator can potentially damage an amplifier just as using a speaker as a load can, if you are driving the amplifier into heavy distortion. Some production attenuators are the Rockman Power Soak, the Marshall Power Brake, and the THD Hot Plate.
There are two approaches to power attenuation to obtain any desired amount of power-tube distortion at a quiet or independently controllable speaker volume: the power-soak approach and the power-supply reduction approach. In the power-soak approach, the power tubes are pushed into their maximum possible power output, and then the unwanted resulting wattage is directed into the dummy load portion of the power attenuator, which is placed between the output transformer and the guitar speaker, routing only a portion of the output wattage to the guitar speaker.
In the power-supply reduction approach, as with a Variac, Power Scaling, Power Dampening, or Sag circuit, the B+ plate voltage available to the power tubes is reduced, producing power-tube distortion at arbitrarily low output power levels -- the entire resulting output wattage is sent directly to the guitar speaker. This removes power-tube wear, prevents blowing an output transformer, prevents overheating and shutdown, and obviates purchasing and transporting a separate, bulky power attenuator in addition to the guitar amp.
There is a less electronic way to attenuate a guitar amp in order to get power distortion at a controlled volume: isolate the guitar speaker in a soundproof box or room, together with a microphone.
Re-amping is a recording-studio technique to separate guitar playing from guitar amplifier processing. It can be used to process other instruments such as software-based virtual synthesizers or recorded drum tracks, to "warm them up", which means to add complex, musically interesting compression, distortion, and filtering.
Reverse direct input (DI) has been in use for decades. John Cuniberti patented the idea of an integrated level control with dedicated reverse DI transformer. The term reamp may have been coined and first used by John Cuniberti; 'Reamp' is a trademarked product name and circuit approach for the Cuniberti Reamp. In the strict, patented sense, terms such as reamping, re-amping, or re-amplification refer to the process of impedance-correct guitar pickup emulation with integrated level control.
The term reamp or re-amp has also been used in the guitar amplifier field to refer to the approach of running a vacuum tube power amp into a dummy load and then again amplifying the resulting line-level signal back up to a high-power level to drive a guitar speaker.
Like running a guitar signal through a guitar effects pedal that is set to Bypass, re-amping introduces some degree of noise and dynamic reduction compared to playing a guitar live directly into a guitar amp rig; however, products such as the Cuniberti Reamp are designed to enable such an approach properly, minimizing the degradation to negligible levels.
A re-amp box is a transformer-based Direct Inject (DI) box used in reverse, with some resistors and a level control. It converts a balanced to an unbalanced connector, reduces the high +4 dB studio-level signal down to a -10 dB level, and a low- to a high-impedance instrument level (typically a guitar pickup impedance).
The recorded signal is sent into the +4 dB balanced XLR and an unbalanced TRS (Tip-Ring-Sleeve) connector is used for the output, which is connected to the guitar amp rig. The -15 dB or -20 dB pad attenuator switch on the DI box must be engaged.
Sometimes a guitar volume pedal or buffered effects pedal can work adequately for re-amping, depending on grounding, levels, and impedance. Another approach to simulating the high impedance of a guitar pickup is to use the passive DI and add a 10 K-ohm resistor in series with the signal connection inside a 1/4" plug.
The general process of re-amping has been used throughout the history of recording studios. In 1913, Italian Futurist Luigi Russolo recorded various sounds on Berliner discs and played them back through machines to add noises, recording the result on master disc cutters. Pierre Schaeffer in the 1930s and 1940s used recorded sounds such as trains, played them back with alteration and recorded the result. Karlheinze Stockhausen and Edgard Varese later used similar techniques.
Les Paul and Mary Ford recorded her layered harmonies, modifying the past recording pass such as by reverb, while recording the result together with the new live singing. He placed a loudspeaker at one end of a tunnel and a microphone at the other end. The loudspeaker played back previously recorded material, and the microphone recorded the resulting altered sound.
Phil Spector further refined the re-amp process with the Beatles. Re-amping is used in film to add room ambience to dry recorded voice, a technique the industry refers to as worldizing.
Bob Ohlsson of Motown used reamping in 1968 to separately record direct guitars, clavinets and electric pianos -- instruments that were initially individually recorded direct to tape one at a time, to reduce microphone bleed.
Roger Nichols re-amped in 1972 for Steely Dan, partly to spread the stress on cranked tube amps across multiple amps, one at a time. A sound would be dialed-in for several hours on one cranked guitar amplifier, and if this stress wore out the amplifier components, another amplifier would be used to record the final processing run.
Radial, ART, Little Labs, and Millennia Media products use the Cuniberti Reamp company's patent under license, or a variant of the patent.
A guitar speaker cabinet contains one or more guitar speakers - usually 1, 2, or 4 speakers, most commonly 12" in diameter. A speaker cabinet can be open-back or closed-back. A 4x12 cabinet is a guitar speaker cabinet containing four 12" speakers. A cabinet is usually mono, but can be stereo.
The speakers in a cabinet can be wired in parallel (lowering the impedance) or in series (increasing the impedance). For vacuum tube amplifiers, the cabinet impedance must match the output impedance the amplifier is designed for or the impedance value it is set to.
A combo amp for guitar is a single integrated cabinet that contains the amplifier head and one or two guitar speakers. A 2x10 combo amp contains two 10" guitar speakers.
Speaker compliments are often abbreviated such that a 4x10" cabinet is written as 410 cab and a combo amplifier with a single 12" speaker is referred to as a 112 combo amplifier.
A guitar speaker isolation cabinet contains a guitar speaker and one or two microphones in a single- or double-layer soundproofed box.
I carried out the following heavy refactoring and great expansion of the previously existing Wikipedia articles.
GUIDING PRINCIPLE: Articles about guitar gear should have 'guitar' in the title.
JUSTIFICATION: The distinction between general theory about a technology, versus the popular *application* of that technology to electric Rock guitar, justifies a set of articles explicitly devoted, in the title, to *guitar* application. Several articles claim in their title to be general-focused, when in fact, they are focused largely or almost exclusively on guitar application. Titles should match common, de facto, popular usage.
PROPOSED ARTICLE TITLES AND CHANGES:
The guitar application of a topic should not be subsumed as though it were a minor subcase the subject. Wiki has tended to suppress electric Rock guitar in the technology articles. There is a major precedent supporting my proposal: notice that "Electric guitar" is not subsumed into the "Guitar" article. Neither should Guitar distortion be subsumed into Distortion. Same with Guitar attenuators, and Guitar amps.
Guitar amps are more like an essentially independent subject than a subcase of Amps. Guitar amps have outgrown the Instrument amps page, and Guitar attenuators have outgrown the Attenuator (electronic) page. Guitar applications of technology need their own dedicated pages.
A separate page on guitar distortion is warranted; it is not best lumped with all the other guitar effects. Guitar distortion is the main, major, predominant topic in Rock guitar gear. It's not only a pedal to buy and plug into. It's not merely an effect to add; it's the very essence and central point of reference of Rock guitar tone.
The recent good books on guitar sound (such as Dave Hunter's series), and the magazines (Vintage Guitar, ToneQuest Report), advise to begin with a tube power amp running on the edge of audible distortion, so that as you pluck the guitar strings harder, the amount of distortion and the resulting volume both increase, or pluck less hard to clean-up the tone.
All effects are to be added to that starting-point, that baseline foundation of edge-of-breakup. In that sense, distortion is what electric guitar is all about. Guitar distortion is not a minor subtopic of Guitar amps, nor a minor subtopic of Guitar effects; guitar distortion transcends the separate topics of guitar amps and guitar effects units.
Distortion is the main, central topic in the subject of Guitar signal processing. The burgeoning but controversial field of guitar amp modelling is entirely about various guitar-specific distortion qualities -- it's not about amplification or effects; it's about modelling cataloged varieties of distortion. At the moment, the subject of guitar distortion is spread out among several guitar related and general electronics articles.
The complex and central subject of guitar distortion won't be adequately understood, as long as it is tucked away under "pedals" (which many "amp distortion only" tone-hounds disparage) or "effects" (a term which has overtones of silly unmusical flanging excess obscuring the guitar tone -- obscuring the subtle distortion qualities that have become *the* goal for many guitar tone purists).
The large subject of "distortion basics for guitarists" would outgrow an effects listing.
The straight world ("context = encyclopedia") is biased against a proper up-front treatment of distortion in guitar amps, belittling and underestimating the complexity and sophistication (development) of the topic.