About
The guitar amplifier (usually called "guitar amp") is an electrical device used to restore the sound of a guitar, whether electric, electro-acoustic or bass. We can consider two main parts consitutents a guitar amp:
- Some electronic amplification (broadly defined) to format the electrical signal provided by the instrument.
- Some electro-mechanical where a speaker converts the electrical signal into an acoustic signal.
A Story Structure
The audio rendering of a guitar signal is done in several steps. On one side are the electronic amplification, where the electrical signal from the guitar is formatted. This part may be sub-divided into preamp and power amp. On the other hand, we find electromechanical part where a loudspeaker converts the electrical signal into an acoustic signal.
Somewhat misleading, the term "guitar amplifier" is often used to designate the whole. This is because many models combine the different floors in a single device. This is known as "combo". It is however possible, and this is very common for hardware high-end, separate floors in various devices for more modularity. This is called "head amp" to which we will connect a speaker, mostly consisting of 4 speakers 12 "(4x12).
Preamp
This is the part that has most influence over the sound. Its purpose is to receive and format the input signal to impersonate the sound, to color. It is primarily a work on the signal spectrum emphasizing certain frequency ranges, by mitigating other, controlling the harmonics.
To do this, the user has several control buttons:
- EQ, usually on three bands: low (150-200Hz) / mediums (1 to 1.2 kHz) Treble (4-5kHz)
- Contour, an active filter which is usually to increase the bass and treble while digging mediums,
- Distortion (drive or gain) which can saturate the signal.
Power Amplification
The signal from a guitar is not a carrier of power, the amplitudes of the tension and intensity are low. If the preamplifier is already giving more substance to the signal, it is still not sufficient enough to vibrate the membrane of a loudspeaker. The function of the power amplifier is to amplify the signal from the preamp to make carrier power to be transmitted to the speaker.
The role of an electronic amplifier is only to modify the parameters of the input signal amplitudes. The power amplifier generally has a linear frequency response, that is to say that each frequency spectrum is amplified in the same way. His influence on the coloration of the sound is limited, the task back to the preamplifier. Nevertheless, many musicians who use the power stage to add the coloring to the sound. This is common with tube amplifiers in which it is saturating the power tubes to add distortion to the signal.
Speaker
The speaker is the last link in the chain of restitution. Its role is to transform the electrical signal into an audible acoustic signal.
The loudspeaker is automatically put into an enclosure. An enclosure may contain several speakers and they are then considered as a whole.
The speaker is involved in the coloration of the sound. Therefore, when music only a guitar, the signal does not come from the line output of the amplifier. The signal is transplanted through a suitable microphone, placed differently to the speaker, to have the desired sound.
Effects
Many models incorporate effects add to the signal. The most common is the reverb, which simulates the phenomenon of sound reflection on the walls of a room. Thus, it gives the impression that you play in a room more or less. It is often done through a "delay line is clear.
The Tube Amp
The first amplifiers were tube (also called "tube"), the first electronic element (historically) for the amplification of an electrical signal.
A Tube
The tube technology (including the grid) is sensitive to mechanical vibrations causing a reverberation and a warm color and "singing". The tubes have a better impedance and store more energy: they saturate "soft" and can withstand peak intensities easier (better dynamic impulse). These properties make for an equivalent transistor amplifier "classic" will be roughly two times more powerful than its "equivalent" tube.
The three main drawbacks are its brittleness of the tube (shock), its wear and high cost.
It has some cultural prestige, its sound is considered more "warmer" than a transistor amp, which is why the vast majority of guitarists generally preferred by far a tube amp, like many passionate hi-fi. [ref. needed] This impression is due to heat generated by even harmonics lamps (transistors generating odd harmonics less pleasant for the human ear).
For professionals and stars of the guitar, and despite the rigors of the road, the amplification tube remains the standard unavoidable.
The Amp Modeling
The tube amps are more expensive, manufacturers have found a way to simulate the color of its product as a lamp. The ease and reliability of these simulations have allowed the explosion of this market, although the sound quality and resemblance to the original are questionable.
For reasons of trademark law, different names mask famous amp models:
Names usual (even if there is no standard set):
- Fender = Black Face/Tweed, Twin
- Vox = ACXX
- Marshall = UK (Brit.)
- Mesa Boogie = Numetal, Treadplate, Diamond Plate, Boogie
- Soldano = US
Names Vox:
- Boutique Cl = Dumble Special Clean Channel
- Boutique Od = Dumble Special Overdrive Channel
- Black (2x12) = Fender 65 (Twin Reverb)
- Tweed (4x10) = Fender 59 Bassman
- AC15 = 1962 VOX AC15
- AC30 TB = 1964 VOX AC30 With Top Boost
- UK 70'S = 1968 Marshall Plexi 50 Watts
- UK 80'S = 1983 Marshall JCM 800
- UK Modern = 2000 Marshall JCM 2000 TSL 100
- Numetal = 2001 Mesa Boogie Dual Rectifier
- US Higain = 1993 Soldano SLO 100
Names Berhinger:
- Brit. Class A = Vox AC30 Bass + Trebble Boost (Utilisateurs connus : Beatles, The Who, Bryan May (Queen) & U2)
- Brit. Blues = JTM 45 (1er ampli Marshall)
- Brit. Classic = 1959 Marshall Plexi 100 Watt (Utilisateurs connus : Jimi Hendrix, Eric Clapton &Jeff Beck)
- Brit. Hi-Gain = Base "Marshall JCM 800" (Utilisateurs connus : Slash & Michael Landau’s)
- Brit. Class A 15W = Base "Vox AC15"
- Numetal Gain = Base 1994 Mesa Boogie Dual Rectifier Trem-O-Verb (Utilisateurs connus : John Petrucci & Steve Lukather)
- Numetal Gain = Tête de "Mesa Boogie Dual Rectifier"
- American Blues = Fender Bassman
- Modern Class A = Matchless Chieftain
- Modern Hi-Gain = Soldano (contrôles Basses-Med-Aigus post gain, à cause de la distortion. Utilisateurs connus : Steve Vai, Joe Satriani, Steve Lukather, Nuno Bettencourt )
- Classic Clean = Roland JC-120
- AND Deluxe = Mix entre le "1960 Fender Blackface Deluxe" et le "’50s Fender Bassman"
- AND Custom = Modélisation sur une base de "1965 Marshall JTM 45 Bluesbreaker"
- Small Combo = 1960 Tweed Champ
- Non Top Boost = Vox AC30 (Pas de trebble boost, première version de l'ampli, utilisé par Bryan Adams en studio)
- Classic 50W = Base "Marshall Plexi 50 Watt", modifiée pour que les effets appliqués puissent être entendus
- Savage Beast = Engl Savage 120
- Calif. drive = Base Mesa Boogie Mark II c (simulation du canal de distorsion. Son se rapprochant de Santana)
- Calif. clean = Base Mesa Boogie Mark II c (simulation du canal clean. Son se rapprochant d'un Fender)
- Custom Clean. = Dumble Special (simulation du canal clean)
- Custom Drive = Dumble Special (simulation du canal de distorsion)
- Custom Class A = Budda Twinmaster
- Custom Hi-Gain = 1969 50-Watt Marshall Plexi.