 |
 |
 |
 |
|
 |
||||
Guitar Amps |
||||||
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
|||
Like any other amplifier a guitar amplifier is usually designed specifically for guitar. It amplifies the sound from the guitar pickups and is considered just as important to the sound of the guitar as the guitar itself. They come in all types, sizes, and colors. Depending upon the sound you are looking for will determine what type of amp you should get. Guitar amps are meant to color the sound which is the exact opposite of what you want from a PA or stereo system. For instance a guitar amp won't sound very good at all when used for amplifying a vocal mic or keyboard. These amps are made with a limited frequency response not only from the amp but from the speakers used as well. They are made to color/change/modify the sound of the signal coming in. They of course amplify the sound to the level of volume for use with the musical situation. For the most part the guitar amps of today are actually amplified signal processors. It should be mentioned that speakers also have an effect on the sound of the amp. The size, manufacture, model, and type of speaker make a big difference in the sound. Speakers also distort and are meant to – in this case. Types of Guitar Amps: There are two basic types of amps those which use tubes or valves as they are called in Europe, and those which use transistors called solid state amps. Of the two most guitarists prefer the sound of tubes over that of transistor. At the same time the reliability of a transistor amp is much better. Tube amps consist of just that, tubes. They have a round, fat, and more musical tone than solid state. They also produce more even harmonics which gives them their rich warm sound. Even when turned up until they distort the sound of a tube amp is still preferred by most guitarists even today. Some of the problem with them is they are usually heavier in weight and noisier than solid state. They are also more likely to fail especially if you just drop your amp on the floor, so you have to be more careful with them. You should let your amp warm up before trying to play anything through it. You’ll have to periodically change the tubes this will depend upon how often you play and the style of music. Solid State amps are usually made of transistors or what is more commonly known as op amps (small scale integration). They can also be made of integrated chips which contain a number of op amps and other chips, capacitors, and resistors all on a single chip. The output section is transistor based as well. You can tell what the amp uses, tube or transistors, by looking at the back of the amp. If you see transistors then you probably only see a large heat sink which is usually a black or silver block of metal with cooling fins. The tube amps will obviously have tubes in the back but they might be a Hybrid Amp (Tube and Transistor). Some of the more popular tube amps are the Marshall JCM800, Fender Twin Reverb, and Vox AC30. Some solid state amps are the Roland JC120, Line 6 Spider, and the Fender FM212r. Hybrids (Combo of Tube and Transistors) Hybrid amps are a combination of tube and transistor. They usually have a tube preamp section and a solid state power amp section. This gives a similar effect to what an all tube amp would sound like. Other types of hybrid amps use a transistor preamp section with a tube power amp section. Some amps may only use a single 12AX7 preamp tube on one of the channels of the amp. Some Hybrid Amps include the Vox Valvetronix (tube pre, solid state power), and Marshall Valvestate amps. DSP or Amp Modeling Amps: These amps are digital emulations based upon the data of other amplifiers (tube, solid state, and hybrid). Each amp is recorded at various states of use: clean, bluesy, loud, and extremely loud where the recording is then analyzed to see how it behaves in the various states. A mathematical model is then created base upon this information and programmed into a Digital Signal Processor. A number of different parts of the guitar amplifier can be analyzed and linked together like you would link together a guitar to chorus pedal, to amp, to speakers, and finally to a microphone. This allows you to select a particular type of preamp, say a Marshall Plexi, and then run it through a 2 x 12 open back cabinet and finally through a shure 57 microphone. Some of these amps also include built in digital effects as well. These amps usually use a transistor power amp stage with a DSP (Digital Signal Processing) preamp stage. It is actually a hybrid of Analog and Digital technologies. It consists of a guitar input (1/4 inch) which is feed into an Analog to Digital converter where the guitar signal is digitized. This resulting digital audio data is then sent to the DSP unit where the DSP is preprogrammed with a number of different emulations as well as various effect type of algorithms. Some of these algorithms include digital delay, digital reverb, digital distortion, and many other guitar related effects. These are the latest thing going mainly because this type of technology has lowered the price of guitar amps considerably. You can also find many guitar amp modeling preamps in the form of table top or rack mount boxes and even software you can run on your computer. Some Modeling amplifiers include: Many amps by Line 6, Native Instruments Guitar Rig, and Epiphone Triggerman. History of the Guitar Amp: As with the Electric Guitar the origins of the guitar amp aren’t really known. The first guitar amp was probably a hi-fi or pa amplifier. The transistor hadn’t yet been invented. Rickenbacker and Gibson started making guitar amps in the late 30’s. Gibson had a model that was meant to be sold with the ES-150 which was their first hollowbody electric. This was in 1937 where it appeared in the Gibson catalogue. Rickenbacker is known to have manufactured their first electric guitar in 1932 but there is no mention of an amplifier to go with it. When they and Gibson started manufacturing amps they were based on the current amps used in radio and hi-fi amps. Fender got in to the act in the mid 40’s (1945) with the company was still called K&F Manufacturing. They were also very simple amps and didn’t have any controls (volume or tone). You used the guitar’s volume and tone controls. It wasn’t until after the aliens landed at Roswell J (1947) that Fender introduced their first amp. It still didn’t have any volume, and tone controls. It was the Model 26 which used a 6V6 and Jensen speakers. The transformer was actually mounted onto the speaker rather than inside the amp housing. The first guitar amp with a volume control was the Fender Champion 600. These amps where beginner’s amps (similar to the Champ Amp of today) and used a single 6V6 output tube. Also in 1947 Fender introduced the Dual Pro which had two channels and two volume controls (one for each channel) and a single tone control. These amps where used for the pedal and lap steel guitars as well as hollow and solid body electrics. In the early 50’s Gibson introduced the Les Paul Amp which used the 6L6 output tubes. It was also of a similar designed to that of the Fender which was based upon the RCA tube application manual. The demand for louder amps came around this time as well. Fender responded with the Tweed Series of amps and most notably the Fender Bassman. These amps had more tone controls (treble, middle, and bass) as well as a Presence control and found the use of the now very popular 12AX7 and 12AY7 preamp tubes. These tubes allowed the amps to have more tone variation than any amp. With the Tweed amps you found one of the first uses of ‘Vibrato’ (modulating pitch changes) and ‘Tremolo’ (modulating volume changes). Each of these functions further advanced the sound of guitar amps. Vox introduced the AC15 in 1956 which was the first amp to use a class ‘A’ design. The Fender and Gibson amps all where class ‘B’. The Vox amps even though only had 15 watts or so where loud and sounded great when turned up (distortion). They became the amp of choice for England guitarist mainly because Fender amps cost too much. The Beatles for instance used Vox Amps quite extensively. Some of the more important Vox amps are the AC30, AC50, as well as the AC100. The number was the amount of watts the amps put out. There was one great Vox amp called the Vox AC30TB. The TB meant Top Boost which it had because of the addition of an extra tube. The 1960’s found the guitar amp in even more demand with the start of Rock-n-Roll. Fender introduced there famous BlackFaced amps. These amps were known for their great tone and reliability. These amps are the first Fenders where the controls of the amp are on the front panel instead of the top panel. The Fender Tweeds, Gibsons, and Vox amps all had their controls mounted on the top of the amps so the guitarist could clearly see the amp settings. This change to move the control knobs to the front of panel probably came from the amps being louder. With the amp being louder caused the guitarist to be located further away from the amp. This meant that they couldn’t see the controls if they were on top of the amp. So they got moved to the front. From what I can find out is the Fender VibroVerb was the first amp to have a spring reverb. Gibson had around the same time as this something called a Maestro EchoPlex. The EchoPlex was the first tape delay system that used a ¼ inch tape to record the guitar and then delay it and then play it back. This could be used to create a not so convincing reverb effect. |
|
|
|
 |
|
