8. Glossary of Technical Terms

A cliche name for amps that use type 6L6 tubes and sound softer/warmer than their British counterparts.

A cliché name for amps that use type EL34 tubes and sound more robust or rougher than the 6L6 variants.

It refers to a circuit layout for tube amps. A well-known example is the Vox AC30. A warm, dynamic sound, and an assertive yet creamy distortion are the standout features that all amps of this design can boast. Since most amps are produced without a master volume control, you have to be prepared to get heavily distorted sounds, which are only deliverable at max volume. A disadvantage of the Class A technology is the relatively high tube wear, meaning they need regular maintenance and replacement of the components.

It refers to a type of circuit layout for tube amps. Power amplifiers based on a Class B circuitry stay clean longer, a fact that makes them the ideal amplifier for multi-channel amps.

It is a broadly applied term for a clean, undistorted sound. To many mids are usually undesirable in this case, but clear highs and a clean bass can give an E-guitar acoustic characteristics. The most precise clean sound can be achieved, for example, by hooking a Strat directly into a mixer with a DI-Box. However, most guitarists prefer a slightly fuller, warmer clean tone than what this method produces. The most widely known amps for a good ''clean'' sound are the Fender Twin Reverb (Tube) and the Roland Jazz Chorus (Transistor).

The inventors of the Mesa Boogie were one of the first companies to add a third channel to their amps (specifically the Mk. III) at the end of the 80s, and when they did they called it the onomatopoeic 'Crunch' channel. This refers to a sound that has just passed from clean into distorted territory, but that hasn't become sustain rich yet, rather it ''crunches''. Great for riffs or rock rythyms but also for bluesy solos, the classical version of this sound can be achieved by turning the power up on an amp without a master volume control. In modern amps there is usually a designated channel for this, but you can produce crunch sounds in the lead channel by carefully controlling the gain. Recently smaller amps like the Vox AC 30 and the Fender Deluxe are becoming legendary for their harmonious crunch sound, but old Marshalls (without master volume) can also deliver it, though much louder.

An output (pre-amp out, send) and an input (main in, return) in the effects, which should not be passed through the pre-amp and distorted. Modulation effects like chorus and flanger belong here in addition to time effects such as delay and reverb. It is important that the effects signal not be overdriven which is why many better amps have the option to soften it in the loop (e.g. -10 dB). Another variant is the parallel effect path: In contrast to the serial paths, where the entire signal passes through the effect chain, only an adjustable portion is sent through and mixed with the original signal of the amplifier. This is off interest primarily for those using studio-/rack effects, where the direct signal can be hidden. In this case the guitar signal goes through 100% of the effect and is then added to the original signal.

For amps with a master volume this is where the overdrive in the pre-stage can be controlled.

An amplifier that combines the advantages of transistor technology with the sound characteristics of tube amplifiers.

Normally made up of treble, mid and bass. On most guitar amplifiers the controls affect one another so that, for example, a change in the treble means that the mid range needs to be adjusted as well - this varies though from model to model. Some sound controls are before the pre-amp and serve as a kind of distortion control for each frequency range, others are after the pre-amp, which provides greater flexibility for sound distortion. The layout of these sound controls influences the sound of the amp significantly, which is why modern modeling amp manufacturers produce them as true to the originals as possible.

In the early years of rock music the lead guitarist was simply the guitarist who played chords and from time to time was also allowed to play a melody (Lennon was the rhythm guitarist and Harrisson the lead guitarist for the Beatles for example). With the arrival of Clapton, Hendrix, Beck, Page, etc. what was expected of a lead guitarist changed, now you had to play spectacular solos in the new sustain-rich and distorted ''lead'' sound. This is the origin of the term and it is also used for riffs, ''dirty rhythms'' and so on. Legendary classic lead sounds are provided by various Marshalls and Boogies but the spectrum of amazing amps is vast.

The master volume controls the total volume output of the amp. If the distortion is generated in the pre-stage, you can play with distortion even at room volume, but most amplifiers sound better and more dynamic when the power amp is warmed up a litte. For multichannel amplifiers, the volume can also be changed here, but the ratio of the individual channels to one another remains unchanged.

After the input (jack) it is the first stage which the signal from the guitar passes through. This is a bit over simplified however as there are technically multiple stages: For amps without a master (volume) control, where distortion is only generated at the final stage, 2 ''gain stages'' are enough, for classic crunch 3 and modern high gain amps need 5.

Initially the signal would only be amplified to a level that the power amp could use to bring it to the desired volume. But rock guitarists in the late 60's and 70's wanted more distortion to create their characteristic sound and this in turn meant extreme volume levels. Then some really smart guys like Randy Smith, who's Mesa Boogie amps (which have multiple pre-stages combined one after the other - the so called cascade set up) were very succesful, came up with the idea to create distortion right in the pre-stage. This allowed for the desired sound to be achieved at normal room volume.

The amp then has a pre-amp or gain control (which defines distortion) and a master knob that limits the power-amp volume. However, many guitarists still prefer the power-amp distortion of a full-blown tube amp with no masters to the thinner, fuzzier, and more compressed pre-amp distortion. Often a pre-amp producing moderate distortion is combined with a power-amp driven into saturation to get a good mix of both. As with many things, the style of music plays a role here.

It is a control available on many amps but is still somewhat of a special feature as it is placed after the power-amp as opposed to the EQ's which influence the pre-amp stage. It boosts high frequencies above what the treble would do and makes the sound more ''present'' or crisp. Most guitarists change this to find their specific 'sound' and then leave it where it is.

The final stage of tube amps, the tubes of the power-amp take the signal from the pre-amp stage and bring it up to the desired volume. If you were to turn the tubes up to 11 at this stage they become saturated and create that classic, distored rock sound. This is obviously done at a very high volume but is still the best way to get classic distortion. The typical ''punch'' and dynamic sound are simply not achievable with distortion produced purely in the pre-stage (pre-amp). A good solution for guitarists who want to work with power amp distortion, but can do without hearing damage and hysterically waving club owners and bandmates, are smaller, less powerful tube amps - in this case less is more!

The last (but not the least) link in the sound chain. The same amplifier can sound completely different depending on the speakers or combinations used. The standard size for a guitar amplifier is 12'' but both 10'' and 15'' are also widely used. A 4x12'' box (typically used by those playing 'harder' music) sounds completely different than a rear facing half-open backed 2x12'' or a typical 1x12'' combo. As you can see, the sheer number of speakers and combinations available brings its own problems.

The term for the combination of one or more stacked (speaker) boxes and a top (amp).

Introduced at the end of the 60's they offer many technical benefits over their tube predecessors (no need to change tubes, higher reliability with more serviceability, lower weight, significantly lower price) but still never managed to overtake them in popularity. The main reason for this is their acoustic characteristics, which are naturally the first thing a musician cosndiders. In comparison to tube amps they sound 'colder' and too clean (individual models have built their reputation on this however, most notably the Roland Jazz Chorus, which, with its built-in chorus effect, is largely responsible for the popularity of the effect in todays music), additionally the distortion created by transistor amps is traditionally considered horrible. Today though, this view isn't so easily maintained because even before there were modeling amps, transistor amplifiers were built which were very close to their tube predecessors. Even hybrid amps (tube pre-amplifier and transistor output-stage, rarely vice versa) have become very popular, producing distortion in the pre-amp stage but staying light in weight due to their transistor power-amp stage.