Tag Archives: guitar tone

Guitar Amplifiers and Tone

by Chad Crawford, PMI Guitar Instructor

The wonderful sound that comes out of an amplifier begins with a tiny electromagnetic impulse in your guitar’s pick-up coil(s). This tiny, constantly varying impulse imposes an electronic signal at the guitar’s output port which travels along the cord into your amplifier. The amplifier receives this signal and sends it through several stages of amplification to produce a signal powerful enough to drive the speaker(s).

An amplifier typically consists of two overall stages of amplification: pre-amp, and power amp. The pre-amp stage is the one that receives the input from your guitar and processes it into a larger signal with tone alterations for presentation to the power amp stage. The pre-amp is where the amplifier allows you to alter specific tonal features such as bass, mid range, and treble, as well as apply built-in effects such as distortion (a.k.a. gain) and reverb.

The job of the power amp stage is to pick up the output signal from the pre-amp and magnify it up to a power level sufficient to drive your speakers via an output transformer. The purpose of the output transformer is to match the electromagnetic characteristics (impedance) of your amplifier’s power stage to the electromagnetic characteristics of your speaker(s), so that the amplifier will couple the maximum amount of available power to the speakers.

Tube vs. Solid State

It is important understand the difference in response between vacuum tube and solid state amplifiers. Tubes bring two very important characteristics to guitar amplification. First, they inherently add content known as harmonics, also often referred to by guitarists as overtones. In audio amplification outside the realms of guitar, these added audio components constitute an undesirable form of distortion. In guitar amplification they provide a pleasant sounding addition to the otherwise pure guitar tone. Secondly, tubes tends to react more strongly than transistors to changes in input, such that tube amps tend to provide a more sensitive response to the input from the guitar player. This tends to magnify the effect of changes in dynamics provided by variations in pick attack, such that the tube amp feels to many guitarists more like dancing with a willing partner, as opposed to the solid state amp’s more simple and indifferent magnification of the volume. For the less experienced guitarist these differences in response between the two types of amplification may be meaningless, but as experience accumulates these things will become more noticeable.

On some more elaborate amplifiers you may be able to pick off the signal at various stages of amplification for additional processing and/or routing. Many amplifiers have an effects loop which will allow you to insert patch cords after the pre-amp stage that will route the signal to an external effects processor and then back into your amp. Some amps also have a patch port between the pre-amp stage and the power amp stage that allows you to completely separate the two stages. This would allow you for instance to use the pre-amp stage from one amp to provide a signal to the power stage of another amp.

Tone Implications of Combo vs. Head/Cabinet

Guitar amps come in two basic physical configurations: combo and head/cabinet. A combo (short for combination) amp has the electronic circuitry and the speaker(s) all in one convenient box. Alternatively, you may wish to keep your amplifier itself separate from the speakers so that you have tonal options by matching up different amplifiers and speakers, as well as weight management for heavier amps and speaker cabinets. In this case you would want the amplifier in a box by itself. We call these amp-only boxes amplifier heads, or head for short. So we attach the head via a speaker cable (not the same cable as a guitar cable!) to a separate box that has only a speaker or multiple speakers. This is why many amp heads have several speaker output ports, so that you can use the head to drive speaker cabinets of varying load (impedance).

The most popular head/cabinet arrangement is the half-stack. The half stack is a head sitting on top of a large speaker cabinet with typically four speakers, usually 12 inch diameter speakers. The name half stack is a derivative of the stack, an amp with one head sitting atop two speaker cabinets with four speakers each. Hence the name stack – it is literally a stack of big boxes. A stack is a big, heavy, and loud amplifier arrangement that is only needed for the largest of venues, either a large arena or outdoors. A half stack, while still bulky and loud, is more manageable and thus is suitable for a wider variety of venues.

The combo amp may contain one speaker of sizes from 4 inch up to 12 inch. Some combos contain two twelve inch speakers, and some contain four ten inch speakers. More speakers means more power, and also more bass response. My rule of thumb … for good tone I recommend that if the combo amp has only one speaker, then stick with amps that have a 12 inch speaker.

Take note of this: you do not need a half stack to achieve high volume levels. A good quality combo with two 12 inch speakers will produce volumes comparable to a half stack of similar power. For large live venues the sound that the audience hears is coming through the much louder P.A. system anyway, via a microphone on the guitar amp speaker.

Fender vs. Marshall Tone

There are two basic guitar amplifier architectures on the market, both based on amps designed around specific power stage tubes. One is the Fender sound which is a clean tone based on the 6L6 tube. The Fender amps are coveted for pristine clean tones at higher volumes (a.k.a headroom – the amount of volume an amp can produce before distorting). The Fender sound is great for Blues, Jazz, and Country styles. The Marshall amps are based on the EL34 tube which produces a desirable distortion or break-up at moderate volume levels. This makes them desirable for any kind of guitar music that features distortion, such as rock or metal.

Since most guitarists use additional effects pedals to add various effects, there is some overlap between these tones. Most tube amps on the market today are some kind of imitation or derivative of the Fender or Marshall amps. Another popular tone is the EL84 tube tone associated with the classic VOX amps and often used on lower power tube amps. The EL84 tone has a sharp bright treble response and less bass response than the physically larger 6L6 and EL34 tubes.

If you want to know whether your amp is a Fender or Marshall type of amp, just check the power tubes. However, every amp consists of many components and built-in tone coloring characteristics, so you will not be able to know for sure what an amp sounds like without actually playing through it. There are many good quality amps on the market today besides Fender and Marshall. Let your ears be the judge. I prefer the tone of a Marshall, although I have heard great sounding tones coming from many other amps.

Amp Simulators

Modern computer technology has brought us guitarists the ability to include computers in our arsenal of music making tools. Popular simulators such as Pod Farm, Amplitube, and Guitar Rig allow us to plug our guitar into our computers via an interface box and then play through the computer. This is a great tool for practicing, as the simulation software will allow us to mimic a wide variety of tones from different iconic amplifiers and effects, all with just a few clicks of a mouse. For practicing guitar and learning about various amps and effects, this is the best thing that has happened to guitarist in decades. These simulators, in conjunction with other computer programs, also allow for pro-quality recording of your playing right in your bedroom, at volumes that will not disturb your neighbors or even the people in the next room. Assuming you already have a computer, these simulators are not nearly as expensive as a real guitar amp of good quality, so I highly recommend a simulator program for those new to electric guitar. After spending some time with a simulator you will have a better idea of the tone variation among the popular amps, so you will have a better sense of what you are looking for when you go to invest in a real amp.

Miscellaneous Considerations …

Guitar amps often have multiple channels to allow you varying tonal options from the same amp, from pristine clean to raucous distortion. In addition, each of these channels will usually have separate volume controls and maybe even separate input (gain) and output volume controls. Finally there will be one master volume control that controls the final output volume of the amp regardless of which channel you select. It is important to understand that there is a significant difference in volume from your guitar when you are playing rhythm versus solo. The multiple amp channels allow you to change for instance from a clean or slightly distorted tone for chords, to the richer harmonic content and increased sustain of distortion for playing individual notes of a solo. You will lose a significant amount of volume from the guitar when you change from playing chords to playing individual notes, such that if you set your amp up during sound check to match the band volume when you are playing chords, when you go to play solo at the same volume you will be drowned by the band. So you must set the volume on your solo channel significantly higher than that of your rhythm channel.

It is important to note that the amp tone will change drastically as you increase the volume. For instance, at low volumes the bass response will be weak so that you have to turn the amp up to get a balanced sound across the frequency spectrum. The electronic components will affect the tone to different degrees at different power levels. Power tubes deliver a certain coveted distortion that only appears when the tube is pushed to higher power levels. Speakers have a certain inherent stiffness so that they will only yield their best tones when pushed into lively motion to a certain degree (speaker excursion). Altogether, what this means is that the best electric guitar tones often come at the price of higher volumes. It is a never ending quest for guitarists to coax a good tone from our electric guitar amps at lower volumes, especially with distorted tones. It can be done, but it will take some time and effort learning how to tweak your amp.

Any given guitar amp is going to produce a wide variety of tonal qualities based on the options available on the amp, the guitar and effects plugged into the amp, and importantly the playing characteristics of the player playing through the amp. Pros often have their amps modified away from the manufacturer designs. So just because a certain guitarist you enjoy uses a certain kind of amp, that does not necessarily mean you will be able to reproduce their tone easily by purchasing the same amp. Before you rush out and buy the same amp as your guitar hero, be sure you play through a number of amps first. It may be that you will find your preferred tone coming from a box that you wouldn’t have expected.

Primer on Guitar Effects

Definitions

Tone – At the root of all discussion of guitars, amp, and effects, is one core concept: Tone. You will see this term in all manner of advertisements for guitars, amps, and equipment, and you will hear it discussed and even argued among musicians. What does it mean? It has somewhat of a subtle meaning that will be hard to understand well until you develop a little skill on the guitar and begin to develop your discernment for sound quality. For the moment let’s try to understand it this way. Tone refers to the overall sound quality of your instrument. I do not mean quality in the sense of good or not so good, but rather quality in the sense of characteristics. For example you might say that wood has certain qualities and metal has certain qualities. Likewise, sound has different qualities and these qualities vary among different guitars, amps, and effects, and various combinations of the above. As you develop as a musician you will naturally gravitate toward a certain preferred quality of sound from your instrument. Musicians refer to this quality of sound as tone.

Pedal – a floor standing effect device usually actuated by a foot switch, leaving the rest of you free to work your guitar magic. Guitarists often install pedals in a Pedal Board, which is simply a suitcase specifically designed for mounting guitar pedals and associated wiring.

Rack Mount – the effect circuitry does not care if it is mounted in the floor, wall, ceiling, amp, or wherever you want. So some effects come in a convenient box that is designed to mount into a specific type of instrument electronics travel cabinet (rack). This allows for manipulation of the parameters of the effect without having to kneel to the floor. Rack effects are also more typically able to be controlled via “midi”, which allows for advance programming of various combinations of effects such that one can have preset effects combinations for each song, readily accessible either by foot control or else remotely by the sound engineer at the control board. Rack effects tend to be more sophisticated than their floor pedal counterparts.

Sensitivity – the ability of the guitar to sound out clear notes with minimal finger pressure and string striking power. This will depend largely on the guitar and amp, but some effects also affect sensitivity. Generally, more is better.

Sustain – the ability of the guitar to continue sounding out a note after it has been plucked. As with sensitivity, this will also depend largely on the guitar and amp. Some effects will affect sustain and in fact some effects are specifically to enhance sustain. As with sensitivity, more is generally better.

Utilities:

Some devices referred to as “effects” are not really so much effects but rather are more like utilities. This will make more sense as we discuss specific devices. So let’s dive into specific effects now. Keep in mind we are speaking in general terms. There are literally thousands of effect devices on the market with various combinations and qualities of various kinds of utilities and tone alterations. We will highlight the basic concepts here.

Noise Suppressor or Noise Gate – the purpose of a Noise Gate is not to alter tone but rather to remove noise, as the name implies. If you have had some opportunity to play around with your guitar and amp you may have noticed a hum from your amp when you are not playing the guitar. The purpose of the Noise Gate is to remove that hum or at least reduce it to a very low level. If you are new to guitar and mostly playing at bedroom volumes then the hum may not bother you so much. As your ear for music develops and you begin to gravitate toward higher volumes for live group performance, the hum will grow louder and more annoying! Then you will want a Noise Gate.

Volume – more of a utility than an effect, although you can use a volume pedal prior to the pre-amp to create a keyboard-like tone from your guitar (a.k.a swell). The main purpose, however, is to control the guitar volume without having to use your hands to manipulate knobs.

Tuner – an electronic device that provides a tuning reference for you to measure your guitar’s tuning against. It allows for very rapid and accurate tuning.

General Purpose Effects:

Echo – May also be called Reverb. This is a very common effect and many modern amps will have this effect built in. The echo or reverb effect is similar to the natural phenomenon of echo. It works like this: you play a note on your guitar. The echo processor will expand that as if you played it in a large room or cavern. This effect adds fullness to your tone, making it sound more natural and thick. Of course you can dial it in to an extreme that does not sound natural at all.

Delay – similar to echo, but delay is a more specific, narrow reproduction of the note you just plucked. Unlike natural echo, you control the volume level and timing of repeats, as well as the decay (attenuation level or loss of volume level) of the repeat notes. As with echo, this effect adds fullness to your tone, making it sound more natural and thick. And again you can dial it in to an extreme that does not sound natural at all.

Expression – this effect is often referred to as Wah, Wah Wah, or Crybaby. It is typically a pedal that you oscillate with your foot to move an internal tone control through a range from very pronounced high/mids to very diminished high/mids. It will also alter your overall tone. You may also see it in the form of a device that automatically cycles throughout a preset tone range without oscillating foot pedal input.

Distortion – Distortion is the characteristic electronic fuzz sound associated with electric guitars. There are different levels of distortion and different types of distortion that yield different overall guitar tones. Most modern amps will include a distortion effect by design, often referred to as Drive, Overdrive, or Gain. Additionally, you can usually achieve a certain natural distortion by over powering your amp speaker(s) at high volume levels. A distortion pedal can enhance tone, sensitivity, and sustain at lower volume levels. Choosing a distortion pedal can get complicated because this is very much a matter of personal preference. Also, the different types and degrees of distortion have trade names, such as crunch (mild distortion), overdrive (substantial distortion), and fuzz (extreme distortion). Beyond this, the brand names of distortion pedals, like the popular Tube Screamer, may not indicate distortion at all. You will often see distortion pedals referred to as a Stomp Box.

Compressor – the purpose of a compressor is to raise low volume signals and suppress high volume signals. The intent is to level out the harshness of extreme variation in volume levels. Because it raises the power level of lower volume or weaker signals, it will also enhance sustain.

Modulation – this effect comes in a variety of forms and goes by different trade names even though it is all the same underlying effect. You may see it identified as Flange, Chorus, Phaser, Rotary Horn, Tremolo, or Uni-Vibe. The basic idea is to impose a varying frequency signal over your guitar signal, creating a wobbling sound. As with other effects, you control the rate and degree of the wobbling. The various names indicate different types or tonal qualities of the effect.

Many vendors have floor controllers or rack-mount controllers that incorporate some or all of these effects and more all in one box, such as the POD products by Line6.

Now that you know the terminology, you may be wishing you had some sounds to associate with these names. You can easily find demonstrations on various vendor sites such as MusiciansFriend or Sweetwater, or video hosting sites such as YouTube. Alternatively, if you’re willing to invest around a hundred twenty dollars for an entry level converter box (interface) such as the Focusrite Scarlett solo, along with another hundred for an entry level guitar simulator program such as Amplitube or Bias FX, then you can experiment with a variety of guitar effects with a simple click of the mouse.

Hardware or software, experiment and enjoy!

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Tag Archives: guitar tone

Guitar Amplifiers and Tone

Primer on Guitar Effects

Definitions