Finding your ideal tone and piecing together your perfect guitar rig that functions exactly how you want it to is one of the most satisfying and rewarding parts of pursuing the instrument. But even for those of us who have been playing for a long time, there’s still an overwhelming amount of information and different kinds of gear available that it can be tough to educate yourself on what it all means.
So today we’ve put together a concise and easy to read overview of everything relating to guitar amplifiers, skipping the fluff so you can get up to speed as easily as possible.
- The common amplifier formats
- The amplifier types
- The amplifier sections
- All about tubes
- Amp classes
- Amplifier wattage
- Amplifier channels
- The effects loop
- Speakers and speaker cabs
- Amplifiers for different instruments
- Common controls on guitar amplifiers
- Common brands of amplifier
- Other notable amp manufacturers
- Additional amplifier terminology
The common amplifier formats
Ignoring some of the newer digital modelers which we will cover shortly. Generally speaking, to get sound from a guitar amplifier you need 2 parts: the amplifier itself which takes your guitar signal and, you guessed it, amplifies it so it can be sent through the second part which is the speaker cabinet.
This amp/speaker combination comes in two main formats. Firstly we have what’s called a ‘combo’ which is where both amplifier and speaker are housed in a single box.
Secondly, we have the ‘head and cab’ setup which is where the amplifier is in its own self-contained box and can be paired with a separate speaker cabinet of your choosing.
The amplifier types
So we know we need an amplifier to pair with our speaker. Over the years, as both consumer demand and technology has progressed we now have quite a few different ‘types’ of amplifiers to consider when deciding what will work best for our needs.
This is your traditional kind of guitar amplifier which utilizes vacuum tubes (also referred to as valves). These valves power 2 separate parts of the amplifier, first is the preamp section which although can be quite involved, you can easily think of this as giving your tone it’s personality and character. Secondly is the power amp section which takes the output of the preamp and boosts it in order to drive the speakers.
The solid state amplifier forgoes the use of vacuum tubes and instead opts for electronic circuit boards to produce its sound. There are a few benefits to this, they are generally more durable as they don’t use the more fragile glass vacuum times, and they are quite a bit cheaper to produce. However, many guitarists still prefer the warm and dynamic response of a tube amplifier over solid state and there is a general sentiment in the guitar community that solid state doesn’t sound quite as desirable as tube.
We briefly covered the advantages/disadvantages between tube and solid state. Hybrid amplifiers hope to draw upon the best of both worlds, using a tube-driven preamp section to get that warmth and dynamic response, but will often use a solid state power amp which is both cheaper to produce and weighs less. There are some rare cases where these will be flipped and it’s actually the preamp which is solid state combined with a tube driven power amp.
This kind of amplifier is one we’ve seen go through the largest change over the last decade as digital signal processing and computer technology have progressed so far. A modeling amplifier is one that uses a microprocessor and digital code to recreate the sound of high end amplifiers right down to the individual component level at a much cheaper cost. Originally, these did not sound great, but over the years they have improved substantially and are now commonplace in many professional musicians’ setups.
Pedal (amp in a box)
The simplest way to think of pedal amplifiers is the manufacturer took the preamp section out of a full amplifier and put it in a convenient stompbox. These have proven very popular for their small form factor and portability. There are also many variations on the market, sometimes the preamp is tube, sometimes digital. Some might have a power amp built in, some might forgo the power amp for a digital cabinet loader. Some of them even try to emulate full rigs with various in-built effects and routing features.
Rackmount guitar amplifiers were extremely commonplace during the ’90s, but have unfortunately waned in popularity a little as the ‘pedal’ format has dominated the market. The word ‘rack’ is referring to equipment that would have a universal size of 19’’, all the manufacturers would adhere to this standard so you could pick and choose the exact items and components in order to build your perfect rig. This allowed for ultimate customization as you could buy a pre-amp from one company and a power-amp from another company and build a rig that’s completely unique to you.
Much like modeling amplifiers, amp sims have seen a huge surge in popularity in recent years as technology has allowed this format, which previously didn’t sound all that great, to really start holding its own. To where nowadays it’s not unusual to find high end amp sims being used on top-end professional music productions. They are essentially software recreations of amplifiers that you will run on your computer (usually inside a digital audio workstation, or DAW). You can then plug your guitar into the computer via an audio interface and play them just like a real amplifier.
The amplifier sections
In the most general terms, when we refer to an amplifier we are technically referring to 2 individual parts or sections. The preamp and the power amp. When combined we are able to take out the guitar’s signal, give it its tone, distortion, and the volume it needs to then be sent to a speaker. But what are these 2 parts responsible for?
The preamp really serves two functions. The first is to take your guitar’s signal, which when taken straight out of the instrument is quite quiet and weak, and bring it to what we call ‘line level’. This signal is then loud enough to be sent to other equipment, either straight to the power amp, out to a mixer, or even to a cabinet simulator.
Its other function is tone shaping, most preamps have at least a simple 3 band EQ comprising of bass, mid and treble. Then, if your preamp has a distortion section that will also be applied.
Ok so we’ve taken our quiet raw guitar signal and the preamp has boosted it, EQ’d it, and added distortion, what’s next?
If you were to send that preamp signal straight to a big speaker cabinet, it simply wouldn’t have enough juice to drive them. This is where the power amp comes in, it takes your preamp signal and ‘amplifies’ it so it can drive the speakers. The power amp is generally the final section of an amplifier. The power amp can also color and distort your tone too so is an important thing to consider when deciding on which one is right for you.
All about tubes
As popular as modelers and amp sims are, tubes and tube amplifiers are still major players in the guitar space. So it’s worth talking a bit about how they work.
A valve’s tone will be affected based on the voltage that is running through them. So whenever you change tubes, especially if it’s to a different brand, you need a trained professional to ‘bias’ your amplifier to ensure the optimum voltage is passing through your valves.
A large part of where the appeal of tubes over things like solid-state or digital modelers lies is in the way tubes distort and saturate your tone. It provides a very warm and even type of distortion that oftentimes has a smoother top end when compared to the more harsh qualities that we associate with amplifiers in the digital realm.
Another big factor that makes tube amplifiers so beloved is in the dynamics. Tubes respond very well to the guitar’s volume control, meaning as you roll up the volume the gain will also saturate giving you a great deal of control over your sound without needing to adjust the amplifier directly.
In much the same way it also reacts to your playing, if you pick harder your tone will saturate more which gives the feeling of everything being more alive and reactive.
What happens if my bias is off?
If you are not running enough voltage through the tubes (also called being over-biased) your tone will sound very thin and brittle, the valves don’t have enough juice to give it that warm saturation that we’re looking for from a tube amplifier.
But on the other hand, if you are running too much voltage through them (also called under-biased) your tone will saturate far more than desired and become unwieldy. Not only that, it will reduce the lifespan of the valves significantly and potentially even damage other components in your amplifier.
This is why you need to have an ‘optimum bias’ where the tubes have just enough resistance against the signal being sent through them that you can achieve a great balance between perfect tone and longevity from your new tubes.
An often under discussed topic when it comes to amplifiers, but is something still worth covering. You’ll probably have noticed when browsing a store and looking at the amplifier’s specifications that it will often say something like ‘Class A’ or ‘Class C’ amplifier.
These classes, of which there are nine in total, refer to the power amplifier sections characteristics and performance. It’s a way of categorizing the time periods in which the amplifier is passing current based on the input.
There are various pros and cons to each of the classes which are a little too in-depth to cover in this article, and unless you are going pretty deep down the audiophile rabbit hole then it’s generally not something you should worry about too much!
A commonly misunderstood area of amplifiers, many people think wattage refers to the volume or loudness of an amplifier when it actually refers to the power.
The simplest way to think of it is a higher amplifier wattage gives you more ‘headroom’, which refers to how loud you can push the amplifier before it starts to break up and distort. So for example your 100w amplifier can go much louder before it starts to break up than a 50w one.
You will want to pick your amplifier’s wattage based on your application, if you’re only playing at home or in the studio you could easily get away with a lower wattage amp. But if you are playing big gigs and competing with a drummer, perhaps a high wattage is more appropriate.
An important thing to note is double the wattage does not mean double the volume, these scale logarithmically so a 200w amplifier is not twice as loud as a 100w amplifier, they are actually much closer in volume than you might think.
It’s very common these days to see amplifiers that have 2, 3, or sometimes even 4 channels. These most commonly refer to the ability to kick in different distortion stages and significantly change the tone of the unit at the press of a button.
The most common way these are set up is channel 1 will be the clean tone, then as the channels increase in number the amount of distortion goes up. For example, a 4 channel amp might have channel 1 as clean, channel 2 as crunch, channel 3 as hi-gain, and channel 4 as a lead.
Sometimes channels also have additional ‘booster’ switches allowing for increased versatility.
The effects loop
Certain effects such as a time based delay or reverb can sound extremely messy when put in front of a pre-amp that has a lot of gain on.
This is where the effects loop comes in, you can think of it as a spot for you to plug in pedals and effects AFTER the preamp, but BEFORE it hits the power amp. This allows you to use all your modulation effects such as reverb and delay after your initial preamp distortion so they sound nice and clear and aren’t being distorted by the preamp itself.
You don’t need to run every effect this way, sometimes things sound better in front of the amp, but the fx loop is an important addition you will see on almost all modern amplifiers.
Speakers and speaker cabs
As important as choosing the right preamp and power amp for your rig, picking the right speaker setup will heavily influence your guitar’s final sound and is worth taking a few minutes to educate yourself on the essentials so you don’t purchase something that isn’t going to work for you.
Most simply, this is a representation of how many watts the speaker can take before it’s going to either take damage or at the least have its lifespan significantly reduced. If you have a 100w amplifier, you want to make sure the speakers you are powering have more than 100 watts between them in order to handle the amplifier.
This refers to the size of the speaker in inches, and can be available in anything as small as 6” up to 15” and really depends on the tonal qualities you are looking for. Generally speaking 12” is the most common speaker size and is considered to have the best overall balance of sound, so is a fairly safe option.
Ohms refers to the resistance level of the speakers, if you look on the back of any amplifier’s power amp it will tell you the impedance level, sometimes they are even switchable allowing you to use the amp with a wider variety of speakers/cabs. For valve amplifiers, you will want to make sure these match otherwise you may cause unnecessary wear on the components.
This is less important on solid state amps and mostly just affects the volume.
When people refer to speaker cabinets you may hear some terms floating around such as open or closed back. This refers quite literally to whether the back of the cabinet is closed off or left open. Generally speaking, an open back will sound a little more natural and organic as the sound is able to project from both the front and back, you can also capture the tone from the back of the cabinet with a microphone as the tone will sound a little different from there.
On the other side is a closed back cabinet where all of the sound will project from the front of the cabinet which generally produces a more punchy and focussed sound, with a bit more prominence in the low mid and bass frequencies.
Other types of cabs you might see around are isolation cabinets (also called iso cabs) which are designed as sealed enclosures where you will put the cabinet in with a microphone for a clean recording signal. But it’s also able to stop the very loud sound produced by the cabinet from bothering other people or interrupting other instruments which need to be recorded. Especially common in live situations.
You may have heard terms like 4x12 or 2x12 being used to describe cabinets. The first number refers to the number of speakers in the cabinet while the second refers to the size of the speaker. So for example a 4x12 cabinet means there are four 12’’ speakers, or a 1x12 means there is a single 12’’ speaker.
Amplifiers for different instruments
So not all amplifiers are designed to work with all electronic stringed instruments. There are specific models for electric guitar, bass guitar, and acoustic guitar.
Generally speaking, bass guitar amplifiers have a higher output, and usually larger speakers because it needs to both produce and amplify very low frequencies which are more difficult to both power and control.
That is why guitar amplifiers designed for the electric guitar will seldom go above 200watts, but it’s pretty common to see bass amplifiers go all the way up to even 500 watts.
Acoustic amplifiers on the other hand don’t need to add distortion or effects and are much closer to a traditional PA speaker in that they just output the incoming signal at a louder volume with a much flatter tone. The goal being a more transparent and organic type of sound.
Certain modelers such as the Axe Fx or Kemper profiler can accommodate all 3 types because their amplification is software based so there are no hardware limitations on what it can model.
Common controls on guitar amplifiers
Although amplifiers can come in a range of sizes with a range of features and special buttons/controls. There are some common settings that are essentially universal across all models so you can be presented with an amplifier that you have never seen before and still be able to navigate your way around it.
3 band EQ
Probably the most common feature you will see on an amplifier is a simple 3 band EQ with bass, middle and treble knobs. How exactly these are voiced and respond can change from amplifier to amplifier, but the basic principles are the same, twist them to make the named frequency band louder or quieter.
Some amplifiers will have a dedicated 3 band EQ for each channel. For example, the ENGL Invader is a 4 channel amp but still has a dedicated EQ for each one (which makes for a very busy front panel). Other amplifiers use what we call a ‘global EQ’ which means that EQ is applied to the overall tone regardless of which channel you are on.
This represents how hard it is driving your signal, more gain means more distortion! Sometimes you will find 2 gain knobs on an amplifier, the one on the left is generally the preamp gain, and the one on the right (which will sometimes be labeled as a ‘master’) is your power amp gain.
Named as such because it’s designed to push your sound and let it cut through better, essentially becoming more ‘present’. What this means in terms of frequencies is an increase in the upper mid range. Use this to help your lead guitar pop or to brighten up a particularly dark sounding guitar.
A little bit more common on vintage amplifiers and combo amps. An in-built reverb can offer great convenience for players who don’t need many effects and can have everything packaged in their amplifier. The exact type of reverb such as whether it’s a spring or plate will depend on the amplifier.
Another common effect to have inbuilt on older amplifiers. It might also contain individual knobs for the speed of the tremolo effect as well as its intensity.
Common brands of amplifier
There’s a huge number of amplifier manufacturers out there from household names such as Marshall to more niche and boutique efforts such as Splawn. Let’s walk through the most common brands so you can familiarize yourself with the big ones you’ll encounter most frequently.
Most well known as creators of the Telecaster, the first mass-produced solid body electric guitar, as well as the Stratocaster. With their headquarters being based in Los Angeles, California, they are also the parent company of several other brands including the well known guitar brand Squire.
Fender amplifiers are known for that quintessential American sound, they have more pronounced bass and treble giving a little bit of that scooped style. They are also known for being quite loud and giving you a ton of headroom before the tone breaks up.
Their current best selling amplifiers are the Hot Rod series which are mid-range combo packages that give that traditional Fender sound, with vibrant clean tones, but still retain that top-end smoothness and don’t sound harsh. Another player favorite is the classic 60’s Fender Twin which is a timeless workhorse that’s versatile enough that it’s as common to see it in a rock guitarist’s set up as jazz players.
One of the most famous amplifier manufacturers based in England which was founded by Jim Marshall back in 1962. Many prolific rock bands use Marshall amplifiers including AC/DC’s Angus Young and Guns ‘n’ Roses’ Slash.
Marshall amps are known for being gain powerhouses, with a wonderfully saturated crunch tone that we often associate with world-class bands like AC/DC and Guns n Roses.
Some of their most popular amplifier models include the legendary JCM 800 which, while popularised during the ’80s is still as common as ever. It has crushing high gain tones and is used by many prolific artists including Slash and Zakk Wylde.
They also produce the MG series which are some of the best low-priced solid state combo amps around, making them extremely popular choices for new players.
Originally starting out as a modification company that would take Fender amplifiers and ‘hotrod’ them to have more gain. As some prominent players including Carlos Santana and Keith Richards began to use them their name grew in notoriety allowing them to form into Mesa Engineering amplifier manufacturers. Their amplifier, the Mesa/Boogie Dual Rectifier, had a prolific impact on the landscape of high gain guitars.
Another popular choice for Mesa players is the Mark series which are known for extreme versatility and has been used by guitar legends such as John Petrucci of Dream Theater, even James Hetfield from Metallica used it for a while.
Another famous British amplifier manufacturer most known for the invention of the Vox AX30 as used by legendary artists such as The Beatles, The Rolling Stones, and Queen. More recently they have delved into the digital modeling market and also have a fairly large catalog of popular pedals.
Sound wise they are another quintessential ‘British’ sounding company. With pronounced mids that have a great presence and bite to them.
Of course, we have to mention the legendary AX30 which was used by bands such as Queen, The Beatles, and the Rolling stones. It’s chimey and articulate top end has made it extremely desirable and it’s used as commonly now as back in the 60s.
A very popular British amplifier company well known for creating no-nonsense products. Well constructed and have models available for almost any style of music. While not quite the household name of Marshall, they nevertheless have a very dedicated player base and have some big artists on their roster including Jim Root of the metal band Slipknot.
In terms of their sound, they are not dissimilar from Marshall in that they can accommodate all your crunch and hi-gain tones with ease. However, the tonal quality of Orange tends to be a little more rounded with a little bit more low end, exchanging
a degree of tightness for thickness.
The Orange Tiny Terror was one of their most popular amp models and is credited with popularising the ‘lunchbox’ style head. Another favorite is the Rockerverb which is a 100w powerhouse and was famously used by Jim Root of Slipknot who used it
as the base for his future signature head.
Other notable amp manufacturers
- Line 6
- ENGL Amplification
- Hughes & Kettner
A common point of discussion when it comes to amplifiers is the difference between US vs British amps.
This is because British amplifier manufacturers such as Vox, Marshall, and Orange all tended to have some common tonal qualities to them. They had a little bit more content in the mids and generally had a sharper, more articulate top end.
Whereas many American companies such as Mesa/Boogie, Peavey, and Fender tended to lean towards warmer sounds. They have a smoother top end, slightly more pronounced bass with a little bit of mids being scooped out. Nowadays all of these companies have broken those barriers and make amplifiers that can handle any tone you can imagine.
The thing to take away is the fact we still use this kind of terminology ‘British’ and ‘American’ to help describe the qualities of tone.
Additional amplifier terminology
We use this term to describe how loud an amplifier can go before it starts to break up and distort. Generally higher wattage amplifiers have more headroom while lower wattage amplifiers have less so will break up much faster as you increase the volume.
This is a unit of measurement that we use to measure how loud a sound is. There are multiple units and scales people can use in the audio production world to describe volume such as LUFS or peak loudness. But Decibels is by far the most common.
This describes what percentage of a ‘wet’ sound (wet meaning your effects signal such as delay or reverb) you can hear alongside your dry tone. For example, a 60% wet signal means the noise you can hear is 60% the delay and 40% your dry amplifier sound. If you turn this up to 100% it means you are only hearing the effect and there is no raw amplifier sound in the mix.
An attenuator is used to lower the volume of the signal coming out of the amplifier, in between the power amp and speaker cabinet. We use this as many amplifiers need to be driven quite hard to get that nice, saturated tube tone. But doing this also makes the amplifier extremely loud, sometimes too much so for many given situations. So we use the attenuator to essentially ‘soak’ some of the volume up and dissipate it as heat.
Impulse Response, this is essentially a very elaborate EQ curve that has been ‘profiled’ from a real cabinet/microphone set up in order to emulate their tonal qualities for use in the digital world. For example, you might capture an impulse response of a 4x12’’ cabinet and an SM57 microphone which you can then use on your computer with a software amplifier to recreate that sound.
Also known as direct injection or direct input, both mean the same thing. This refers to the signal that comes out from your guitar’s pickups and into the cable BEFORE it has touched any kind of amplifier or pedal. You can capture this DI simultaneously while playing or recording for later use, commonly you will take a DI and use it to re-amp the guitar sound at a later date.
The world of guitar amplification can become extremely in depth and complex the further down the rabbit hole you wish to go. But having a good general knowledge of the common components and terms we as guitarists use when conversing with each other is going to dramatically increase your ability to communicate with other musicians, as well as verse you in what options are available when it comes to choosing your own amplifier.
We hope you have found this insightful and informative.