What do I want to sound like?
This should be the most fundamental of the three questions that were asked in the Introduction to this series of articles, since the purpose of an amp is generally to produce sound (unless you’re a pure collector, but these articles don’t address them). A large part of this question is determined by whether you want a specific sound (by genre or artist, for example), or a wide range of different sounds.
Types of Sound
The basic division of amp sounds is between ‘clean’ and ‘dirty’ sounds, where dirty sounds are distorted (for a good explanation of distortion, see the related Wikipedia article). Guitar amps generally have between one and four channels, each of which is dedicated to a particular type of sound (clean or variations on distorted sounds); amps for acoustic guitars will generally aim to be as clean as possible (i.e. not to change the sound apart from amplifying it and allowing the player to adjust the equalisation, or EQ), which incidentally also allows many of them to have an additional microphone input to amplify your voice, which you won’t find on an electric guitar amplifier because distorting vocals is generally not desired. Acoustic amps also sometimes include effects such reverb and chorus.
Coming back to electric guitar amps, many of them will include two or more channels, one of which will be a clean channel, although the clean channel will often include some mild distortion and produce a particular ‘colour’ of sound. Some amps only have one channel and focus exclusively on that type of sound, whether clean or dirty. It’s also important to remember that as well as the amp controlling the distortion, you can affect this drastically using the volume control on your guitar, particularly if the amp has been turned up past its limit of clean amplification (‘headroom‘) and is distorting, since reducing the input volume will reduce the distortion before it actually reduces the output volume.
Dirty sounds are more variable than clean ones, depending on the technologies used to produce the distortion (see the Wikipedia article linked above). The most common descriptions you will see for dirty sounds are ‘British’ or ‘American’, although these are very generic terms often used simply to mask the brand of an amplifier that is being copied (in itself no bad thing; the original Marshall amps were made to be copies of the Fender amps that were hard to get hold of in England in the 1960s). ‘British’ generally refers to the sound of a classic Marshall amplifier such as the Bluesbreakers, Plexis or JMP series, although there are other classic British amplifiers, particularly from Vox which have a very different tone.
The definition of ‘American’ sounds depends on whether you are talking about clean or dirty sounds. American cleans tend to refer to the clean sound of Fender amplifiers, whereas American dirty sounds are generally the more modern (1980s) Mesa Boogie amplifiers that are used for a lot of heavy rock or metal sounds.
There is, however, significant variation between different dirty sounds, and different models from the same manufacturer will not sound exactly the same, even though the classic amp brands tend to focus on the areas for which they are best known (this generalisation is becoming less true since many big brands are trying to diversify in order to keep market share – look at the recent Marshall Code or Fender Bassbreaker amps).
Some amps just have a very basic feature set, with the simplest normally just having a single tone and volume control (I know of one amp that doesn’t even have those). Most will have at least a 3-way EQ (Bass, Mid and Treble) plus gain and/or volume, and a channel switch if the amp has more than one channel. Many amps also sport a variety of other tone-shaping features, including reverb, presence, and different voicings. Some amps also include basic modulation effects such as delay and chorus, and modelling amps will have a way to select the different amps that are simulated. Some of these features tend to be found on cheaper amps that are aimed at players who don’t have separate pedals, and they are not generally as versatile as separate effects, but they can be practical for some players.
An FX loop is a useful feature that enables you to add effects pedals in the signal chain between the preamp and the power amp, which can be helpful in some circumstances, so while it doesn’t affect the tone directly, it helps you to do so with other equipment. It’s usually high on my list of desired features, especially for amps without reverb.
Some modelling amps have advanced features such as the ability to download tones for specific players or songs.
Other, non-tonal features will be discussed in the other articles in this series.
Genres / Artists
You might want to reproduce the sounds of a specific genre or artist, and be guided by that in your choice of amp. However, this is not as straightforward as you might think. It’s certainly true that, for example, classic rock sounds often use Marshall amps, country players often use Fenders and metal players use Mesa Boogie, but you will also find a lot of variation, and players using an amp, perhaps with certain effects pedals, that is not an obvious fit, particularly if they want to establish a distinct sound within their genre. Then again, many famous guitarists will have multiple amps on stage, and switch between them for different sounds. If you dig in, there are few players who exclusively use one type of amp (such as Brian May with his Vox AC30 amps, which he always uses live although he did use other amps in the studio).
As a result, I can’t give you a list saying for this genre or artist, use this amp. Instead, you should do some research of your own. There are many pages on the Internet describing the gear used by certain artists (search for an artist’s name and ‘rig’, ‘gear’ or ‘amps’); there are also many videos on YouTube, either of the artists playing live where you may be able to spot their amps, or (probably more reliably) videos talking specifically about their gear. As good starting points, take a look at the Rig Rundowns by Premier Guitar, or the Sound Like… series from Anderton’s Music Co. You will probably learn things along the way, which will be a good side-effect!
Sound Like Everyone!
If instead of targetting a specific sound, you want an amp that will give you a broad variety of sounds, allowing you to explore different tones and genres, then you have two main choices. Either find a good clean amp and use pedals to achieve particular sounds, or get a modelling amp that uses digital processing to replicate many different amp sounds.
The choice of a good clean amp is not straightforward since they will all affect the sound to some extent, and many clean amps will still have a gain control that gives a certain amount of distortion (like my Victory V40). This can be an advantage since it will provide a basic tone that can be recognisably yours, with variations from your pedals.
Modelling amps are a different ball game, and this is an increasingly complex topic with more and more variety in the available products. These range from amps that look fairly standard, like a Fender Super Champ X2 or a Line 6 DT25 but which can model many different preamps (both of those use valves in the power section), through amps with more digital processing and options (like the Blackstar ID Core series or the Marshall Codes) and even to soft amps, which are just software running on computers (such as GarageBand or AmpliTube). You also have a growing number of multi-fx units which can also be connected directly to a PA system, completely removing the need for a separate amplifier, such as the Line 6 Helix or the Fractal Axe-FX units. The choice is bewildering, so again I suggest doing your research, and looking at comparative reviews for products in your price range.
Choice of Speakers
Many people don’t think about the speakers that come with their amp, particularly when buying combos, but the speaker is the last link in the tonal chain and the element that actually produces the sound that you and your audience hear.
Speakers in guitar amps are not the same as speakers in hi-fi systems, which are designed to reproduce all sounds perfectly. Guitar speakers are designed to colour the sound, and even sometimes to produce speaker distortion (meaning that the different parts of the cone move in different ways because they cannot keep up with the driver). There are several well-known manufacturers that specialise in guitar speakers such as Celestion, Eminence and Jensen.
The size of a speaker affects its sound significantly too. There is a definite reduction in sound quality below 10 inches, and many people consider that 12″ speakers are significantly better again. Some amps or cabs contain multiple speakers, usually two or four, and some of those combine different speakers to mix their tones. If your sound will be sent through a PA system, though, there may be little point in having multiple speakers in your amp or cab, since typically the PA will be fed either by a direct output or from a microphone positioned close to a single speaker.
Variety versus Quality
In all of these discussions of amp sounds and particularly their variety, it’s worth bearing in mind the quality aspect. Generally, if an amplifier focuses on a particular sound, it will be designed specifically for that sound and the resources of the amp (and the designers) will be used for that. If an amp produces lots of sounds, for the same price the resources will be spread across multiple tones and so each one will receive less attention. Hence at a particular price point, an amp that focuses on its own sound will probably be of higher quality than an amp that tries to create multiple sounds, and so you have to pay a lot of money for amps which do that very well (such as the Kemper Profilers). Further, the most expensive, ’boutique’ amps tend to focus on a particular sound, and on doing that very well.
As with most products, you get what you pay for with amplifiers, and so it really is necessary to ask yourself some tough questions before buying, especially if you are on a tight budget.