Since the electric guitar went on the market in the 1950s, there has been a great variety of possibilities and, today, there is also a series of patterns, both sonic and aesthetic, that are within reach of most guitarists, although to me there are basically only two types of “sonorities”: warm amplified sounds and cold amplified sounds.
These two colors of amplification come from the same starting point: as a metal string vibrates near a coil of copper wire with a magnet in the center (the guitar's pickup), a voltage is created, and that voltage is what has to be amplified to get the instrument's sound.
I'm not going to get into a lot of technical definitions that may sound like Greek to many of you about the ways and elements of amplification, but I will give you my point of view in terms of listening, practicality and aesthetics, starting from the guitar and going to the amp, since it's all part of a chain.
The difference in sound between one guitar and another comes down, besides the woods, strings, design and so on, to the type of “pickup,” the distance between them if there are several, and how far they sit from the strings. I divide pickups into three types: humbucker, single-coil and piezo, the last being a latest-generation type of pickup that works by inducing voltage through vibration in a solid material placed where the string rests on the guitar's bridge.
The differences between them are big, so you have to know how to choose the right pickups for your instrument. Humbuckers have, in principle, less noise than single-coils and a warmer, “fatter” and rounder sound; they are, without a doubt, my favorites, and my guitar, built by Daniel Marcovich in Amsterdam, carries just two of them. Single-coil pickups, usually three of them, have a thinner, more metallic sound and a slightly looser low end, for example the Stratocaster sound of Eric Clapton or Robert Cray. Piezo “pickups” are always one per string and have a very crystalline or transparent sound, sometimes even emulating an acoustic guitar.
Most of the time it's possible, with a switch, to combine them with each other (even humbuckers and single-coils) and also to change their phase, that is, wire them in reverse, which sounds even thinner and a bit lower in volume. As you can see, there is already a huge number of sonic combinations, and we haven't even reached the amp, but as I was saying before, in the end, for me there are only two types of guitar amplification “sonorities,” and you'll see why.
Once you have the right instrument, we move on to the next step, the amplifier. It has two notable variants in how it works electronically, tubes and transistors. Both come in two formats: combo amp and separate components (preamp, power amp and speaker), and these are their characteristics:
Tube amp: gives us a warmer, more classic tone, somewhat vintage (I imagine, in part, because it was invented before the transistor), with a pretty, sweet treble that is easy to work with; you have to be careful with the mids, but if you find the sweet spot for the guitar you have, they are a marvel; the lows tend to be a little looser, somewhat slower, but for me that is part of the sound I like, a round sound that cuts through the cymbals but has body down low. With distortion comes the best part of tubes: from Jimi Hendrix to today, there are several well-known guitarists famous for their tube distortion, such as Jeff Beck, Stevie Ray Vaughan, Santana, Keith Richards and so on. They have all always been loyal to tubes and use more or less the same brands, such as the Fender Twin, Bassman and their whole range, Marshall, Rivera, VOX, Mesa Boogie, Orange, Soldano, Koch and so on. There is a great variety of brands out there today, and I think each person should choose the one that best fits their taste, and I'm truly sorry, because there is only one way, and that is by trying them.
Solid-state amp: has a more compact tone, and you can even get an almost artificial sound through a broad EQ response, since they never depend on the condition of tubes. Also, with no tubes, they are more practical for transport. The highs are bright and hold up very well even with piezo “pickups”; the mids have little character and the lows are quick to respond and very clear. Among the guitarists who use these amps the most are Prince, John Scofield, Allan Holdsworth (combinations) and so on. The best-known brands are Roland, Peavey (not all of them), Session, HH and so on. When I think about it, I really struggle to come up with guitarists known for a solid-state amp sound; although these amps are practical, tubes seem to take the prize, especially for their warm sound in distortion.
Finally, the speakers, which are of utmost importance. If you have a rig, whatever it is, that gives you a good tone and needs sound pressure, and the speakers don't measure up, it's like driving a Ferrari in the old center of Madrid; it makes no sense, you have to be consistent along the amplification chain. The most common are Celestion speakers across their whole range; I use the G12M, the ones called “greenback,” because the dust cap is that color. Each one is about 25 W; that's not a lot of power, but I figure a guitarist who can't hear 50 W at 2 meters away must be deaf. I also used Peavey speakers for a while, which, although they weigh quite a bit more, sound very sweet. There are other brands such as Hartke, JBL and so on.
I've gone through several phases with my amplification. I always played combos, both solid-state and tube, until I was 22; then I tried every kind of three-piece combination, digital, solid-state and tube preamps, multi-effects of every generation, solid-state and tube power amps connected to different types of speakers from various brands; in total I think it cost me a fortune to experiment with all the new things that kept coming onto the market. I also had to put in several gym sessions to be able to haul everything around when we got back from tours, until about 8 years ago, when I started playing what suits my music and my ear best; finally a solution to all that searching. The funny thing is that now I basically play what I started with: a guitar, some floor pedals and a tube combo amp. I used to play a Fender Bassman and now a Koch, which is the best thing that has ever happened to me. Dolf Koch wanted me to endorse his amps at the Frankfurt show in 97/98; I tried a few models and they were fine, but I was very happy with the Bassman. Almost a year later, while playing in Belgium, they lent me a 50W Koch Multitone combo and I couldn't believe the harmonic and dynamic response; I called Dolf and he told me that if I wanted to endorse it, I had to sell my Bassman; he probably wanted to know whether I was truly that convinced, and I was.
One last piece of advice for sound seekers. The human ear has common reception characteristics. For example, the squeak of a door displeases us, but ocean waves relax us; be aware of the kind of sound and volume that makes you enjoy music the most (the human ear withstands about 80 dB, and excess is paid for over time with deafness); use technical means to get as far as you need, don't focus on brands or aesthetic design, and keep searching, because the ear evolves too. In the end, there are two terms, just as with speed it's fast and slow, with sound it's warm and cold; all our tastes lie between those two parameters. Surprise yourselves.