A beginner’s guid to guitar amps and their digital replicas

An electric guitar needs to be amplified because it’s lacking a sound box and is therefore very quiet. In theory, you could plug the guitar cable right into the audio input of a stereo system, mixing console or computer. But it won’t sound great, as you can hear in the video below.

A hi-fi amplifier reproduces the audio signal as faithfully as possible. But that’s not what you want for an electric guitar. On the contrary, the sound should be shaped in a certain way. This requires a special guitar amplifier.

To this day, many guitar amps still work with tubes – a technology that largely died out in the 1960s due to the rise of transistors. The reason why tubes have survived in guitar amplifiers is because they produce a distorted sound when they’re overdriven typically associated with rock guitars. Although there are many guitar amplifiers that work with transistors instead of tubes, the sound of tubes is generally just imitated. This means the tube remains the measure of all things.

The speaker (cabinet)

It’s not only the amplifier that shapes the sound, but also the speaker(s). Again, guitar equipment has its own peculiarities here. Speaker cabinets for guitars usually have one, two or four identical speakers. Ten or twelve inch diameters are common. This gives the sound a clear profile that emphasises the mids and, if necessary, the upper bass range.

Many guitar amps have a built-in speaker cabinet. This is called a combo. In other cases, an external speaker must be connected. Typically, combos have one or two speakers, while separate speakers have two or four.

Distortion

A guitar amplifier produces different tones depending on how it’s set. The gain control, i.e. the input level, plays an important role here. If you turn it up, the volume increases first. But only as long as the level isn’t overdriven. If you turn up the volume even further at the beginning of the overdrive, the sound will not become louder, but more distorted.

Originally, this distortion was considered a mere technical flaw; only later was it used as a stylistic device. Ironically, completely distortion-free amplifiers only became available when they were no longer asked for.

Today, distortion is a feature. How strong it is depends on the style of music. Some amplifiers distort at the lowest gain level, some don’t even at the highest. Then there’s the whole spectrum in between. Many amplifiers have two or three channels, their main difference being that the distortion sets in earlier or later. The more distorted channel is usually also louder and activated via the foot switch before a solo.

The cons of tube amps

Apart from their amazing sound, tube amplifiers almost only come with disadvantages. Take their weight, for example. Even a small tube combo weighs well over ten kilos, a large one up to 30 kilos. Tube amps are considerably more expensive than their transistor counterparts. They’re not ready immediately after switching them on, but have to warm up first. The tubes wear out over time and the sound becomes duller. This means they need to be replaced every now and again. Many models don’t allow you to play quietly and distorted, as distortion only starts at a volume that’s far too loud for home practice.

So it’s not surprising that products imitating the tube sound without tubes have been coming onto the market for decades. Initially, transistor circuits were devised for this purpose. Even though some of them sounded quite decent, that real tube sound was never attained.

Modelling amps

A more recent approach creates a digital model of a real amplifier, usually a tube amplifier. The process has been around for over 20 years and has improved considerably during this time.

At first glance, the modelling amps look like classic tube amplifiers. They’re also similar to use. The typical disadvantages of tubes have been eliminated, plus this type of amp offers more possibilities. There are usually several amplifier models to choose from. In other words, this kind of amp lets you simulate the sound of different amplifiers.

Here is a modelling amp and a tube amp for comparison. Both have a 12-inch speaker built in, yet the modelling amp is only half as heavy. The Boss Katana 50 weighs 11.6 kilogrammes, the Black Cat 21 kilogrammes. The far heftier price tag of the Black Cat has to do with its tube technology, among other things.

Amplifiers

BOSS (Electronics) Katana 50 MkII

Guitar, 50 W

4

Amplifiers

Bad Cat "Black Cat" 1x12 Combo

Guitar, 20 W

Amp modelling without an amp

The digital amp simulation can also be outsourced to an external device. This kind of device is usually a foot switch. It can simulate both amps and guitar speakers. This means you can connect it straight to a computer for recording – no need for time-consuming microphones. But you can also connect it to a mixing console for a rehearsal, jam session or live performance.

In this video, I’m playing the same thing as in the video above. Also on the stereo system, but with a small upstream amp simulator, the Line 6 Pod Express.

It’s also possible to use this kind of foot switch in combination with a real guitar amplifier. You can also switch off the speaker simulation so it doesn’t interfere with the real guitar speaker. The preamp of the real amp can also be bypassed to avoid strange mixes. However, you can only do this if the amp has an effect loop. You plug the cable into the input of the effect loop.

A pedal makes an existing amplifier more versatile. This is particularly useful if the amplifier itself is more of a one-trick pony. I have two amplifier combos that both have the same problem: the distorted sound isn’t all that because it’s based on an old transistor circuit. Having said that, both of them sound really good when the sound isn’t distorted. The amp sim pedal turns them into versatile and solid-sounding amplifiers.

One step further: software only

As far as recording on a computer is concerned, you could also leave out the foot pedal and install software that simulates the amplifier and speakers instead. After all, modelling technology is essentially software.

Well-known products in this area include Guitar Rig from Native Instruments or AmpliTube from IK Multimedia. But even Apple’s GarageBand comes with some guitar amps.

This procedure allows you to freely change the sound of a recording once it’s been made. With a foot pedal, on the other hand, you decide how your music should sound when during recording.

Why guitar amps aren’t obsolete yet

Less lugging around, lower costs, more flexibility – amp modelling obviously has great advantages. Almost sounds too good to be true, in fact. And yet, many guitarists still stick to their classic setup. They shlep their tube amps from gig to gig, or occasionally switch to a modelling amp. But very few want to do without an amp altogether.

There are many different reasons for this. Perhaps the original sounds a little better after all, despite all the advances in digital technology. Or the feeling while playing is more direct and dynamic. Then again, this could also just be imagination.

In my opinion, there are two main things that can cause problems with amp modelling. One of them is the endless possibilities, which isn’t necessarily an advantage. Even with a simple, classic amp, it takes some time to find out how to set it up so it sounds best for you. With the Line 6 Helix, for example, you have 106 amplifiers, 83 speaker cabinets and 273 virtual effect pedals to choose from. This gives you countless possible combinations that easily feel overwhelming. And the more complex your sound is, the more difficult things become. Besides, it can also be weird during live performances if your instrument sounds different in every piece of music.

The other issue is that just because you can save presets doesn’t mean things will always sound exactly the same everywhere. Whether the sound is right depends on numerous factors that are beyond your control: the acoustics of the room, the setting of the mixer, the mix with the other instruments, the positioning of the speakers. This means you’ll have to make adjustments on site again. If you only have one amp, these adjustments will be easier because you have fewer options but all the more experience.

You can also limit yourself to a few simple sounds with the modelling technique. It’s a learning process. One I’d say is definitely worth looking into today. Especially given the fact that there are tools available that are inexpensive but still useful.