Tube Amplifier Emulation (part 1 of 4)
Why Tube Amps?

This blog series covers some of the technical work underpinning Swanky Amp’s guitar tube amplifier model. It is structured to give musicians, producers and even technology enthusiasts an insight into the world of tube amplifier emulation.

The series is split into four parts:

  1. why tube amplifiers,
  2. why emulate a tube amplifier,
  3. how can a computer do emulation,
  4. and the approach taken in building Swanky Amp.

If you know too many guitarists, then you’ve probably heard of tube amplifiers spoken of with some degree of reverence. In this first post, you will read about what tube amplifiers do, and why otherwise normal people sound like manic cultists when talking about them.

Tube amplifiers are … well, amplifiers: they take a small guitar signal, and amplify it into a signal large enough to vibrate a speaker which can fill a room with ear-shatteringly loud rock and roll. Or just get on the nerves of every employee at a guitar store.

Signal here refers to the voltage created by the guitar. That’s right: when you hit the strings on an electric guitar you generate a (small) voltage. Connected directly to headphones, you could maybe hear a faint sound: the sound of the headphone’s speaker being pushed and pulled by that voltage. Connected to an amplifier, then to a larger speaker, you will hear the blissful sound of the electric guitar in all its glory.

At the time when electric guitars where first being built, tubes were found in all sorts of consumer electronics that needed to amplify a voltage. So it makes sense that guitar amplifiers were based on such tubes. But tubes do more than just amplify the signal, they also distort the signal when it exceeds the tube manufacturer’s recommended spec.

And we all know that rock stars definitely like to keep to recommended spec. So, as you can imagine, people started plugging guitars into amplifiers and pushing the tubes past the threshold for distortion (i.e. the signal coming out of the guitar is too large for the tube to amplify accurately). And so the sound of the electric guitar was born.

The astute reader might now be thinking: wait, you’re saying tube amplifiers have one job, to amplify a signal, fail at that, and this is what guitarists like about them? The answer is: yes, that’s right. It turns out guitarists like that distortion so much that amplifiers are now regarded as having two jobs: to amplify the signal and to distort the signal.

A small amount of distortion (sometimes called saturation) can make an instrument sound fuller, warmer, louder and generally more pleasant. A large amount of distortion can make an instrument … rock!!!

And so, this blog series is about how to get a computer (which can amplify a signal with near perfection) to replicate the same imperfections arising from tube amplification.

Part two explains why emulating tube amplifiers is something you might want do.