Guitar Effects
Introduction
On its own, an electric guitar produces mid-range sounds only. To make it sound more varied, the signal can be modified using digital signal processing. In this application, a guitar input can be given treble boost, reverberation added and the sound distorted.
Treble Boost
On an electric guitar, sounds from the treble strings fade much quicker than do those from the bass strings. To make the sound more even, a treble boost is added. In this case it is implemented using a high-pass FIR filter to reduce the effect of the bass strings.
Valve Sound
A valve amplifier differs from its solid-state counterpart in that its transfer function is non-linear. What this means is that the output level is a non-linear function of the input level. This has the effect of changing the harmonic content of the input signal in a way that is pleasing to the ear. Here the input/output transfer function is implemented a simple polynomial.
Reverberation
Guitar sounds die away quite quickly, especially on treble strings. Adding reverberation helps the sound to die away less quickly and therefore gives more sustain. It also makes the guitar sound as if it is being played in an auditorium rather than a small room.
Frequency Doubler
A simple frequency double can be implemented by squaring the input signal. This doubles the frequency of the input signal because cos 2a = 2 cos2 a - 1
Fuzz
Fuzz is one of the well-known rock sounds. It works by “clipping” the output waveform. This means is that small signals are unchanged, but large signals have the top chopped off. The effect is to increase the amount of harmonics and also increases the treble and sustain.
Distortion
The most brutal effect and the one to remove the neighbours! This is a mixture of a polynomial transfer function to generate a nasty mixture of extra notes with clipping for more sustain and treble.
Additional Equipment Required
Multimedia loudspeakers
Electric guitar
Cable for inch jack to 1/8 inch jack.