Project V – Digital Signal Processing System Design Final project Guitar Effects

Joshua “Rock Star” Jenkins

Jeff “Tremolo” Smith

Jairo “the boss” Rojas

Table of contents

Typical Guitar Effects Pipeline.

Classifying Effects for guitar implementation.

Theory of the Effects.

Design Process.

Learning Lessons relating to the class.

Conclusion.

Time for questions (1 only).

Live Demonstration by Josh ($5 per group).

Typical Guitar Effects Pipeline

This is a layout of the common standard guitar pedal effects processes as shown below such as;

Classifying Effects for guitar implementation

Audio effects can be classified by the way do their processing:

We will have a Master channel control to regulate these effects.

Equalizer – Treble, Midrange, Bass, Volume.

Non-linear Processing — Fuzz.

Delays — Flanger, Reverb, Digital delay.

Modulators — Ring modulation, Tremolo.

Theory of the Effects (Equalizer)

The equalizer is normally use to adjust the sound quality of a song or music instrument whether in a mono or stereo system.

Treble.

Bass.

Midrange.

Non-linear Processing

Non-linear Processors can generate harmonic and inharmonic frequency components not present in the original signal.

Dynamic Processing.

Intentional non-linear harmonic processing.

Exciters/Enhancers.

Fuzz Effect

A non-linear function harsher alteration of the original sound than distortion. Fuzz and distortion can be represented by the formula;

The representation above is a non-linear exponential function:

The gain (α) controls level of distortion/fuzz.

Combined to the mix part of the distorted signal with original signal for output.

Fuzz Effect block diagram

Comb Filter Delay Effects:Flanger, Chorus, Slapback, Echo

Many useful audio effects can be implemented using a delay structure.

Basic delay structures out of some very basic FIR and IIR filters comb filters.

Combination of FIR and IIR gives the Universal Comb Filter

These popular guitar effects can be implemented with a comb filter (FIR or IIR) and some modulation effects.

Flanger, Chorus, Slapback, Echo are same basic approach but different sound outputs:

IIR Comb Filter

Simulates a single delay and endless reflections at both ends of cylinder y(n) to input, x(n).

The input signal circulates in delay line (delay time τ) that is fed back to the input.

Each time it is fed back it is attenuated by g.

Input sometimes scaled by C to compensate for high amplification of the structure.

It’s represented by the formula:

The transfer function is:

Flanger Effect

The Flanger effect utilizes continuously varying Low Frequency Oscillator (LFO) of delay.

The signal rises and falls in a regular, periodic way. It is produced by mixing two identical signals together.

Works similarly as the Chorus effect, however, it uses a significantly shorter delay time.

Reverberation (Reverb) Effect

Reverb is consider one of the most heavily used effects in music.

A reflected sound wave like this will arrive a little later than the direct sound.

This effect is typically use in very big rooms like concert halls and cathedrals.

Digital Delay

Discrete element in digital filter theory, which allows a signal to be delayed by a number of samples.

If the delay is an integer multiple of samples digital delay lines are often implemented as circular buffers.

The delay by one sample

is notated    and delays

of     samples is

notated by the role the z-transform plays in describing digital filter structures.

Modulation

Modulation is the process where parameters of a sinusoidal signal (amplitude, frequency and phase) are modified or varied by an audio signal.

The types of modulation implemented for our project are;

Amplitude Modulation — Tremolo

Phase Modulation — Flanger

Ring Modulation (RM)

Signal-processing effect in electronics, an implementation of amplitude modulation or frequency mixing, performed by multiplying two signals.

very simple to implement digitally:

For example a sine wave with frequency (fx) we compute the DSB: fc + fx and fc - fx.

A input is periodic with at a fundamental frequency (fo), then a spectrum with amplitude lines at frequencies |kfo ± fc|

Ring Modulation and Tremolo block diagrams

Amplitude Modulation (AM)

Can be best defined by:

Normalize the peak amplitude of m(n) to 1.

α is depth of modulation

α = 1 gives maximum modulation

α = 0 turns off modulation

x(n) is the audio carrier signal.

m(n) is a low-frequency oscillator modulator.

When x(n) and m(n) both sine waves with frequencies (fc) and (fx) respectively we hear three frequencies: carrier, difference and sum: fc, fc - fx, fc + fx.

Tremolo Effect

Tremolo describes various trembling effects, falling roughly into two types. The first is a rapid reiteration of a single note.

A second type of tremolo is a variation in amplitude;

Using electronic effects in guitar amplifiers and effects pedals which rapidly turn the volume of a signal up and down.

Modulates the amplitude of the incoming signal, resulting in periodic volume changes.

Design Process

We incorporated our knowledge of what we have learned from the assignments in class from filters and audio effects.

We designed our project in Labview using Matlab script as well.

We implemented one effect at the time and then we combined them together.

We will utilize myDAQ to demonstrate the project in real time.

Design Process

Testing the Design

Learning Lessons relating to the class.

Basic theory and applications of modern digital signal processing.

Basic theory of real-time digital signal processing.

Develop ability to implement and simulate digital signal processing algorithms using Labview and Matlab on real-time DSP platform.

Analog to Digital implementation and simulation using myDAQ.

How to work as a team to make this project successful.

Conclusion

Understanding basic concepts of digital signal processing guitar effects theories and techniques.

Understanding of real-time digital signal processing.

Ability to implement digital signal processing guitar effects in Matlab and LabVIEW.

Ability to implement analog to digital signal processing on real-time DSP platform with myDAQ.

Preguntas