GFX Abstract

The existing technology used to create guitar sound effects is often prohibitively expensive to the amateur guitarist. The object of this project is to provide an affordable alternative that uses the computational power of modern personal computers to simulate guitar effects. The Universal Serial Bus (USB) provides a fast interface with the PC, allowing for soft real time communication with the multi-effects pedal. Through this interface, the computer modifies the guitar signal based on mathematical models for each effect. This software implementation well enable the addition of other effects in the future.

Technical and Testing Approach

The project is implemented using a parallel approach and is divided into four parts: microcontroller and hardware, interface between hardware and software, graphical user interface, and effects programming. An iterative approach is used for testing which involves testing at each stage of development.

Design Requirements

The Guitar Effects Synthesizer must be easy for the guitar player to use and have an easy to use software interface. It must support a wide berth of effects and be inexpensive. The user interface must allow users to switch and chain effects just like an existing analog effects pedal. The pedals must be programmable so that the user can choose what effects to use. The synthesizer must correctly sample the input from the guitar, process the input, and correctly output the modified signal. The Guitar Effects Synthesizer must have negligible latency and be USB compatible. It must also operate in a normal PC environment.

End Product Description

Team number may0017:1. Kevin Crotty CprE

2. Lukasz Darowski CprE

3. Nathan Linquist CprE

4. Sriram Narayanan CprE

5. Dan McPartland CprE

Advisor/Client: Dr. Stephenson

Web Page http://seniord.ee.iastate.edu/may0017

Software Guitar Sound EffectsSynthesizer

IntroductionThe electric guitar is a popular instrument in today’s music due to its broad range of effects. The cost of the effects hardware, however, is often too high for amateur players, so the GFX project solves that problem by leveraging the PC and the new USB interface. The remaining hardware consists of USB microcontroller and mechanical pedals for switching between effects, while the software simulates effects on the PC and controls the communication on the USB. The GFX system tolerates temperature range within 50 to 80 degrees Fahrenheit and accepts electromagnetic interference from 60 Hz power lines. The major assumption involves the user’s ownership of the electric guitar, audio amplifier with speakers, necessary cables, and a modern PC compatible with USB and a minimum processor speed of 500MHz. The limitations include a maximum of three mechanical on/off pedals and one analog pedal, while the sound quality will be limited by the resolution of the ADC and DAC. The maximum amount of sound effects in a sequence will be limited by the speed of the host PC such that the maximum latency will be 10ms.

Milestones•Selecting hardware•Selecting development environment•Establishing communication between PC and synthesizer's microcontroller•Implementing guitar effects signal processing algorithms•Implementing graphical user interface

The Guitar Effects Synthesizer pedal has standard quarter inch audio in and out phono jacks to be connected to an electric guitar and guitar amplifier. The device also has a USB interface so that it can connect to a standard PC. The pedal has three digital switches and one analog “expression” pedal for interactive control of the effects produced. The PC software applies the user-defined combination of effects (such as distortion, chorus, and wah) to the audio signal, and can be controlled by the foot pedals as well as standard PC input devices.

BudgetThe total estimated cost of this project is $340. The total estimated hours of personal effort estimated is 1651.

Multi-Effects Pedal

Audio Output Device

Electric Guitar

Personal Computer