On Show

Sam Cox

BSc [Hons] Creative Media Technologies

I chose to study Creative Media Technologies because I have always had a keen interest in the audio/visual field and have always tinkered with electronics and computers. As a guitar player, I have a particular interest in music related technologies such guitar amps, pedals, and MIDI devices and this has been a constant throughout all of my projects over the last number of years. One example of this is my third-year project which involved incorporating piezo sensors into a custom laser-cut Stratocaster pickguard to allow the user to add percussive elements to their playing electronically using MIDI or samples.

The amplifier unit is the most important element created for this project. It has been designed from the ground up to allow users to add audio effects to their acoustic guitar without the need for a traditional amplifier or even mains power. The unit has been created with user experience in mind and connects to the modified guitar via one stereo cable. By connecting the guitar directly to the unit, the user can add delay/reverb effects to their instrument. This signal is then amplified, send back to the guitar via the stereo cable and causes the resonance speaker to vibrate the guitar in the same manner it vibrates when strummed. This creates an authentic acoustic sound with the guitar’s natural frequency response intact while adding any audio effects the user desires. Furthermore, the unit incorporates an effects loop which allows the user to connect any guitar pedal to their signal chain, all without the need for a heavy amplifier or even mains power (provided the effects pedals run on 9V batteries). The unit runs on a single 9V battery but can also be powered with the same 9V power supply used traditionally for guitar pedals. **The product is currently in the process of being registered with the patent office as of the time of writing**

This diagram shows how the project can be used in its most unique way. As well as creating the delay/amplifier circuits and enclosure, a guitar was also modified to be used with the device natively. This modification was done with the one key stipulation that the guitar could not be permanently modified in any way as this would not only deter potential user but could also potentially reduce the value of the guitar. The features added, a resonance speaker and power switch, were simply attached using 3M tape giving a strong but not non-permanent bond. These components were soldered into the guitars output circuit, but this process is easily reversed or could be done without solder through the use of custom designed adapters. The guitar retains all of its original functionality, allowing it to be plugged into traditional guitar amps via a mono cable. The only significant change made in relation to this was the inclusion of a power switch placed inside the sound hole of the guitar. This allows the user to turn off the guitars pre-amp circuitry which is usually powered on when a cable is inserted. Due to the output jack modification, this input detection feature was replaced by a power switch which has the benefit of allowing the user to keep the guitar cable connected without draining the guitar’s battery. This feature is particularly useful in a live environment as removing the cable usually results in an audible popping noise unless the amp/PA is turned off.

This diagram shows how the project can be used with any electric or acoustic guitar with a pickup. The guitar’s output is then connecting the mono input of the unit (effects pedals can be incorporated before this is desired) and the audio is then processed by the unit, adding the built-in effects, and then outputting the signal to an external resonance speaker. This speaker can be placed on any surface, transforming it into a speaker while also incorporating the materials unique audio characteristics. For example, when placed on a large metal surface, natural reverb can be created. This allows for an endless number of potential options allowing the user to sculpt a truly unique sound.

This video is a demonstration of how the product works when connected to the modified guitar used for this project as well as how it can be used with any electro-acoustic or electric guitar using the external resonance speaker add-on shown in the video. A number of pedals are used throughout the video including chorus, wah-wah, distortion, overdrive and a looper pedal. These pedals are connected to the project via the built-in FX loop designed to place all effects before the delay and amplifier circuit. When pedals are not in use the circuit is completed with a patch cable perfectly measured to imitate a carrying handle and means the user always has a patch cable for their pedals when needed.

Project Description

This project aimed to incorporate resonance speaker technology into an acoustic guitar allowing the playing to use standard effects pedals without the need for a traditional amplifier. The project involved the fabrication of a delay and amplifier circuit allowing the user to play acoustic guitar with reverb and delay without any external equipment and it can be run on a 9V battery or standard 9V power supply. It requires only one stereo cable to interface the guitar with the circuitry.
The product has additional functionality in regard to the FX loop added to allow standard guitar effects pedals to be used seamlessly as well as having additional mono input and output jacks. This allows for any guitar with a pickup to be connected and have the output play through an external resonance speaker add-on, allowing the user to transform any surface into a speaker, incorporating its unique properties.

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Thesis: Acoustic Guitar with Resonance Speaker Technology

This document outlines the in-depth preliminary research, experimentation and prototyping carried out over the course of the year in order to create the finished product showcased. The thesis examines areas such as resonance speaker technology, traditional guitar effects pedals and guitar peripherals in order to better understand how the finished product could fit within the market and what is necessary for it to succeed. It examines competing products in the market and outlines the steps taken to overcome limitations these other products face. The document also outlines the different types of testing and prototyping used in the fabrication of the project given the limitations faced over the course of the year. It outlines how software-based testing was utilised including how circuit simulation was completed with LTspice and circuit and PCB design was carried out using Eagle and Fusion 360. Furthermore, it shows how hardware testing was carried out with limited testing equipment available through the use of mobile apps, PC audio hardware and the construction of a DIY signal generator.

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