1. Guitar Effects Processor Preliminary Design Review September 9th, 2003 Groups Members: Adam Bernstein Hosam Ghaith Jasenko Alagic Matthew Iyer Yousef Alyousef

2. Goals Provide a guitar effects generator that Provide a guitar effects generator that Has a user friendly interfaceHas a user friendly interface Takes input from standard audio sourceTakes input from standard audio source Produces output to standard amplifiersProduces output to standard amplifiers Employs a modular designEmploys a modular design Produces real-time outputProduces real-time output Can be programmed by userCan be programmed by user Produces reasonably good audio qualityProduces reasonably good audio quality

3. Baseline Objectives Working CPU (microcontroller, memory, etc.) Working CPU (microcontroller, memory, etc.) Common interface between controller and all effects Common interface between controller and all effects Minimum of two working audio effects Minimum of two working audio effects User interface User interface Ability to program combinations/duration of effects Ability to program combinations/duration of effects Ability to adjust properties of effects (such as intensity) Ability to adjust properties of effects (such as intensity)

4. Block Diagram

5. Digital Control System Live adjustments Live adjustments Effect programming Effect programming Effect driver Effect driver

6. Live Adjustments PC and/or keypad/button interface PC and/or keypad/button interface Buttons turn effects on/off, control real-time parameters, and run programs. Buttons turn effects on/off, control real-time parameters, and run programs. Extension – Ideally, analog controls such as light (photo-resistor), levers, and knobs will be provided to the user. These analog controls can be mapped to any desired effect. Extension – Ideally, analog controls such as light (photo-resistor), levers, and knobs will be provided to the user. These analog controls can be mapped to any desired effect.

7. Effect Programming ASCII text file can written to program the effects generator ASCII text file can written to program the effects generator Controls ramp/sweep of different effectsControls ramp/sweep of different effects Program A sweeps Distortion effect from 0-100 percent intensity in span of 5 seconds. Program A sweeps Distortion effect from 0-100 percent intensity in span of 5 seconds. Program pre-set state of effectsProgram pre-set state of effects State A loads 50% Distortion, 20% Tremelo, and 80% Wah State A loads 50% Distortion, 20% Tremelo, and 80% Wah Map buttons to functionsMap buttons to functions Example: Button1 will trigger Program A, Knob1 controls intensity of Effect3, Button2 loads State A, and so on… Example: Button1 will trigger Program A, Knob1 controls intensity of Effect3, Button2 loads State A, and so on…

8. Effect Programming Sample ASCII file: state 0 : 0 128 1 64 [state 0] : [effect 0 50%] [effect 1 25%] program 0 : sweep 0 128 255 2000 [program 0] : [effect 0] [50%-100%] [2000 milliseconds] knob 0 : 1 0 3 [knob 0] : [map to effect 1] [bits 0-3] Extension: GUI application that helps user write programs.

9. Effect Driver Sends control commands to individual effects Sends control commands to individual effects Support for 2 n effect modules, where n is the number of address bitsSupport for 2 n effect modules, where n is the number of address bits k-bit messages sent on data busk-bit messages sent on data bus Commands customized to control parameters of each effect. Commands customized to control parameters of each effect. Example: Distortion Example: Distortion

10. Diagram of Effect Driver

11. Mixed-Signal Interface Block Diagram

12. Mixed Signal Interface Digital to Analog (D/A) conversion methods Digital to Analog (D/A) conversion methods Standard D/A converters translating an array of digital bits into a bias voltageStandard D/A converters translating an array of digital bits into a bias voltage Digitally controlled componentsDigitally controlled components

13. Digitally Controlled Components Determine the components in each individual circuit that have the largest impact on the intensity of the effect Determine the components in each individual circuit that have the largest impact on the intensity of the effect Devise specific interface scheme between data bits and analog component value Devise specific interface scheme between data bits and analog component value Continuously update component value through interface scheme as data bits are passed on the bus Continuously update component value through interface scheme as data bits are passed on the bus

14. Xicor X9111 Xicor X9111 Digitally Controlled Potentiometer Digitally Controlled Potentiometer Turns on/off a series of ~1000 gates moving a “Wiper Arm” up and down the potentiometer altering the effective resistance Turns on/off a series of ~1000 gates moving a “Wiper Arm” up and down the potentiometer altering the effective resistance

15. Xicor X90100 Xicor X90100 Digitally Controlled Capacitor Digitally Controlled Capacitor Turns on/off numerous capacitors in parallel increasing and decreasing the effective capacitance Turns on/off numerous capacitors in parallel increasing and decreasing the effective capacitance

16. Analog Signal Processing

17. Block Diagram of Signal Processing Circuits

18. Requirements for Effect Circuits Input over-voltage protection Input over-voltage protection Ability to operate with DC power supply Ability to operate with DC power supply Switch that turns on the effect or bypasses it Switch that turns on the effect or bypasses it High input impedance unity-gain buffer to match the high output impedance of a guitar High input impedance unity-gain buffer to match the high output impedance of a guitar Low pass filter to compensate for the high harmonics added in the effects stages Low pass filter to compensate for the high harmonics added in the effects stages An output buffer to provide a low output impedance An output buffer to provide a low output impedance A level control allowing the adjustment of effect intensity A level control allowing the adjustment of effect intensity When bypassed, the effect is shorted without degradation of signal When bypassed, the effect is shorted without degradation of signal LED indicating if the effect is on or off LED indicating if the effect is on or off Metal shield enclosing the circuit to eliminate noise interference Metal shield enclosing the circuit to eliminate noise interference

19. Effect Circuits Distortion Distortion Wah Wah Other effects can be implemented if time permits Other effects can be implemented if time permits

20. Distortion Effect Overview Distortion can be produced by clipping and/or compressing a sound wave. There two kinds of distortion: Distortion can be produced by clipping and/or compressing a sound wave. There two kinds of distortion: Harmonic: more ‘musical’Harmonic: more ‘musical’ Intermodulation: disturbing to the human earIntermodulation: disturbing to the human ear Smooth edged clipping (soft clipping) produces more harmonic distortion than sharp edged clipping (hard clipping) Smooth edged clipping (soft clipping) produces more harmonic distortion than sharp edged clipping (hard clipping) Objective: Objective: maximize the harmonic distortionmaximize the harmonic distortion reduce intermodulation distortion.reduce intermodulation distortion.

21. Hard vs. Soft Clipping

22. Wah Effect Overview Mimics the sound of the word ‘Wah’. Mimics the sound of the word ‘Wah’. 3 ways to control: 3 ways to control: ButtonButton Program (Auto-wah)Program (Auto-wah) PhotoresistorPhotoresistor

23. Wah Effect Implementation The main component is a simple resonator The main component is a simple resonator The resonator acts as a band-pass filter The resonator acts as a band-pass filter The center frequency and resonance (Q-factor) can be adjusted by the user. The center frequency and resonance (Q-factor) can be adjusted by the user.

24. Wah Effect

25. Order of Effects 1. Volume 2. Distortion 3. Tone controls 4. Small time delays and Phasers 5. Longer time delays - chorus 6. Reverb and echo, etc. Courtesy of: http://www.geofex.com/effxfaq/fxorder.htm

26. Extensions Extra effects Extra effects Equalizer/Tone Control Equalizer/Tone Control Computer screen display Computer screen display Ability to program the order in which effects are applied Ability to program the order in which effects are applied Superposition of different signals Superposition of different signals

27. Risks/Contingency Plan Noise resulting from analog signal processing Noise resulting from analog signal processing Use low pass filters and metal structuresUse low pass filters and metal structures Interfacing with Mixed-Signal components Interfacing with Mixed-Signal components Add additional effect-side controlAdd additional effect-side control Use standard D/A converters instead of programmable componentsUse standard D/A converters instead of programmable components

28. Return on Investment Investment/Return Items Amount Labor 5 EE’s * 225 hrs/EE * 20 $/hr = $22,500 Parts$30/unit Cost of the Unit $100 Profit on the unit w/o Labor $70 Units to break even 321

29. Division of Labor Tasks: Done by: Analog Signal Processing Adam, Jasenko and Yousef Mixed-Signal Interface Adam, Jasenko, and Hosam Microprocessor Matthew, Yousef, Hosam Systems Integration Everybody Testing and Quality Assurance Everybody

30. Schedule

31. Questions?