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Digital/Analog Guitar Effects Processor

Digital/Analog Guitar Effects Processor. Team 17 Mike Burns, Mark Rovedo, Eric Harter. Overview of Project. Digital echo, modulation, and distortion effects Two types of analog distortion effects (Fuzz, Overdrive) Analog buffers and gain stages. Goals of Project.

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Digital/Analog Guitar Effects Processor

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  1. Digital/Analog Guitar Effects Processor Team 17 Mike Burns, Mark Rovedo, Eric Harter

  2. Overview of Project • Digital echo, modulation, and distortion effects • Two types of analog distortion effects (Fuzz, Overdrive) • Analog buffers and gain stages.

  3. Goals of Project • Easy user customization of digital effects • Warm distortion tones through analog circuitry • Buffered input and output to avoid high frequency attenuation of guitar signal

  4. Digital Provides versatility Ease of implementation for some effects Analog “Warmer” sound Cheaper to implement for single effects Advantages of Mixed Circuitry

  5. Block Diagram

  6. Analog Section • Fuzz Circuitry • Overdrive Circuitry • JFET Buffer

  7. Fuzz • Dual BJT Design • Square wave clipping • Buffered output

  8. Fuzz Schematic

  9. Overdrive Circuit • Emulates overdriven vacuum tube through asymmetrical diode clipping • Dual op-amp design • Op-amp output provides adequate buffering at the output

  10. Overdrive Schematic

  11. JFET Buffer • Simple unity-gain JFET amplifier • Flat frequency response across wide frequency band • Provides “gentle” clipping if overdriven

  12. JFET Buffer Schematic

  13. Comparator • Four-LED indicator to signal when input of DSP may be clipping • Circuitry consists of 4 op-amps running open loop

  14. Comparator schematic (Condensed Version)

  15. Digital Section • Flange • Tremolo • EQ • Reverb • Distortion

  16. Motorola 56302 DSP • Provides 24-bit processing • Serial interface • Ideal for audio applications

  17. Flange • Frequency Modulation • Rate • Depth

  18. Flange (cont.)

  19. Tremolo • Amplitude Modulation • Depth • Rate

  20. Tremolo (cont.)

  21. EQ • Low and High band • FIR filters

  22. EQ (cont.)

  23. Reverb • Feedback from previous samples • Delay control

  24. Reverb (cont.)

  25. Distortion • Hard Clipping • Pre-Gain • Post-Gain

  26. Distortion (cont.)

  27. GUI • Matlab Interface • Sliders for each function • On/Off Switch per function • Outputs to Serial Port

  28. Cost Analysis • Parts………………………………………..……….$348.00 • Labor (at $40.00 / hr, 10 hr/wk, 15 wk) • Development and Design…………….$15,000.00 • Manufacture………………………………..$3,000.00 • Test and Verification……………………$22,000.00 • Total…………………………………….$40,348.00

  29. Problems • Mixer and series/parallel switch ineffective • Poor tone out of Fuzz circuitry • JFET buffer and input gain stage somewhat redundant

  30. Changes made • Removal of output gain stage • Removal of series parallel switch • Addition of distortion bypass switch

  31. New Block Diagram GUI Impedance bypass switch Distortion bypass switch JFET Buffer Gain Stage DSP Distortion Effects Input Output Comparator

  32. Future Enhancements • Redesign and retest Fuzz circuitry • Add more analog effects • Fine-tune DSP’s user interface • Headphone amplifier

  33. Conclusion • Tone of Overdrive and DSP exceeded our expectations • Developed into a useful, versatile tool • DSP distortion not nearly as “pleasing” as analog distortion

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