1. School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006

2. Audio Processing: EE113D: DSP Design Earvin Caceres Warren Tsu Fall 2006 Valve Pre-Amp Filter School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006

3. Project Specifications Design a non-linear DSP transfer algorithm that will clip an analog input beyond a processing threshold to produce an adjustable pre-amp distortion A/D D/A Anti-Aliasing Filter Smoothing Filter DSP Chip TLC320AC01 AIC Overdrive Assembly Algorithm Analog Input Amplified Output DSKplus Chipset Assembly Program School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006 Clipping

4. School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006 Standards and Applications Standards: Universal 5-V power supply Standard 1/8” RCA mini-jack 8-bit bidirectional parallel port ‘AC01 analog interface Cell phones Portable players Software Guitar Amps

5. School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006 Distortion Theory & DSP Clipping Distortion arises when a signal changes in characteristic from the original waveform. In DSP, clipping occurs when the signal is exceeds beyond the range of binary representation and is truncated. Filter Effects on Signal Integrity

6. School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006 Hard vs. Soft Clipping & Timbre Non-linear effects on timbre: Increase in harmonic content Sustain or compression A DSP Amplifier is versatile with programmable performance. Three Clipping Devices: 1.Tube (Valve) Amplifier 2.IC (Solid State) Amplifier 3.DSP Amplifier Model

7. School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006 Valve Distortion Algorithm Amplify input signal Test sign of input signal Add nonlinear element for negative input Subtract nonlinear element for positive input MATLAB Sinusoidal example y = a * x + b * x ^ 2

8. School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006 DSP Assembly Implementation cmps(a, *ar2) if (TC) goto neginput goto posinput. neginput b = *ar3 * *ar3 a = *ar1 * #2 a = a + b goto send. Compares MSW and LSW in a Sets flag TC. 0 if MSW is bigger. 1 otherwise Nonlinear distortion factor Add distortion Amplify input signal

9. School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006 Design Problems and Lessons Learned Excessive Distortion –Original signal characteristics lost Arithmetic operations in assembly –Multiplication and Division using bit shifting Coding Strategies –Use incremental Development

10. School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006 Results DEMO

11. School of Engineering and Applied Sciences EE113D: DSP Design Fall 2006 References http://www.uaudio.com/webzine/2005/october/index2.html http://tons-of-tone.tripod.com/non_lin1.html http://www.trueaudio.com/at_eetjlm.htm http://en.wikipedia.org/wiki/Guitar_effects http://en.wikipedia.org/wiki/Distortion http://en.wikipedia.org/wiki/Clipping_%28audio%29 http://users.chariot.net.au/~gmarts/ampsmain.htm