ECE 492 Capstone Design: Multi-Effect Guitar Group 4: Aaron Arnason, Byron Maroney, Edrick de Guzman

Motivation As guitarists, we wanted to explore how audio effects are applied Interesting to see what we could do with digital signal processing We wanted to explore the analog domain by building our own amplifier

Project Overview The project consists of the following: Digital Signal Processing Hard-clipping (Distortion) Delay Effect (Reverberation) Amplifier

Audio Properties The audio core handles 44.1 kHz sample rate. Since the DE2’s audio codec uses 16-bit sampling, the required bit-rate the DE2 audio codec’s output is determined by: sampling frequency * bits per sample = bit rate This calculation results to 689.10 kbps (0.673 Mbps)

Distortion Effect Implementation Utilized hard clipping technique Clipping is a form of distortion Considered “hard” when clipping produces a flat-cutoff Flat-cutoff results in a waveform closer to a squarewave Square waves introduce higher frequency harmonics Results in “fuzzy” or “dirty” audio effect

Distortion Effect Demo Challenges Clipping the amplitude introduces power loss Resulting in volume drop Resolved by amplifying the sample after the clipping process

Reverberation Effect Implementation The basic idea of reverb was first created using a variable delay with its signal fed back to create a series of delays that fade out over time Feedback gain must be less than 1

Reverberation Effect Demo Challenges Comb Filter as a side-effect Required a big enough space of memory (interfacing with off-chip memory)  Frequency cancellations that can mimic room effects, but can also yield ringing and instability

Amplifier Implementation Using the LM384N as the amplifier IC The amplifier`s gain is internally fixed at 34 dB Which equates to voltage gain 50 times input signal Designed to boost signal coming from the DE2 Operational voltage between 12-26 volts DC. Potentiometer used for volume control Cost is around $4.00 w/o speakers.

Amplifier Demo Challenges Heating issue Clipping issue

Components List Altera DE2 Amplifier Electric Guitar Nios II Processor DSP Wolfson WM8731 Audio CODEC Amplifier LM384N IC Chip Visaton FRS 7 W – 8 ohm speakers Electric Guitar

Optional Features Guitar Tuner Live Streaming Wireless Playability More Effects: Chorus Flanger Infinity Mirror (Visualizer) [1] - https://en.wikipedia.org/wiki/Infinity_mirror#/media/File:Ultraviole t_infinity_mirro.jpg

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