Andrew Lash ECE 3551 DSP on BlackFin BF533 Bass Effects Andrew Lash ECE 3551 DSP on BlackFin BF533

Purpose Create a bass guitar multi-effects processor Delay Chorus Flanger Vibrato Single unit to replace multiple effects processors

Solution - Operation Board has 4 Pushbuttons Left: Switches between effects Middle-Left: Current delay time Middle-Right: Varies on effect Delay: None Chorus, Flanger, and Vibrato: Frequency Right: Amount of decay

Solution – Operation Board has six LEDs Two on left: Show current effect mode 00 – Delay 10 – Chorus 01 – Flanger 11 – Vibrato Four on right: Show the current value for the selected effect characteristic

Solution – Usability Use the first button to switch between modes Other 3 buttons: Press once to set that characteristic as active LEDs will update Press more to increment value by 1 as desired

Solutions – Delay Professional Samples My Samples  *x[n-D] h[n] 1  Z-D y[n] D Professional Samples My Samples

Sinusoidal Low Frequency Oscillator Variable sinusoidal Delay d(n) Solutions - Chorus Sinusoidal Low Frequency Oscillator LFO  x[n-d(n)] x[n] Z-N y[n] Delay-Line Gain Modulating Center of Delay-Line Professional Samples My Samples x[n] Variable sinusoidal Delay d(n)

Solutions - Flanger Flanger effect is similar to Chorus The amount of overall delay is lower The frequency rate is much higher Professional Samples My Samples

Modulating Center of Delay-Line Solutions - Vibrato Sine Wave  x[n-d(n)] x[n] Z-N y[n] Delay-Line Gain Modulating Center of Delay-Line Professional Samples My Samples N=Variable Delay d(n)

Difficulties Flanger and Chorus are very similar Hard to differentiate between effects Designing with only 4 buttons and 6 LEDs is very limiting Had to be creative when designing user interface Limits how much functionality that can be implemented in the display

Results Delay effect works extremely well! Chorus sounds as expected Flanger works ok but not as well I as I would like it to Vibrato works really well

References http://my.fit.edu/~vkepuska/ece3551/ http://www.musiciansfriend.com