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Microcomputer Systems 1

Microcomputer Systems 1. ECE 3551 Audio Control & Effects Vishan Hosein. Project Goals. Effects: Echo Chorus Control : Balance Original Audio Output Volume. System Operation. PF8 controlled the original input source being ON / OFF PF9 controlled the modes

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Microcomputer Systems 1

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  1. Microcomputer Systems 1 ECE 3551 Audio Control & Effects Vishan Hosein

  2. Project Goals • Effects: • Echo • Chorus • Control: • Balance • Original Audio Output • Volume

  3. System Operation • PF8 controlled the original input source being ON / OFF • PF9 controlled the modes • The first mode was the Volume control button. • The other two switches, PF10 and PF11 would then control either decreasing or increasing the volume respectively. • The second mode would turn on the Balance Control. • As before, PF10 and PF11 would control either left or right audio output. • The third mode would use the effects • PF10 and PF11 controls the particular effect either chorus or Echo

  4. Original Output Feedback: • LEDS 4 & 5 are Turned OFF • This mode allows the user to switch back at anytime to the original input signal that was passed into the board.

  5. Volume Control Feedback: • LEDS 4 & 5 reflect“1”in binary. • LEDS 6 – 9 shows Volume Gain • Increasing volume, turns on LEDS 6 through 9 • Decreasing volume turns off LEDS 9 through 6 • Control of Output Gain • 7 Steps From Zero to Maximum Gain • Done by multiplying a gain value to Input Signal

  6. Balance Control Feedback: • LEDS 4 & 5 reflect“2”in binary. • LEDS 6 – 9 shows Balance ratio • Balance adjusts Left and Right Gain • By reducing the gain on one side while increasing the gain to the other.

  7. Echo • The flow diagram is used to implement the echo effect • The echo effect may be created by delaying the input signal by approximately 15-30ms. The delayed version of the input signal is sent as an output to one channel and the original signal sent as an output to a different channel • This gives the impression of a stereo effect using a mono source

  8. Chorus • The chorus effect “thickens” sound. It may be used to duplicate the effect of many instruments being played simultaneously. • This effect was created with a variable delay line rotating about a tap center and adding the time varying delayed result together with the original signal. • The varying time delay was updated using the equation: • The “LFO” or low frequency oscillator was used to introduce variations in the time delay. The frequency of the LFO was very low at around 3Hz. The LFO was created using a cosine wavetable lookup. • The time delay algorithm for the chorus effect is usually around 15-35ms. This time delay determined the depth or how much time would change during a sinusoidal cycle.

  9. Chorus Flow Diagram • The flow diagram shown was used to implement a stereo chorus effect. Two cosine wavetables were used. A time varying delay signal was sent to the right channel output. Another time varying signal combined with the original input signal was sent to the left channel output.

  10. References • http://my.fit.edu/~vkepuska/ece3551/7056820721065L_Audio_Tutorial.pdf • http://www.harmony-central.com/’ • http://en.wikipedia.org/wiki/ • http://mathworld.wolfram.com/

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