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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 1 Examinations 2012/
Module Title: Audio Electronics
Module Code: ELTR
School: Mechanical, Electrical & Process Engineering
Programme Title: MA in Music & Technology
Programme Code: GMUTE_9_Y
External Examiner(s): Mr D. O’Connell, Mr M. Kelleher
Internal Examiner(s): Mr Patrick Collins
Instructions: Answer all questions.
Q1 = 25% , Q2 = 25% , Q3 = 35% , Q4 = 15%
( M = 10^6 , k = 10^3 , = 10-6^ , n = 10-9^ , p = 10-12^ )
Duration: 2 Hours
Sitting: Winter 2012
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
(a) Design a voltage divider circuit to give a 10:1 division of voltage. The divider should take a current of 50mA from a 10V supply. Include a circuit diagram in the answer. [ 7 marks ]
(b) If a 1kW speaker has a resistance of 4 then how much current will flow when 1kW is being consumed? [ 3 marks ]
(c) Draw a diagram showing how four 8 speakers can be connected to an amplifier so that the total resistance is still 8.
i. If the amplifier output voltage = 5V, calculate the voltage across each speaker. ii. Calculate the total power dissipated. iii. Calculate the power dissipated by each speaker. [ 5 marks ]
Fig Q1d. (d) For the circuit shown in Fig Q1d, V 9 = 10V, R 33 = 1k, R 34 = 2k, R 35 = 3k, R 32 = 100 and R 36 = 125.
i. Find the total resistance and the total current. ii. Find the current through and the voltage across each resistor [ 10 marks ]
(a) Explain the principle of operation of a dynamic microphone. [ 6 marks ]
(b) Why does the Shure SM58 microphone have a transformer? [ 3 marks ]
(c) Draw a circuit diagram for a condenser microphone and explain its principle of operation. [ 6 marks ]
(d) What is an electret microphone? Why is a FET circuit needed to interface to it? [ 5 marks ]
(e) Describe the operation of a guitar pickup. Clearly identify the various parts of the pickup and explain how the output signal is generated. [ 7 marks ]
(f) Describe the purpose, construction and principle of operation of a humbucker. [ 8 marks ]
Q4.
(a) A 16-bit ADC has an input voltage range of 0V to 5V. What is the smallest voltage change at the input that can be detected? [ 2 marks ]
(b) If a 16-bit ADC is sampling at 44.1kHz then how many bits/sec are being produced? How long will this system take to a 500MB memory stick? [ 3 marks ]
(c) What is aliasing? [ 2 marks ]
(d) If the sampling frequency is 8kHz then at what frequency will aliasing start to occur? [ 1 marks ]
(e) How does an anti-aliasing filter work? [ 2 marks ]
(f) What is SNR? What is the formula for the relationship between the number of bits in an ADC and the SNR? [ 2 marks ]
(g) An 8-bit ADC has an input voltage range of 0V to 3.3V. Initially the output is 10111010. It then changes to 10101011. What was the change in the input voltage that caused the ADC output code to change? [ 3 marks ]
