Headphone Amplifier & Equalizer

Size: px

Start display at page:

Download "Headphone Amplifier & Equalizer"

Cory Sullivan
6 years ago
Views:

1 May05-01 Headphone Amplifier & Equalizer April 26, 2005

2 Project Team Information Team Members Jennifer Bruner, Electrical Engineering Mike Dierickx, Electrical Engineering Rachel Hager, Electrical Engineering Kurtis Kenne, Electrical Engineering Advisors John Lamont Ralph Patterson III Client Senior Design

3 Presentation Outline List of Definitions Problem Statement & Proposed Approach Operating Environment Intended User(s) & Use(s) Assumptions & Limitations End Product Approaches Considered and Used

4 Presentation Outline Cont. Accomplishments Schedules & Hours Worked Resource Requirements & Project Costs Project Evaluation Lessons Learned Risk & Risk Management Closing Summary

5 Acknowledgements HeadWize, specifically Chu Moy, for the audio schematics Jason Boyd, the brain behind the PCB layout and soldering

6 List of Definitions Amplifier The circuitry that allows one to adjust the overall power and thus volume. Cross-fed Delay Filter - A filter which simulates a surround sound experience by combining both channels with time delay and attenuation in each ear. Equalizer The circuitry that allows one to tune the relative power of individual frequency bands of an audio signal.

7 Problem Statement Design a portable audio device capable of driving a set of high-fidelity headphones with a soundstage offering the user the ability to adjust a 3-band equalizer. Proposed Approach Research and test audio schematics provided by HeadWize and develop a design fitting the functional requirements set forth by the project advisors.

8 Operating Environment Encompasses all portable uses in both indoor and outdoor environments Portability Dimensions no greater than 5 x 5 x 2.5 Durability Extreme temperatures Possibility of being dropped

9 Intended User(s) & Use(s) General public Specifically enthusiasts of music Use in conjunction with a portable audio source, such as a CD or MP3 player

10 Assumptions Drive a pair of high fidelity headphones with an impedance range up to 32 ohms Will use 3-band equalization with a max of ±20 db amplification Equalization will be in stereo, but each channel will not be equalized separately

11 Limitations The device must have the capability to charge on 12 VDC, and operate on an internal power supply of six 1.2 V (AA) NiMH rechargeable batteries The device will include at minimum a 3.5 mm input jack, a 3.5 mm headphone jack, a volume control, a power switch, 3-band equalizer, and a pilot light Since the device will be portable, it must be able to withstand extreme temperatures and be durable enough to withstand being dropped The MSRP (Manufacturers Suggested Retail Price) should not exceed $50.

12 End Product A completely encased prototype of a portable audio device capable of driving a set of high-fidelity headphones with a soundstage offering the user the ability to adjust a 3-band equalizer A users manual

13 Technical Approaches

14 Approach Considerations

15 Approach Used There are four primary components Amplifier Equalizer Soundstage Simulator Battery and Casing

16 Amplifier Should be superior to the digital Class D part contained in portable players Designed to have a voltage gain from zero (off) to about 2.5 Guarded at the input by an AC couple to eliminate noise

17 Amplifier

18 Equalizer Both passive and active types Chose an active Baxandall type with about ±20 db in each channel with centers at 300, 1050, and 1700 Hz This design was highly tunable, it can very nearly silence a band

19 Equalizer

20 Cross-fed Delay Filter Creates a proper soundstage using passive filters The soundstage is typically not present in studio recordings, but much more in symphonic or marching band tracks

21 Cross-fed Delay Filter Headphone User

22 Cross-fed Delay Filter Speaker User

23 Cross-fed Delay Filter The effect of hearing the path difference depends on both a time delay and a change in volume due to attenuation The volume change for a given path difference depends on the frequency of the sound

24 Cross-fed Delay Filter

25 Casing and Power Supply Power Supply was designed by a previous team finishing in December 2004 Has 4.5, Ground, and 4.5 V, although currently other methods of power are being used

26 Casing and Power Supply Right now, casing has been chosen to accommodate the single 9 V cell Case for our first prototype has been chosen

27 Accomplishments

28 Accomplishments Researched different audio schematics published by various authors at

29 Accomplishments Ran PSpice simulations on selected circuit schematic

30 Accomplishments Completed breadboard testing

31 Accomplishments PCB layout is complete and was ordered using Orcad Layout All three layers Bottom Layer Silkscreen Top Layer

32 Accomplishments First Prototype PCB from Advanced circuits $46

33 Accomplishments Soldered surface mount components onto PCB

34 Accomplishments Encased PCB Dimensions 5 x2.5 x1

35 Accomplishments Tested prototype with different types of input

36 Accomplishments Created users manual

37 Schedule and Resources

38 Project Schedule

39 Schedule Power supply caused major delays Some tasks took longer than expected Research Parts and technology considerations Breadboard implementation & testing Team finished on schedule

40 Hours Worked (To Date) Team Personnel Jennifer Bruner Mike Dierickx Rachel Hager Kurtis Kenne Number of Hours

41 Hours Worked (To Date) Kurtis, 166, 25% Jennifer, 159, 24% Jennifer Mike Rachel Kurtis Rachel, 164, 25% Mike, 162, 26%

42 Other Required Resources Item Project Poster Parts: PCBs Axial Lead SMT and Case Subtotal: Cost $50.00 $46.87 $67.50 $89.25 $ Assembly Services: Soldering Subtotal: Donated $0.00 Total: $303.62

43 Other Required Resources SMT & Case Item Axial Lead PCBs $0 $20 $40 $60 $80 $100 Cost

44 Project Costs Item Project Poster Parts: PCBs Axial Lead SMT and Case Subtotal: W/O Labor $50.00 $46.87 $67.50 $89.25 $ With Labor $50.00 $46.87 $67.50 $89.25 $ Assembly Services: Soldering Subtotal: Labor ($10 per hour): Jennifer Bruner Mike Dierickx Rachel Hager Kurtis Kenne Subtotal: Total: Donated $0.00 $0.00 $ Donated $0.00 $1, $1, $1, $1, $6, $6,763.62

45 Project Evaluation Project Completed Successfully Met design requirements Product is durable and portable Met expected cost Provides unique listening experience

46 Lessons Learned Gained knowledge of audio schematics Importance of breadboard testing group knowledge of board layout Set-back with the power supply Issues with noise Start testing earlier

47 Risk & Risk Management Anticipated few problems with design layout Ran PSpice simulations Breadboard testing Unanticipated problems with the power supply developed by previous senior design team Sent power supply to get fixed Fabricated device using a 9V battery supply Unanticipated noise during breadboard testing Fixed some issues due improper grounding Fabrication of PCB eliminated noise issues

48 Closing Summary Problem Need a portable audio device capable of driving a set of high-fidelity headphones with a soundstage offering the user the ability to adjust a 3-band equalizer. Solution Designed a device that includes an amplifier, equalizer, and acoustic simulator, all placed into an economical package Result Functional prototype was developed with users manual

49 Questions?

HARDWARE OPERATIONS MANUAL

HARDWARE OPERATIONS MANUAL Table of Contents INTRODUCTION... 2 SECTION 1: HARDWARE COMPONENT ASSEMBLIES... 2 MECHANICAL HARDWARE AND CASE... 2 PCB ASSEMBLY... 4 ISD RECORDING CIRCUIT... 5 BREADBOARD ASSEMBLY...