Audio Amplifier with circuit diagram

G.H.R.I.E.M. JALGAON

1. INTRODUCTION

1.1 Abstract Amplifiers, which are devices that increase the gain of an audio signal,

dominate modern audio technologies. In this project, we designed and built our own

audio amplifier from scratch in order to demonstrate that such a key device can be

constructed using basic electrical engineering principles. After performing major circuit

calculations by hand, we modeled our circuit in PSpice, which is computer software that

analyzes electrical circuits. In particular, we studied the variance that using budget

electrical components introduced into the circuit overall by comparing three different

amplifiers that we constructed. We found the variance between our three amplifiers to

be minimal, confirming our method of building a low budget, low power audio

amplifier.

1.2 Introduction The term amplifier refers to any device that increases the amplitude of a

signal, usually measured in voltage or current. This versatile device is used in a variety

of different electronic applications. Especially in audio technology, a wide range of

amplifiers can be produced based on product specifications (i.e. power, voltage,

current). Currently, there are many types of audio amplifiers available for consumers.

Sound signal amplification is used for instruments, such as the guitar or the bass. They

are also used commonly in home theater systems and with stereo speakers. The basic

design behind all of these amplifiers is derived from the simplest concepts of circuit

design.

For our project, we set out to design an audio amplifier. The inputs of our

circuit were stereo signals from a portable music player. Although we used a low-power

speaker, we needed to achieve approximately three times gain over the entire circuit. In

addition, the amplifier had to be produced at a low cost with available materials. Before

building the actual amplifier, we realized that we had to design, simulate, and test the

circuit. Each step was necessary to understand the concepts involved in amplification

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1.3 Background Before beginning the design process, it was necessary to understand several core

concepts of electrical engineering. When designing electronics, three main specifications

govern all circuit components; voltage [V; measured in volts (V)], current [I; measured in

amps (A)], and resistance [R; measured in ohms (_)]. These three concepts are connected by

Ohm’s Law,

where 1V = 1 A * 1 _.

For amplifier circuits, it is also important to consider both types of current in the

design because both alternating and direct current run through the system. Alternating

current (AC) acts like a sinusoidal curve, providing the signal for the amplifier. On the other

hand, direct current (DC) runs through the circuit as a voltage source. Used together, AC

source creates the signal at the horizontal axis, which is determined by the value of the DC

source. Each is analyzed independently of the other, but without one type of current, it is

meaningless to include the other.

1.4 Musical instrument amplifiers An audio power amplifier is usually used to amplify signals such as music or

speech. Several factors are especially important in the selection of musical instrument

amplifiers (such as guitar amplifiers) and other audio amplifiers (although the whole of the

sound system – components such as microphones to loudspeakers – affect these

parameters):

Frequency response – not just the frequency range but the requirement that the signal level

varies so little across the audible frequency range that the human ear notices no variation. A

typical specification for audio amplifiers may be 20 Hz to 20 kHz +/- 0.5dB.

Power output – the power level obtainable with little distortion, to obtain a sufficiently loud

sound pressure level from the loudspeakers.

Low distortion – all amplifiers and transducers distort to some extent. They cannot be

perfectly linear, but aim to pass signals without affecting the harmonic content of the sound

more than the human ear can tolerate. That tolerance of distortion, and indeed the possibility

that some "warmth" or second harmonic distortion (Tube sound) improves the "musicality"

of the sound, are subjects of great debate.

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2.COMPONENT LIST

There are component which are used in making of the project circuit as given below

Table No 1 Componant Discription

Sr No Componant Name Value Quantity

1 PCB cu Plane 1

2 Hole Type 1

3 Battery Supply 12v DC 1

Connecting Wires 1m 1

Solder -- 1

4 Soldering Wire -- 1

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3.DISCRIPTION OF COMPONENTS

3.1 TBA810

The TBA810 chip is a class B amplifier with high efficiency and very low harmonic

distortion . The input voltage range of the TBA810 is from 4 volts to 20 volts . Main

features of the TBA810 circuit are : low noise , few external components required , polarity

inversion protection , high supply voltage rejection ( 40dB min.) . TBA810 monolithic

audio amplifier can be used in many audio applications for car radios ,other audio devices

or portable applications .

3.1.1 TBA810 Pin Diagram

Figure TBA 810 Pin Diagram

3.1.2 TBA810 Pin Details

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No Function Voltage1 Positive (+Ve)supply voltage 12

2. Not connected NC

3. Not connected NC

4. Ground (-Ve) supply voltage 0


6. Bootstrap 12

7. Compensation 0.6

8. Feedback (output to input ) 1.4

9. Ripple rejection 6.2

10. Audio input 0.3

11. Negative voltage (substitude) 0




15. Not connected NC

16. Audio output 6.5

3.2 RESISTORS

A Resistor is a heat-dissipating element and in the electronic circuits it is mostly

used for either controlling the current in the circuit or developing a voltage drop across it,

which could be utilized for many applications.

There are various types of resistors, which can be classified according to a number of

factors depending upon:

(I) Material used for fabrication

(II) Wattage and physical size

(III) Intended application

(IV) Ambient temperature rating

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(V) Cost

Basically the resistor can be split in to the following four parts from the construction

viewpoint.

(1) Base

(2) Resistance element

(3) Terminals

(4) Protective means.

The following characteristics are inherent in all resistors and may be controlled by

design considerations and choice of material i.e. Temperature co–efficient of resistance,

Voltage co–efficient of resistance, high frequency characteristics, power rating, tolerance &

voltage rating of resistors. Resistors may be classified as

(1) Fixed

(2) Semi variable

(3) Variable resistor.

In our project carbon resistors are being used.

3.3 CAPACITORS

The fundamental relation for the capacitance between two flat plates separated by a

dielectric material is given by:-

C=0.08854KA/D

Where: -

C= capacitance in pf.

K= dielectric constant

A=Area per plate in square cm.

D=Distance between two plates in cm

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Design of capacitor depends on the proper dielectric material with particular type of

application. The dielectric material used for capacitors may be grouped in various classes

like Mica, Glass, air, ceramic, paper, Aluminum, electrolyte etc. The value of capacitance

never remains constant. It changes with temperature, frequency and aging. The capacitance

value marked on the capacitor strictly applies only at specified temperature and at low

frequencies.

3.4 Potentiometer

A potentiometer informally a pot, is a three-terminal resistor with a sliding contact

that forms an adjustable voltage divider.If only two terminals are used, one end and the

wiper, it acts as a variable resistor or rheostat.

A potentiometer measuring instrument is essentially a voltage divider used for

measuring electric potential (voltage); the component is an implementation of the same

principle, hence its name.

Potentiometers are commonly used to control electrical devices such as volume

controls on audio equipment. Potentiometers operated by a mechanism can be used as

position transducers, for example, in a joystick. Potentiometers are rarely used to directly

control significant power (more than a watt), since the power dissipated in the potentiometer

would be comparable to the power in the controlled load.

3.5.Transister A transistor is a semiconductor device used to amplify and switch electronic

signals and electrical power. It is composed of semiconductor material with at least three

terminals for connection to an external circuit. A voltage or current applied to one pair of

the transistor's terminals changes the current through another pair of terminals. Because the

controlled (output) power can be higher than the controlling (input) power, a transistor can

amplify a signal. Today, some transistors are packaged individually, but many more are

found embedded in integrated circuits.

The transistor is the fundamental building block of modern electronic devices,

and is ubiquitous in modern electronic systems. Following its development in the early

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1950s, the transistor revolutionized the field of electronics, and paved the way for smaller

and cheaper radios, calculators, and computers, among other things.

4.OPERATIONAL PRINCIPLE

The task of an audio amplifier is to take a small signal and make it bigger without

making any other changes in it. This is a demanding task, because

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A musical sound usually contains several frequencies, all of which must be

amplified by the same factor to avoid changing the waveform and hence the quality of the

sound. An amplifier which multiplies the amplitudes of all frequencies by the same factor is

said to be linear. Departures from linearity lead to various types of distortions.

The operational details of amplifiers are buried in the field of electronics, but for

audio purposes it is usually safe to say that current commercial audio amplifiers are so good

that a normally operating amplifier is seldom the limitation on the fidelity of a sound

reproduction system. One must be sure that the amplifier can provide enough power to drive

the existing loudspeakers, but otherwise amplifiers are typically one of the most trouble-free

elements of a sound syste

The amplitudes of all frequencies within an amplifier's operating range must be

amplified by the same factor to avoid distortion. An amplifier which satisfies this

requirement is said to be perfectly linear. If the peaks of the waveform are clipped, this

gives rise to what is called harmonic distortion. Another type of distortion is

intermodulation distortion, which occurs when different frequencies in the signal mix to

produce sum and difference frequencies which didn't exist in the signal. Transient distortion

occurs when amplifier components cannot handle the rate of change of the signal, for

example in rapid percussive attacks. There is also transient intermodulation distortion (TIM)

to which modern integrated circuits are susceptible. Such circuits depend upon feedback for

their linearity, but time delays in the feedback can cause intermodulation distortion on fast

transients in the signal.

5.CIRCUIT DESIGN

5.1 CIRCUIT DIAGRAM OF AUDIO AMPLIFIRE

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Fig .5.1 CIRCUIT DIAGRAM OF Audio Amplifire

5.2 PCB LAYOUT

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Fig .5.2 PCB LAYOUT DIAGRAM OF Audio Amplifire.

6.WORKING

6.1 WORKING OF THE CIRCUIT

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The circuit is mainly depends on IC TBA810. This is a 12 pin IC there are metal

stripes coming out of both sides of IC. This is heatsink for the IC. Pin no.1 of IC is supply

pin. We can give 6V to 18V to this pin. Pin no.9 and 10 are negative supply pins. Pin no.8 is

signal input pin. The signal to this pin is given through a volume control and 0.1 capacitor.

The signal is obtain from condensor mike or output of tape recorder. Pin no.12 is the output

pin which gives amplified signal and given to speaker through 1000/25V capacitor. Thus

the sound from microphone is amplified and given to the speaker.

6.1.1 The Power Supply The power supply takes the large AC signal from a household wall socket and

reduces and rectifies it to the +/- 12 Volt DC signals required to operate the circuit. The

first step is to pass the signal through a transformer with a ratio of approximately 6:1. The

secondary of the transformer outputs an AC signal with 30V peak waves. The signal is then

fully rectified1 into positive and negative only signal sweeps using a standard bridge

rectifier configuration

6.1.2Volume Control There were several alternatives for digitally controlling the volume of the signal.

One way was to alter the state of the amplifying CEC circuit by using the dipswitch to

change resistance values. This method introduces no noise, but there are several obstacles

that make it impractical. Most importantly, specifications require exact decibel volume

control, corresponding to 0.707 and 10 V/V gains. The gain of the CEC is most easily

controlled by changing the value of Rc in the circuit. However, such changes have far

reaching implications. By changing Rc, the bias of the entire circuit is altered. Furthermore,

the output impedance of the circuit depends directly on Rc, so these changes also affect the

transfer of the signal to the Power Amp. All of these interconnected reliances make precise

calculation of overall gain levels impractical. The circuit was designed with gain control

happening at the input of the circuit.

When plugged an 8 ohm loud-speaker to the output and applied power to the amplifier, with

a voltage of only six alken from a battery of four cells in a series connection. If everything

has been done correctly, the unit starts working from this first connection...your will hear a

faint background sound on the speaker. Now, if you touch the active terminal of the audio

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input cable, you should hear a loud noise created from the electromagnetic filed of your

home electrical system. Feel releived...you are now a successful constructor. This is the

easiest was of testing an amplifier.

6.1.3 Testing The Forms of Audio Signals Nevertheless, an amplifier can introduce deformation in the audio signals with

which you are feeding it. So a more precise test must be taken. It is necessary to have an

oscilloscope, preferable a double-trace oscilloscope, and an audio signal generator. For the

generator, I used a Heathkit Electronic Design Experimentor, which has frequencies from

200 Hz to 20 Khz. With a double-channel oscilloscope, you plug one of the channels to the

input signal of the amplifier and the other channel to the output. Now you can compare the

forms on the screen and see if the amplifier deforms the input signal. I found in my project

that a signal of .4 volts, at 1 KHz, was amplified to an output of 6 volts. The audio signal

amplified was an exact replica of the input, without any appreciable deformation. It is

important not to introduce an excessive audio voltage to maintain the senoidal form of the

wave.

The TBA 810 IC has sensitivities that can reach minor values of 80 milli-volts

and frequencies from 40 Hz to 20,000 Hz. By adding different power supply voltages and

the facility of connecting speakers of 4 or 8 ohm, you will realize that this IC is an ideal tool

for most of your audio related projects!

7.P.C.B. MANUFACTURING PROCESS

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7.1 P.C.B.

It is an important process in the fabrication of electronic equipment. The design of

PCBs (Printed Circuit Boards) depends on circuit requirements like noise immunity,

working frequency and voltage levels etc. High power PCBs requires a special design

strategy.

The fabrication process to the printed circuit board will determine to a large

extent the price and reliability of the equipment. A common target aimed is the fabrication

of small series of highly reliable professional quality PCBs with low investment. The target

becomes especially important for customer tailored equipments in the area of industrial

electronics.

The layout of a PCB has to incorporate all the information of the board before one can go

on the artwork preparation. This means that a concept which clearly defines all the details of

the circuit and partly defines the final equipment, is prerequisite before the actual lay out

can start. The detailed circuit diagram is very important for the layout designer but he must

also be familiar with the design concept and with the philosophy behind the equipment.

7.2BOARD TYPES:

7.2.1 Single Sided Boards

The single sided PCBs are mostly used in entertainment electronics where

manufacturing costs have to be kept at a minimum. However in industrial electronics cost

factors cannot be neglected and single sided boards should be used wherever a particular

circuit can be accommodated on such boards.

7.2.2 Double Sided Boards

Double-sided PCBs can be made with or without plated through holes. The

production of boards with plated through holes is fairly expensive. Therefore plated through

hole boards are only chosen where the circuit complexities and density of components does

not leave any other choice.

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7.3 CHRONOLOGY

The following steps have been followed in carrying out the project.

1. Study the books on the relevant topic.

2. Understand the working of the circuit.

3. Prepare the circuit diagram.

4. Prepare the list of components along with their specification.

5. Estimate the cost and procure them after carrying out market survey.

6. Plan and prepare PCB for mounting all the components.

7. Fix the components on the PCB and solder them.

8. Test the circuit for the desired performance.

9. Trace and rectify faults if any.

10. Give good finish to the unit.

11. Prepare the project report

7.4DESIGN SPECIFICATION

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7.4.1 PCB DESIGNING

The main purpose of printed circuit is in the routing of electric currents and signal

through a thin copper layer that is bounded firmly to an insulating base material sometimes

called the substrate. This base is manufactured with an integrally bounded layers of thin

copper foil which has to be partly etched or removed to arrive at a pre-designed pattern to

suit the circuit connections or other applications as required.

The term printed circuit board is derived from the original method where a printed

pattern is used as the mask over wanted areas of copper. The PCB provides an ideal

baseboard upon which to assemble and hold firmly most of the small components.

From the constructor’s point of view, the main attraction of using PCB is its role

as the mechanical support for small components. There is less need for complicated and

time consuming metal work of chassis contraception except perhaps in providing the final

enclosure. Most straight forward circuit designs can be easily converted in to printed wiring

layer the thought required to carry out the inversion cab footed high light an possible error

that would otherwise be missed in conventional point to point wiring .The finished project

is usually neater and truly a work of art.

Actual size PCB layout for the circuit shown is drawn on the copper board. The

board is then immersed in FeCl3 solution for 12 hours. In this process only the exposed

copper portion is etched out by the solution.

Now the petrol washes out the paint and the copper layout on PCB is rubbed

with a smooth sand paper slowly and lightly such that only the oxide layers over the Cu are

removed. Now the holes are drilled at the respective places according to component layout

as shown in figure.

7.4.2 LAYOUT DESIGN

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When designing the layout one should observe the minimum size (component body

length and weight). Before starting to design the layout we need all the required

components in hand so that an accurate assessment of space can be made. Other space

considerations might also be included from case to case of mounted components over the

printed circuit board or to access path of present components.

It might be necessary to turn some components around to a different angular

position so that terminals are closer to the connections of the components. The scale can be

checked by positioning the components on the squared paper. If any connection crosses,

then one can reroute to avoid such condition.

All common or earth lines should ideally be connected to a common line routed

around the perimeter of the layout. This will act as the ground plane. If possible try to route

the outer supply line to the ground plane. If possible try to route the other supply lines

around the opposite edge of the layout through the center. The first set is tearing the circuit

to eliminate the crossover without altering the circuit detail in any way.

Plan the layout looking at the topside to this board. First this should be translated inversely,

later for the etching pattern large areas are recommended to maintain good copper adhesion.

It is important to bear in mind always that copper track width must be according to the

recommended minimum dimensions and allowance must be made for increased width

where termination holes are needed. From this aspect, it can become little tricky to negotiate

the route to connect small transistors.

There are basically two ways of copper interconnection patterns under side the

board. The first is the removal of only the amount of copper necessary to isolate the

junctions of the components to oneanother. The second is to make the interconnection

pattern looking more like conventional point wiring by routing uniform width of copper

from component to component.

7.4.3 ETCHING PROCESS

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Etching process requires the use of chemicals. acid resistant dishes and running

water supply. Ferric chloride is mostly used solution but other etching materials such as

ammonium per sulphate can be used. Nitric acid can be used but in general it is not used

due to poisonous fumes.

The pattern prepared is glued to the copper surface of the board using a latex type of

adhesive that can be cubed after use. The pattern is laid firmly on the copper using a very

sharp knife to cut round the pattern carefully to remove the paper corresponding to the

required copper pattern areas. Then apply the resistant solution, which can be a kind of ink

solution for the purpose of maintaining smooth clean outlines as far as possible. While the

board is drying, test all the components.

Before going to next stage, check the whole pattern and cross check with the circuit

diagram. Check for any free metal on the copper. The etching bath should be in a glass or

enamel disc. If using crystal of ferric- chloride these should be thoroughly dissolved in

water to the proportion suggested. There should be 0.5 lt. of water for 125 gm of crystal.

To prevent particles of copper hindering further etching, agitate the solutions carefully by

gently twisting or rocking the tray.

The board should not be left in the bath a moment longer than is needed to remove

just the right amount of copper. Inspite of there being a resistive coating there is no

protection against etching away through exposed copper edges. This leads to over etching.

Have running water ready so that etched board can be removed properly and rinsed. This

will halt etching immediately.

Drilling is one of those operations that calls for great care. For most purposes a

0.5mm drill is used. Drill all holes with this size first those that need to be larger can be

easily drilled again with the appropriate larger size.

7.4.4 COMPONENT ASSEMBLY

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From the greatest variety of electronic components available, which runs into

thousands of different types it is often a perplexing task to know which is right for a given

job.

There could be damage such as hairline crack on PCB. If there are, then they can be

repaired by soldering a short link of bare copper wire over the affected part.

The most popular method of holding all the items is to bring the wires far apart after

they have been inserted in the appropriate holes. This will hold the component in position

ready for soldering.

Some components will be considerably larger .So it is best to start mounting the

smallest first and progressing through to the largest. Before starting, be certain that no

further drilling is likely to be necessary because access may be impossible later.

Next will probably be the resistor, small signal diodes or other similar size

components. Some capacitors are also very small but it would be best to fit these

afterwards. When fitting each group of components mark off each one on the circuit as it is

fitted so that if we have to leave the job we know where to recommence.

Although transistors and integrated circuits are small items there are good reasons

for leaving the soldering of these until the last step. The main point is that these components

are very sensitive to heat and if subjected to prolonged application of the soldering iron,

they could be internally damaged.

All the components before mounting are rubbed with sand paper so that oxide

layer is removed from the tips. Now they are mounted according to the component layout.

7.4.5 SOLDERING: -

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This is the operation of joining the components with PCB after this operation the

circuit will be ready to use to avoid any damage or fault during this operation following care

must be taken.

1. A longer duration contact between soldering iron bit & components lead can exceed the

temperature rating of device & cause partial or total damage of the device. Hence before

soldering we must carefully read the maximum soldering temperature & soldering time for

device.

2. The wattage of soldering iron should be selected as minimum as permissible for that

soldering place.

3 .To protect the devices by leakage current of iron its bit should be earthed properly.

4. We should select the soldering wire with proper ratio of Pb & Tn to provide the suitable

melting temperature.

5. Proper amount of good quality flux must be applied on the soldering point to avoid dry

soldering.

8.ADVANTAGES OF THE CIRCUIT

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Linear behavior

Hi-Fi quality sound

Simpler design

Still pretty simple and basic.

Generally better THD+N performance than the single supply, single-ended design since

all capacitors in the signal path may be eliminated.

The output is biased to GND so this makes controlling the output waveform during

power up and down much easier resulting is less audible 'click' or 'pop' sound.

No physically large and large value output coupling capacitor is needed improving

THD+N performance

.

9.DISADVANTAGES OF THE CIRCUIT

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Power dissipation (which generates heat and require large heatsinks)

Low power efficiency usually have an average efficiency of less than 50% (Theorically

they have an efficiency in excess of 70%)

The design tends to be much more complex

Higher part count and more complicated supply design since two symmetrical voltages

are needed.

Typically more expensive than single supply amplifiers.

10.APPLICATION OF THE CIRCUIT

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Audio Amplifier Uses Car Aux Input, Cell Phone Amplifier ,DVD

Players ,Earbuds ,GPS Audio, Headphone Amplifier ,Hearing Amplifier, iPads,Laptops,

Motorcycle Audio, MP3 Players, PC Audio, Race Scanners, Satellite Radio ,Tablet,

Travel Amplifier, TV Listening, Wireless Headphon etc

Important applications include public address systems, theatrical and concert sound

reinforcement, and domestic sound systems such as a stereo or home-theatre system.

Instrument amplifiers including guitar amplifiers.

11.PRECAUTIONS

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1. The soldering iron being used for soldering of semiconductors should be of low

voltage.

2. While soldering semiconductors heat sinks should be used.

3. While soldering solder should not spread over the entire circuit and solder tip should

be sharp and smooth.

4. While mounting components their values should be visible.

5. Semiconductors and other polarized components should be mounted with correct

polarity.

6. Time should be carefully observed while etching process takes place on the PCB.

12.REFERANCES

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Jerry Del Colliano (20 February 2012), Pass Labs XA30.5 Class-A Stereo Amp

Reviewed, Home Theater Review, Luxury Publishing Group Inc.

Robert S. Symons (1998). "Tubes: Still vital after all these years". IEEE Spectrum 35

(4): 52–63. doi:10.1109/6.666962.

Audio and Hi-Fi handbook, Third edition, 1998, ISBN 0-7506-3636-X p. 271

http://CyrusAudio.com/product-archive/amps/1-integrated-amplifier-all-versions Cyrus

Audio: Product Archive: Cyrus One

http://nobelprize.org/educational_games/physics/transistor/history/ The Transistor in a

Century of Electronics

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Audio Amplifier with circuit diagram

Education

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