• Audio amp design

    Audio amp design

    Electronics hobbyist love to design their own gadget which cam be used in our daily life. In this post you will learn how to design your own Best audio amplifier circuit with premium specification.

    The circuit of audio amplifier need separate power supply unit thus, we are also going to show the power supply circuit and designing method. Power supply unit is designed around step-down transformer, rectifier and series voltage regulator.

    Mains line input is given to primary winding of the transformer which step-down the voltage to 15V AC. DC output available at pin 3 of IC 1 is filtered by capacitor C 3. One diode 1N D 1 is connected across the output pin pin 3 to input pin pin 2 of IC 1 as shown in circuit diagram of power supply unit in order to protect the IC from reverse voltage. A LED is also connected with series current limiting resistor in order to indicate the power supply whereas resistor protect the diode from over voltage and current.

    Input audio is given to inverting terminal of IC 2 pin 2 through variable resistor VR 1 and electrolytic capacitor C 4. Capacitor C 5 is used as bypass capacitor. Two capacitors, one electrolytic capacitor C 6 and one ceramic capacitor C 7 connected in parallel used as de-coupler i.

    Best Audio Amplifier Circuit

    Electrolytic capacitor C 6 reduce the low frequency noise and min-frequency noise available in power supply, whereas ceramic capacitor reduces high frequency noise available in power supply lines.

    Gain of the amplifier is set by two resistors i.

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    R 2 and R 5where bandwidth of the amplifier is set by resistor R 5 and capacitor C 8. Bias Current is set by two resistors R 6 and R 7 which is further adjusted by variable resistor VR 2. Two diodes D 2 and D 3 do the job of multiplier. This bias current set by these resistive elements solves the problem of turn on base emitter drop of transistors T 1 and T 2this current is also used to keep the transistors T 1 and T 2 active in-order to produce the output power when either load is connected or not.

    Transistor T 1 and T 2 is used to drive the loudspeaker capacitor C 10 is used here to block the DC signal. This network reduces the high frequency noise available at loudspeaker by forming a low-impedance path. Like this: Like LoadingI added a bunch of extra capacitors to reduce the noise, and I added a bass boost control as well to make it sound even better. The LM is quite a versatile chip. The chip has options for gain control and bass boost, and it can also be turned into an oscillator capable of outputting sine waves or square waves.

    The actual output power you get will depend on your supply voltage and speaker impedance. The datasheet has graphs that will tell you.

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    I used a 9V battery for the power supply and it works great, but you can go down to 4V or up to 12V. LM Datasheet. The LM is a type of operational amplifier Op-Amp.

    Operational amplifiers have a basic task. Volume lets you adjust the sound level within the range of amplification set by the gain. For example, if your gain is set to 20, the range of volume is 0 to If your gain is set tothe range of volume is 0 to Make it a goal to keep the input ground separate from other ground paths as much as possible.

    For example, you can connect the grounds for the power supply, input, and output directly to the ground pin pin 4 of the LM like this:.

    Keeping the wires as short as possible will also help. A cool feature of the LM is the option to add an adjustable bass boost to the amplifier.

    The bass boost is basically just a low pass filter, and it removes most of the noise not taken out by the decoupling capacitors.

    Thanks for reading! Hope you had fun experimenting with these amps as much as I did. Be sure to subscribe to keep updated on our posts as soon as they are published.

    And feel free to leave a comment if you have any questions or need help with anything in this article. Great little article, thanks. BTW the number sure do bring a lot of old memories back. My first pc,40mhz with 4mb ram. Some how I miss old dos, in some ways it was less complicated back then. Thanks yaboc, glad you liked it. I used the LMN-1, but the setup would be the same for each model, the main difference being the power output.

    Sir you can use a 3. Hi Sanjeev, double check to make sure everything is connected properly, and the polarity of the electrolytic capacitors are correct…. Hi I was wondering about this amp are those mono amps? Dear Sir, What will be the maximum power output from this configuration? Very informative! Thank you for sharing!It is my first instructable.

    Lets see how to make an audio amplifier which you can use with any of your musical instruments like guitar,piano and with ipod and other devices. So Lets begin the journey Disclaimer: If following this guide anything damages i shall not be held responsible. Do it at your own risk. Did you use this instructable in your classroom?

    Add a Teacher Note to share how you incorporated it into your lesson. You need the following components 1- LM semiconductor IC 2- micro Farad capacitor 3- micro Farad capacitor 4- 10 ohm resistor 5- 5 kilo ohm variable resistor 6- ohm variable resistor 7- 0.

    audio amp design

    The circuit which we are going to make is. Thanks to cld for schematic drawing. Take a wire and join the 3rd pin to 4th pin GND pin. Join the one pin of 0. Join th A pin of this variable resistor with the C pin.

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    Lastly join the 8th pin of IC with the B of this variable resistor. This becomes the GAIN. This becomes the Volume controller. Now the time to check it out. Join the male jack with your mp3 player or musical instrument and female with the speakers.

    Now adjust the Volume and Gain to get the best and loudest possible sound. I should notify you that with this amplifier only one speaker will work. And do the adjustment from low to high. Do the adjustment carefully or it can damage your speakers. You can change the input jacks as your requirement.

    You can add a micro farad variable capacitor instead of simple micro farad capacitor to change the bass. Hi, It is good, but it has so many components, there are simpler ways, like here:. Question 1 year ago. Question 1 year ago on Step 5. I made speaker box for my laptop and added two speakers. Sound is low. It needs amp? Can you help me? I used 2 LM chips and did mine on a pcb. At first the sound was soft and easily distorted.

    I then went to check out the data sheet for LM and realized this chip could take 18v max.No matter the specific application DD Audio offers an amplifier to cover your needs. Our amplifier designs emphasize high performance, functionality and reliability. All DD Audio amplifiers are built using industry leading part manufacturers and are held to the highest level of build quality. You can rest assured when your system is powered by DD Audio, you're using the best power on the planet.

    For the SS Series the main design focus was to pack as much full-range stereo output capability as possible into as compact of a chassis as possible. We utilized discrete circuit class D technology for ultra low distortion levels that rival class AB designs. The resulting amp is capable of driving multiple driver mid-range and tweeter arrays while consuming less current, taking up less space and delivering more power.

    They are ultra-high performance class D monoblocks with compact footprints and big power. The M Series has an amp for virtually every size of power application. All M Series feature our innovative LV power supply technology that gives you the most power possible from your vehicle's charging system. The D Series amplifiers are designed to be the best amps on the market for the everyday mobile audio enthusiast.

    These class D amplifiers feature compact chassis, superb sound quality, reliable circuits, and powerful output sections. They're available in several channel and power configurations assuring there is a D Series amp to power your system.

    Their Class AB circuitry offers a warm dynamic sound at an incredible value. The new chassis design features a single side control panel that gives the C Series an elegant aesthetic and while making cable management and audio adjustments easy for quick clean installations.

    Other features include band-passable crossover networks, durable internal components, set screw terminals and engraved logos. For additional control, if you're using a C Series as a sub amp an optional remote subwoofer control is available. Find a Dealer Become a Dealer. History Partners Evolution. SS Series For the SS Series the main design focus was to pack as much full-range stereo output capability as possible into as compact of a chassis as possible.

    D Series The D Series amplifiers are designed to be the best amps on the market for the everyday mobile audio enthusiast.

    Pro Audio. Signal Processors. Installation Accessories. Product Archive. Lifestyle and Gear.With the right layout and component selection, you can build an excellent sounding Hi-Fi audio amplifier that will rival high-end amps retailing for several thousand dollars or more. I highly recommend reading the datasheet before building your amplifier. LM Datasheet.

    Application note AN has additional information that fills in gaps left out of the datasheet. Overture Application Note AN This is an Excel spreadsheet that calculates output power, heat sink size, gain, and other useful parameters:.

    Overture Design Guide. You can also check out this video to see a quick overview of the design process. At the end I wire up the amp so you can hear what it sounds like:. The formula to use is:. Sound quality is severely compromised when the SPiKe circuitry is enabled, so to prevent this we need a heat sink with a thermal resistance low enough to dissipate the maximum power dissipated by the LM The minimum gain setting of your amplifier will depend on your input voltage, speaker impedance, and output power according to the formula:.

    Setting it too low might make your amplifier too quiet.

    audio amp design

    To convert voltage gain to decibels db gain, use this formula:. I decided on a gain of around 27 db Which is close enough to 27 db, and above the If these resistors vary much between the two channels, the gains will be different and one channel will be louder than the other. Metal film resistors with a tolerance of 0. After setting the gain, the next step is to balance the input bias currents by choosing values for R in and R b :.

    If the currents at the non-inverting input pin 9 and the inverting input pin 10 are different, a voltage will develop between them. Lower than 2 to 4 Hz is ideal. I started with 1. Electrolytics, ceramics, and tantalum capacitors should be avoided. A good quality polypropylene metal film, or even better a polypropylene metal film in oil capacitor will sound best here. We can use the F c equation with R i and C i :.

    Broadcast radio frequencies in the USA are:. With a pF capacitor, the F c becomes:.An audio power amplifier or power amp is an electronic amplifier that amplifies low-power electronic audio signals such as the signal from radio receiver or electric guitar pickup to a level that is high enough for driving loudspeakers or headphones. Audio power amplifiers are found in all manner of sound systems including sound reinforcementpublic address and home audio systems and musical instrument amplifiers like guitar amplifiers.

    It is the final electronic stage in a typical audio playback chain before the signal is sent to the loudspeakers. The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification of the signal this is particularly associated with record turntable signals, microphone signals and electric instrument signals from pickups, such as the electric guitar and electric bassequalization e.

    The inputs can also be any number of audio sources like record playersCD playersdigital audio players and cassette players. Most audio power amplifiers require these low-level inputs, which are line level. While the input signal to an audio power amplifier, such as the signal from an electric guitar, may measure only a few hundred microwattsits output may be a few watts for small consumer electronics devices, such as clock radiostens or hundreds of watts for a home stereo systemseveral thousand watts for a nightclub 's sound system or tens of thousands of watts for a large rock concert sound reinforcement system.

    While power amplifiers are available in standalone units, typically aimed at the hi-fi audiophile market a niche market of audio enthusiasts and sound reinforcement system professionals, most consumer electronics sound products, such as clock radiosboom boxes and televisions have relatively small power amplifiers that are integrated inside the chassis of the main product.

    The audio amplifier was invented around by Lee De Forestmade possible by his invention of the first practical amplifying electrical component, the triode vacuum tube or "valve" in British English in The triode was a three terminal device with a control grid that can modulate the flow of electrons from the filament to the plate.

    The triode vacuum amplifier was used to make the first AM radio. Audio power amplifiers based on transistors became practical with the wide availability of inexpensive transistors in the late s. Since the s, most modern audio amplifiers are based on solid-state transistors, especially the bipolar junction transistor BJT and the metal—oxide—semiconductor field-effect transistor MOSFET. Transistor-based amplifiers are lighter in weight, more reliable and require less maintenance than tube amplifiers.

    In the s, there are still audio enthusiasts, musicians particularly electric guitaristselectric bassistsHammond organ players and Fender Rhodes electric piano players, among othersaudio engineers and music producers who prefer tube-based amplifiers, and what is perceived as a "warmer" tube sound.

    Key design parameters for audio power amplifiers are frequency responsegainnoiseand distortion. These are interdependent; increasing gain often leads to undesirable increases in noise and distortion.

    While negative feedback actually reduces the gain, it also reduces distortion. Most audio amplifiers are linear amplifiers operating in class AB. Until the s, most amplifiers were tube amplifiers which used vacuum tubes. During the s, tube amps were increasingly replaced with transistor -based amplifiers, which were lighter in weight, more reliable, and lower maintenance.

    Nevertheless, there are still niche markets of consumers who continue to use tube amplifiers and tube preamplifiers in the s, such as with home hi-fi enthusiasts, audio engineers and music producers who use tube preamplifiers in studio recordings to "warm up" microphone signals and electric guitarists, electric bassists and Hammond organ players, of whom a minority continue to use tube preamps, tube power amps and tube effects units.

    While hi-fi enthusiasts and audio engineers doing live sound or monitoring tracks in the studio typically seek out amplifiers with the lowest distortion, electric instrument players in genres such as bluesrock music and heavy metal musicamong others, use tube amplifiers because they like the natural overdrive that tube amps produce when pushed hard.

    In the s, the Class-D amplifierwhich is much more efficient than Class AB amplifiers, is widely used in consumer electronics audio products, bass amplifiers and sound reinforcement system gear, as Class D amplifiers are much lighter in weight and produce much less heat. Since modern digital devices, including CD and DVD players, radio receivers and tape decks already provide a "flat" signal at line level, the preamp is not needed other than as a volume control and source selector.

    One alternative to a separate preamp is to simply use passive volume and switching controls, sometimes integrated into a power amplifier to form an integrated amplifier. The final stage of amplification, after preamplifiers, is the output stage, where the highest demands are placed on the transistors or tubes. For this reason, the design choices made around the output device for single-ended output stages, such as in single-ended triode amplifiers or devices for push-pull output stagessuch as the Class of operation of the output devices is often taken as the description of the whole power amplifier.

    For example, a Class B amplifier will probably have just the high power output devices operating cut off for half of each cycle, while the other devices such as differential amplifier, voltage amplifier and possibly even driver transistors operate in Class A.

    For some years following the introduction of solid state amplifiers, their perceived sound did not have the excellent audio quality of the best valve amplifiers see valve audio amplifier. This led audiophiles to believe that "tube sound" or valve sound had an intrinsic quality due to the vacuum tube technology itself. InMatti Otala published a paper on the origin of a previously unobserved form of distortion: transient intermodulation distortion TIM[7] later also called slew-induced distortion SID by others.

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    TIM did not appear at steady state sine tone measurements, helping to hide it from design engineers prior to Problems with TIM distortion stem from reduced open loop frequency response of solid state amplifiers.

    Further works of Otala and other authors found the solution for TIM distortion, including increasing slew ratedecreasing preamp frequency bandwidth, and the insertion of a lag compensation circuit in the input stage of the amplifier. This new idea helped audio design engineers to better evaluate the distortion processes within an amplifier.

    Important applications include public address systems, theatrical and concert sound reinforcement systemsand domestic systems such as a stereo or home-theatre system. Instrument amplifiers including guitar amplifiers and electric keyboard amplifiers also use audio power amplifiers.

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    In some cases, the power amplifier for an instrument amplifier is integrated into a single amplifier "head" which contains a preamplifier, tone controls, and electronic effects. These components may be mounted in a wooden speaker cabinet to create a "combo amplifier".I offer the educational material I have created on this website free of charge to the global community for its elucidation and use as it sees fit, with the understanding that it must be attributed to the author, as it is copyrighted material.

    Having said that however, should you find that it is of value to you, and wish to make a contribution to the ongoing viability of this site, I have set up PayPal account for your convenience and hereby express my gratitude for whatever you may be able to forward. In many power amplifiers the op-amp circuit is constructed with discrete components specifically designed for higher rail Voltages.

    Output transistors are added to provide extra current to drive a speaker. Large output transistors only have a small HFE current gain, therefore driver transistors are placed in front of the output transistors to increase to total current gain to approx The bias string can now be placed in the Class A driver circuit.

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    Output transistors can be arranged in three different ways. This description is a basic overview. But germanium transistors were unstable and not reliable. Reliable Silicon transistors were invented later. High power amplifiers could only be built with silicon transistors. The below pic shows parallel output transistors.

    audio amp design

    Some large power amplifiers use many parallel output transistors. These emitter resistors force the output transistors to equally share current and therefore will be equal in heat dissipation. All output transistors are arranged as emitter followers.

    The collectors are connected directly to the rails. The emitter follows the signal on base within mV. The output transistors do not increase the size of the audio signal. Output transistors can only add current. When PNP power transistors 2N became available they were twice the price.

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    The output transistors on the -V rail appear not to be wired as emitter followers. However the PNP driver transistor manages the output transistors collectively as a single compound large Emitter follower with a high HFE current gain.

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    The compound complementary arrangement has two advantages over the Darlington and Quasi complementary arrangements. Power amplifiers have a signal gain of approx 20 to 40 adjusted by R1 R2. The primary disadvantage of FETs is that they deliver less power than a Bi-polar transistor amp using the same supply voltage.

    They are expensive, difficult to manufacture and only a few companies supply them. The Source output will be 12V less than at the Gate.

    To solve the 12V loss problem requires the Gate to be driven 12V above the 70V rail supply at the peak of the sine wave. To achieve this the driver circuit would need to be powered from a separate higher rail supply 90V exampleto enable the input signal to reach at least 12V above the 70V amp rail supply. The 6V difference between the peak of the sine wave and the rail supply shown in the above pic could be reduced to a lower voltage enabling greater power.

    Outside of this single point Valves and FETs have no similarity whatsoever. Music is capable of a 60dB 1, dynamic range. The transients in music are very small in energy but are approx 20dB above the RMS music level. The average RMS power of fully dynamic music can not go above dB of the amplifiers full power capacity without the transients clipping the rail supplies.


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