Building the simplest, best sounding, yet most inefficient Audio Amp! || Class A Audio Amp Tutorial


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    More project information (schematic,.....) on Instructables:
    Parts list (affiliate links):
    2x BC337 NPN BJT:
    2x 100Ω, 2x 22Ω, 2x 3.3kΩ, 2x 1kΩ Resistor:
    4x 10µF Capacitor:
    1x USB Type-C breakout board:
    1x Audio jack:
    1x Audio plug:
    1x Perfboard:
    Useful sites which were partly shown in the video:
    In this project I will be showing you how to create a class A audio amp. The great thing about such amps is that they only require a few components and sound awesome. On the other hand though, their efficiency is not that great. But since I will be creating this amp for a smartphone with a USB Type-C port for powering the amp, it should be just fine. So let me show you how to calculate a design for such an amp and how to build it! Let's get started!
    Thanks to JLCPCB for sponsoring this video.
    Visit to get professional PCBs for low prices.
    2011 Lookalike by Bartlebeats
    0:00 Why I want to build a class A audio amp
    1:02 Intro
    1:39 General circuit design
    3:03 Closer look at the Base Input side
    4:24 Comparison of class A, B & AB amplifiers
    5:30 Closer look at the Collector Output side
    6:23 Selecting the complementary components
    8:34 Extra Information about class A amps
    9:05 Modifying a USB Type-C board to get 5V
    9:53 Practical build & End

    Am Vor 17 Tage


    1. Farijal Nour Akbar

      Circuit diagram and PDF please?..

    2. Fantasy Engineered.

      the ''most inefficient''? don't U mean: most ''efficient''? & what U'r looking 2 design, and build. though, it's U'r channel. U'r video. and U'r business!! the last thing U need, is some dude. sticking his giant chip's in2 the comments....... the main design that U would be looking 2 engineer, would be a hifi audio amp!! U are an ''electronic engineer'' so U will have no problem designing a ''hifi'' headphone amp! personally!! I would find a nice premium hifi amp and deconstruct!!! good luck stranger?

    3. Deadwindshadow

      I love your videos, BUT FOR THE LOVE OF GOD STOP TRACING OVER THE INK 3-4 TIMES LIKE AN OCD MAN LOL And raping the paper with highlighters too! Hahah otherwise great content!

    4. Chris Davis

      That "Weed" album is great!

    5. Aidan Chappelle

      Can you make a Type-C version of this? Some phones don't have headphone jacks.

    6. Zevski

      I made this circuit but i changed audio and power to female connectors (power to micro usb) and i get a noise. It changes depending on the power source. Not sure how to deal with that

    7. Savita Ray

      I don't know why but I was stuck with class A amplifiers the time you posted the video. May be god heard my prayers! And (saving your reverence) the tutorial was fucking good.

    8. Gacheru Mburu


    9. Jussapitka

      It connects to my phone's what jack now?

    10. Graeme Fowles

      But what is the impedance of the headphone????

    11. Arindam Das

      Systemic elimination of the physical 3.5 mm headphone jack from smartphones is the worst thing that has happened to the smartphone industry.

    12. ashwin mhaskar

      Make a mosfet based audio amplifier

    13. Juan Sanchez

      What if I want to use a battery so I can charge my phone and not drain it? what battery you recommend?

    14. Erik van Gerven

      Scott, Why not taking 4-pole 3,5 mm plug and chassis and connect the 2 mic connections. Now all functionality of the headset will work (call accept button, volume control and microphone)

    15. N9.The_Noob

      your sketches look like they were printed

    16. mushfiq walid

      I lost my enthusiasm about electronics for the last two years.This video reminded me how enthusiastic I still am.

    17. IPCTech

      I would like to get into soldering and building this kind of stuff, while these videos give me good info how to do stuff, would anyone have a video on supplies needed and brand recommendations

    18. Phong Nguyễn

      @GreatScott! how is it usable on google pixels phone? Thank you sir

    19. Dev HONK

      0:02 iS tHaT a JoJo ReFeReNcE????

    20. Kadimi Venugopal

      Really It greatly satisfying my curiosity.👍

    21. Anton Nilsson

      I Love your videos! It would be very interesting if you could compare external noise hifi psu vs wall bricks! 🙂

    22. Abhishek Sharma

      Hi, will this also work if we use this amplifier with an electret condenser microphone?

    23. Davide Bisio

      You forgot to draw the load (O_O) You know that since it is a common emitter amplifier, gain can be calculated as Av = - Rc / Re. Right? And what is Rc in your schematic? (The answer is not 130 Ohm) I really liked this video, but I think you started on the wrong hypotesis. Ok, I know you wanted to use the simplest schematic possible. But why you haven't used a common collector stage? Or a common emitter, followed by a common collector? Or the simplest one: to use a small 2 channel opamp. This latter is the most understandable for everybody, I think.

    24. Robert Klauco

      This is how amplifiers should be thought in schools! Thanks for this.

      1. GreatScott!

        Glad it was helpful!

    25. FerrybigGaming

      9:44 You mention cc "pins". There is only 1 CC pin with a plug, the other one is called VCON, and should be left open

    26. Tomáš Varga

      Or root your phone

    27. edge of tomorrow

      omg just unlock ur bootloader and then increase volume of phone by editing system mixers.

    28. Aammoojan Hastam

      302 people disliked this video? god I don't know what to say

    29. orshemesh1213

      2 commercials at the beginning of the video. 2 commercials during the video. After years of subscription to your channel and suscribe to yours patreon I unsubscribe. Thank you for this years

      1. Clarito resdiano

        DEfasts premium?

    30. Super Hero

      #Request #MiSoundbar Hey scott ! You are the only man on this planet i know who can help me 😉. I have a soundbar by Xiaomi called Mi Soundbar. Its very cheap and has very good sound quality. But it doesn't comes with remote control. I hate to goto the soundbar everytime to switch the audio source and to adjust the volume. Please help me and other many Mi Soundbar users to build a remote control and have a peaceful life. I repeat, you're the only man on this planet that I know, who can solve this issue. -Looking forward Scott Fanboy.


      Why didn't you used operational amplifier for this job. It would have been dead easy to do. NE5534 would have done the job like a pro.

    32. Prince Shehzad

      Doesn't the earphones get damaged after a while??

      1. Clarito resdiano

        No. It looks the dangerous is excess more voltage and signal distortion.

    33. Rdd KEuns

      Or use a chip with usb dac and built in amp but yoill need a pcb witch is a pain to get

    34. ggsmith48906

      I didn't understand the part around 9:30. Why again did the breakout board present you with the phone's 5 volts? And why exactly did you need to make the mods to the board to fix that?

    35. hugeshows

      Very cool project! Don't worry, my audio amp is far less efficient than yours, I promise. It dissipates 600w at idle (not a typo)

    36. Martin Clark

      Hey Scott, you always make great "A class" projects. Have you thought of making an A class metal detector.

    37. Dominic Bouchier

      Guy makes money from copying shit from a book. Good man.

    38. Dominic Bouchier

      Type C is rated at 5V

    39. Cylon39

      FYI adding a 10uF capacitor across the collector resistor will increase your gain considerably.

    40. Jeetender Kakkar


    41. MrCrapentertainment

      so how does it sound

    42. Senecato Aurelius Epictetus

      Could you perhaps do one with cmoy amps?

    43. Max

      Great video! I am wondering what you think about getting 3D printed project boxes made by external companies. I don't have space for a 3D printer and I am tempted to have some project box printed by sculpteo, which has a lab in the region. Do you think it works? It is pretty cheap, it looks to me.

    44. Klam Kong

      I had an anxiety attack from him inhaling.

    45. Demon Lili

      The project very nice, I'll made it but can use the battery 3.7 volt.

      1. Clarito resdiano Use rating 5v battery or above

      2. Volodumur Kalunyak

        Why? Phone will boost it to 5V (and provide a stable voltage, not 3,3V to 4,2V) for you

    46. Bunna Tang

      why not use opamp IC and compander IC ?

    47. Adriano Rheis

      Hi Scott, I have a question for you, I’m from Brazil and I’ve been following your channel for some time. I would like to know how I can set up an "all in one" using a tv and a notebook, and i want to make the two connect at the same time using just ONE BUTTON. Please help me and congratulations on the channel, greetings from Brazil stay creative!

    48. AlienEYE

      Or just download an app????, Sorry mate, I found this video useless

    49. mr ham

      very good tutorial

    50. Nazim Uddin

      Graet vedio. I gess this vedio great for electronic basic

    51. taith2

      With design that small you could try ancient art of point-to-point construction, trying to miniaturize whole thing as much as possible without PCB!

    52. just_twistah

      This what I've been looking for 2years man I've been looking for this😭😭

    53. nacer ben


    54. Techy Adarsh Pro

      Contrlino has lots of pin left for work

    55. Techy Adarsh Pro

      Install something in your garage

    56. 'se://A

      Dude writes: easy Me: I didn't understand a word

    57. KoMaHu3λM

      keeping those algorithms happy...

    58. S7

      Great project!!! Is there a way of connecting 2 - (Tang Band T0-2008S Speaker Module 2-5/32" x 1") to the amp and still be able to connect it to your phone so the audio is coming out of these speakers as well?

    59. Stephin Koshy John

      instead of using audio jack i think it's more convenient to take audio out from type c itself

    60. Ojas Raj

      @great Scott Are u lefty??👍👍

    61. Mohamad Waliyuddin

      Umm....USB C have audio output..You don't have to use two connectors...But great video nonetheless

    62. Ant Man

      I always listen quietly with my headphones. -I like my ears working in the future.

    63. Electronic Mania


    64. kin kong Chew

      getting signal from audio jack is the worst option, USB DAC to class A amplifier is way better low noise too

    65. James Pang

      Output capacitor choice 10uF is too small especially if your earbud impedance is 32ohm, it’ll cause the -3dB low cut frequency is around 500Hz, you’ll miss many bass when you listen music.

    66. Shrikrishna Aghaw

      Nice project...Sir..

    67. Arnold Rimmer

      You'd get better amplification with a feedback resistor from collector to base. I'd have just used an LM386 and an output capacitor it's much more simpler. The simple transistor amplifier is great for learning the basics though.

    68. M12Howitzer

      Take power _from_ my mobile? You Monster!

    69. Perry Lovewhistle

      Not that it matters for this signal, but won't a common emitter Amp invert the signal?

    70. Mr Frog

      Or you could get a phone which doesn't decide for you what's the maximum allowed loudness.

    71. OuchDamn

      There is something I didn't quite understand when you were selecting your components. When you were figuring your collector current, you said 1ma was too quiet, 10ma clipped at max volume, and 20ma was the sweet spot. Was the clipping caused by the transistor running out of power at 10ma?

    72. kelvin phitrow

      Re => Re + Ce

    73. DarkIzo

      gold nichicons 😂

    74. lone wrecche

      I dont know why but the way you draw over your words and images, gives me subtle asmr tingles oO I think you know that :)

    75. Muhammad Husni Muttaqin

      you must listen twice - yes or yes using that amplifier

    76. Falxie_

      Bold of you to assume phones have headphone jacks nowadays

      1. michael falk

        Most have

    77. Soolo

      why not buy better earphones

    78. Quoc Dang

      How come you didn't just opt for an audio chip?

    79. Thibaut Snoeijs (3WEA)

      USB passtrough and it's perfect, a extra bat tree would be nice for the phone also having to power the amp

      1. Company


    80. Alex Kohlman

      Why not use a potentiometer for fine tuning your gain?

    81. Thierry Coton

      Why didn't you use opamps?

    82. play store

      Could you show how to build a "microphone blocker" for smartphones? I think most of the people will agree with me about being listened by smartphones, tablets and laptops. Scary Personalized ads and others. This mic blocker may end us being a product.

    83. John Hansen

      very cool.

    84. Emrah Çokünlü

      disturbing english pronunciation and good content :) I'm confused

    85. pear7777

      WAIT!! No audio signal in USB - C?? No, but converters cost about $10.. maybe hack those so no 3,5mm plug is needed!

    86. Dougal Tolan

      Class D?

    87. Mark Gilder

      Clever old boy.😎👍🏻

    88. steev jobs

      Use Audacity to boost those audiobooks, oh wait, that has nothing to do with electronics......... Carry on.

    89. keith king


    90. anup Satpati


    91. Tech Pill

      I could easily give answers to any questions because of you bro thanks to your detailed explanation

    92. Tech Pill

      Do same project just with usb c my phone doesn't has headphone jack 😕

    93. Arabic from Zero

      You could get audio from that type c port...

    94. Nitish Takale

      Which type of pen use for drawing its looking so awesome

    95. Seazilia Liabond

      Dear brother,i want to get suggestion from u,about DIY or BUY of sms rework station....

    96. Immernoch anders

      Jetzt haben die Leute einen problem die Keinen Kopfhörer Anschluss haben. Denkst du du kannst auch für diese Leute so einen verstärker bauen? Wehre cool wen du dir auch diese Idee vornehmen würdest.

    97. Bien Crafts • 32 years and

      Why inneficient?

    98. TechnoZombie

      After all these years, the way he says "I will see you next time" is still cringy af

    99. Pranav Dharmadhikari

      Nice topic sir.

    100. The Vatner

      Обычный усилок на ТЗ шоль? Хех