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

14. 02. 2021
270 019 zhlédnutí

$2 for 4-Layer PCBs:
Previous video:
Transistor (BJT) as a Switch video:
Low Budget Bluetooth Music System video:
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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

  • I have no idea what you said, but I like it 🤣

    Adam SieffermanAdam SieffermanPřed 3 dny
  • Ummm lots of Android music apps can increase the audio volume to 150%

    Edward FletcherEdward FletcherPřed 9 dny
  • how do you think of making USB-C Soundcard? so many phones in these days dont even have a headphone port.

    Blue-ONBlue-ONPřed 10 dny
  • Awsome vid bud ty.

    Mel PlishkaMel PlishkaPřed 19 dny
  • Phone battery will drain quickly due to amplifier

    Techy Adarsh ProTechy Adarsh ProPřed 22 dny
  • i'm also a Queen fan

    Abhishek ThakkerAbhishek ThakkerPřed 26 dny
  • under what circumstances that you need a Class A or Class D amplifier.?

    Prince BelialPrince BelialPřed 29 dny
  • Back in the eighties I had a Musical Fidelity A1 100Watt Class A amp, it was great, listen to music and make yourself a toasted cheese sandwich at the same time.

    Mark LatimerMark LatimerPřed měsícem
  • This is the best explanation for each component of Class A amp and it has real life demo.

    Kanye FullerKanye FullerPřed měsícem
  • I have to build it for my Car Radio, I placed a F-6188 with a BK8000L Bluetooth Module in There, but I'm not happy. I'll design a Proper PCB and this A Class Amplifier on it.

    Persoana a 3-aPersoana a 3-aPřed měsícem
  • Why didn't you use a bypass cap? Just curious, it's just a single component even if in this case its not as useful.

    Mubashir SoomroMubashir SoomroPřed měsícem
  • Does it work with high impedance headphones as well?

    this person is dumbthis person is dumbPřed měsícem
  • Most knowledgeable video and great explanation every video

    Save WaterSave WaterPřed měsícem
  • HI I AM COSTAS ,can you please if posible make an ESP32 internet radio project ,with more detail on the programing of the esp32. thank you

    costas papadopouloscostas papadopoulosPřed měsícem
  • this is something I actually want to build really bad. already bough some of the parts wish me luck. but quick question. can you make a guitar amp? like a diy marshall ms-2. there are even schematics online.

    Hi I'm MikeHi I'm MikePřed měsícem
  • Circuit diagram and PDF please?..

    Farijal Nour AkbarFarijal Nour AkbarPřed měsícem
  • 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?

    Fantasy Engineered.Fantasy Engineered.Před měsícem
  • 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!

    DeadwindshadowDeadwindshadowPřed měsícem
  • That "Weed" album is great!

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

    Aidan ChappelleAidan ChappellePřed měsícem
  • 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

    ZevskiZevskiPřed měsícem
    • Decoupling capacitors.

      Its DextrinIts DextrinPřed 29 dny
  • 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.

    Savita RaySavita RayPřed měsícem
  • 👍👍

    Gacheru MburuGacheru MburuPřed měsícem
  • It connects to my phone's what jack now?

    JussapitkaJussapitkaPřed měsícem
  • But what is the impedance of the headphone????

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

    Arindam DasArindam DasPřed měsícem
  • Make a mosfet based audio amplifier

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

    Juan SanchezJuan SanchezPřed měsícem
  • 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)

    Erik van GervenErik van GervenPřed měsícem
  • your sketches look like they were printed

    N9.The_NoobN9.The_NoobPřed měsícem
  • I lost my enthusiasm about electronics for the last two years.This video reminded me how enthusiastic I still am.

    mushfiq walidmushfiq walidPřed měsícem
  • 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

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

    Phong NguyễnPhong NguyễnPřed měsícem
  • 0:02 iS tHaT a JoJo ReFeReNcE????

    Dev HONKDev HONKPřed měsícem
  • Really It greatly satisfying my curiosity.👍

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

    Anton NilssonAnton NilssonPřed měsícem
  • Hi, will this also work if we use this amplifier with an electret condenser microphone?

    Abhishek SharmaAbhishek SharmaPřed měsícem
  • 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.

    Davide BisioDavide BisioPřed měsícem
  • This is how amplifiers should be thought in schools! Thanks for this.

    Robert KlaucoRobert KlaucoPřed měsícem
    • Glad it was helpful!

      GreatScott!GreatScott!Před měsícem
  • 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

    FerrybigGamingFerrybigGamingPřed měsícem
  • Or root your phone

    Tomáš VargaTomáš VargaPřed měsícem
  • omg just unlock ur bootloader and then increase volume of phone by editing system mixers.

    edge of tomorrowedge of tomorrowPřed měsícem
  • 302 people disliked this video? god I don't know what to say

    Aammoojan HastamAammoojan HastamPřed měsícem
  • 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

    orshemesh1213orshemesh1213Před měsícem
    • CSworld premium?

      Clarito resdianoClarito resdianoPřed měsícem
  • #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.

    Super HeroSuper HeroPřed měsícem
  • 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.

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

    Prince ShehzadPrince ShehzadPřed měsícem
    • No. It looks the dangerous is excess more voltage and signal distortion.

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

    Rdd KEunsRdd KEunsPřed měsícem
  • 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?

    ggsmith48906ggsmith48906Před měsícem
  • 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)

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

    Martin ClarkMartin ClarkPřed měsícem
  • Guy makes money from copying shit from a book. Good man.

    Dominic BouchierDominic BouchierPřed měsícem
  • Type C is rated at 5V

    Dominic BouchierDominic BouchierPřed měsícem
  • FYI adding a 10uF capacitor across the collector resistor will increase your gain considerably.

    Cylon39Cylon39Před měsícem
  • 10000

    Jeetender KakkarJeetender KakkarPřed měsícem
  • so how does it sound

    MrCrapentertainmentMrCrapentertainmentPřed měsícem
  • Could you perhaps do one with cmoy amps?

    Senecato Aurelius EpictetusSenecato Aurelius EpictetusPřed měsícem
  • 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.

    MaxMaxPřed měsícem
  • I had an anxiety attack from him inhaling.

    Klam KongKlam KongPřed měsícem
  • The project very nice, I'll made it but can use the battery 3.7 volt.

    Yoshiko TsushimaYoshiko TsushimaPřed měsícem
    • Use rating 5v battery or above

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

      Volodumur KalunyakVolodumur KalunyakPřed měsícem
  • why not use opamp IC and compander IC ?

    Bunna TangBunna TangPřed měsícem
  • 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!

    Adriano RheisAdriano RheisPřed měsícem
  • Or just download an app????, Sorry mate, I found this video useless

    AlienEYEAlienEYEPřed měsícem
  • very good tutorial

    mr hammr hamPřed měsícem
  • Graet vedio. I gess this vedio great for electronic basic

    Nazim UddinNazim UddinPřed měsícem
  • 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!

    taith2taith2Před měsícem
  • This what I've been looking for 2years man I've been looking for this😭😭

    just_twistahjust_twistahPřed měsícem
  • 👍

    N . BN . BPřed měsícem
  • Contrlino has lots of pin left for work

    Techy Adarsh ProTechy Adarsh ProPřed měsícem
  • Install something in your garage

    Techy Adarsh ProTechy Adarsh ProPřed měsícem
  • Dude writes: easy Me: I didn't understand a word

    'se://A'se://APřed měsícem
  • keeping those algorithms happy...

    KoMaHu3λMKoMaHu3λMPřed měsícem
  • 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?

    S7S7Před měsícem
  • instead of using audio jack i think it's more convenient to take audio out from type c itself

    Stephin Koshy JohnStephin Koshy JohnPřed měsícem
  • @great Scott Are u lefty??👍👍

    Ojas RajOjas RajPřed měsícem
  • Umm....USB C have audio output..You don't have to use two connectors...But great video nonetheless

    Mohamad WaliyuddinMohamad WaliyuddinPřed měsícem
  • I always listen quietly with my headphones. -I like my ears working in the future.

    Ant ManAnt ManPřed měsícem
  • (Y)

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

    kin kong Chewkin kong ChewPřed měsícem
  • 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.

    James PangJames PangPřed měsícem
  • Nice project...Sir..

    Shrikrishna AghawShrikrishna AghawPřed měsícem
  • 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.

    Arnold RimmerArnold RimmerPřed měsícem
  • Take power _from_ my mobile? You Monster!

    M12HowitzerM12HowitzerPřed měsícem
  • Not that it matters for this signal, but won't a common emitter Amp invert the signal?

    Perry LovewhistlePerry LovewhistlePřed měsícem
  • Or you could get a phone which doesn't decide for you what's the maximum allowed loudness.

    Mr FrogMr FrogPřed měsícem
  • 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?

    OuchDamnOuchDamnPřed měsícem
  • Re => Re + Ce

    kelvin phitrowkelvin phitrowPřed měsícem
  • gold nichicons 😂

    DarkIzoDarkIzoPřed měsícem
  • 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 :)

    lone wrecchelone wrecchePřed měsícem
  • you must listen twice - yes or yes using that amplifier

    Muhammad Husni MuttaqinMuhammad Husni MuttaqinPřed měsícem
  • Bold of you to assume phones have headphone jacks nowadays

    Falxie_Falxie_Před měsícem
    • Most have

      michael falkmichael falkPřed měsícem
  • why not buy better earphones

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

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

    Thibaut Snoeijs (3WEA)Thibaut Snoeijs (3WEA)Před měsícem
    • r/boneappletee

      CompanyCompanyPřed měsícem
  • Why not use a potentiometer for fine tuning your gain?

    Alex KohlmanAlex KohlmanPřed měsícem
  • Why didn't you use opamps?

    Thierry CotonThierry CotonPřed měsícem
  • 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.

    play storeplay storePřed měsícem
  • very cool.

    John HansenJohn HansenPřed měsícem
  • disturbing english pronunciation and good content :) I'm confused

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

    pear7777pear7777Před měsícem