Building the simplest, best sounding, yet most inefficient Audio Amp! || Class A Audio Amp Tutorial
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- เผยแพร่เมื่อ 12 พ.ค. 2024
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Twitter: / greatscottlab
Support me for more videos: www.patreon.com/GreatScott?ty=h
More project information (schematic,.....) on Instructables: www.instructables.com/Buildin...
Parts list (affiliate links):
2x BC337 NPN BJT: s.click.aliexpress.com/e/_9I1F1z
2x 100Ω, 2x 22Ω, 2x 3.3kΩ, 2x 1kΩ Resistor: s.click.aliexpress.com/e/_dTP...
4x 10µF Capacitor: s.click.aliexpress.com/e/_d7d...
1x USB Type-C breakout board: s.click.aliexpress.com/e/_AonKUJ
1x Audio jack: s.click.aliexpress.com/e/_9IfcXd
1x Audio plug: s.click.aliexpress.com/e/_ABC7UL
1x Perfboard: s.click.aliexpress.com/e/_A5V4B5
Useful sites which were partly shown in the video:
www.electronics-lab.com/artic...
learnabout-electronics.org/Am...
learnabout-electronics.org/Am...
www.tutorialspoint.com/amplif...
www.electronics-tutorials.ws/...
www.electronics-tutorials.ws/...
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 jlcpcb.com to get professional PCBs for low prices.
Music:
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 - วิทยาศาสตร์และเทคโนโลยี
After 4 years of engineering some of my basic doubts got cleared😂 thanks for the video🙌
Happy to help
True 😂
Agreed, same here. I wish that they taught us like this in engineering.
@@anuragmahajan5919 I have learned more from this one man's work on TH-cam than any 1 teacher I ever had in school. Gotta love the time we live! We have almost infinite acess to information, and so many good people sharing what they know to help us all learn and create.
good job
Really like your writings and sketches. They are so helpful.
Glad you like them!
Yeah keep going! I also like that left-handed drawings
Strong agree!
100% agree! I love how he explains each step in the process too. One of my favorite subs.
i just realized he's a fellow leftie too. LHFTW
_We all know that to achieve the best sounding hardware, you'll need to gold-plate everything. The connector, the wires, the PCB, the insulators._
/s
hahaha nice one! :D
the enclosure... :D
Dammit, I forgot that.....
Ah, that explains all the gold-plated optical S/PDIF / Toslink cables for sale!
👀
And you need to use cryogenically frozen, unobtanium coated power cables made by nude virgins in utopia land for $9000
It is 25 years since I studied class A amplifier calculations, what a great explanation. I wish you had been my teacher at the time, you would have made it much easier! I built several BJT amps for college projects, always satisfying plugging them in and seeing the Vin vs. Vout.
I keep being surprised how simple most electronics are. For the longest time I had this block in my head, telling me to not even try understanding.
As soon as you properly understand the basics, everything else will fall into place ;-)
Just keep learning :)
Probably the biggest challenge of this project is finding a phone with a headphone jack ;)
you can get a usb c audio card thing i believe? then the unit only needs the usb c port!
@@Epsicronics USB-C (in fact ANY USB connection) only carries digital signals. So you'd need something that does digital to analog conversion plus supplying you voltage to run the amp.
That makes it quite more complicated.
@@Ni5ei I don't fully agree, i understand what USB is, and while this is more hacking than building, you could take a small usb c to audio jack adapter and fit it in the same case as the rest of the circuit, giving you both audio and power through the USB C interface.
@@Ni5ei no, it can also support analog audio via audio accessory mode, although this is not implemented on all phones (one plus, Xiaomi have it, but not pixel, Samsung).
If you want to do this with an external DAC, why not have a more powerful amp integrated after that DAC anyway? Fiio makes a few, either bluetooth or wired.
Bonus: LG V/G series owners can use the built in DAC in high impedance mode, it essentially does just this, look it up!
Wow, I feel like this is one of your best videos! Very short, simple, clear explanation and useful application. 10/10
Scott, you really make "complicated" things simple. It's education and entertainment as well. Stay tuned ;-)
Not to mention, he make simple things - complicated :) Like you can just use software audio volume increase, there is a lot of options :)
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for sure im joking, but
He's not called Scott XD
@@mr.coolio4321 what would be correct?
@@lernenmitrobin his real name is Jeremy Pascal, I'll send you the video link
@@lernenmitrobin here m.th-cam.com/video/0Xo0oKr8Thc/w-d-xo.html (it's not a Rick roll, I hate that stupid song)
Lovely! Will steal the design and build a higher voltage one for my 400 OHm headphones
Edit: I've done it! Adjusted the resistors to match the higher voltage and current required by my AKG 340 and it sounds unreal! Way better than it has any right to. Can be powered for hours on end with just a small 3s lipo as the power consumption is so low. I could also boost the 5V USB power from the phone up to 12, but I fear it would add noise...
Mods I did are: increase current to 30mA, adjust the bias voltage divider to work correctly at 12v (2.2k + 22k) and replace the bc337 with two bc238 (they were what I had lying around, as a bonus they have a Gain product of 250)
Edit2: been using it for days, it's downright amazing! So much so, that I've ordered all the necessary parts to build a proper one, with integrated battery + charger, and isolated 24V boost converter. I think I'll 3D print a cute case for it to make it pocketable and make it a daily carry gadget. I don't really care that it's not power-efficient either, since it'll be pushing 200mW per channel at most...
Hey Francesco, It's been a year or so but I wanted to ask if you ever built your final amp and if you still use it? I'm gonna dive into it as well for my Sennheiser HD569s (28ohm). Is the amp pretty loud with your AKG's? Do you still like the design? Have you made any changes or has there been any issues after a year? It looks like a really fun project
@@tgirard123 hi! It worked, but I couldn't make it produce decent sound reliability, I ended up using a speaker amp to power them.
When you started comparing the headphone audio I was expecting Scarlet Fire to play :-D
Headphones go dankkkkkkkkkkk
@linus femboy tips DankPods.
DankPods
Reunion: Life is a Rock
"Gotta turn it up louder--so my DJ told me!"
Dankpods!!
I started watching your channel from the very beginning and I had no idea what you were talking about. It's taken me 2 years at uni and now I finally actually understand!
Just want to thank you for always name-dropping JLCPCB. We designed some PCBs for at-home kits for engineering classes last semester and used JLCPCB to bulk fab them all way cheaper than anywhere else. And I only knew about them because of you. You saved the day for us!!
Upcoming:
Buílding the simplest hearing aid device
*yet most inefficient
I visited the Danish hearing aid producer Widex already 15 years ago. At that time they just started to give their hearing aids a modern and fresh design, because their customers were not any more the 60 year old roadworkers but the 20 year old ipod kids. Your „it is not loud enough“ might be already a sign of a hearing loss. Take care.
Pardon???
@@willofirony 🔇🔕🦻🏼🦻🏼
@@Herr_Bone Oh bullshit. iPod hearing loss is a hoax and a typical media scare. Hearing loss is induced by the city, with loud traffic, loud work environments, previously by machines in manufacturing jobs, now by open plan offices, disco and concerts if weekly, and drugs, amphetamine, molly and lsd can help you tolerate loud noises, but don't do much to protect your hearing, and there has always been some hearing loss in very young people just due to genetics, it was probably merely ignored previously, and the kids instead got punished for bad behaviour when really they just couldn't hear very well. I have spent all of my life in headphones, a lot of it in those with pretty high passive attenuation, a lot of it to suppress outside noises, but also listening to music a lot. I had done a hearing test a couple years ago, in my mid 30s, and i maxed out their measurement rig, i had an exceptionally good hearing threshold for my age group.
It's really cool that LG still provides built in 32 bit dacs in their phones.
True bro
@@mygfleftmeforatrans3593 your name. Damnnn
32-bit DAC’s are a scam though
@@lotrbuilders5041 how?🙄
Now if only they could engineer a phone that lasts longer than 6 months. I had 5 of them over the course of 2 years and they all failed due to bad solder allowing the chips to come loose over time.
The best quote that is in every one of your videos, `Let's get started!`
Thanks for the clear and simple explanation of the class A amp. I knew some of this bit learned something, too. Always enjoy listening to good teaching.
A follow-up with designing a PCB would be nice. I think this could actually be a project you could sell as small DIY-kits as it is actually practical, you can learn something and it is simple enough to solder it yourself :)
I feel like the point is to buy the needed parts yourself and learn a few things about eginering along the way
Great video as always 👍🙂
Thanks for sharing your knowledge to all of us 👍😊
My pleasure!
ive been having trouble understanding amplifiers and this made it easier for me to understand. thank you for including the links in the description as well!
I really like that kind of project with simple components and good explanations to cover the basics. Thank you very much !
having a jlcpcb cooperation but soldering the components in a curde way on perforated board.😂
Lol. You make good points ironically. But this guy I have to admit is a professional. It does make sense though to have him doing PCBs in collaboration with his sponsor.
@@trentjackson4816 of course, I watch him since this channel exists. But still think it’s a bit funny that he fist talks about the professional/cleaner way and then continues with the “quick and Dirty”.
litterally GreatScott!
@@gregory9211 mmmm I like the super neat and complicated handwriting. I am not going to throw any stones at any authors since I know that I could not provide the content and entertainment that they give. I lack the self-confidence and overall 'ability'
lol yeah i noticed that too😂
Great video! If I remember correctly from my classes at university, input and the output create a high pass filter, so input's cut frequency in your circuit with 10uF and an equivalent resistance of ~657 ohms (R1//R2//(Re*Beta)) is 24Hz which is fine but for the output you would need to have around 220uF to have a cut frequency of ~ 38Hz instead of the current ~837Hz you currently have. so you will hear more bass, which might not be so important if you are listening to audiobooks :)
I post the same comment. True, this need a bigger cap in the output.
Actually, you're missing the point that the output impedance of the amplifier (130R) is considerably greater than the load impedance (probably around 20R to 32R), and so the sum of those impedances is what determines the high pass roll-off frequency, which is actually more like 100-120Hz in this case. Using a 22μF capacitor would be fine as I seriously doubt that the headphones have any usable response below 50Hz.
Man... I recently started studying electrical engineering in Germany (Elektrotechnik) and it's pretty much mission impossible... Huge respect for your work GreatScott, keep it rolling!!!
I like how you put separations for each part of the video good job
More audio DIY's, they are so useful!
I will see what I can do :-)
@@greatscottlab simple multi connection wireless audio circuit!
@@MohitSharmaxp then just build a bluetooth receiver, there're super cheap half done products
greatscott: And just like that you can make an audio amplifier.
Everyone else: :0
Brilliant project. I am hard of hearing and usually like to have the volumes turned up on most things when using earphones. This is the perfect project for my phones and tablets. Thank you.
I could easily give answers to any questions because of you bro thanks to your detailed explanation
Could U show how to build an RF Power amplifier for Ham or Pirate Radio? Would be really cool.
I can put it on my to do list :-)
@Darren Munsell that can easily be fixed using a router such us the ac68 from Asus (tossing a random one there, just cause I'm familiar with it) and changing the stock antennas some some directionals one.
Run the router in access point mode, point the antennas where you need signal and you are done :)
Seriously thou, amplifying WiFi signals it's not an easy feat with DIY electronic, it's rather complex and really cost inefficient.
@@greatscottlab great👌
That's a can of worms yargggghh lol
@Darren Munsell Take a look at LORA communication... Maybe that's what you want.
You should do an update on the great scott intro, with a next gen LED PCB :)
My first audio amp was a pair of random mosfets connected to the audio pins of my pc and drawing 5V from a spare power supply pin on a bread board. A really fun and simple way to give my pc some decent sound and volume. Next time I should build a soldered one because loose pins vibrated and added static
I’d like to say I really enjoy your handwriting and design styles.
Thanks GS for another excellent video.
Please be careful with amplified earbuds. In a lot of cases, you can't fix damaged hearing.
That can not be stressed enough. When they started teasing me, I told the guys on my crew, any time you hear a ringing in your ear, it is permanent hearing damage. They all wear plugs now.
Dear, Great Scott this is good and usefull vedio,and may you explain about "mosfet driver transformer".
Ok coming soon
@@greatscottlab thank you.
Very basic audio circuit and with your explanation it becomes a very good tutorial indeed. Good job !
Thank you very much for your awesome video’s. I am a electrical student myself. And i love your explanation of the circuits.
I can't believe it took me this long to realize you're left handed, yet you don't smudge anything with your hand while writing.
What is this sorcery and tell us all your secrets! :D
Fast dry inks or learn to hover over the paper.
@@Broken_Yugo lol
Superb explanations usual. But doesn't having such a small value 10uF capacitor on the collector limit the bass response through your earphones? I would have thought maybe 100 or higher?
Since the amplifier has an output impedance equal to Rc (130R), the output at the earphones (likely around 32ohms impedance) is reduced by a factor of 32/(130 + Xc + 32), where Xc is impedance of the capacitor at a given frequency. When Xc is negligible at high frequencies, the reduction is fixed at 32/(130 + 32). So the -3dB frequency occurs when Xc = (130 + 32) ohms, not just the impedance of the earphones. A quick calculation show that 10μF has an impedance of 162 ohms at a frequency of about 100Hz. Although a 22μF capacitor might show a little improvement in bass response, I think you'll find a 100μF capacitor would be no improvement on that, as I seriously doubt anybody building their own amplifier owns earphones with a bass response extending down to 10Hz.
Thank you for the amplification basics video!
Thankyou, thankyou, thankyou....your video and links got me over a hump on tranistor amps.
Imagine walking into the plane with that plugged in
“uH sIr”
Anirudh Krishnan lol
You are my electronic teacher
Brilliant :-)
You gotta be the most creative electronic engineer out there ....big fan ....
Not only the diy, the facts, comparisons and details about circuit elements are the most important (for eng,tec students.) Excellent.. 👌
Thank you ❤
You're welcome :-)
I like your approach on this video. Keeping it simple and not bother with the advanced details, and ofc it works so why bother changing it.
BUT There are a few details tho when it comes to audio. You went with "Best sounding" in the title so a little slap on the wrist doesn't hurt ;)
Tental capacitors in audio path are typically a nogo as their capacity change versus the voltaqge which is across it. therefor you actually can get a different frequency response and distorsion.
Typically you also add a capacitor between collector and base to reduce oscillation(the easist explaination) Also known as "Miller cap"
A pulldown resistor on both input and output capacitor may save you a pop under startup
And more minor things but the tentals surely caught my eyes when i saw this video.
Miller capacitor on a single common emiter stage ? :) really?
You're right that tantalum capacitors in the signal path are frowned on in hi-fi applications, but if you look carefully, the voltage across each capacitor doesn't actually change at frequencies in the pass-band of the amplifier, so the change in capacitance with applied voltage has no real effect here. It probably doesn't matter with earphones if the cut-off frequency varies by a few Hz for frequencies below 100Hz because the earphones won't have much response there anyway.
It wouldn't hurt to add a small polyester capacitor (maybe in the range 30pF-300pF) from collector to base to roll off the highest frequencies - only bats would be likely to be affected if listening through the earphones. But it's really rarely necessary in a single stage common emitter - especially one with hardly any voltage gain.
"A bit of hot glue for stability"
Great Scott , 2021
it's satisfying to watch you draw the cirtuits. but what i miss at all is the link to the final ciruit you build in the description.
what amazing !!!
i enjoy each part of your video brother
Glad to hear that
Tantalums in audio path? What kind of 1960's madness is it? :D
You are right. They sound horrible in the audio path. They should only be used for decoupling. Use a small mks, mkt or mkp instead.
What about creating an esscencial class AB amplifier?
I've seen some with those C5200 A1943 transistors which are super simple for it's power.
(Not those class A ones, those don't work)
Im pretty sure you need to tweak the resistors a lot so both are in cutoff so its a pain
it is great project. it is not only a tutorial. it is like an education. great work. thanks a lot
Sometimes in design they add a bypass capacitor at the emitter to make AC analysis easy, then they match the input and output capacitor to the low and high critical response frequencies.
Make an AB class amplifier! Will be interesting see that 😁
I believe he has already.....as mentioned in the video
i love how he says cay-culate lol
Thanks for the video! I’ll actually build it right now, btw how is your musical career going? Maybe a Talkbox would be an awesome fun project as well :)
Hi @GreatScott!, I was wondering what pens do you use in your videos? Thank you for making quality content, I always make time to watch your videos.
do you keep reading my mind? i was thinking about building a class a amplifier to modify my little sisters toy with a microphone and small speakers
I do read minds.....
@@greatscottlab would it be possible to use an audio amplifier for iphones?
@@94mac sure just use a Bluetooth I2S Module
lol its just a cash register toy
Nice Work. For the future you could make an Upgrade with only a USB C connetion and a high quality DAC. Than it would be even more neat.
I'd like to see him design and build an R2R dac.
The DAC chip used in those USB-C adapters is hard to get by itself for less than a complete adapter and often are in very difficult to work with packages like WLP.
I like your Queen playlist at the beginning of the video!
Hey Scott, you always make great "A class" projects. Have you thought of making an A class metal detector.
FYI: if you solder around your phone like that, cover the screen with something because the solder spatter can damage the screen.
Fun project
Thanks 😁
Video came out today ur comment is one week ago
@@osa1121- Patreon supporter
@@osa1121- patreon exclusive...
@@attackaffection5444 oh now I understand
Interesting timing, last week my wife and I wanted to watch a movie and the sound level through my computer speakers was way too low even with the volume all the way up. I wound up designing almost this same amp to use between the output of my computer and the speaker input. I just left it on proto-board, as I doubt I'll need it again, it was just that one movie with the low sound. I powered mine with 12V from a bench supply. I learned to design amplifiers like this many years ago by reading a book called "Transistor Circuit Approximations" by Malvino. I think it's still in print, I highly recommend it.
Nicely done. Great build.
Watching the intro, I thought this video was sponsored by audible
Not quite
Raspberry pi pico project, tutorial!!
Noted!
@@greatscottlab 😄
@Greatscott , yes please .
Excellent project
I love your handwriting so much.
How have I never noticed your one week break?
No idea. I do it for 2 years now though.
Is there any chance of a version that is a USB DAC and Amp?
Not sure.....sorry.
Just add a usb dongle. Go to aliexpress and search for ALC5686. You'll see $10 circuit installed in a USB plug. It sounds like a dream. You'll need to add a battery though.
@@greatscottlab Ich beantrage eine Version mit DAC. Da hier ja noch mehr Ohrgenuss herausgekitzelt werden kann.
Leider ist hier das Angebot gerade im >100€ Bereich eher mau.
I mean the FiiO uBTR is a bluetooth and maybe USB DAC that you can connect to your phone over bluetooth or hook into a computer via USB and hook in a set of headphones or earbuds. Only runs $20USD on amazon. Or if you wanna shill close to 100USD on amazon theres the FiiO BTR3 bluetooth and confirmed USB DAC.
@@warmesuppe Antrag wird unterstützt!
As an old engineer, this tutorial was quite good. My process to choose R1 and R2 is different, but mathematically the same. Very good job.
Awesome Thanks for it got what i was looking for ❤️
My seeing a greatscott notification .Finger go brrr...
Niceeeeee
How to break off headphones jack and type-c in one go :)
BTW, if _some_ of your audiobooks are quiet, the amp is not the solution - raise the volume of the audio in software.
I Love your videos! It would be very interesting if you could compare external noise hifi psu vs wall bricks! 🙂
Cool! You are very talented, thanks for sharimg
Watching on my iphone and crying near a corner
Me too 🤣
Do it anyway
Rest in peace those guyys with no headphone jack!😂
Actually in this case it would just make the box smaller because you can get audio and power from just the USB C connector.
You could pass audio through the usb c / micro port, though that requires more complex solutions.
Not sure if getting the audio from USB Type C is easily possible with such a USB Type C breakout board.
@@greatscottlab
Yeah, you would need something to negotiate with the phone to pass audio, and a DAC on top of it.
@@greatscottlab well, there are some breakout boards with both.
This what I've been looking for
2years man I've been looking for this😭😭
Noting better than a break from study with great scott upload notification
Where's JLC PCB?
You can find their ad after my intro ;-)
Hardware solution to a software problem
Big fan and I love your creative works solid you make a perfect 12 volt battery charger
love your videos. Just wanted to chime in as somebody who has calibrated transducers for audiologists. the correct way to couple an insert earphone with a microphone is to use a coupling cavity that simulates your ear canal. you just need an air tight link between the mic and transducer that is about 20 cubic centimeters in volume. This will more accurately present the sound to the speaker in the same way you would have it presented to your ear. not really necessary for this application where you are taking a quick look but for any more precise determinations this is the proper method. Thanks for creating such great content for us!
Fun fact: You can do this with out any hardwork,money with full efficiency with basic apps that amplify sound
That's true!
@@greatscottlab yup
Thanks for replying ☺️
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Interesting, I was just looking at a design for a headphone amplifier the other day. I was originally looking at a class AB design since I assumed a small BJT wouldn't be able to drive them in class A with a 27 ohm impedance. But the guide looks pretty through, so maybe it's worth going through the process and trying it out.
I built this project with a PAM8403 and an OTC plug. It worked well but I was not sure if the otg was cheap enough for such a simple project. I have the same male type c plug. Thanks to you now I know how to supply my project with a cheaper and space saving 5v solution.
Further question. Is it possible to rearrange the type c plug to charge the phone at the same time? Or is it too much to ask from a simple project like this one?
This might be a handy project. Thanks.
Great Scott : with JLCPCB you can make custom pcbs that are super convenient for projects !!
Also Great Scott, 30 seconds later : so I used this piece of perfboard for my project
Its hard order a custom PCB and then wait week or more to deliver it. Maybe they weren't able to send the boards because of "health concerns in our current climate"
there's no need for ordering a custom pcb for such a simple project, bit wasteful of money
Your videos are realy well made, thanks for improaving the TH-cam
This makes me want to go to the basement and not come up until I have an amp for my phone. Super straightforward project. Thanks!
Nice video man!!
Nice explanation of the circuit diagram.
Great revision, thanks!
Very good explanation. Takes me back to my electronics technology coursework. :)
Glad you liked it!
That looks so professional in that case, nice one :)
Now it needs rgb for more power
I love this simple but we'll explained videos, i prefer them over complex long simplify projects. Both are great too xD
cool little Amp.... should there also be a decoupling cap across Re ?
Back in the college days I used to make and sell headphone boosters with LM386 amps running from a 9 volt battery.
Worked alright and 0.6 watts per channel went loud enough to make my ears ring. ha ha