The World's Simplest Audio Amp just got BETTER?! (MOSFET Amplifier)

[@johnbaldwin143]

I appreciate the way you revisit your past projects as it helps those with less experience 'like myself' to improve by learning.

[@greatscottlab]

My pleasure! And also I had to revisit it for a future home audio project of mine ;-)

[@johnbaldwin143]

@@greatscottlab Ah yes! Now that is just a part of the lesson. Thank you.

[@Runco990]

"Our imprecise ear cannot really tell apart such subtle differences" EVERY Audiophile in the world just got triggered!! 🤣

[@ABaumstumpf]

There are also people triggered when the shape of the earth comes up. But flerfers and audiophile alike can screen as much as they want: It does not change the facts. And i love it when the audiophiles claim that they can hear the difference between 24bit and 32bit 96kHz audio.

[@Pyrotek28]

FR tho. i noticed instantly

[@bansheedearg]

I went straight to op amps like the venerable 741 and hooked that up to an LM386 which, at 1 watt, is pretty loud. Since then I've moved to class-D board amps, which run on 35Vdc and are amazingly loud, run floor speakers, and are the size of a credit card. I use an old laptop power supply to run them, with a usb wifi dongle to make it work in our home theater.

[@greatscottlab]

Thanks for the feedback :-) Sounds like a fun journey ;-)

[@matikaevur6299]

Used opamp with resistor matrix DAC. even fitted both in (big) LPT port connector. Good old days.. sb-emu, LPT DAC and third-hand car speakers:) Wolfenstein never soundd so good before :) (nostalgically .. after, too)

[@bansheedearg]

@@matikaevur6299 cool =)

[@yanikb.1312]

My friend has a class-D amp, this thing sounds great, is really powerful and, as you said, tiny

[@petersage5157]

Collector feedback bias is even simpler, and since it has local negative feedback, should distort a bit less. The distortion of a single ended MOSFET is actually very close to that of a triode, and triode output amplifiers have been something of a holy grail for audiophools. That distortion adds a warmth that many people find more pleasing than a clean, undistorted signal.

[@Kirillissimus]

Thankfully today we have audio signal level standards in place so you can get away with just a single MCU with a built in ADC, PWM timer and an OpAmp combined with a MOSFET pair and 2 MOSFET driver ICs per channel. The "D class amplifier" is a nice and relatively simple project for MCU programming students, just don't forget to add a PolyFuse to the MOSFET power circuit to protect it from programming mistakes causing both transistors to open at the same time. And the best part is that you can even experiment with some DSP here starting from basic stuff like converting stereo to mono and pseudo-linear filtering up to FFT-based graphic equalizers and continue with more advanced stuff like synthetic chambers and stereo effect enhancement. The sound quality and the power you can easily get from the thing makes even quite advanced commercial analog solutions just pale in comparaison to even the simple kind of a project for electronics students. Just make sure to choose a powerful enough MCU for that, something at least with a Cortex-M4 running at lesst at 100MHz if you want to test all the modern techniques.

[@H3adcrash]

I've built a fair few higher power class A amps through the years. The biggest one was a stereo setup that drew 25A at 24V, requiring a lot of cooling and very big ceramic resistors. It sounded awesome though! Also a great space heater. Haha.

[@greatscottlab]

Haha sounds like fun :-) Thanks for the feedback ;-)

[@H3adcrash]

@@greatscottlab Hehe yeah it's a fun thing to tinker with! And the fact that everything just scales up the more power you want, it's a very simple thing to build if you have a bunch of high power components already. A vastly improved version that requires no massive resistors is the "Death of Zen" circuit form Elliott Sound Products. It's a lot more complicated and sounds just as good. So it takes away some of the simplistic charm of a big raw class A stage. Thanks for a great video as always! :D

[@Nachos-sk7od]

This video is really a reminder of how much fun people had exploring the possibilities of analog circuits before integrated circuits simplified every design. Nice work!😃

[@StanleyKubick1]

EDIT: it looked like the THD on the mosfet was happening at around -75db to -95db (circa) which is not really an issue in a small speaker like this and can be further mitigated with a good enclosure to the point of becoming insignificant. original comment: man, this is such a cool and practical project to draw in noobs like myself. I think I've been subbed since 2017-ish and this is the first project I'm going to attempt. I'm not sure what that says about your turnover rate, but I'm super thankful at least ;) ps. please consider doing a simple preamp some day

[@therealjammit]

Another problem with high power MOSFETs is that they were designed as switches. In other words they try to design them to go from "off" to "on" in a narrow range. By modifying the gate design and the geometry of the source and drain the turn on voltage doesn't operate as a linear input. It's what allows a power MOSFET to quickly turn on and off at high frequencies without a long transition period. I've used a tungsten lamp (like a car headlamp) for the collector or drain resistor. It has a non linear resistance and sort of acts like a current source, plus it was designed to get hot. You can get them for free if you check out a car repair shop. Most cars have a dual filament, so if the low beam goes bad the high filament still works.

[@piconano]

I'm not an audio guy, but I know Mosfets are very much suited for class-D amplifiers. With a good LC output filter, it can't be beat. Both in efficiency and sound quality. I guess that's why they're the most popular. Some chips are so efficient, they require no heat-sinks.

[@angofficial3738]

I have made these kinds of amplifiers quite a few times but thanks to you now I understand how they work quite clearly 😊

[@greatscottlab]

Glad to hear that! Cheers :-)

[@maheen-]

When I was 14 years old, I made an amplifier with this exact same mosfet but used a single resistor. I don't know how it works but I still remember the circuit. I added a 1k resistor between the gate and drain of MOSFET and connected the drain to the -ve terminal of a speaker, +ve terminal to a 5V supply, Source of MOSFET to the 0v rail and connected the audio into the Drain of the MOSFET. It works like magic.

[@putraadriansyah8082]

add a USB C DAC in the future amp project, so you can just use 1 cable to the phone/laptop to provide both small power and audio signal

[@greatscottlab]

Will do ;-)

[@gosdeCarrer]

A common way to approach it is to put first a pre-amp, e.g. your initial circuit, followed by a power amp circuit. The pre-amp just amplifies the voltage and focus on low noise and distortion. And the power amp adds the current (power) needed to drive the speakers. Also, low noise audio op-amps makes things simpler and modular. For example the ubiquitous NE5532, present in many audio devices for many years. Probably there is not a single piece of music in the world that has not gone through an NE5532 many times.

[@uwezimmermann5427]

The common emitter or common source configuration you are showing here is not really a good choice for a power amplifier. The low RDSon of the MOSFET is not at all utilized in this configuration since the current to the speaker is not actually passing through the transistor. That's unless you also make the drain resistor quite small, which would result in an unreasonably high quiescent current. But it's nice to see that you could make it working at all...

[@greatscottlab]

Thanks......I guess.

[@bentfishbowl3945]

A follower like it's usually done would have been more useful for driving loads, and can still be technically called an amplifier (of current). Or maybe just lots of feedback to have a low output impedance

[@matthope_qc]

If you want to improve efficiency, you need to start looking at Class A/B. Class A amplifier are not really scalable. Class A/B are easy enough to do with discrete components, but if you want there is "chipamp" solution that are efficient (50-70%) and has a good audio quality. I did a stereo amp using a LM4766 and it was surprisingly good. Overall a nice analog project to do for fun.

[@Sireoja]

I still use my wired headphones. Good audio quality, low price and no dead batteries to worry about in the future. Also 1 less device to charge every day.

[@featheredskeptic1301]

Class A amplifiers are fine, but if you want something more functional, you have to go to dedicated integrated circuits. Something like NJM2073 for instance (at least if you want it to be in a small package and working with low supply voltage).

[@Jenny_Digital]

I think voltage gain by bipolar followed by MOSFETs in push-pull and using feedback should do a nice job. The feedback can be used to tame the non-linearities.

[@nicholasmascioni3333]

This was a nice little project! I remember studying and building CE amplifiers like that in school

[@greatscottlab]

Glad you liked it!

[@jeremyfmoses]

Great Scott - If you're interested in audio amplifiers, I would direct you to the work of Nelson Pass and his Zen and First Watt series of amplifiers. The former are simple (but great sounding) class A DIY projects for instruction, and the latter are commercial products that he's released the schematics for. Pass himself hangs out in the DIY Audio forums, but there are lots of crazy audio/electronics enthusiasts there answering questions all the time.

[@敗北王測試用頻道はいぼく]

電晶體「我還可以戰上萬年」 MOSET「小晶體你太嫩了我將永久替代你」 電晶體「摩斯飛的你只不過是個我的變形體 你最大的弱點就是靜電」 MOSET「我的缺點也是你的缺點」 電晶體「…」

[@Disillusioned_one]

At 6.27 you should have decoupled the emitter with an electrolyte capacitor as without it you get very reduced volume.

[@kenengel620]

Great video! You should put something together on the various uses of an op-amp.

[@ABaumstumpf]

Wired headphones all the way: They don't need to be charged, drain the phone less (at least with the phones i tested it), and best of all: No losing anything just cause they drop out of your ears. The lack of a 3.5mm jack would not be so bad if phone-manufacturers at least used USB3s features - yes, it DOES offer the option for analog audio but sadly hardly any phone supports it.

[@lmbruguera]

Very good video, I really liked it. Very explanatory, I understood some concepts that I missed. Thank you

[@greatscottlab]

Glad to hear that! :-)

[@MCsCreations]

Fascinating stuff, dude! Thanks a bunch for the lesson! 😃 Stay safe there with your family! 🖖😊

[@greatscottlab]

Thanks :-) You too

[@AyebaleIsaacMagezi]

My electronics mentors. Big ups great scott, 🎉

[@greatscottlab]

Much appreciated

[@maneeshs3876]

Nice build Video 👍

[@haraldlonn898]

Nice. If you only want current amp. you can use a voltage regulator like the LM317 or eqv. and make a class A amp of it. Thanks for your great videos.

[@greatscottlab]

Cool, thanks

[@SKElectronics]

Class D would be great compact and efficient with pd trigger board we can get high voltage from mobile charger and get a high watt output at the speakers.

[@juansanchezserantes894]

Class D aren't really easy to grasp though. Not so good for a video. I would go from class A, to class AB, then filtering and FFT basics, PWM and then Class D. Maybe even some sampling theory.

[@roobisk]

Is this a speaker from a Logitech PC speaker system? I have a couple of those from a broken system and it looks very similar. Interesting video!

[@greatscottlab]

I actually think it is one. Thanks :-)

[@Pyrotek28]

So when we getting the vid on the nrf54l15? You know I'm dieing for it big bro. You teasing us or what!?!?!?!?!?

[@MML66]

I use an IEM so honestly I need a high quality DAC AMP with little or no noise but I might use this to make an electric motor speaker and turn it into a nicely impressive circuit and put it on wood or something else.

[@greatscottlab]

Go for it!

[@MML66]

@greatscottlab Thank you for the information. I will do that. Have a nice day

[@Electrophile-d4w]

Design a simple op amp amplifier which are much simpler to build and sounds great because they use class b amplifier at the output and gain is controlled by op amp

[@inventorsyndrome8894]

Annnnd I was just researching this topic Well Done

[@greatscottlab]

Hope it helps ;-)

[@electronichome1153]

The mic is connected to the amp right? Are you testing it for speech? It was not clear to me why you provide a distance of the microphone from the speaker. Because when you connect the music from your phone, you pass the audio signal from the audio jack to the capacitor circuit of the amplifier, isn't? Then why is the microphone still attached near the speaker? Or is it turned off in these tests?

[@kokodin5895]

did you try replacing the big resistor with 12 v 3-40 w light bulb? google bulb amp

[@Sysshad]

Interesting, i have never seen anyone build a MOSFET amp before as ive been told its a voltage amplifier and not a current amplifier like the BJT is, and that it wouldnt work.

[@RomanoPRODUCTION]

00:01:27 Mandatory smile checked

[@rhiantaylor3446]

Suggest you build a PLH amplifier if you want real quality from Mosfets.

[@greatscottlab]

Thanks for the feedback :-) I will have a look ;-)

[@tushar673353]

Those are simply Class AB and Class D

[@simonlenhard1712]

How funny. I was doing same audio amplifier in my prototype yesterday.

[@greatscottlab]

Did it work?

[@rene0]

The previous Nordic (nRF52) was a disaster for claiming half of memory for the wireless stack, placed hardcoded at an inconvenient place somewhere half away RAM space, as Blob. Both with Arduino/C and micropython (actually running when jumping hoops) i totally gave up on this supplier. Yes, i you have a need for their specific RF functionality, and are willing to (rewrite) your app to compile with their tools, they may be your game. As a generic uC, they suck big time. Maybe their new offering (N54) is better, but for pretty much anything we rather use an ESP32 which at least tries to standardize stuff. Yes, an ESP has inferior ADC and yes, all microcontrollers have their quirks. But i wasted way too much time working with Nordic, and am not willing to try again until properly supported. Your mileage may very, but i am not that smart.

[@Scott-e8h]

Me literally using corded headphones in my phone to watch this😂

[@atyla7067]

Which platform do you design 3d objects with?

[@TomboRectify]

Could a 2 channel Class-D TDA audio amplifier be used to drive a stepper motor? Stepper motors have coils, speakers have coils, what's the difference If I'd just give the TDA7266 two sine waves shifted by 90°, wouldn't that effectively be a silent stepper motor driver?

[@kelvin1316]

My modern phone has an audio jack because it isn't trash lol

[@JoeSmith-lo9wb]

Nope you haven't yet used bypass capacitor to make source ac gnd.

[@greatscottlab]

Yep. You can increase efficiency a bit this way and also lower distortion a bit. To keep it the World's Simplest Audio Amp though, I didn't include it here. Still pretty good quality results though.

[@JoeSmith-lo9wb]

@greatscottlab but this will also increase gain and just by using one more component it doesn't gonna be world's toughest amplifier circuit 😅

[@achhcityshorts4646]

can you make more videos abot where to salvage and what to salvage for spare parts please?

[@achhcityshorts4646]

and also imna give a challenge: make an oscilloscope

[@greatscottlab]

I can put it on my to do list :-)

[@achhcityshorts4646]

@@greatscottlab OH THANKS

[@rudolfvaavra8859]

only push-pull for this performance

[@greatscottlab]

Next time....maybe ;-)

[@Akuma_zenblood]

Hiii love your video and all your project ❤.. I have little knowledge tho ...but i want to learn more , is this type of amplifier Design called class A? This type of design swing only 0 to +0 unlike push pull method right? ...i build like this before just one transistor tip122 it produces alot of sound and bass but the distortion clipping I can't fix it ....

[@firenado4295]

can you do one of these but for a high gain amp? I really want to be able to get a line level output from a tape head so i can mess around with it on my pc. But I cant make a high enough amplification for it to would as the output from a tape head is so small. A nice simple design like this would be really convenient to make

[@greatscottlab]

Maybe my next audio project will feature a suitable circuit ;-) Stay on the lookout for that :-)

[@butterscotchpanda]

As someone who hates wireless stuff, and will be buried with her wired headphones, I am insulted by the first minute of this video! :P

[@Team_Reaper.]

can you make a mosfet push pull ampilifier

[@uninsignificant]

What is the name of the music used while playing the speaker?

[@Prashant5479]

It seems like the speaker only needs voltage changes for operation and not much current. If this is true, so instead of using a mosfet, would an opamp be a suitable candidate for signal amplification?

[@bclamore]

Speakers have a low impedance and so require a lot of current. You can also think of this in terms of the physics involved. Current creates a magnetic field in a wire. When you coil up the wire, the magnetic field multiplies. It's that magnetic field that interacts with the permanent magnetic in the speaker.

[@greatscottlab]

Well, both Voltage and Current is important. OpAmps can do voltage amplification excellent with their high gain and low distortion. However they can not provide that much current. That is why they are often "only" used as preamplifiers. As the output stage you can then use BJTs or (not optimal) MOSFETs to get more current flowing 🙂

[@SoonerRoadie]

I’m very much an electrical novice, but I think of it in terms of Ohm’s law. V=I*R ( voltage = current * resistance). Loudspeakers are often 8 ohms, sometimes 4. So to have a large voltage change the current has to be high as well. You could also think of it in terms of power - P = V * I; you have to have current to deliver power to the speaker.

[@baudneo]

How does a 6 minute old video have a 9 day old comment?

[@ammhg8642]

Why is your comment 9 days ago Video was released 5 min ago Or is it only me

[@Pr3Va1L]

Wouldn't that design be super noisy and prone to amplifying power supply noise? There's a reason we usually use a differential amplifier as the first stage.

[@greatscottlab]

Well, I did not experience any noise problems here......

Ac Great Job again!

[@greatscottlab]

Thanks :-)

[@NatasPvPMontagesz]

just build the "blameless" amplifier from dr. Self

[@bentfishbowl3945]

I recommend the books from Douglas self too

[@destiny_02]

wouldn't that mosfet circuit potentially Damage the phone, since audio in is connected to high voltage.

[@greatscottlab]

No. Because DC is "blocked" due to the input capacitor.

[@A3Kr0n]

There you go. Better, but not better, but doesn't matter to silly humans.

[@SimonBauer7]

id just use an opamp to trigger the mosfet.

[@dcallan812]

Interesting video 2x👍

[@greatscottlab]

Thanks :-)

[@achhcityshorts4646]

​@@greatscottlab can you make more videos for beginners and where to salvage parts bcoz im broke asf

[@krisnakant6454]

can you upgrade this amp to only deep bass amp plzzz

[@greatscottlab]

Sure. Simply use a filter to only let the low frequencies pass and get yourself a loudspeaker that is made for such frequencies and you are pretty much done ;-)

[@RetiredRhetoricalWarhorse]

It's so weird, I understand why things are happening, I understand the terms but for the life of me I have no concept of why the components are where they are or how they need to be calculated. I'm a pretty smart cookie. Very little has so far even remained outside my comprehension if I was interested in it. But for the live of me I cannot get the hand of electronic circuits.

[@greatscottlab]

Keep going and one day it all clicks. I promise ;-)

[@RetiredRhetoricalWarhorse]

@@greatscottlab I'm afraid I have many other areas where success is much quicker to find :D

[@dan2800]

isn't anything under 1% THD considered good

[@kalashnikov_47z]

Can you make a 12V to 220V inverter using farrarite transformer please! There is no such video on your channel

[@greatscottlab]

Not really interested in making a proper inverter design on this channel.

[@kalashnikov_47z]

​@@greatscottlab Thank you! 😢

[@lewin_sim5119]

Wohnst du in Sachsen anhalt ?

[@greatscottlab]

Why?

[@ACOnetwork]

I use wired headphones 😁

[@greatscottlab]

One of the few I would say. Or?

[@aadhil__kassim]

Same here.

[@ACOnetwork]

@greatscottlab I always prefered wire than wireless, only portable speaker is wireless (mostly) 😁. Maybe because I was born in the 80's is partial reason and preference 🤣😂

[@ee_fa_21]

Am I seeing an s24+ ?

[@muthumohan9947]

20watts class a amplifier

[@greatscottlab]

Next time? This was more like around 10W max.

[@crazyfurnaceguy1229]

Me: PAM8610 (10W per channel stereo Class-D audio amplifier chip) done! ¯\_(ツ)_/¯ 😂🤣

[@greatscottlab]

Haha also very very simple ;-)

[@tubeDude48]

👍

[@aryan1211_]

You said audio ampere instead of amplifier a lot of times😭

[@greatscottlab]

Maybe it only sounded like it.

[@aryan1211_]

​@@greatscottlab2:57 and i think another time before that, but great video I was recently researching about this

[@조민혁20]

Hack out usb C DAC

[@duong1123]

Are u a Samsung fan?

[@sultanshah9434]

You're video are very informative but people without proper electronic knowledge can't understand your video and it's value, that's why your normally videos get more view then a circuit related videos.

[@greatscottlab]

Probably true. But I like to make both kinds of videos ;-)

[@sultanshah9434]

@@greatscottlab and i also love yours all type of videos and watch them as soon as possible. Love your work , there are very few KZbinr available like you

[@bentfishbowl3945]

I think this a very basic video that is meant for beginners. People that know about audio electronics already don't have anything to learn from it

[@sultanshah9434]

@@bentfishbowl3945 i know that but not everyone is same. Even i can't understand his videos 5 years age

[@imaginitivity7853]

Next step, add some tubes to the front end...

[@greatscottlab]

Oh boy.....I tried tubes before in previous videos. Let's just say the topic is controversial

[@SpaceBird-Founder]

first

[@greatscottlab]

Well,....almost ;-)

[@SpaceBird-Founder]

@@greatscottlab oh my god he replied

[@b_70_saurabhvishwakarma84]

Big fan

[@sultanshah9434]

Bro i can buy more efficient and better quality amplifier so why should i make this amplifier?

[@greatscottlab]

This one you can usually build with spare parts you have at home and comes with outstanding quality. Only efficiency is terrible. Also understanding how amp work, really helps with understanding electronics in general :-)

[@volvo09]

It's a project you can build out of spare parts and mess around with. you don't have to build it.

[@hanyolo105]

I am using my cable headphones when I am making music on my phone. They are absolutly required since bluetooth has way to much latency to maintain a beat