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

Parts list (affiliate links):

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.

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

[easyelectronics]

After 4 years of engineering some of my basic doubts got cleared😂 thanks for the video🙌

[navid]

Really like your writings and sketches. They are so helpful.

[Niei]

Probably the biggest challenge of this project is finding a phone with a headphone jack ;)

[coccoborg]

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...

[nobodyleftbehind]

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.

[Asu]

_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

[matejpavel]

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.

[lernenmitrobin]

Scott, you really make "complicated" things simple. It's education and entertainment as well. Stay tuned ;-)

[burt]

When you started comparing the headphone audio I was expecting Scarlet Fire to play :-D

[shinnok]

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!!!

[GauravSharma-dyxv]

It's really cool that LG still provides built in 32 bit dacs in their phones.

[codebeat]

I made a similar device in the past but with a class D amp inside that can be used with a set of audio speakers. In the past it only worked with several phones with a powerful OTG connection but now since USB-C it is not a problem anymore. Let the party begin, grab some speakers and take it to the garden and enjoy 2x5w of audio. 😀👍

[ganopterygon]

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 :)

[paulho]

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!

[victorbarroscoch]

Wow, I feel like this is one of your best videos! Very short, simple, clear explanation and useful application. 10/10

[D.Axtmann]

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 :)

[Mojomanultra]

greatscott: And just like that you can make an audio amplifier.
Everyone else: :0

[vickielawson]

I like your Queen playlist at the beginning of the video!

[gregory]

having a jlcpcb cooperation but soldering the components in a curde way on perforated board.😂

[marklatimer]

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.