@@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!
@@electroquests I have learned more from this one man's work on UA-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.
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.
@@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.
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”.
@@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'
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
Not to mention, he make simple things - complicated :) Like you can just use software audio volume increase, there is a lot of options :) . . . . . . . . . . . for sure im joking, but
@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.
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.
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.
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.
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 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
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)
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.
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 :)
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.
Oh damn I thought this was going to be for speakers. Still good video! But... Am I the only one that powers 2, 4 ohm Alesis Point 7s with an iPhone XS built in amp? Honestly I just did it for fun one day. Results are surprising. Distortion? A little not as much as you'd think surprisingly. Volume? About the same as a portable 10 watt Bluetooth speaker at 60% volume (Yes I tested this). Quality? Not too shabby, definitely not audiophile quality but if you don't care then its really not that bad. Lighting adapter get hot? Hell yes it did. Battery drop rapidly? Oooh yes. Why am I explaining this? Because I can.
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?
Nah, he just got the quiescent dc bias point for the collector too far away from the mid-point of the output range. It was a design error, nothing more. The circuit will work with a collector resistor of 260R at 10mA and will clip at just the same point as when you have a collector resistor of 130R at 20mA.
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.
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.
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
I was wondering ,what is the input impedance of the headphones, I saw 19 ohms on the multimeter, and that should load your 130 ohms collector resistor quiet heavily. 20mA peak into 19 ohms is 0.38v peak voltage and so it defies the amplification purpose all together
In practice, the earphone's ac impedance is likely to be more like 32 ohms typically, sometimes a little more. After all, a speaker is mainly an inductance at audio frequencies. Nevertheless, you're right that they will load the 130R collector resistor, perhaps reducing the output available by a factor of 4. Considering that the stage has an unloaded gain of around 5, it is true that not much amplification will be seen unless high impedance headphones are used.
That USB C breakout is flawed. You need *separate* pull-up or pull-down resistors for each of the CC pins. You cannot tie them together, or it will not work correctly in all circumstances! Also your description of the purpose of the emitter resistor is not quite there. When you build a degenerated class-A circuit like this, the emitter resistor linearizes the gain by essentially acting as negative feedback: With no emitter resistor, the collector current varies nonlinearly and very sharply with the base-emitter voltage. With the emitter degeneration, the voltage at the emitter of the transistor will change in proportion to the emitter current (which is proportional and roughly equal to the collector current) due to the resistor. This change will be much larger than the small change in the base-emitter voltage, and thus the collector current will be much more linear in relation to the base voltage with a lower gain. This gives you more leeway in your input bias network, and reduces the gain to a more manageable level. Ie ~= Ic. Ve ~= (Vb - 0.7). Ie = Ve/Re. Thus Ic ~= (Vb - 0.7)/Re your output voltage will be roughly Vs - Rc*(Vb-0.7)/Re and therefore the overall voltage gain (ignoring the DC offset) is approximately -Rc/Re. Much simpler than the non-degenerated version, where you have Vout = Vs - Rc*[Is * exp (Vb/Vt) * (1 + Vout/Va)], a very non-linear relationship. With careful biasing and a very small input signal this can be approximately linear, but with input signals varying by hundreds of millivolts and simple resistor biasing, it's not workable. It's also much more affected by unit to unit variation of the transistor.
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!
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.
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.
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.
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.
And all this because some bored Norm guys with not enough to do on their task list decided to force in a volume limiting threshold on the OS level. "To protect yourself from hearing impairment". Aaaahh yes.
Cool. I don't really care about the efficiency. My class A amp sounds the best and I can't feel a ton of heat coming off of it. The class D amps that are so ubiquitous these days are much more efficient but they sound l like crap in comparison.
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 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.
the LM3886 amplifier in combination with NE5532 preamp with tone setting potentiometers is pretty good... and i wouldn't buy a class A amp like this... i would make it way better (but still bad efficiency...)
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.
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.
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.
Great video!. You could have bypassed RE with a capacitor, in which case voltage gain would be around RC/re, where re is 26mV/Ic. Now, the voltage gain is RC/RE. If you put a trimer instead of RE with its wiper to the capacitor you could adjust the voltage gain. The design is ok its just a consideration, as you could drop Ic whilst obtaining the same gain.
Yes but you'd completely wreck the linearity of the circuit because the gain now becomes completely dependant on the instantaneous value of the collector current. The distortion from that is horrible.
@@matejmeza3930 Oh yes you will. That predominantly third harmonic distortion is completely independent of frequency and is very, very noticeable. I think you'll find that decent modern headphones produce a flatter response than older ones, There are databases of frequency responses available on the web, and searching for "headphone frequency response database" will gives you plenty of examples to check. For what it's worth, in-ear earphones usually have less bass response, and Apple EarPods shows a distinct roll-off below 100Hz.
@@RexxSchneider If you want linearity, slap in an opamp and add feedback. Or use multistage with seperate VAS and OPS and add feedback. If i understood the video, he wanted to get an amp that is eficient as he is powering it out of a phone. Of course the fidelity isnt good with a single CE stage driving relatively low impedant headphones. If we are talking about fidelity, its best to build a serious headphone amp to have distortion curves to taste. In case of modern music, a little of third harmonic does not hurt, even if it makes it crack, it makes it richer. With todays bass drum and autotune, the music is boring. So distortion is welcome ;) im joking of course
Let's be honest, this solution looks quite janky & ugly next to the elegant & beautiful enginearing marvel that is your phone, If you're interested in having high quality smartphone/Linux audio in whatever earphone/speakers you have, I recommend you root your phone, and try Viper4Android on phone, or Viper4Linux on Linux distros(if you have one of those, Viper4Windows lacks features ). Viper4Android not only has audio gain control, equilizer, surround sound options, but bass/clearity boost and Dynamic bass system with a large number of device configs, and much much more. I've tried Viper4Android with a 0.8USD cheapo earbuds, with V4A, the quality of audio was comparable to much more expensive 10-15USD earbuds. Only caveat is that you need root, but the improvement in audio quality in completely worth it. I bet not even Apple/Samsung earbuds sound that good by themselves.
Agree Viper is great, and Rooting is life changing smartphone user experience!! Now before to think about to buy a phone, first I look is it rootable or no lol
@@DrZipZwan yeh, once you get a taste of those sweet *_su_* per user privileges, you can't really go back to the boring & locked down state. I'll just have to get a year old phone and root asap warranty is over, till then, my trusted old phone for all audio-phile-ic needs
Really nice design! I really like how it connects to the phone. I wonder; Would this win a DIY vs. Buy video? Audio amps are cheap and small, and I believe the sound, for the spoken voice like an audiobook, is pretty good.?.
It would also introduce lots of ugly distortion, because of the BJT's inherent non-linear transfer characteristic. The emitter resistor is needed to swamp out the non-linearity and reduce distortion to tolerable levels.
Clipping sounds horrible? Tell that to all the rock and metal guitarists! Ps. How is your guitar playing going? Any more projects related to it? Effects or amps?
A few things to consider. 1. At the collector you have an impedance that is the parallel combination of the collector resistor (100 ohms) and the load resistor ( impedance of the headphones). With 22 ohm emitter resistor, this circuit offers no gain or attenuation with headphones at or below 32 ohms impedance, and it explains why attempts at lower bias current weren't successful because emitter resistor was big and the collector resistor was relatively small. The final results shows some decent amplification which means the headphones used were higher impedance. 2. If you want a 1 volt peak signal, for example on a 32 ohm speaker, there will be a peak current of 1 V/ 32 ohms = ~31 milliamps, so the ~20 milliamps flowing in the circuit will have a hard time with that requirement for lower impedance headphones. Emitter followers are great for driving lower impedance loads such as headphones (they represent a simple solution). 3. 10 microfarads at 1 kilohertz is 15 ohms worth of impedance, lower impedance headphones will have more gain for higher frequency audio signals than for lower frequencies signals. 100 microfarads seems a good deal, some electrolytic caps rated at 16 volts are small enough to fit in that case. 4. The base sits at around ~1 volt, would be bad if there was a loud signal with 500 millivolts+ peaks, would bring the base voltage below 0.6 - 0.7 volts required and cause distortion. And, good video, transistors and op-amps are worth exploring, we have many in our computers and smartphones :)
1. The collector current determines the output impedance (and input impedance but that doesn't matter in this case) and nothing else. I agree that the headphones used must have had a higher impedance than 32 ohms, otherwise there would indeed have been no overall gain. At lower collector currents, the ratio of Rc/Re would remain constant (hence the unloaded gain would be constant), but the effect of the larger collector resistor would naturally reduce the overall gain because of the increased attenuation into the fixed, low-impedance load. 2. The other way of looking at it is that a 32 ohm load would attenuate an unloaded signal by a factor of 5, so you would need a 5V peak signal unloaded to get 1V peak loaded. And getting 5V peak out of a circuit with a 5V supply is tricky. Emitter followers look like a good solution until you realise that they still have to supply that peak current into the load, so an emitter follower stage would have to have a high enough emitter current to have a low enough emitter resistor. You might as well just increase the collector current in the common emitter stage and do away with the complication of a second stage. (Note that this only applies in this case because lowering the _input_ impedance of the stage won't cause a problem because of the low impedance drive from the phone.) 3. 10μF at 1kHz is around 16 ohm impedance, but that's still negligible compared with the 130R output impedance. The -3dB frequency is when the capacitor's impedance equals the sum of the output and load impedances, which would be around 100Hz for a 30 ohm load. Maybe use 22μF, but anything more is a waste of space and money. Check that the voltage at a 32 ohm load is given by the resistive divider formula: 32R / (130R + Xc + 32R). That shows why the -3dB frequency is when Xc = 162R, not when Xc = 32R (as it would be if the amplifier had a very low output impedance). 4. You really need the base to sit at about 900mV to maximise the gain, but the circuit is crippled by the load impedance being so much smaller than the output impedance. If you raised the base voltage to say 1.5 volt in order to cater for 500mV inputs, you'd have to increase the emitter resistor to around 42R to keep Ic=20mA. But then the gain of the loaded circuit would be reduced below 1, which kind of defeats the purpose of the project. Also, a negative 500mV implies a 1Vp-p signal input, and this circuit hasn't the supply headroom to amplify that by very much anyway, without worrying about the input excursions. Actually, although I've criticised some of your commentary, I very much appreciated that you've considered so many factors. I probably agree with a lot more of what you wrote than I disagreed with, apart from the fine detail.
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.
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
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!
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
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.
@@electroquests I have learned more from this one man's work on UA-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
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.
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 :)
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😂
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!!
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.
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.ua-cam.com/video/0Xo0oKr8Thc/v-deo.html (it's not a Rick roll, I hate that stupid song)
greatscott: And just like that you can make an audio amplifier.
Everyone else: :0
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
Imagine walking into the plane with that plugged in
“uH sIr”
Anirudh Krishnan lol
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.
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.
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.
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
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
"A bit of hot glue for stability"
Great Scott , 2021
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
You are my electronic teacher
Brilliant :-)
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'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.
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.
Make an AB class amplifier! Will be interesting see that 😁
I believe he has already.....as mentioned in the video
Oh damn I thought this was going to be for speakers. Still good video!
But... Am I the only one that powers 2, 4 ohm Alesis Point 7s with an iPhone XS built in amp? Honestly I just did it for fun one day. Results are surprising. Distortion? A little not as much as you'd think surprisingly. Volume? About the same as a portable 10 watt Bluetooth speaker at 60% volume (Yes I tested this). Quality? Not too shabby, definitely not audiophile quality but if you don't care then its really not that bad. Lighting adapter get hot? Hell yes it did. Battery drop rapidly? Oooh yes. Why am I explaining this? Because I can.
damn that's actually really cool. Makes sense though.
Raspberry pi pico project, tutorial!!
Noted!
@@greatscottlab 😄
@Greatscott , yes please .
I like your Queen playlist at the beginning of the video!
i love how he says cay-culate lol
Really It greatly satisfying my curiosity.👍
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.
good video, nicely explained but what the f. was that outro
Hardware solution to a software problem
You could get audio from that type c port...
Watching the intro, I thought this video was sponsored by audible
Not quite
If you really love music your major video on audio subject. Don't lie. Just few class a ab and d video not enough.
Dear, Great Scott this is good and usefull vedio,and may you explain about "mosfet driver transformer".
Ok coming soon
@@greatscottlab thank you.
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?
Nah, he just got the quiescent dc bias point for the collector too far away from the mid-point of the output range. It was a design error, nothing more. The circuit will work with a collector resistor of 260R at 10mA and will clip at just the same point as when you have a collector resistor of 130R at 20mA.
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!
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
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.
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
You should do an update on the great scott intro, with a next gen LED PCB :)
I was wondering ,what is the input impedance of the headphones, I saw 19 ohms on the multimeter, and that should load your 130 ohms collector resistor quiet heavily. 20mA peak into 19 ohms is 0.38v peak voltage and so it defies the amplification purpose all together
In practice, the earphone's ac impedance is likely to be more like 32 ohms typically, sometimes a little more. After all, a speaker is mainly an inductance at audio frequencies. Nevertheless, you're right that they will load the 130R collector resistor, perhaps reducing the output available by a factor of 4. Considering that the stage has an unloaded gain of around 5, it is true that not much amplification will be seen unless high impedance headphones are used.
Wow, I feel like this is one of your best videos! Very short, simple, clear explanation and useful application. 10/10
That USB C breakout is flawed. You need *separate* pull-up or pull-down resistors for each of the CC pins. You cannot tie them together, or it will not work correctly in all circumstances!
Also your description of the purpose of the emitter resistor is not quite there. When you build a degenerated class-A circuit like this, the emitter resistor linearizes the gain by essentially acting as negative feedback:
With no emitter resistor, the collector current varies nonlinearly and very sharply with the base-emitter voltage. With the emitter degeneration, the voltage at the emitter of the transistor will change in proportion to the emitter current (which is proportional and roughly equal to the collector current) due to the resistor. This change will be much larger than the small change in the base-emitter voltage, and thus the collector current will be much more linear in relation to the base voltage with a lower gain. This gives you more leeway in your input bias network, and reduces the gain to a more manageable level.
Ie ~= Ic. Ve ~= (Vb - 0.7). Ie = Ve/Re.
Thus Ic ~= (Vb - 0.7)/Re
your output voltage will be roughly Vs - Rc*(Vb-0.7)/Re
and therefore the overall voltage gain (ignoring the DC offset) is approximately -Rc/Re.
Much simpler than the non-degenerated version, where you have Vout = Vs - Rc*[Is * exp (Vb/Vt) * (1 + Vout/Va)], a very non-linear relationship. With careful biasing and a very small input signal this can be approximately linear, but with input signals varying by hundreds of millivolts and simple resistor biasing, it's not workable. It's also much more affected by unit to unit variation of the transistor.
Watching on my iphone and crying near a corner
Me too 🤣
Do it anyway
Bold of you to assume phones have headphone jacks nowadays
Most have
FYI: if you solder around your phone like that, cover the screen with something because the solder spatter can damage the screen.
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!
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.
RIP the headphone jack on newer phones
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.
You should do an Arduino alternative video on the raspberry pi Pico microcontroller.
Great video as always 👍🙂
Thanks for sharing your knowledge to all of us 👍😊
My pleasure!
FYI adding a 10uF capacitor across the collector resistor will increase your gain considerably.
No, it really won't.
How have I never noticed your one week break?
No idea. I do it for 2 years now though.
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.
Fun project
Thanks 😁
Video came out today ur comment is one week ago
@@osa1121- Patreon supporter
@@osa1121- patreon exclusive...
@@attackaffection5444 oh now I understand
Pls Make a stereo power amp which can make loud sound in stereo speakers and can be mounted directly to the phone
My seeing a greatscott notification .Finger go brrr...
Niceeeeee
Your videos are realy well made, thanks for improaving the UA-cam
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.
And all this because some bored Norm guys with not enough to do on their task list decided to force in a volume limiting threshold on the OS level. "To protect yourself from hearing impairment". Aaaahh yes.
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.
Cool. I don't really care about the efficiency. My class A amp sounds the best and I can't feel a ton of heat coming off of it. The class D amps that are so ubiquitous these days are much more efficient but they sound l like crap in comparison.
Where's JLC PCB?
You can find their ad after my intro ;-)
Hi genius, I tried to make the laptop fingerprint scanner on my PC(usb) but i failed, can you help me ??? Or can you put a video on this idea?
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 ☺️
You could just install viper4android app. It's really amazing booster audio
video:47second ago
comment:4 days ago
Patreon
Patreon supporter can watch earlier.
Why you didn't install one ui 3.0 update
nice amp project... er.. automatic deafening apparatus! I will build and gift to people I do not like!
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
can we have a pcb advert for a company based in Europe for a change?
Excellent project
Can you plz make a video on
Automatic liquid dispenser without Arduino DIY or BUY
Watch my cocktail machine project
I have seen that but I am kid though it's too hard and expensive for me , hoping for a reply:)
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.
Please do a video to make a home Inverter. (12v dc to 230v Ac)
Do same project just with usb c my phone doesn't has headphone jack 😕
Nice old school project, no arduino at all 👍
the LM3886 amplifier in combination with NE5532 preamp with tone setting potentiometers is pretty good...
and i wouldn't buy a class A amp like this... i would make it way better (but still bad efficiency...)
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.
What polarity am I supposed to put the capacitors? also, if I wire in a potentiometer, do I hook that up to power?
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.
why not use an lm386 op amp with a low gain value
@great Scott
Are u lefty??👍👍
Contrlino has lots of pin left for work
cool little Amp.... should there also be a decoupling cap across Re ?
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.
bro i am your big fan
Or root your phone
Great video!. You could have bypassed RE with a capacitor, in which case voltage gain would be around RC/re, where re is 26mV/Ic. Now, the voltage gain is RC/RE. If you put a trimer instead of RE with its wiper to the capacitor you could adjust the voltage gain. The design is ok its just a consideration, as you could drop Ic whilst obtaining the same gain.
Yes but you'd completely wreck the linearity of the circuit because the gain now becomes completely dependant on the instantaneous value of the collector current. The distortion from that is horrible.
@@RexxSchneider i know, but you probably wont hear it anyway trough modern headphones which only output bass.:)
@@matejmeza3930 Oh yes you will. That predominantly third harmonic distortion is completely independent of frequency and is very, very noticeable.
I think you'll find that decent modern headphones produce a flatter response than older ones, There are databases of frequency responses available on the web, and searching for "headphone frequency response database" will gives you plenty of examples to check. For what it's worth, in-ear earphones usually have less bass response, and Apple EarPods shows a distinct roll-off below 100Hz.
@@matejmeza3930 The link for the Apple EarPods report is reference-audio-analyzer.pro/en/report/hp/apple-earpods.php
@@RexxSchneider If you want linearity, slap in an opamp and add feedback. Or use multistage with seperate VAS and OPS and add feedback. If i understood the video, he wanted to get an amp that is eficient as he is powering it out of a phone. Of course the fidelity isnt good with a single CE stage driving relatively low impedant headphones. If we are talking about fidelity, its best to build a serious headphone amp to have distortion curves to taste.
In case of modern music, a little of third harmonic does not hurt, even if it makes it crack, it makes it richer. With todays bass drum and autotune, the music is boring. So distortion is welcome ;) im joking of course
Лайк за видео! Автор, напиши пожалуйста марку авторучки, которой ты писал. Давно я искал такую.
это Stabilo point 88
Let's be honest, this solution looks quite janky & ugly next to the elegant & beautiful enginearing marvel that is your phone,
If you're interested in having high quality smartphone/Linux audio in whatever earphone/speakers you have, I recommend you root your phone, and try Viper4Android on phone, or Viper4Linux on Linux distros(if you have one of those, Viper4Windows lacks features ).
Viper4Android not only has audio gain control, equilizer, surround sound options, but bass/clearity boost and Dynamic bass system with a large number of device configs, and much much more.
I've tried Viper4Android with a 0.8USD cheapo earbuds, with V4A, the quality of audio was comparable to much more expensive 10-15USD earbuds.
Only caveat is that you need root, but the improvement in audio quality in completely worth it. I bet not even Apple/Samsung earbuds sound that good by themselves.
Agree Viper is great, and Rooting is life changing smartphone user experience!!
Now before to think about to buy a phone, first I look is it rootable or no lol
@@DrZipZwan yeh, once you get a taste of those sweet *_su_* per user privileges, you can't really go back to the boring & locked down state.
I'll just have to get a year old phone and root asap warranty is over, till then, my trusted old phone for all audio-phile-ic needs
Really nice design! I really like how it connects to the phone. I wonder; Would this win a DIY vs. Buy video? Audio amps are cheap and small, and I believe the sound, for the spoken voice like an audiobook, is pretty good.?.
how the f you commented 1 week ago
@@Mark-tv4df patreon early access I believe
did you consider adding capacitor between emitter and gnd? It would result with better amplification ratio
See 8:38
It would also introduce lots of ugly distortion, because of the BJT's inherent non-linear transfer characteristic. The emitter resistor is needed to swamp out the non-linearity and reduce distortion to tolerable levels.
Clipping sounds horrible? Tell that to all the rock and metal guitarists!
Ps. How is your guitar playing going? Any more projects related to it? Effects or amps?
Still playing guitar. Just learned "Imagine" and "Yesterday". Guitar projects will definitely come sooner or later :-)
@@greatscottlab Yay!
A few things to consider.
1. At the collector you have an impedance that is the parallel combination of the collector resistor (100 ohms) and the load resistor ( impedance of the headphones). With 22 ohm emitter resistor, this circuit offers no gain or attenuation with headphones at or below 32 ohms impedance, and it explains why attempts at lower bias current weren't successful because emitter resistor was big and the collector resistor was relatively small.
The final results shows some decent amplification which means the headphones used were higher impedance.
2. If you want a 1 volt peak signal, for example on a 32 ohm speaker, there will be a peak current of 1 V/ 32 ohms = ~31 milliamps, so the ~20 milliamps flowing in the circuit will have a hard time with that requirement for lower impedance headphones. Emitter followers are great for driving lower impedance loads such as headphones (they represent a simple solution).
3. 10 microfarads at 1 kilohertz is 15 ohms worth of impedance, lower impedance headphones will have more gain for higher frequency audio signals than for lower frequencies signals. 100 microfarads seems a good deal, some electrolytic caps rated at 16 volts are small enough to fit in that case.
4. The base sits at around ~1 volt, would be bad if there was a loud signal with 500 millivolts+ peaks, would bring the base voltage below 0.6 - 0.7 volts required and cause distortion.
And, good video, transistors and op-amps are worth exploring, we have many in our computers and smartphones :)
1. The collector current determines the output impedance (and input impedance but that doesn't matter in this case) and nothing else. I agree that the headphones used must have had a higher impedance than 32 ohms, otherwise there would indeed have been no overall gain. At lower collector currents, the ratio of Rc/Re would remain constant (hence the unloaded gain would be constant), but the effect of the larger collector resistor would naturally reduce the overall gain because of the increased attenuation into the fixed, low-impedance load.
2. The other way of looking at it is that a 32 ohm load would attenuate an unloaded signal by a factor of 5, so you would need a 5V peak signal unloaded to get 1V peak loaded. And getting 5V peak out of a circuit with a 5V supply is tricky. Emitter followers look like a good solution until you realise that they still have to supply that peak current into the load, so an emitter follower stage would have to have a high enough emitter current to have a low enough emitter resistor. You might as well just increase the collector current in the common emitter stage and do away with the complication of a second stage. (Note that this only applies in this case because lowering the _input_ impedance of the stage won't cause a problem because of the low impedance drive from the phone.)
3. 10μF at 1kHz is around 16 ohm impedance, but that's still negligible compared with the 130R output impedance. The -3dB frequency is when the capacitor's impedance equals the sum of the output and load impedances, which would be around 100Hz for a 30 ohm load. Maybe use 22μF, but anything more is a waste of space and money. Check that the voltage at a 32 ohm load is given by the resistive divider formula: 32R / (130R + Xc + 32R). That shows why the -3dB frequency is when Xc = 162R, not when Xc = 32R (as it would be if the amplifier had a very low output impedance).
4. You really need the base to sit at about 900mV to maximise the gain, but the circuit is crippled by the load impedance being so much smaller than the output impedance. If you raised the base voltage to say 1.5 volt in order to cater for 500mV inputs, you'd have to increase the emitter resistor to around 42R to keep Ic=20mA. But then the gain of the loaded circuit would be reduced below 1, which kind of defeats the purpose of the project. Also, a negative 500mV implies a 1Vp-p signal input, and this circuit hasn't the supply headroom to amplify that by very much anyway, without worrying about the input excursions.
Actually, although I've criticised some of your commentary, I very much appreciated that you've considered so many factors. I probably agree with a lot more of what you wrote than I disagreed with, apart from the fine detail.
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.
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