Understanding Amplifier Class A & Class AB

[@davidmiller8618]

This video really made me think! That capacitor in the output is not as simple as it seems at first. Excellent! Thanks for taking the time to really walk through that. You make several good points that are often skipped completely. Thumbs up!

[@johncunningham5435]

I am a retired engineer; always nice to have a refresher, "excellent presentation", thanks Tony.

[@I-Libertine]

Beautiful and thorough explanation. Best video I've found covering this question. Thanks!

[@SteveBrace]

I understood all this "instinctively"... I have been playing with electronics since I was 7 years old, I trained as an electronics technician-engineer in the 80s and I'm now in my mid-50s. I watch basics edutorials like this to fill holes in my understanding and you, sir, have educated me in a thing that sometimes trips me up! NEVER be too proud to admit that there are some things you have basically misunderstood.

[@billmcdonald2436]

See this video is a prime example of why KZbin needs a “love” button along side the thumbs up “like” button. Thank you so much Tony for putting this together. You are an excellent teacher and I’ve learned so much from your channel.

[@g.fortin3228]

Digging back through the videos.. So thankful for these as they are helping me to get my head wrapped around the operation of the amps and understanding the circuit better than I was. Great explanations, you are doing the vintage audio DIY community a service like no other. Many thanks ! I may now be able to solve some problems as I continue to learn .

[@johnmarchington3146]

Thanks or another great video. I built my class A amplifiers from a renowned circuit that had been upgraded for extra power output and ease of 'setting-up' adjustments. They each have four output transistors - all NPN types - and produce between 50 and 60 watts into 8 ohms, drawing over 3 amps quiescent current so the ample heatsinking definitely get warm. I'm very pleased with their sound quality.

[@TheZacharySutliff]

Thank you. This video was very informative and easy for me to understand with your explanation. I can’t wait to learn more. My passion for audio has fueled my desire to learn and I’m glad I found your channel.

[@BStrapper]

By very far the best video i have ever seen explaining the basis of audio amplifiers.

[@marcodoria]

You don't confuse anyone! Hope you keep up the good work for a really long time! Be safe and thank you sir! Best wishes from the Azores, Portugal!

[@osliverpool]

That's by far the best explanation of class A and class AB I've ever seen, thank you. I have a scope, and you've inspired me to get a breadboard now and have a play!

[@isoguy.]

You have an amazing mind Sir and an incredible talent for teaching. Thank you for this awesomely educational lesson ⭐⭐⭐⭐⭐

[@SinnerSince1962]

All of my life I've heard audiophiles explaining how important it is to get DC offset and idle current right, never knowing exactly why. Now, I know. Thanks Tony for this graphic and well demonstrated explanation! You rock!

[@Snwman_]

Thank you for your time and effort in putting this wonderfully explained video together. Kind regards from the UK.

[@bannanafruitsalad]

As a self tought student, this was a godsend. I feel like my knowledge was always fuzzy when it came to how amps worked and this really cleared up what was going on, at least in class a amps lol. Thank you!

[@henry-o7236]

This has to be the best explanation of transistors and amplifiers hands down. Your explanations are very clear and easy to understand. Thank you very much for such a great job.

[@bparker86]

an hour and 21 minutes of gold. thank you for this fantastic breakdown on ac and dc waveforms and bias and transistors. ive learned so much from this and ill be watching several more times. thank you again for this!!!!

[@bugdrvr]

Thanks for taking the time to put this video together. It's very informative!

[@pda49184]

Great tutorial Tony... I'm an amateur tinkerer and it never hurts to have the basics drilled in ...

[@anthonyderosa5181]

Well done Tony. Great video. Very good explanations of some very important concepts. The three diodes are drawn backwards on your schematic. IMHO if the volts/div settings were the same when showing the input signal versus the output signal , the amplification of the transistor would be easier to appreciate. I love your woodworking skills... the cabinet you made for the Marantz 2500 was awesome!

[@georgeh1352]

Very good, swept away a few cobwebs and learnt a few things new. Much better explained and demonstrated than lecturers I've had before.

[@tonybalm1513]

My late Father taught me this many years ago but my understanding kinda got a bit rusty since. I was a little confused to start with but all became clear as the video went on. This is by far the best explanation video on here of how different class amplifier's work. You mentioned Pioneer amplifiers and non switching. I have the A70 which is non switching but has two high current 50V & 70V rails. I am still from the circuit diagram trying to understand how this works. I think you worked on a Carver which was class G with two voltage rails. I don't think it is class G but may be class A at lower volumes it seems to sound much smoother and warmer. If you turn the volume up it seems to sound less warm and slightly harsh. This is an outstanding video. Thank you

[@matthewh4550]

Thankyou for putting this video together, it really helped me understand this topic after quite a few failed attempts at doing so from reading alone. Much appreciated!

[@mr-iago]

The Best video explaining amplifiers I have seen up until now :).

[@kennyrmurray]

You are the only one that finally made me understand this as I am an amateur. Thanks again, and you also stay well!

[@brianfletcher9774]

Tony, I figure working on medical equipment pays very well. However...why are you not a teacher at the technical college level ? You and Uncle Doug (he has his KZbin channel). I WISH I had you guys as instructors when I went to electronics school in 1997. You are a gifted individual ! Thank you so much. I learn more now than I did in school.

[@scrappy7571]

Thanks Tony! This one really helped me to understand the DC bias, and how the transistors work in a amp.

[@brucebuckeye]

Awesome video! This puts together many things in my head, connecting dots that I've needed to connect! Thanks so much!!

[@kristiannaess5565]

A very useful video that contains what I needed to get the basic understandings of Class A and A/B amps. I enjoyed it very much and it inspired me to do some simulations and circuit building :-)

[@michaelpeck8868]

Hi Tony, I'm just starting to get into electronics for a hobby and this was the first of your video's I seen. I just wanted to say thanks the the great explanation of what BIASing is and how to use it. Looking forward to watching more of your Video's.

[@robbspro]

Thanks Tony! your video was of great help! I appreciate your patience in discussing theory and practice! Great!

[@lukenicholls2522]

Great explanation. I'm trying to diagnose a faulty Rotel 1062 and this has helped me understand the circuit diagram a lot!

[@stevegwardify]

Greeting from England, What an awesome channel, great work. I look forward to watching your videos from the bench and your wood shop.... Thank You.... P.S just bought my first Scope...

[@mangist]

Amazing video, I wish books could explain this concept the way you do. Thank you.

[@ronaldolehrbach]

That was a great, great teaching! Very good explanation, with very good practical demonstrations. Thank you so much! I am looking forward to learning more with your help!

[@martovify]

superb, this went step by step on why each component is there and why it cant be as one would imagine it in the first place!

[@sandraledger2612]

You are doing a great job explaining. Now throw in an explanation of the datasheet transistor curves, choosing Q point and load lines.

[@petrisz]

Thank you for all your effort and time. Now I understand this topic much better.

[@dhpbear2]

12:27 - Wow. This is SO much better than the DC I'd been listening to :)

[@johnmarchington3146]

Thanks Tony for an excellent video on class A amplifier biasing.

[@siavoshkasravi398]

I am in the middle still, 38:04. Its amazing thank you. Answering the exact questions I had.

[@losaminos59]

Good stuff man! Really like your style of teaching this

[@garrybrewster5821]

god bless, i've had some training with tube and transistors manly RF, this has re-started my interest, I've always had a little trouble with biasing (TR cut-off) this has helped a lot ....thank you

[@ronaldpaul533]

good video. I watched the whole thing. I have a better understanding on how both work now.

[@Conservator.]

Thank you for a crystal clear explanation. 🙏 1:20:37 Yes, I’m still with you! 😉

[@C0wb0yh3nk]

Tony, you drew the diodes in the wrong way around or are they zeners?

[@xraytonyb]

I drew them wrong. That's what happens when you get in a hurry. Thanks for catching that!

[@widecast]

But then why would you draw 3 zenor diodes in series. As explained they are drawn the wrong way around.

[@C0wb0yh3nk]

@@widecast here is a new concept for you: en.wikipedia.org/wiki/Sarcasm

[@Wicker83]

Easily within the top five of all videos I've watched on this subject......Great Work! Thanks

[@davids4610]

Tony, you're an amazing teacher! Thanks

[@elinbenson]

I've been waiting for someone to make a video putting all these concepts together. I have an amateur understanding of all of this, but I haven't had someone connect all the dots. I think your explanation was great.

[@Mrsteve4761]

Very enlightening and understandable to this beginner of electronics. Thanks for this!

[@DJVybeBeats]

This is such an excellent video. Thank you very much Tony.

[@walkertownvet4108]

Very good. Cleared up a lot of questions I had. Thank you!

[@wobboonstra9290]

Great explanation, great video Tony, learned something again. Look forward to the next series.

[@highflyingfalcon1380]

It's very helpful for me! Thank you for spending your free time for us!

[@mcaddc]

Thanks for the easy to follow information & explanation! Love the presentation!

[@alanvandusen76]

Well done, Even with a what I think is a good understanding of how they all work I proved tonight even an old dog can learn a new trick. Thanks for the great lesson.

[@oskarsfreimanis8192]

One of best explanations ever! Thank you very much!

[@tonysfun]

Very nice Tony (I'll remember your name easy!)! You are a working electronic dictionary and I just wish you are my neighbor! In my case, I'm trying to learn after 50+ years of inactivity in electronics and it is much harder to learn than back in my teen age.... Thank you for details and explaining everything! I'll show your videos to my friends Sunday and Monday in our meetings.

[@magrumb]

Easiest to understand and well explained video on the subject!💙

[@danadaniels4812]

What is the brand and model of your breadboard you are using at the start of your video.love your channel

[@PeterMilanovski]

Great video Tony, What I would love to know is what effect would the ESR of the output capacitor have on the output signal? Would more smaller capacitors with very low ESR be better than a single larger capacitor? Or maybe a combination of both? The reason why I ask is because I feel like the smaller capacitors can respond faster than the larger ones, I could be wrong but it's just a feeling and I don't know for sure! I purchased a bridge rectifier kit off eBay that came complete with the rectifier, PCB and a lot of smaller low ESR capacitors in DIY form. I purchased it because I remember seeing a video somewhere how a large capacitor does fine with the bulk of the ripple but by simply adding a smaller low value capacitor cleaned up the DC output even more whereas adding more larger capacitors wouldn't have done the same... In the case of the output on an amplifier, faster responding capacitors should make an impact on the output signal? I guess that this is one of the areas where amplifiers get their characteristic sound from.. Yeah I'm still not sure though but something is giving me the feeling that it would make a difference...

[@RicardoPenders]

Because I don't have an oscilloscope myself I never see the signals the way you showed it here in this video so thank you for sharing, now I have a better idea of a DC signal through a diode.

[@boybravo689]

Thumbs up done nice video tutorial new subcriber from the philippines tnx sir

[@surakeneni1310]

Thank you very much 🙏🏾🙏🏾🙏🏾🙏🏾especially with capavitor thing.... You solved one of my headache my saddnes

[@bradcfi2]

Thanks a bunch. You are a great teacher. Don't mind long videos if I am learning.

[@jean-lucpicard2418]

Thanks very much man for this lesson. I enjoyed every minut of the 81 of them.

[@teeeeeeeeeet]

Exceptional video. Keep them coming.

[@amoontube]

I gained a lot more understanding from your video - love your way of explanation - thankyou. Could you do a transistor 101 please?

[@SIXSTRING63]

Basically you’re saying having a DC biased sine wave, which you don’t want on speakers but is common in the amp circuits such as the signal that gets amplified riding on negative DC to the grids of output tubes and positive on the plates. AC components on a DC voltage. That is why I love my Brymen BM869s meter, has a nice dual display showing both, my Fluke 189 does it too but the Brymen displays much nicer. Saves breaking out the scope at times.

[@SS-mj2mq]

I really loved how you explained everything you're awesome great video 🤗💯✌️

[@rudyg2295]

Hello Tony, thanks for this video. I have learned a lot. Quick question, can you make video about how bias circuits controlling idling current in amplifier? There are a lot of video on how to adjust it, but none explaining from the beginning and how it work in the circuit amplifier.

[@patrikprekop8975]

The best amplifier explanation 🙏👍

[@all.n.1]

Perfect. Great explanation, thanks.💥

[@ziggfreud9820]

I learned a tremendous amount I didn't know, very satisfying!

[@c3kkos]

Very nice video! Thanks. One question: are those diodes on the right polarity wiring? I'm talking about the three u used to adjust the bias voltage in the first scheme. It does feel wrong if those diodes block the DC to ground isnt it?

[@erikdenhouter]

They are indeed in the wrong way, I noticed trough the video.

[@kgsalvage6306]

Even though I know all of this, but you gave a great analogy of it. I'm not through much of the video yet, but I think you are getting to DC offset. Which is more or less what an ac signal is riding on some dc current. Or AC ripple.

[@xinjin5427]

The best explanation I ever see

[@rolfts5762]

_1) Thanks for sharing good quality knowledge in nice interesting and pedagogic way. _2) You announced yourself the reversed cap on breadboard, nice :). ...though regarding the 'diodes' (in the schematic), those has been drawn in wrong direction(but coupled Ok on breadboard). Just wanted to make aware of it. ,,Thanks again Tony, and have nice week over the pond there. /br, from norway.

[@robnic52]

Lightbulb moment! Beautifully explained. Thank you.

[@bradcfi2]

What a great video. Learned much.

[@richardredcastle7911]

OMG, I just learnt so much and it was beautifully explained to a novice like me. Thank you.

[@NICK-uy3nl]

Great video. I noticed there is no output capacitor on class AB amp, even though both transistors are still biased a little bit in the linear region with some DC voltage present on the output signal, isn't that harmful to the speaker however small that DC bias voltage might be ?

[@xraytonyb]

In a class AB amp, both the positive and negative output transistors have equal and opposite amounts of bias on them at idle, so when added together, they equal zero volts. For example, if there were +50 millivolts of bias on the NPN output side and -50 millivolts on the PNP side, then (+50) + (-50) = 0 volts. The only way to see DC on the speaker terminal is if one side were biased more than the other. That's where the DC offset adjustment (when available) comes into play. DC offset adjustment insures that you have equal and opposite bias on both sides. Lower cost amps don't have adjustable DC offset and rely on component matching to insure low/no DC offset. Thanks for watching.

[@NICK-uy3nl]

@@xraytonyb - So why not use an output cap on a class AB as an insurance, anyway? Do output capacitors introduce undesirable distortions, like slowing down fast rise times, phase distortion, or attenuating lower frequencies? - aside from the fact that electrolytic caps have a limited lifetime and degrade rapidly at higher temps.

[@Roflcopter4b]

@@NICK-uy3nl A capacitor will always allow more high frequency current through than low frequency. But more importantly you'd need a humongous capacitor to allow several dozen watts through. It would be refrigerator sized. That's hardly practical.

[@NICK-uy3nl]

@@Roflcopter4b - I must disagree. All high powered class A amps use output caps and they are not humongous.

[@jonka1]

@@NICK-uy3nl A perfectly balanced AB output stage can supply unlimited current response to the speaker within the capacity of the components. Introducing a capacitor will interfere with that ability unless a very large and expensive cap is used. It's a design choice to use a circuit that balances well and gives a good current delivery.

[@bobof673]

Great video thank you Tony. You explain circuits well. Can you do a similar vid explaining a typical AB classic pioneer amp. Im currently working on a pioneer SA1040 100w per channel.

[@pandouros]

Thank you very much for the lesson. Have you done a video fort he bias on cassete decks and how it works?

[@chefbink61]

really nice job look forward to the next one!!

[@air54plane]

excellent, way you explain that. now I understand!!!

[@montech5647]

12:27 - so, which of the tones is DC? The first more "open" tone, or the following more "muddy" tone at 13:30?

[@johnadams9041]

Not explained and not clear at all why is this , because may be not an amplifiers that working only with a positive current

[@deang5622]

@@johnadams9041 If you listen to his explanation at around 17 minutes, it becomes clear that the phenomenon is nothing to do with an amplifier, it is simply a question of what is the best way, the right way to drive the speaker.

[@StealthParrot]

Great video. What are you using for scope software to display it on the video monitor? Or is that just a video output on your scope?

[@jonka1]

Tony one explanation that can help some to understand a changing DC signal is to tell them to imagine an AC signal riding on top of a DC voltage. Many people have spent years believing that DC is (as per a battery) a steady voltage and the mind can get stuck with this idea.

[@keybutnolock]

Vitamins 1:05:01 Don't overdose vitamins or 'the bottom will fall out of your world' no visa-versa ! But great vid, thanks

[@Mezmorize99]

Really appreciate the video, I learned quite a lot!

[@buildstoys]

Thanks Tony, time to make some popcorn for this one!

[@vernonbosshard9317]

What PC based scope and bread board do you use?

[@oswaldwabbit8986]

Really Nice thanks for the imformative video, made a couple things a little clearer, really enjoyed it thank you

[@antraciet]

Thank you so much for this vid. I understand things much better now.

[@rohanlean2779]

This is a very well explained video. Thank you.

[@dl7majstefan753]

Hmmmm.. At 20:20 i´d have expected that the input- and output signals (Base & Collector) are in reverse phase (180 deg). So i assume you connected the scope (yellow trace) to the emitter instead of collector.

[@wollaminfaetter]

Wow! It actually took THIS to make me understand. Thank you very much.

[@user-su5sq5ib3i]

When a transistor is turned completely on is there any voltage drop to be considered or not worth considering for our purposes?

[@EnvoyOfFabulousness]

Fantastic video. Great explanations