I agree. He complains too much though. Life isn't that bad. Shit, no one is giving me gear to complain about and the whole personality is borderline. It's a shame.
I had noodled out an amp design sort of like this, using op amp to drive a transistor push pull output stage. But I haven't got around to making the video. And its good. Because you do a much better job of explaining it than I would have! Thank you for the video.
It was pretty obvious from the outset that using the biasing resistors were going to be a problem, since the peak current occurs when the drive voltage is closest to the rail, and that's when you have the least voltage across the bias resistor that needs it. Having added the bootstrapping, the only other trick you might like to try is to split that 47R resistor across the biasing diodes into two 27R or 22R and connect the junction to the opamp output, in effect using separate resistors across each diode. That would mobilise the ability of the opamp to supply a decent drive current, albeit via 22R/27R, but it's a free bonus when your opamp has significant current capability.
I've drawn balls for 40 years. It is just what you learn, you usually stick to ..inc wiggly Rs.and half moon caps but those because they look nice too.
I've tried using opamps as simple amp circuits a few times. I always find to get decent performance out of them you end up adding enough extra components to offset the simplicity. Best one I did used two opamps each directly running one output transistor with DC offset applied to the +input for bias, and NFB taken from the emmiter of the transistor that opamp drives. Then a 3rd opamp for global NFB taken from the output, and providing voltage gain. Works, but you've just lost all the simplicity you were aiming for.
Many AV amps have used this method with glorified op-amps as pre drivers and then traditional push pull outputs. Sony comes to mind. Edit: I noticed when you said it was clipping on the bottom you should have changed the V/Div on the scope. Pretty sure you were at the displays clipping limit.
Thanks. I like 4556 very much. It is said it was used in the famous Grado RA-1. BTW, is it good to use a push-pull Class-A output stage in a headphone amp, and how to implement it?
Hi John! That's great videos of yours. I'm experimenting on these simple amps too in the moment. What about using diodes in the 220-package and mount them alongside with the transistors for thermal stability? And what I found today is to put a resistor of about 120R between the bases in the basic circuit. I achive full power with this, but with a bit of crossover distortion. I'm using BD 910/911 (hfe 152) which perform better than 2SC5200/2SA1943 when testing the amp with square waves. May be you want to try it. If you want, have a look at my square wave video. Regards!
I would skip the 23 ohm resistor that shunts current around the bias diodes. Instead I would increase the two 220 ohm resistors to maybe 1k each. But then there would not be enough current to drive the bases. So instead use the 4556 opamp to drive the bases. To make the current bidirectional, put another diode across each bias diode, cathode to anode, or anti-parallel. That way the opamp can sink or source current to each transistor.
Could the two diodes be connected to the collector of the bottom MJE3055 and have the Op-Amplifier drive the Base of the bottom MJE3055 which will give us a Class A amplifier with a wide Bandwidth. this type of amplifier was of the type used to drive the cathodes of color CRTs.
,voltage from +12 volts will flow through the series diodes going to -12 volts supply ,if you connect 220ohms resistor from the rail +/- supply, instead reverse the diodes position, i notice them on some other amplifier design ,?
I really enjoy these small design, build, and test videos because all the key concepts are very concrete and tied to easy-to-identify components or small subsystems. I was able to get your headphone amp working on a breadboard and tweak it to run off coin cells and drive a small 4 ohm speaker instead of headphones fairly easily, which was the first amp I built and very satisfying. A lot of questions come to my mind from videos like this one and the headphone amp one like, what if you added a transistor to amplify the op amp current or made the output drivers Darlington or complementary feedback? How would you replace the op amp with a discrete VAS? What issues would pop up that one would have to compensate for? Can you implement global negative feedback with discrete components (you might already have a video about this, I haven’t watched them all yet)? Maybe it’s not interesting to people who can design a decent amp on a blank page already, and it’s definitely not efficient, but for me personally it helps bring all the design considerations and tradeoffs together better than a more complex upfront design like the JAT501. Thanks for all the hours of great content, hope Snickers is doing well and we get to see/hear him again soon!
Is the low output power actual inefficiency? Are you burning loads of power or is it just not taking and then delivering the power from the supply? I could live with getting 5 watts instead of 10 but only at 5 watts worth of power from the wall (i know amps arent 100% efficient, hence the "worth") - lets say, using this amplifier in a situation where 3 watts is enough.
This circuit reminds me of the example circuit in the TDA2030A datasheet!!!! Always wanted to know if it was any good! Especially the active 3 way circuit in the same datasheet, in one of the other TDA amplifier ic datasheets of the same vintage had a 2 way active circuit example in it as well! I have Fostex 3 way powered studio monitors and they are amazing, they are using chip amp's which are shielded a bit to well and I can't see which one's they chose to use but going by what's around them, they appear to be class AB... I don't really understand the principal of using a power amplifier IC to drive two transistors in that TDA2030A datasheet but it's there and it supposedly works! How good though.... I wish I knew... I wonder if that same circuit example would work well with the TDA2050A? I have a heap of the 2030's, I might have to grab a heap of the 2050's considering how well they performed in your tests...
Can we have an amplifier working well with just a single npn transistor at input stage and two transistors (npn and pnp push pull) at output stage along from where we connect the speaker with the whole circuit working on single 12 Volt supply ? How much power we can expect from such a circuit ?
As both an electronics tech and a guitar player, I'm always thinking how to make circuits like these have a more pleasing type of distorted sound when pushed to those levels. So, what happens if I add a diode clipper to the feedback circuit? 😅
I have questions - 1. How much Watts can we expect from a Single supply Single ended amplifier @ 4 ohms on 12 - 14 volts ? 2. Does a Bridged amplifier output 30 - 40% more power than single ended one operating at same supply voltage ?
3 or 4 watts. In theory a bridged amp will deliver 4 times the power into the same load using the same supply voltage. In reality it is more like 3 times. The amp in your question 1 would deliver around 10 - 12 watts when bridged.
Great video John 👍 Thank you for the video. I do have a suggestion on this amplifier. Without a bootstrap circuit I just added a capacitor 1uF from NPN transistor base to PNP transistor base, it sounded just right. What you think about such a configuration?
I tried connecting the opamp to each transistor's base through a 100uf cap. At high signal levels, the bias spread collapsed and I get crossover distortion due to no consistent bias current at high signal levels. The cap's voltage discharges and collapses the bias. May work with the smaller cap but you get weaker output at lower frequencies.
@@EngineeringEssentials I personally like to use logic level MOSFETs in the output stage of an opamp driven power amplifier. So there is no need to use a high current opamp. The issue with high current opamps is the voltage drop. So I prefer to use rail-to-rail opamps together with MOSFETs. ibb.co/m5JwyZZ
I recently picked up some OPA551 op amps for that purpose. +/-30v with 200mA continuous output. I have no idea how it will perform as an audio amplifier but it's fun the play with none the less
@@JohnAudioTech to get around op amp limits I've put regulators on amps just to drive the op amps. If you lay the circuit out good it's no biggie to use 3 terminal regulators.
Opamps outperform any discrete setup by miles. See nwavguy.blogspot.com/2011/08/op-amps-myths-facts.html Also take a look at sound-au.com/project07.htm I've measured opamps vs discrete amplifiers myself, and there's no contest
You can certainly build discrete opamps of any performance level. I’ve got below -140dB thd at 20kHz out of mine and check out the Weiss op-2 discrete opamp for the best commercially available opamp of any stripe. That said, most of the shelf discrete opamps don’t measure half as good as an opa1612 or similar and very few bother designing for power efficiency.
Next time show us what it does then explain it. Because I'll be more engaged then. I get too distracted otherwise wondering what it's going to do. It is show and tell, not tell then show.
70s rock is garbage if you're a modern progressive player. They were the giants whom their betters have stood on generation after generation. People forget that what used to be the creative and technical bleeding edge is just a step on a pleasant journey to getting better and learning to have an open mind. I grew up with people who think music ended in the 70s as far as talent goes. My opening statement was a joke. Cool circuit. Maybe not moan so much, life is for living and not having a dangling noose attitude.
Thanks for this video, John. I really like to see how the designs evolve, and how you explain each tweak. Keep these videos coming!
I agree. He complains too much though. Life isn't that bad. Shit, no one is giving me gear to complain about and the whole personality is borderline. It's a shame.
I don't know a lick about electronics other than power, ground, and relays, but I still find it fascinating.
Electronics is the art of waveform shaping. With that knowledge in hand you're an expert now.
Bang! is great. I actually got to see them play in the early 2000's when they did a reunion tour.
It may be nothing special, but seeing it come together step by step is fascinating!
From design point of view this video is great.
I had noodled out an amp design sort of like this, using op amp to drive a transistor push pull output stage. But I haven't got around to making the video. And its good. Because you do a much better job of explaining it than I would have! Thank you for the video.
I was just looking to building a similar circuit with the bd139 and bd140. Perfectly timed video. Thanks.
Excellent project! Thanks for sharing with the community
Excellent video, clear, concise and to the point, GREAT work please keep it up.
Nice video and I am starting to understand amp design. Glad to see you figured out the FFT on the Siglent.
It was pretty obvious from the outset that using the biasing resistors were going to be a problem, since the peak current occurs when the drive voltage is closest to the rail, and that's when you have the least voltage across the bias resistor that needs it.
Having added the bootstrapping, the only other trick you might like to try is to split that 47R resistor across the biasing diodes into two 27R or 22R and connect the junction to the opamp output, in effect using separate resistors across each diode. That would mobilise the ability of the opamp to supply a decent drive current, albeit via 22R/27R, but it's a free bonus when your opamp has significant current capability.
Nice i needed to see something like this.
A+ on the connection dots. Connection dots removes the ambiguity and shows without doubt you intended to make a connection.
I've drawn balls for 40 years. It is just what you learn, you usually stick to ..inc wiggly Rs.and half moon caps but those because they look nice too.
Nice. Very similar to a project I've been tinkering with. This will help me. Thanks!
Originally the circuit looked a lot like an amp I built years ago. I got the schematic off red circuits I think it was called?
They thought of everything back in the day. I mostly just reinvent the wheel, but I enjoy it
@@Spentelectrons nothing rolls as good as a wheel does. So why not use it?
I've tried using opamps as simple amp circuits a few times. I always find to get decent performance out of them you end up adding enough extra components to offset the simplicity.
Best one I did used two opamps each directly running one output transistor with DC offset applied to the +input for bias, and NFB taken from the emmiter of the transistor that opamp drives. Then a 3rd opamp for global NFB taken from the output, and providing voltage gain.
Works, but you've just lost all the simplicity you were aiming for.
Elliott sound, project 76. Thats a similar circuit worth experimenting with.
Many AV amps have used this method with glorified op-amps as pre drivers and then traditional push pull outputs. Sony comes to mind. Edit: I noticed when you said it was clipping on the bottom you should have changed the V/Div on the scope. Pretty sure you were at the displays clipping limit.
Thanks. I like 4556 very much. It is said it was used in the famous Grado RA-1. BTW, is it good to use a push-pull Class-A output stage in a headphone amp, and how to implement it?
Hi John! That's great videos of yours. I'm experimenting on these simple amps too in the moment. What about using diodes in the 220-package and mount them alongside with the transistors for thermal stability? And what I found today is to put a resistor of about 120R between the bases in the basic circuit. I achive full power with this, but with a bit of crossover distortion. I'm using BD 910/911 (hfe 152) which perform better than 2SC5200/2SA1943 when testing the amp with square waves. May be you want to try it. If you want, have a look at my square wave video. Regards!
I would skip the 23 ohm resistor that shunts current around the bias diodes. Instead I would increase the two 220 ohm resistors to maybe 1k each. But then there would not be enough current to drive the bases. So instead use the 4556 opamp to drive the bases. To make the current bidirectional, put another diode across each bias diode, cathode to anode, or anti-parallel. That way the opamp can sink or source current to each transistor.
Could the two diodes be connected to the collector of the bottom MJE3055 and have the Op-Amplifier drive the Base of the bottom MJE3055 which will give us a Class A amplifier with a wide Bandwidth. this type of amplifier was of the type used to drive the cathodes of color CRTs.
,voltage from +12 volts will flow through the series diodes going to -12 volts supply ,if you connect 220ohms resistor from the rail +/- supply, instead reverse the diodes position, i notice them on some other amplifier design ,?
I really enjoy these small design, build, and test videos because all the key concepts are very concrete and tied to easy-to-identify components or small subsystems. I was able to get your headphone amp working on a breadboard and tweak it to run off coin cells and drive a small 4 ohm speaker instead of headphones fairly easily, which was the first amp I built and very satisfying.
A lot of questions come to my mind from videos like this one and the headphone amp one like, what if you added a transistor to amplify the op amp current or made the output drivers Darlington or complementary feedback? How would you replace the op amp with a discrete VAS? What issues would pop up that one would have to compensate for? Can you implement global negative feedback with discrete components (you might already have a video about this, I haven’t watched them all yet)? Maybe it’s not interesting to people who can design a decent amp on a blank page already, and it’s definitely not efficient, but for me personally it helps bring all the design considerations and tradeoffs together better than a more complex upfront design like the JAT501.
Thanks for all the hours of great content, hope Snickers is doing well and we get to see/hear him again soon!
Is the low output power actual inefficiency? Are you burning loads of power or is it just not taking and then delivering the power from the supply? I could live with getting 5 watts instead of 10 but only at 5 watts worth of power from the wall (i know amps arent 100% efficient, hence the "worth") - lets say, using this amplifier in a situation where 3 watts is enough.
this is pretty nice
That thing sounds phenomenal. Could you make a 400-700 watt version of this?
This circuit reminds me of the example circuit in the TDA2030A datasheet!!!! Always wanted to know if it was any good! Especially the active 3 way circuit in the same datasheet, in one of the other TDA amplifier ic datasheets of the same vintage had a 2 way active circuit example in it as well!
I have Fostex 3 way powered studio monitors and they are amazing, they are using chip amp's which are shielded a bit to well and I can't see which one's they chose to use but going by what's around them, they appear to be class AB...
I don't really understand the principal of using a power amplifier IC to drive two transistors in that TDA2030A datasheet but it's there and it supposedly works! How good though.... I wish I knew... I wonder if that same circuit example would work well with the TDA2050A?
I have a heap of the 2030's, I might have to grab a heap of the 2050's considering how well they performed in your tests...
OPA 1612 is best opamp I use it for all my AB designs
Rat Shack for the WIN! :)
hi very interesting Why not use darlingtons output pair ? they should be easier to drive than bjts
hi John, thanks for this very interesting video. Just a question: do the two transistors need to be matched? If yes, in which way?
Can we have an amplifier working well with just a single npn transistor at input stage and two transistors (npn and pnp push pull) at output stage along from where we connect the speaker with the whole circuit working on single 12 Volt supply ? How much power we can expect from such a circuit ?
Yes, I made an amplifier like this in a past video. Good for a watt or so at 12v.
As both an electronics tech and a guitar player, I'm always thinking how to make circuits like these have a more pleasing type of distorted sound when pushed to those levels. So, what happens if I add a diode clipper to the feedback circuit? 😅
make a video on making a multichannel Mic and Instrument Amplifier and mixer
I have questions -
1. How much Watts can we expect from a Single supply Single ended amplifier @ 4 ohms on 12 - 14 volts ?
2. Does a Bridged amplifier output 30 - 40% more power than single ended one operating at same supply voltage ?
3 or 4 watts. In theory a bridged amp will deliver 4 times the power into the same load using the same supply voltage. In reality it is more like 3 times. The amp in your question 1 would deliver around 10 - 12 watts when bridged.
is this a socl 506 amp?
Is signal ground connected to power supply ground?
Great video John 👍 Thank you for the video. I do have a suggestion on this amplifier. Without a bootstrap circuit I just added a capacitor 1uF from NPN transistor base to PNP transistor base, it sounded just right. What you think about such a configuration?
I tried connecting the opamp to each transistor's base through a 100uf cap. At high signal levels, the bias spread collapsed and I get crossover distortion due to no consistent bias current at high signal levels. The cap's voltage discharges and collapses the bias. May work with the smaller cap but you get weaker output at lower frequencies.
@@JohnAudioTech Sorry for the confusion. please have a look at this schematic. easyeda.com/deepakamalan/10w-amplifier
@@EngineeringEssentials I personally like to use logic level MOSFETs in the output stage of an opamp driven power amplifier. So there is no need to use a high current opamp. The issue with high current opamps is the voltage drop. So I prefer to use rail-to-rail opamps together with MOSFETs. ibb.co/m5JwyZZ
@@EngineeringEssentials No confusion, I understand what you meant. I didn't try exactly that but something similar.
@@JohnAudioTechThank you for the reply. just curious, In this scenario will a MOSFET do any better?
Why was the THD so big?
Is it possible to increase input voltage more than 12v to get more power
Moar powah!
Yes you can run it up to the limit of the opamp's max rated supply voltage but I'd keep it at +/- 15v max. You may have to adjust the bias.
I recently picked up some OPA551 op amps for that purpose. +/-30v with 200mA continuous output. I have no idea how it will perform as an audio amplifier but it's fun the play with none the less
@@JohnAudioTech to get around op amp limits I've put regulators on amps just to drive the op amps. If you lay the circuit out good it's no biggie to use 3 terminal regulators.
Would you ever use an op amp based input stage for an audiophile amplifier?
I'd probably go full discrete but it certainly could be done.
@@JohnAudioTech Just wondering
I’m working on a fully discrete audiophile amp right now :)
To be an 'audiophile' you must believe that op amps are the spawn of the devil, so, no.
Opamps outperform any discrete setup by miles.
See nwavguy.blogspot.com/2011/08/op-amps-myths-facts.html
Also take a look at sound-au.com/project07.htm
I've measured opamps vs discrete amplifiers myself, and there's no contest
You can certainly build discrete opamps of any performance level. I’ve got below -140dB thd at 20kHz out of mine and check out the Weiss op-2 discrete opamp for the best commercially available opamp of any stripe. That said, most of the shelf discrete opamps don’t measure half as good as an opa1612 or similar and very few bother designing for power efficiency.
Is Snickers OK?
That sounds like a Vanessa Paradis track sorry.
Next time show us what it does then explain it. Because I'll be more engaged then. I get too distracted otherwise wondering what it's going to do. It is show and tell, not tell then show.
70s rock is garbage if you're a modern progressive player. They were the giants whom their betters have stood on generation after generation. People forget that what used to be the creative and technical bleeding edge is just a step on a pleasant journey to getting better and learning to have an open mind. I grew up with people who think music ended in the 70s as far as talent goes.
My opening statement was a joke. Cool circuit. Maybe not moan so much, life is for living and not having a dangling noose attitude.
what i have ment too say was i was the first person to comment on this video thats all
Great video John = I’ll put a link to this in my next video!
What??
Feedback resister is not connected to output!!!!🙏😀
At the end of the video it is.