There are lots of sections or sub-circuits in this complex design that I hoped would be explained here or in part 2 but part two is just a simple 2 transistor AB circuit. Will you be giving any more comments on this much more complex design? (e.g. comments on what the feedback circuit from output to the diff amp is accomplishing?). There are lots of things in this design that are not obvious to those trying to understand something this complex.
Thank you for your comment. My plan is to work out in detail how each sub-circuit works without shying away from the mathematics including contemporary feedback theory to shape the frequency response and stability of the amplifier. But time is the issue for me at the moment and I apologize in advance for not continuing the series. My plan is to get back to it as soon as I can. I hope you understand.
The input capacitor has a very large value and has no resistor between it and the base of the input transistor. Input capacitors are usually around 10 uF, (and preferably non polarised) with a resistor of 10 K - 22 K. Why did you design your circuit this way?
You should add a capacitor from your feedback translator base to 10k resistor. You don't want gain at DC, you just want the amp to servo the output to 0 V DC with no input.
correct. In this case you don't amplify the input offset voltage. But you have to make sure in this case to replace the 10 k input resistor by a 220 k input resistor. In order to match the input resistances between both differential amplifier inputs. Otherwise you get perhaps more dc offset than before.
The gain is determined by the ratio of the voltage divider between the amplifier output and the inverting input (G = (220k + 10k)/10k). The input resistance is the resistance of the resistor between non-inverting input and ground in parallel with that of the collector resistor at the not-inverting input multiplied by its current gain.
@@gammersunity4117 probably not better but at least simpler. But it depends strongly on the power requirements and the speakter load. At a power supply of +/- 18 V (a typical limit of opamp ICs) you can get a maximum output power of 16 to 18 Wrms at 8 Ohm speaker load. In the most home audio applications this is sufficiently enough if you have speakers with enough efficiency. But you can also use completely integrated power amplifier ICs like TDA2030, TDA2050 if you start to design with ICs. In this case you have also integrated safety means like thermal or short circiut shut down or current limits to use without further effort.
@@gkdresden well I'm just beginning, the thing is I've much to learn, I'm still trying to understand the voltage amplification process. biasing is still confusing to me.
@@gammersunity4117 the principle design of an audio amplifier consists typically of a highly linear high voltage gain differential pre-amplifier stage followed by a power output stage in high-current push-pull collector amplifier configuration to drive the speaker load. A voltage divider at the output of the amplifier is used to generate the feedback signal for the inverting input. This voltage divider must be designed in a way that the resulting voltage gain of the circuit is several orders of magnitude lower than the voltage gain of the pre-amplifier stage. Finally you have a circuit whos voltage gain of typically 1 MV/V (120 dB) is reduced to typically 10 to 100 V/V (20 to 40 dB) with highly linear behavior. The biasing of the output stage is done in a way that the voltage difference at the bases of the output transistors is spread in a way that you have a collector current also in idle state, to provide quasi-Class A operation up to 2 to 5% of its maximum power. So for very small input signals you avoid the switching of the output transistors leading to higher harmonic distortion. The bias current network need to be very well temperature compensated. Otherwise the bias current can drift with temperature changes of the output transistors. You see: for the development of an audio amplifier there are a lot of influences to consider. But there are well established designs which meet all these considerations if they are realized in the correct way.
You can substitute the Darlington output configuration by a Sziklai output configuration in order to get a little more output voltage swing and output power. Probably you can also use the D44VH10 / D45VH10 as single output transistor combination. They have a very high current gain (> 200 @ 1A, > 100 @ 4 A) which should be enough without current gain multiplication. The collctor base capacitor at the transistor of the voltage amplification stage appers to me a bit too large. I would recomment not to exceed 47 pF. Otherwise the amplifier could become too slowly for a sufficient pulse response. Further options are a snubber network at the amplifier output to compensate for wire / spreaker inductances and an input low pass filter (1 kOhm, 1 nF) to avaid rf input penetration.
I agree, although the output stage is the least problematic part of this circuit which has quite a few design flaws (see my comment in the main field).
Video amplifier typically is a wideband amplifier which means it is able to amplify signals with frequencies from few hertzs to hundreds of megahertzs. While an audio amplifier is meant to amplify signals from few hertzs to hundreds of kilohertzs.
For example NE592 is a typical video amplifier while LM386 is an audio amplifier. Take a look at their datasheets to learn the difference between video amplifier and audio amplifier.
I made a similar circuit, used Fallstad simulator, i adjusted the circuit to deliver 1 amp @ 1around 9 V.p.p. swing from a 2 x 15 V transformer, so 2 x 19.6 V. Using BD137, BD140, it follows the input voltage perfectly, pcb made, on it's way. wonder how it sounds, also included 2 pole Sallen Key filter. How much watts would that be would your recon? P = U x I, states like 19 ,6 watts, right or wrong?
Hi there, I hope you are doing well, its good to hear that you made the circuit, I want to ask you about how did you find out what type of capacitors he was using, like ceramic, tantalum or electrolytic. Plus are you talking about the power calculations across the capacitors or at the speaker itself, You could easily calculate that by using a simulator, or by the equations that he had described in the video, if you know the parameters
@@Gagandeepsingh-uf2un I use big 4700 electrolytic, 5 of them, 23500 uF in total and some film/ceramic. for just one speaker. Is that what you're looking for?
1:40 This circuit has quite a few design flaws. The input stage has a very low bias current of abt. 1.7mA, leading to low transconductance and current starving of the voltage amplifier stage at frequencies above 1kHz, which in turn causes poor slew rate and distortion (mostly 2nd harmonic). It's also hugely disbalanced, because one transistor draws abt. 0.46mA (0.7V/1.5k), while the other one draws 1.7-0.46 = 1.24mA. The whole point of a differential pair is to be perfectly balanced. Deviations in transistor currents over 1% cause a significant increase in distortion (2nd and 3rd harmonic). The best solution here would be to use a current mirror - the increase in complexity and cost is negligible compared to the great improvement it makes. It's also beneficial to increase the bias current to abt. 6mA and add emitter degeneration resistors of abt. 33 Ohm to the differential pair. The dominant pole capacitor (220p) is too big. The whole point of the dominant pole compensation is to bring the open-loop gain down to unity just before the phase shift at the output approaches 180 degrees, thus turning an amplifier into an oscillator. The value of Cdom is determined by the current sourcing/sinking capabilities of the transconductance stage and the VAS collector impedance. The open-loop gain here is not that high to begin with, due to the aforementioned low transconductance and current starving of VAS. All of this leads to a poor slew rate and great increase in distortion at higher frequencies. The VAS collector is loaded by a current sink, which is correct, but there is never a need to adjust the exact current flowing through it, so the 10k potentiometer is useless. The 2.24k pot is placed between the Vbe multiplier's base and collector, which is a timebomb, because if it fails, the bias voltage will increase to a maximum, likely causing the output transistors to blow up. It's always a better idea to put it between the base and the emitter. The 3K resistor between the driver transistors' emitters is too big. Reduce it by a factor of ten and put a 0.1-1uF capacitor in parallel. Its purpose is to provide a small reverse-bias voltage to the output transistors, making them turn off faster. Doesn't hugely matter in this relatively low-power circuit. It's always a good idea to couple the lower leg resistor of the feedback circuit (10K) to ground through a large (470uF+) capacitor, thus bringing the DC gain down to unity. The input pair is never going to be perfectly matched, and you don't need to amplify the DC offset voltage. The 220K will then have to be reduced to the same value as the input bias resistor (10K in this case) to match the impedances. It's always better to keep the value of these resistors as low as practically possible to reduce the Johnson noise (the exact values will ultimately depend of the signal source's output impedance). It's also necessary to put a small (4.7-33pF) capacitor in parallel with the upper leg resistor of the feedback circuit. This circuit is likely to work fine without it because its dominant pole frequency and slew rate are very low and therefore the Nyquist stability is not compromised - but the noise and distortion figures most definitely are. That's all. :)
That is some pretty in depth stuff you say right there. I'm trying to learn how to build an amplifier as my amplifier developed a technical glitch. I have no knowledge of electronics and to a practical approach for me is the best way to learn. This video is the first time I have seen someone explain how to build one and from that I am hopeful I can learn how an amp works and then from that maybe how to fix the one I have. Your answer is really interesting as it seems to show both interest and practical experience. Of course (and this is a joke) I know nothing about amplifiers or circuits, so what you are saying could be written by someone who knows nothing, but from a novices point of view, sounds wise and knowledgeable. :) My point here is I am going to look through the comments, but if you could highlight any videos, books or other information to teach me (us) how to do this, that would be great! As for the guy that made this video:- Thank you ever so much for this gem!!! I keep comping across fantastic repair videos, but they all presume we know how an amplifier works and what the components do, we don't. No one seems to point at anything on a PCB board from an amp and explain how each component relates to another. Seems as AB amps are based on the same principles, then know what is going on then means we can learn how to diagnose e.g. like where to put the multimeter to see what current flow is happening to find the exact problem. This subject is a minefield, but like most subjects, practice makes perfect and you video is absolutely stunning for the breakdown, explanation, but also the incredible comments from all the people pointing things out. Cheers peeps!!! ;)
@@waynecummings5021 It's all complete gibberish, I assure you.😊 A really good book to read would be "Audio Power Amplifier Design Handbook" by Douglas Self. You can download it for free. It does require some knowledge of electronics though. Power amps are relatively simple circuits. About 95% of all amps use the same basic topology shown here, it's only the details that differ (but they do make a big difference). The best way to get started is by learning about positive and negative feedback, and how a differential amplifier works. I can't recommend any videos because back when I was learning this stuff, there weren't any, and now I rarely watch them. You could watch some about operational amplifiers, because that's what power amps basically are: big, discrete op-amps. What kind of "glitch"? Analog circuits rarely glitch in the same way computers and other digital devices do. Normally, if they stop working properly, it's due to a component failure. If your amp hasn't blown up, if there's voltage on the supply rails, and the output transistors are not shorted (which you can easily check with a multimeter when the power is OFF), then you could probably fix it.
@@noneofyerbeeswax8194 Thanks buddy! That's a great reply for someone paddling in the Pool of Glitch. I have two Amplifier Receivers amps (I'm not suggesting you recommend talking me through both) that are exactly the same amps i.e. Sony STR-DE585, and both have different glitches:- 1. One turns on for a few minutes and works fine, then after about 10 minutes it cuts off - so I guess something is over-heating and it stops to protect itself or something else; 2. One turns on, but it either recognozes the input signal straight away (optic from the TV), or turning it off and on again it finally recognizes the input and then it's fine; ; There is also an Onkyo AR and that thing just sounds like it's trying to turn on, but just clicks at an exact 5 second interval. All three ARs are getting power and turn on, after that it's a mystery. Sorry to list them all, but that is what's confusing and cool i.e. they all have a different glitch. The reason I have 2 STR-DE 585s is because I bough them from Ebay as back-ups. I actually have a STR-DE585 I bought new 20 years ago and that still works, I just took it off line and used the replacement ones. However, as each one packs in I am slowly looking at using my original 585, and if that goes, then it's tears. Anyway, I thought if I buy other 585s I can reuse the parts to keep one going as long as I can learn to repair them, and here I am on this video trying to learn. I thought if I get used to one type then taking it apart will be familiar as I have three. Then it crossed my mind that I would love to learn what an amp is as they must share common technical attributes basically. :) That was a longer answer than I wanted to give.
@@waynecummings5021 As someone who likes posting huge Walls of Text™, I really don't mind a long answer. :) I've taken a look at the STR-DE585 service manual. Lots of stuff there. If all the channels have the same kind of malfunction simultaneously, then the problem is clearly not with the output amplifiers themselves. It's most likely in the digital circuitry before it. The first problem might indeed be caused by false triggering of the thermal protection circuitry. Or by a leaky diode or transistor that starts drawing too much current as it heats up. The second problem can be caused by lots of things. It can be just a loose contact due to a mechanical failure (cracked solder, SMD resistor or capacitor), or an actual digital glitch - anything. But it's definitely in the input circuitry, not in the output amp. It's very hard to diagnose anything remotely. The process of finding a malfunction is not that hard per se, but it's very tedious. The standard procedure is to connect a signal generator to the input and follow the signal path throughout the entire circuitry until a point where it breaks. Then compare all the logic levels and DC voltages to those given in the service manual to find out what's responsible for that. Oscilloscope is required. The third one sounds like an actual amp problem. If it's a relay that clicks at a 5 sec interval, then it's definitely the speaker protection. You need to measure the DC voltage at the output, it should normally be close (within 100mV) to zero. It could also be the over-current protection. Both these problems are normally caused by an output transistor failure (one of them must be either shorted or non-conducting at all), but not always.
Are you sure about this feedback loop between the power output and base of the "right" transistor in coupled pair ? I mean - if you had a capacitor in series with this 10k resistor then there would be nothing wrong but if you dont have it then the voltage on the power output in bias state will be highier equivalently to the proportion of the resistances of the feedback divider because its connected to the ground. And I assume we want to stabilize the bias voltage having the ground as reference because the "left" transistor of the coupled pair is biased through 10k resistor to ground without any divider. That's little yet tremendously important detail - if missed it will cause disstorsions or in the worst case it's gonna blow up the power stage because the output transistors will be "trying" to put at least several volts above ground on the few ohm resistor which is the speaker in bias state - thats a lot of current. Details of this kind are CRUCIAL for designing even the crudest and most basic power amplifiers.
Hi RedfusionPL . At DC, the base of the two emitter coupled pairs see almost the same resistance which is approximately 10k. The left transistor sees 10k to ground while the right sees 10k in parallel with (220k + 4R) which is about 9.6k. The difference is minimal which won't have any effect on bias of the output transistors since the matching of the two pairs isn't great to begin with (I am using MPQ3904) and the tolerance of the resistors. The amplifier was exactly built as seen on the schematic and didn't have any bias issues. In fact initially I had the 10k resistor on the right transistor connected with 2200uF capacitor to ground and the left transistor connected to ground through 220k resistor (basically connected as an AC amplifier). But I was having DC offset issues with the parts I had on hand and the feedback connection shown on the video solved this issue.
@@SmithKerona Sorry mate it's my bad I didnt notice it. Though both of us are little unprecise in our explanations because what will happen in circuits like this one is strongly dependable from current gain of the transistors, temperature voltage coefficients, differences between offset voltages (as you mentioned above) etc. so to compensate them a much more elegant and complex circuitry would have to be applied :) I dont think there is any sense in digging so deep if this is only for quick and simple applications lol. You get suprisingly nice sound out of it btw. Run some disstortion tests if ya can. I just noticed the release date XD nvm
What you call "headache" I call it fun! There is nothing wrong making 25W power amplifier using TDA2040 if your purpose it to just have something that works out of the box. But it is much more educational and rewarding if you make the amplifier using relatively basic devices.
I wish electronics was taught like this in college. Info is easier to absorb because of an objective which is to design.
nice power amplifier. succses for you. good luck
thank you very much!
To do electronics buy modules and solder, to learn electronics build from scratch...
Magnifico, grandioso !! ⭐⭐⭐⭐⭐
looks like a nice circuit
Very good video.
I also make videos about audio, electronic and I also like your video. They are helpful for audiences
Nice video, thanks :)
There are lots of sections or sub-circuits in this complex design that I hoped would be explained here or in part 2 but part two is just a simple 2 transistor AB circuit. Will you be giving
any more comments on this much more complex design? (e.g. comments on what the feedback circuit from output to the diff amp is accomplishing?). There are lots of things
in this design that are not obvious to those trying to understand something this complex.
Thank you for your comment. My plan is to work out in detail how each sub-circuit works without shying away from the mathematics including contemporary feedback theory to shape the frequency response and stability of the amplifier. But time is the issue for me at the moment and I apologize in advance for not continuing the series. My plan is to get back to it as soon as I can. I hope you understand.
I like design but don't know where to start any help
That is a good comment. I find that with enough watching, reading and experiments I might get something sorted in building or repairing an amp.
How much might it cost to hire an EE to design a custom schematic of a power amplifier? Do you ever take on custom jobs?
the 2nd stage how works?
Good music..good courses
Nice and very good explanation. Can you tell me Why the powe loss at output is taken as 4v?
The input capacitor has a very large value and has no resistor between it and the base of the input transistor. Input capacitors are usually around 10 uF, (and preferably non polarised) with a resistor of 10 K - 22 K. Why did you design your circuit this way?
You should add a capacitor from your feedback translator base to 10k resistor. You don't want gain at DC, you just want the amp to servo the output to 0 V DC with no input.
correct. In this case you don't amplify the input offset voltage. But you have to make sure in this case to replace the 10 k input resistor by a 220 k input resistor. In order to match the input resistances between both differential amplifier inputs. Otherwise you get perhaps more dc offset than before.
Why the input capacitor is so large?
There's no capacitor in Q2 after 10k resistance, so how to ground ?????
thank you very much
Thanku sir
Hi ...can you do schematic?
How would you calculate or determine the gain and input resistance of the pre amplifier transistor?
The gain is determined by the ratio of the voltage divider between the amplifier output and the inverting input (G = (220k + 10k)/10k). The input resistance is the resistance of the resistor between non-inverting input and ground in parallel with that of the collector resistor at the not-inverting input multiplied by its current gain.
@@gkdresden hey buddy instead of those two mq3904 transistors, is it not better to use a op amps there.
@@gammersunity4117 probably not better but at least simpler. But it depends strongly on the power requirements and the speakter load.
At a power supply of +/- 18 V (a typical limit of opamp ICs) you can get a maximum output power of 16 to 18 Wrms at 8 Ohm speaker load. In the most home audio applications this is sufficiently enough if you have speakers with enough efficiency.
But you can also use completely integrated power amplifier ICs like TDA2030, TDA2050 if you start to design with ICs. In this case you have also integrated safety means like thermal or short circiut shut down or current limits to use without further effort.
@@gkdresden well I'm just beginning, the thing is I've much to learn, I'm still trying to understand the voltage amplification process. biasing is still confusing to me.
@@gammersunity4117 the principle design of an audio amplifier consists typically of a highly linear high voltage gain differential pre-amplifier stage followed by a power output stage in high-current push-pull collector amplifier configuration to drive the speaker load.
A voltage divider at the output of the amplifier is used to generate the feedback signal for the inverting input. This voltage divider must be designed in a way that the resulting voltage gain of the circuit is several orders of magnitude lower than the voltage gain of the pre-amplifier stage.
Finally you have a circuit whos voltage gain of typically 1 MV/V (120 dB) is reduced to typically 10 to 100 V/V (20 to 40 dB) with highly linear behavior.
The biasing of the output stage is done in a way that the voltage difference at the bases of the output transistors is spread in a way that you have a collector current also in idle state, to provide quasi-Class A operation up to 2 to 5% of its maximum power.
So for very small input signals you avoid the switching of the output transistors leading to higher harmonic distortion. The bias current network need to be very well temperature compensated. Otherwise the bias current can drift with temperature changes of the output transistors.
You see: for the development of an audio amplifier there are a lot of influences to consider. But there are well established designs which meet all these considerations if they are realized in the correct way.
We are still waiting on part 3!!
12:45 Why is so hard to have a no-damaged speaker, this days? 🤣
and how to finde amplifier watt
google it! One way (proper way) is using oscilloscope, here is link to video ua-cam.com/video/hA12uYxHBXM/v-deo.html
At the beginning you are missing the input voltage or level specification.
You can substitute the Darlington output configuration by a Sziklai output configuration in order to get a little more output voltage swing and output power. Probably you can also use the D44VH10 / D45VH10 as single output transistor combination. They have a very high current gain (> 200 @ 1A, > 100 @ 4 A) which should be enough without current gain multiplication.
The collctor base capacitor at the transistor of the voltage amplification stage appers to me a bit too large. I would recomment not to exceed 47 pF. Otherwise the amplifier could become too slowly for a sufficient pulse response.
Further options are a snubber network at the amplifier output to compensate for wire / spreaker inductances and an input low pass filter (1 kOhm, 1 nF) to avaid rf input penetration.
The Szukilia configuration is used , because he wants to unite the type of Power transistor, ie npn ,or pnp , not both as typical push pull is .
I agree, although the output stage is the least problematic part of this circuit which has quite a few design flaws (see my comment in the main field).
sir pls explain op amp and amplifier part stages
All the 'op-amp' in this case the 'power amplifier' stages will be explained and worked out in detail.
Thanks!
Hi.a question what is difference between video and audio amplifier pls answer me if you know
Video amplifier typically is a wideband amplifier which means it is able to amplify signals with frequencies from few hertzs to hundreds of megahertzs. While an audio amplifier is meant to amplify signals from few hertzs to hundreds of kilohertzs.
For example NE592 is a typical video amplifier while LM386 is an audio amplifier. Take a look at their datasheets to learn the difference between video amplifier and audio amplifier.
I made a similar circuit, used Fallstad simulator, i adjusted the circuit to deliver 1 amp @ 1around 9 V.p.p. swing from a 2 x 15 V transformer, so 2 x 19.6 V.
Using BD137, BD140, it follows the input voltage perfectly, pcb made, on it's way. wonder how it sounds, also included 2 pole Sallen Key filter.
How much watts would that be would your recon? P = U x I, states like 19 ,6 watts, right or wrong?
Hi there, I hope you are doing well, its good to hear that you made the circuit, I want to ask you about how did you find out what type of capacitors he was using, like ceramic, tantalum or electrolytic. Plus are you talking about the power calculations across the capacitors or at the speaker itself, You could easily calculate that by using a simulator, or by the equations that he had described in the video, if you know the parameters
@@Gagandeepsingh-uf2un The pcb's are on the way.
@@AnalogDude_ but that does not answer my question
@@Gagandeepsingh-uf2un I use big 4700 electrolytic, 5 of them, 23500 uF in total and some film/ceramic. for just one speaker.
Is that what you're looking for?
@@AnalogDude_ yes, thank you for the response. Means a lot
do you have a gerber about this desing?
1:40 This circuit has quite a few design flaws.
The input stage has a very low bias current of abt. 1.7mA, leading to low transconductance and current starving of the voltage amplifier stage at frequencies above 1kHz, which in turn causes poor slew rate and distortion (mostly 2nd harmonic). It's also hugely disbalanced, because one transistor draws abt. 0.46mA (0.7V/1.5k), while the other one draws 1.7-0.46 = 1.24mA. The whole point of a differential pair is to be perfectly balanced. Deviations in transistor currents over 1% cause a significant increase in distortion (2nd and 3rd harmonic). The best solution here would be to use a current mirror - the increase in complexity and cost is negligible compared to the great improvement it makes.
It's also beneficial to increase the bias current to abt. 6mA and add emitter degeneration resistors of abt. 33 Ohm to the differential pair.
The dominant pole capacitor (220p) is too big. The whole point of the dominant pole compensation is to bring the open-loop gain down to unity just before the phase shift at the output approaches 180 degrees, thus turning an amplifier into an oscillator. The value of Cdom is determined by the current sourcing/sinking capabilities of the transconductance stage and the VAS collector impedance. The open-loop gain here is not that high to begin with, due to the aforementioned low transconductance and current starving of VAS. All of this leads to a poor slew rate and great increase in distortion at higher frequencies.
The VAS collector is loaded by a current sink, which is correct, but there is never a need to adjust the exact current flowing through it, so the 10k potentiometer is useless. The 2.24k pot is placed between the Vbe multiplier's base and collector, which is a timebomb, because if it fails, the bias voltage will increase to a maximum, likely causing the output transistors to blow up. It's always a better idea to put it between the base and the emitter.
The 3K resistor between the driver transistors' emitters is too big. Reduce it by a factor of ten and put a 0.1-1uF capacitor in parallel. Its purpose is to provide a small reverse-bias voltage to the output transistors, making them turn off faster. Doesn't hugely matter in this relatively low-power circuit.
It's always a good idea to couple the lower leg resistor of the feedback circuit (10K) to ground through a large (470uF+) capacitor, thus bringing the DC gain down to unity. The input pair is never going to be perfectly matched, and you don't need to amplify the DC offset voltage. The 220K will then have to be reduced to the same value as the input bias resistor (10K in this case) to match the impedances. It's always better to keep the value of these resistors as low as practically possible to reduce the Johnson noise (the exact values will ultimately depend of the signal source's output impedance). It's also necessary to put a small (4.7-33pF) capacitor in parallel with the upper leg resistor of the feedback circuit. This circuit is likely to work fine without it because its dominant pole frequency and slew rate are very low and therefore the Nyquist stability is not compromised - but the noise and distortion figures most definitely are.
That's all. :)
That is some pretty in depth stuff you say right there.
I'm trying to learn how to build an amplifier as my amplifier developed a technical glitch. I have no knowledge of electronics and to a practical approach for me is the best way to learn.
This video is the first time I have seen someone explain how to build one and from that I am hopeful I can learn how an amp works and then from that maybe how to fix the one I have.
Your answer is really interesting as it seems to show both interest and practical experience. Of course (and this is a joke) I know nothing about amplifiers or circuits, so what you are saying could be written by someone who knows nothing, but from a novices point of view, sounds wise and knowledgeable. :)
My point here is I am going to look through the comments, but if you could highlight any videos, books or other information to teach me (us) how to do this, that would be great!
As for the guy that made this video:- Thank you ever so much for this gem!!! I keep comping across fantastic repair videos, but they all presume we know how an amplifier works and what the components do, we don't. No one seems to point at anything on a PCB board from an amp and explain how each component relates to another. Seems as AB amps are based on the same principles, then know what is going on then means we can learn how to diagnose e.g. like where to put the multimeter to see what current flow is happening to find the exact problem.
This subject is a minefield, but like most subjects, practice makes perfect and you video is absolutely stunning for the breakdown, explanation, but also the incredible comments from all the people pointing things out.
Cheers peeps!!! ;)
@@waynecummings5021 It's all complete gibberish, I assure you.😊
A really good book to read would be "Audio Power Amplifier Design Handbook" by Douglas Self. You can download it for free. It does require some knowledge of electronics though. Power amps are relatively simple circuits. About 95% of all amps use the same basic topology shown here, it's only the details that differ (but they do make a big difference). The best way to get started is by learning about positive and negative feedback, and how a differential amplifier works.
I can't recommend any videos because back when I was learning this stuff, there weren't any, and now I rarely watch them. You could watch some about operational amplifiers, because that's what power amps basically are: big, discrete op-amps.
What kind of "glitch"? Analog circuits rarely glitch in the same way computers and other digital devices do. Normally, if they stop working properly, it's due to a component failure. If your amp hasn't blown up, if there's voltage on the supply rails, and the output transistors are not shorted (which you can easily check with a multimeter when the power is OFF), then you could probably fix it.
@@noneofyerbeeswax8194 Thanks buddy! That's a great reply for someone paddling in the Pool of Glitch.
I have two Amplifier Receivers amps (I'm not suggesting you recommend talking me through both) that are exactly the same amps i.e. Sony STR-DE585, and both have different glitches:-
1. One turns on for a few minutes and works fine, then after about 10 minutes it cuts off - so I guess something is over-heating and it stops to protect itself or something else;
2. One turns on, but it either recognozes the input signal straight away (optic from the TV), or turning it off and on again it finally recognizes the input and then it's fine; ;
There is also an Onkyo AR and that thing just sounds like it's trying to turn on, but just clicks at an exact 5 second interval.
All three ARs are getting power and turn on, after that it's a mystery.
Sorry to list them all, but that is what's confusing and cool i.e. they all have a different glitch.
The reason I have 2 STR-DE 585s is because I bough them from Ebay as back-ups. I actually have a STR-DE585 I bought new 20 years ago and that still works, I just took it off line and used the replacement ones. However, as each one packs in I am slowly looking at using my original 585, and if that goes, then it's tears. Anyway, I thought if I buy other 585s I can reuse the parts to keep one going as long as I can learn to repair them, and here I am on this video trying to learn. I thought if I get used to one type then taking it apart will be familiar as I have three. Then it crossed my mind that I would love to learn what an amp is as they must share common technical attributes basically. :)
That was a longer answer than I wanted to give.
@@noneofyerbeeswax8194 I've just downloaded Audio Power Amplifier Design Handbook by Douglas Self. Thank you!!
@@waynecummings5021 As someone who likes posting huge Walls of Text™, I really don't mind a long answer. :)
I've taken a look at the STR-DE585 service manual. Lots of stuff there. If all the channels have the same kind of malfunction simultaneously, then the problem is clearly not with the output amplifiers themselves. It's most likely in the digital circuitry before it.
The first problem might indeed be caused by false triggering of the thermal protection circuitry. Or by a leaky diode or transistor that starts drawing too much current as it heats up.
The second problem can be caused by lots of things. It can be just a loose contact due to a mechanical failure (cracked solder, SMD resistor or capacitor), or an actual digital glitch - anything. But it's definitely in the input circuitry, not in the output amp.
It's very hard to diagnose anything remotely. The process of finding a malfunction is not that hard per se, but it's very tedious. The standard procedure is to connect a signal generator to the input and follow the signal path throughout the entire circuitry until a point where it breaks. Then compare all the logic levels and DC voltages to those given in the service manual to find out what's responsible for that. Oscilloscope is required.
The third one sounds like an actual amp problem. If it's a relay that clicks at a 5 sec interval, then it's definitely the speaker protection. You need to measure the DC voltage at the output, it should normally be close (within 100mV) to zero. It could also be the over-current protection. Both these problems are normally caused by an output transistor failure (one of them must be either shorted or non-conducting at all), but not always.
Are you sure about this feedback loop between the power output and base of the "right" transistor in coupled pair ? I mean - if you had a capacitor in series with this 10k resistor then there would be nothing wrong but if you dont have it then the voltage on the power output in bias state will be highier equivalently to the proportion of the resistances of the feedback divider because its connected to the ground. And I assume we want to stabilize the bias voltage having the ground as reference because the "left" transistor of the coupled pair is biased through 10k resistor to ground without any divider. That's little yet tremendously important detail - if missed it will cause disstorsions or in the worst case it's gonna blow up the power stage because the output transistors will be "trying" to put at least several volts above ground on the few ohm resistor which is the speaker in bias state - thats a lot of current. Details of this kind are CRUCIAL for designing even the crudest and most basic power amplifiers.
Hi RedfusionPL
. At DC, the base of the two emitter coupled pairs see almost the same resistance which is approximately 10k. The left transistor sees 10k to ground while the right sees 10k in parallel with (220k + 4R) which is about 9.6k. The difference is minimal which won't have any effect on bias of the output transistors since the matching of the two pairs isn't great to begin with (I am using MPQ3904) and the tolerance of the resistors. The amplifier was exactly built as seen on the schematic and didn't have any bias issues. In fact initially I had the 10k resistor on the right transistor connected with 2200uF capacitor to ground and the left transistor connected to ground through 220k resistor (basically connected as an AC amplifier). But I was having DC offset issues with the parts I had on hand and the feedback connection shown on the video solved this issue.
@@SmithKerona Sorry mate it's my bad I didnt notice it. Though both of us are little unprecise in our explanations because what will happen in circuits like this one is strongly dependable from current gain of the transistors, temperature voltage coefficients, differences between offset voltages (as you mentioned above) etc. so to compensate them a much more elegant and complex circuitry would have to be applied :) I dont think there is any sense in digging so deep if this is only for quick and simple applications lol. You get suprisingly nice sound out of it btw. Run some disstortion tests if ya can.
I just noticed the release date XD nvm
And an $8 I.c. does it with 10 times less distortion...
Stop putting sub tittles ,that is bidding what u r trying to show on book
Your dome is pushed-in. Not serious about the business.
can you help me give my opinion about my circuit? Can we exchange gmail?
Use a TDA2040 and save yourself design headaches.
What you call "headache" I call it fun! There is nothing wrong making 25W power amplifier using TDA2040 if your purpose it to just have something that works out of the box. But it is much more educational and rewarding if you make the amplifier using relatively basic devices.
@@SmithKeronaExactly! Same as baking a cake from scratch versus a box of cake mix.