Jaka Racman said:
Jaka Racman said:
Yes its true. I "paint" this picture in the middle of the night and made some mistake (in original circuit is even circuit to set output offset of the OP AMP (741, because id old design). Now is the morning and I try to find mistakes (look upstairs I start to do this
In original circuit, output is grounded with 47 ohms.
circuit
I show this (the first) picture because of the treade - shortcut protection circuit and to show how to do it with some resistors on the output stage.
When dextroyer wrote, he'll made this circuit, i warn him, because it not exist in reality. Those schemas are only to show (readers of hiendfi) some ideas to build amplifier on those bassis. Regard that, everywhere is writen, that, this is not shematic to build, just to show ideas regard stages and modules.
If somebody wants to build this, some changes and optimisations is cleraly needed.
Those pictures are alike block schemas,....
To work well, it's clearly needet to match those parts together in some logical way (to work like logical chain).
I show this (the first) picture because of the treade - shortcut protection circuit and to show how to do it with some resistors on the output stage.
When dextroyer wrote, he'll made this circuit, i warn him, because it not exist in reality. Those schemas are only to show (readers of hiendfi) some ideas to build amplifier on those bassis. Regard that, everywhere is writen, that, this is not shematic to build, just to show ideas regard stages and modules.
If somebody wants to build this, some changes and optimisations is cleraly needed.
Those pictures are alike block schemas,....
To work well, it's clearly needet to match those parts together in some logical way (to work like logical chain).
Jaka Racman said:
Your knowledge is copie of the text of basis application (motorola applications). Its easy to make copie of it for me
. I dont need to understand what in those applications is, same like you.Regard output resistor, ask PAFI or read upstairs.
Regard 100W in the aplication is (you saw this) 4 Ohm load for 125W and 8 Ohm load for 80W. But depend on output devices (some more modern we have thise days). With some output devicea and with some Vcc voltages, amp will be less efficient regard output power.
Have you Racman your own ideas? Something from your (world known) designs
Re: I am thinking in assembly your schematics
Destroyer X
I'm on hilidays this days and have no datas with. I'll come at home in two weeks. Than I'll send you datas you want.
If you want to build this think, I'll send you (first days of Jule), aprooved shematics (it's not for public), but I'm sure, that you is capable to design your own design on those design basis. Only careful match od all parts (modules) together is needed.
But this platforma is good for change of ideas I think.
If we have some finished circuit, change of ideas isn't so interesting for some DIY makers.
destroyer X said:
Destroyer X
I'm on hilidays this days and have no datas with. I'll come at home in two weeks. Than I'll send you datas you want.
If you want to build this think, I'll send you (first days of Jule), aprooved shematics (it's not for public), but I'm sure, that you is capable to design your own design on those design basis. Only careful match od all parts (modules) together is needed.
But this platforma is good for change of ideas
I think. If we have some finished circuit, change of ideas isn't so interesting for some DIY makers.
Jaka Racman said:
Jaka. Just You is (now (before) again) start with this. Than You will again ask webmaster to protect you against attachs? You make copie of english (USA) text from original application (I wrote from what source is before) and start with personal attachs again (like the first time).
I start with this circuit because to show how is the simplest way to made shortcut protection. You have problem with this idea (like only one) again. Other explanations were regard readers questions, so, i don't know for others, but I'll be happy to see some of your "half basked" ideas on the site. But, class D isn't so interesting to me... . If it's interesting to oher readers, i agree with, to show us. I'll be happy to see something original from you.
Jaka Racman said:
Those power calculations made Motorola before me (you know this). So, I'll be copied this from aplications, for you, to be satisfy.
Seem like:
Sinus / Maximum Power
- 20/35 (16 Ohms, +- 30V) (BD 898 and 897)
- 25/40 (8 Ohms +- 27V) (BD 896 and 895)
- 35/60 (8 ohms +- 30V) (BD 898 & 897)
- 50/80 ( 8 Ohms +- 35V) (MJ 900G and MJ 1000G)
- 80/125 (4 Ohms +- 30V) (2N6052& 2N6059)
But with some of modern Darlingtons on the market (a have datas at home, but who want this, I'll send you datas by the mail if needed), in the last situation, its possible to made (circa) 80W at 8 and 125W at 4 Ohms.
Today its a lot of very good and more powerful Darlingtons on the market.
Hi Bojan,
please do your own calculations again. It says Bojan Hajdinjak on the schematic, not Motorola. I will make allowance for 1V saturation voltage, ideal 30V power supply and 1R " current limiting resistor ". And do not to forget to calculate power on that one too. From your estimations it would be 300W on each, not taking into consideration worst case scenario (square wave or even DC at the input).
BTW, could you post a link to that Motorola AN, or at least post it´s number. It was 9 years ago, when I made a similair amplifier. Actually it was a current source, and it was used to drive a very high speed electromotor, but I feel flattered that I can remember text so well.
Best regards,
Jaka Racman
please do your own calculations again. It says Bojan Hajdinjak on the schematic, not Motorola. I will make allowance for 1V saturation voltage, ideal 30V power supply and 1R " current limiting resistor ". And do not to forget to calculate power on that one too. From your estimations it would be 300W on each, not taking into consideration worst case scenario (square wave or even DC at the input).
BTW, could you post a link to that Motorola AN, or at least post it´s number. It was 9 years ago, when I made a similair amplifier. Actually it was a current source, and it was used to drive a very high speed electromotor, but I feel flattered that I can remember text so well
.Best regards,
Jaka Racman
Jaka Racman said:Hi Bojan,
please do your own calculations again. It says Bojan Hajdinjak on the schematic, not Motorola. I will make allowance for 1V saturation voltage, ideal 30V power supply and 1R " current limiting resistor ". And do not to forget to calculate power on that one too. From your estimations it would be 300W on each, not taking into consideration worst case scenario (square wave or even DC at the input).
BTW, could you post a link to that Motorola AN, or at least post it´s number. It was 9 years ago, when I made a similair amplifier. Actually it was a current source, and it was used to drive a very high speed electromotor, but I feel flattered that I can remember text so well
Best regards,
Jaka Racman
If it would be 300W on each, how much would be than on Loudspeakers
! Sorry, you have much to learn about.It was 2o years ago, when I made s similar amplifier for audio aplications. As current source to drive motors a use better ideas.
Motorola applications is something usual for ewery electronic professional, like RCA aplications on which based most amplifier audi designs past 25 years. Its a book, you know this - zou made this.
Do you need this shematic for the AC or maybe
) ) DC current source? Motorola show this for audio aplications. You want to show us, you don't make copies from motorola i think.Hi Bojan,
I think that anyone with knowledge of Ohm`s law can draw the conclusions. And BTW, ground connecting resistor is missing in all your posted schematics. I was polite enough not to mention it for the first time. You only draw your shematics at midnight, or you did not know what it is used for?
Best regards,
Jaka Racman
I think that anyone with knowledge of Ohm`s law can draw the conclusions. And BTW, ground connecting resistor is missing in all your posted schematics. I was polite enough not to mention it for the first time. You only draw your shematics at midnight, or you did not know what it is used for?
Best regards,
Jaka Racman
Current sensing
Hi everyone,
If you are afraid of VI limiters inside the circuitry you may want to use
an external current sensor like the ones supplied from Honeywll and LEM.
Theese guys have neglible resistanse for the signal path and senses
DC up to some hundreds of kHz (depending on type).
The output signal need I/V conversion with external resistor to get
a voltage signal in proportion to passing current.
To me this is overkill although I'm planning to use some since I have
them in the shelf.
And also as pointed out bipolar transistors destroy pretty fast compared to MOS_FETS and new generations of IGBTS, so trusting
the speed of a relay is like waiting for an accident to happen unless
there are some serious margins in the output devices.
Speaking of damping factor------
How does the DC-resistance of the voice-coil fit into the equation of
having a system damping factor of lets say 200.
/ Mattias
Hi everyone,
If you are afraid of VI limiters inside the circuitry you may want to use
an external current sensor like the ones supplied from Honeywll and LEM.
Theese guys have neglible resistanse for the signal path and senses
DC up to some hundreds of kHz (depending on type).
The output signal need I/V conversion with external resistor to get
a voltage signal in proportion to passing current.
To me this is overkill although I'm planning to use some since I have
them in the shelf.
And also as pointed out bipolar transistors destroy pretty fast compared to MOS_FETS and new generations of IGBTS, so trusting
the speed of a relay is like waiting for an accident to happen unless
there are some serious margins in the output devices.
Speaking of damping factor------
How does the DC-resistance of the voice-coil fit into the equation of
having a system damping factor of lets say 200.
/ Mattias
shematics
This is answer on JAKA RACMAN
At first.
1 - Before (some your replay before this) you maybe think, that resistor of 1W must be BIG if we want to use it for the shortcut protection (i wrote, maybe we need some more ohms in the past ). Mine example is answer on the primary question, regard the simplest way to make DC protection. You know for better idea? Please show us. It has a lot of power resistors in small casses (heatsinks) on the market today. My answer on the first question in this threade is not regard on question what is the optimum option, but what is the simpliest way.
2 - If we need some smaller (smaller Power dissipation) resistor is ewen better (i think) if it blow up when circuit is for a long time in the shortcut position. For a short time of shortcut, its enough about 10W if its on the heatsink.
3 - Ohms Low, like you calculate is for primary school and not for calculating the audio power Amps with (AC - audio signals). Are you electronicher? Do You think its possible that way to calculate audio circuits and think to know how to made design of audio amp? Do you passes some electronic themas after Poberaj?
4 - Regard resistor on the ouput. Do you think thats the only way to made this amp? Please more slowly read again mine conclusions before. It's depends on a driver stage. There are a lot more mistakes if you tray to find them. I'll help you if you don't find something more. If you read carefully all of those texsts with clear mind, yu'll find some interesting things inside and maybe find reason, whay is interesting to see samo modules, possible to made together with the such platforma in some new, interesting amp
This is answer on JAKA RACMAN
At first.
1 - Before (some your replay before this) you maybe think, that resistor of 1W must be BIG if we want to use it for the shortcut protection (i wrote, maybe we need some more ohms
in the past ). Mine example is answer on the primary question, regard the simplest way to make DC protection. You know for better idea? Please show us. It has a lot of power resistors in small casses (heatsinks) on the market today. My answer on the first question in this threade is not regard on question what is the optimum option, but what is the simpliest way. 2 - If we need some smaller (smaller Power dissipation) resistor is ewen better (i think) if it blow up when circuit is for a long time in the shortcut position. For a short time of shortcut, its enough about 10W if its on the heatsink.
3 - Ohms Low, like you calculate is for primary school and not for calculating the audio power Amps with (AC - audio signals). Are you electronicher? Do You think its possible that way to calculate audio circuits and think to know how to made design of audio amp? Do you passes some electronic themas after Poberaj?
4 - Regard resistor on the ouput. Do you think thats the only way to made this amp? Please more slowly read again mine conclusions before. It's depends on a driver stage. There are a lot more mistakes if you tray to find them. I'll help you if you don't find something more. If you read carefully all of those texsts with clear mind, yu'll find some interesting things inside and maybe find reason, whay is interesting to see samo modules, possible to made together with the such platforma in some new, interesting amp
Mr. bojan, despite of all misunderstood, i think that...
Your country, your people are not stupid to put one man without heavy knowledge in the charge you are working, and, in special related to state of the art applications.
Of course, referenced in something, no one born knowing.... all things people said here is from "bordevovisky, Palewshi, Kawsford, Leach, Ma****ouched, Marantzein".... those man, quite all them just words, are the ones that referenced University degrées... this way, they also used information basis to make everything.
Your use of RCA aplications is good, if old is better to me, can you please, send me directly, step by step analises of the circuit, no problem to understand your english.... when you say base open can be conducting, saturated transistor, open to flow of electrons and of course opening electron flows from emitter to colector or inverse if you prefer..... some of them think in open circuit, as a switch off, disconnected, no current flow...opposite related your idea... this is one of the problems.... language...i face this problem daily!
Please, because english is not your language, and not mine too, can you please, when possible, having time... send directly to me some step by step analisys the way i am asking here:
1) Audio signal from source enter base of TR 1, with maximum allowable level of 1322 milivolts, and level spected is around 750 milivolts, VBE voltage in this first transistor will be around 0.605 V and it will conduct from collector to emitter 2.345 miliamperes....
2) that electrons flow will create a potencial diference (voltage) of 4.32 volts in resistor Rx that will polarize base of tr2.....
And this way going on.... i can follow by myself, but when fet appear i stopped!...i have to learn young boys, in a poor school in neighborhood.... Whats is Radio Amateur, Radio Frequency, Bands, Audio amplifier, Description, Construction, measuring and testing. 16 years old young boys, to make them choice their way in life...others cooperators will learn Maths, Phisics, Psychology, Laws, and all kind of knowledge, i have some practice explaing and to reforce theories they already had...now they will do this working.... i will put radio there.... and we will align together... and assembly amplifier... and test them.
This way, i will appreciate your help, i could understand what you mean, some of friends not, others understood.
Please, use simple words to me.... forget long tails, CCS, and those names, some i do not know... explain the way i asked, if possible...because this way you will be helping a lot, not only myself, but 56 young boys leaving in a very hard country to survive.
Carlos
Your country, your people are not stupid to put one man without heavy knowledge in the charge you are working, and, in special related to state of the art applications.
Of course, referenced in something, no one born knowing.... all things people said here is from "bordevovisky, Palewshi, Kawsford, Leach, Ma****ouched, Marantzein".... those man, quite all them just words, are the ones that referenced University degrées... this way, they also used information basis to make everything.
Your use of RCA aplications is good, if old is better to me, can you please, send me directly, step by step analises of the circuit, no problem to understand your english.... when you say base open can be conducting, saturated transistor, open to flow of electrons and of course opening electron flows from emitter to colector or inverse if you prefer..... some of them think in open circuit, as a switch off, disconnected, no current flow...opposite related your idea... this is one of the problems.... language...i face this problem daily!
Please, because english is not your language, and not mine too, can you please, when possible, having time... send directly to me some step by step analisys the way i am asking here:
1) Audio signal from source enter base of TR 1, with maximum allowable level of 1322 milivolts, and level spected is around 750 milivolts, VBE voltage in this first transistor will be around 0.605 V and it will conduct from collector to emitter 2.345 miliamperes....
2) that electrons flow will create a potencial diference (voltage) of 4.32 volts in resistor Rx that will polarize base of tr2.....
And this way going on.... i can follow by myself, but when fet appear i stopped!...i have to learn young boys, in a poor school in neighborhood.... Whats is Radio Amateur, Radio Frequency, Bands, Audio amplifier, Description, Construction, measuring and testing. 16 years old young boys, to make them choice their way in life...others cooperators will learn Maths, Phisics, Psychology, Laws, and all kind of knowledge, i have some practice explaing and to reforce theories they already had...now they will do this working.... i will put radio there.... and we will align together... and assembly amplifier... and test them.
This way, i will appreciate your help, i could understand what you mean, some of friends not, others understood.
Please, use simple words to me.... forget long tails, CCS, and those names, some i do not know... explain the way i asked, if possible...because this way you will be helping a lot, not only myself, but 56 young boys leaving in a very hard country to survive.
Carlos
Re: Mr. bojan, despite of all misunderstood, i think that...
You are very inteligent person destroyer X. You write on very interesting way. I know what you menas. No problem if you want to, I'll do this, but need some time (until 15. Jul, because of working)
Regard this Motorola schematic we newer do such calculations (or measurement) regard this original circuit. In the praksis, design of the audio amp, processes in different way. Wery often we analyse some interesting circuits (analyse regard sound, reliability or cost calculation) but almost never in such way (measurement of potential diference from colector to emiter). For us it's important only regard if it's bettwen secure levels. Nothing else. After working (years past experience) with some modules, we aproximate know, how it sounds and in what load and in which circuits are useful. A lot of this is done on the instinkt and experience of the designer. We often made sonic proovment of some interesting ideas from everywhere. I personaly (after school) almost never calculate circuit this way. I understand, you are professor in school and need some matemathical and physical explenations. If you'll tel your student, you have to try, you have to work with experinece and with instinkt,.....
it's impossible to explain basic theory with this.
So, You are right.
But from our vuew, it is impossible to made some sonic performance we need like this. We have a lot of audiophiles with Dr with their names. They do everything you want to, they will calculate you want to (ideal for digital technic, for software calculations, ...) but they don't know to make sonic perfect amplifier, so they want this from us. We have a lot of opinion exchanges with, they often not understand us, but, they know, something is wrong with their knovlidge (regard HighEnd audio) and often ask us for advises (in practical way). Sach way of exchanges of experience by us is those days something normal. People here (Sloevenia, Croatia, and also Germany and Austria..) often smiles if some ingeneur want to calculate some audio equipment.... Some calculations is sometimes needed, it's true....
destroyer X said:
You are very inteligent person destroyer X. You write on very interesting way. I know what you menas. No problem if you want to, I'll do this, but need some time (until 15. Jul, because of working)
Regard this Motorola schematic we newer do such calculations (or measurement) regard this original circuit. In the praksis, design of the audio amp, processes in different way. Wery often we analyse some interesting circuits (analyse regard sound, reliability or cost calculation) but almost never in such way (measurement of potential diference from colector to emiter). For us it's important only regard if it's bettwen secure levels. Nothing else. After working (years past experience) with some modules, we aproximate know, how it sounds and in what load and in which circuits are useful. A lot of this is done on the instinkt and experience of the designer. We often made sonic proovment of some interesting ideas from everywhere. I personaly (after school) almost never calculate circuit this way. I understand, you are professor in school and need some matemathical and physical explenations. If you'll tel your student, you have to try, you have to work with experinece and with instinkt,.....
it's impossible to explain basic theory with this. So, You are right.
But from our vuew, it is impossible to made some sonic performance we need like this. We have a lot of audiophiles with Dr with their names. They do everything you want to, they will calculate you want to (ideal for digital technic, for software calculations, ...) but they don't know to make sonic perfect amplifier, so they want this from us. We have a lot of opinion exchanges with, they often not understand us, but, they know, something is wrong with their knovlidge (regard HighEnd audio) and often ask us for advises (in practical way). Sach way of exchanges of experience by us is those days something normal. People here (Sloevenia, Croatia, and also Germany and Austria..) often smiles if some ingeneur want to calculate some audio equipment.... Some calculations is sometimes needed, it's true....
motor tubes
Let explain this on some other way.
Here in Slovenia we have one manufacturer of exhaust tubes (for evaporation) for motorcycles.
He is very successful. Made tubes for the best racing teams on the world and made tubes for many motorcycle producers. Now he goes also in formula 1. What’s the point?
He newer calculates anything of this in mathematical (or machine or physical way). He made research for (japanese) racing teams only with experiments and with his experience and with final measurements (Motor Power and moment characteristic, …)
One day he let this to University (machine scientists) to calculate some (ideal) tube for motorcycle. They made this. Tube was so big (almost 3m – L) that isn’t possible to drive motorcycle with this tube. Ideal mathematical calculation, but that impossible to use for the application.
I hope, you understand what I want to explain. Some mathematical calculations (like here) id for schools. For the university some more sophisticated calculations is needed. But everything of this has nothing with real component (sometimes have, but depend on technology and applications). If we want to made some good design, it’s a must to experiment with a lot of circuits, to know how it works and sounds, we need to look in all the ideas is possible to find around and if we are working hard, with the time, will get some experience with a lot of modules, than we know what to do to get some color of sound, ….
No one will explain us, how to build something excellent. It costs a lot if design is really good. But, from time to time, some ideas appears into public like some explanations, like some ideas, like something unusual, … .
Those, who work on ultimate sound at homes (serious music lower) know how hard is to find some good audio designed component. We have to be lucky more than if we play LOTO, if we want to find really good sounding equipment. Where is the reasons for? Maybe somebody thinks that with ordinary ideas is possible to do miracle? Is what we learn in schools all what we knows? If we don’t understand some circuit is normal to want to know how it works. But this way isn’t possible to do something really new.
Let explain this on some other way.
Here in Slovenia we have one manufacturer of exhaust tubes (for evaporation) for motorcycles.
He is very successful. Made tubes for the best racing teams on the world and made tubes for many motorcycle producers. Now he goes also in formula 1. What’s the point?
He newer calculates anything of this in mathematical (or machine or physical way). He made research for (japanese) racing teams only with experiments and with his experience and with final measurements (Motor Power and moment characteristic, …)
One day he let this to University (machine scientists) to calculate some (ideal) tube for motorcycle. They made this. Tube was so big (almost 3m – L) that isn’t possible to drive motorcycle with this tube. Ideal mathematical calculation, but that impossible to use for the application.
I hope, you understand what I want to explain. Some mathematical calculations (like here) id for schools. For the university some more sophisticated calculations is needed. But everything of this has nothing with real component (sometimes have, but depend on technology and applications). If we want to made some good design, it’s a must to experiment with a lot of circuits, to know how it works and sounds, we need to look in all the ideas is possible to find around and if we are working hard, with the time, will get some experience with a lot of modules, than we know what to do to get some color of sound, ….
No one will explain us, how to build something excellent. It costs a lot if design is really good. But, from time to time, some ideas appears into public like some explanations, like some ideas, like something unusual, … .
Those, who work on ultimate sound at homes (serious music lower) know how hard is to find some good audio designed component. We have to be lucky more than if we play LOTO, if we want to find really good sounding equipment. Where is the reasons for? Maybe somebody thinks that with ordinary ideas is possible to do miracle? Is what we learn in schools all what we knows? If we don’t understand some circuit is normal to want to know how it works. But this way isn’t possible to do something really new.
Bojan Hajdinjak,
I see that you are a new to the forum; it’s always good to meet new people through the forum, especially when they provide input.
I’ve have a VERY high regard for Jaka, and find your writing style and comments towards him offensive – he has made very valid and correct comments – which you have failed to understand. Failing to understand is not a fault - as this forum is about sharing ideas and learning - but to be “abusive” is!!
I believe Jaka is correct to point out the basic power loss of driving say an 8-Ohm speaker load with a “1-Ohm” source impendence (the reduced closed loop output impendence due to feedback, does not reduce the real power losses).
Pls. respect, and try to understand what is being said, this is a really great forum, if not the best – with many useful contributors
John
I see that you are a new to the forum; it’s always good to meet new people through the forum, especially when they provide input.
I’ve have a VERY high regard for Jaka, and find your writing style and comments towards him offensive – he has made very valid and correct comments – which you have failed to understand. Failing to understand is not a fault - as this forum is about sharing ideas and learning - but to be “abusive” is!!
I believe Jaka is correct to point out the basic power loss of driving say an 8-Ohm speaker load with a “1-Ohm” source impendence (the reduced closed loop output impendence due to feedback, does not reduce the real power losses).
Pls. respect, and try to understand what is being said, this is a really great forum, if not the best – with many useful contributors
John
Hi Bojan,
since it seems you are not able to do some power calculations, I will do that for you. You can use the same procedure in the future, just change the numbers and use calculator. But be aware that this is only valid for the discussed type of circuit.
So, we have the following conditions:
Vsupply = supply voltage It is 30V in our case, and for the purpose of this calculation it is perfectly stable. Not so in real life.
Vsat = output Darlington saturation voltage. For the purpose of this calculation we will set it to 1V which is a very benevolent estimation, since in real life you would have problems with storage time at such a deep saturation.
Rc = current limiting resistor, 1 Ohm in our case as shown in the schematics.
R = load resistor representing speaker load. This one is typically 8 Ohm when specifying amplifier output power. Sometimes 4 Ohm is used, and also some amplifiers are specified for even lower resistance.
Vpk = amplifier peak voltage. Now when specifying output power, amplifier is fed with 1kHz sinusoidal signal. Signal is increased, until specified level of distortion is reached, and output voltage is then measured. For our calculation we will disregard distortion and we will assume that amplifier is linear until it starts to clip. Clipping starts when amplifier's peak voltage reaches supply voltage minus Darlington saturation voltage. In our case this is:
Vpk = Vsupply-Vsat = 30V – 1V = 29V
Vrms= amplifier effective voltage. For power calculation we use term rms voltage. The rms value of an AC wave is often called the effective value or DC-equivalent value. For example, if an AC source of 100 volts rms is connected across a resistor, and the resulting current causes 50 watts of heat to be dissipated by the resistor, then 50 watts of heat will also be dissipated if a 100-volt DC source is connected to the resistor.
Now for sinusoidal signal rms value is peak value divided by square root of 2. So we have:
Vrms = Vpk/sqrt(2) = 29V/1.4142 = 20.506V.
Irms = amplifier effective output current. Since we have series connection of current limiting resistor and load resistor, equal current is flowing through them and total amplifier power will be shared between them. So:
Irms = Vrms/(R+Rc)
Pc = power dissipated on current limiting resistor.
P = power dissipated on load resistor. So:
P = Irms^2*R = Vrms^2*R/(R+Rc)^2
Now for 8Ohm load resistor:
P = 20.506^2*8/(8+1)^2 = 41,53W
For 4Ohm resistor:
P = 20.506^2*4/(4+1)^2 = 67.27W , still far cry from declared 100W.
For 2 Ohm resistor:
P=20.506^2*2/(2+1)^2 = 93.44W, less than desired
Now if we want to calculate required load resistance for 100W output power, quadratic equation has to be solved, which I will not post here. Suffice to say that required load resistance for 100W output power is 1.585 Ohm.
Now with that load resistance power dissipated on current limiting resistor is 63W. Since we have two of them, each one operating on one halfperiode, they would have to be rated 31.6W for 100W amplifier rated power.
That concludes the lesson.
Now this is only half of the story. As it has been demonstrated, for 100W rated power, amplifier must operate into 1.585 Ohm load and that produce 11.2 A peak output power. Since Darlingtons are driven with 10k base resistors, maximum base current available is 15V-3*Vbe/10k=1.29mA, which requires Darlington hfe to be approx 10k. Such Darlingtons are very rare, but in my amplifier I used MJ11032/33 pair which has typical hfe in the range of 10k in the region of 10 to 20A, so they can be used for example. So in the case of the short circuit, with fully driven output transistors, peak current through Darlingtons would be somewhere in 20 A range not accounting for hfe increase with temperature. Under worst case scenario, with DC at the input you have 400W dissipation on the current limiting resistor. Next time try fuses, if you know how to specify them.
At the end, all this was based on the premise that the proposed amplifier works, which is not the case, since it lacks at least grounding resistor. I do not have time or will to find all the flaws in your design, so be so kind and correct your mistakes
Bojan, design is more than swapping parts. If you put product on the market, it must conform to certain standards. We are in EU now and you must put CE mark on products you sell. CE mark means that product was made in accordance with relevant EU directives. For audio, these are Low Voltage Directive and EMC Directive. And harmonized standards are EN60950, EN60065, EN55103 and EN55104. You better start learning what terms Risk Analysis, Single Fault Condition, Hazard etc mean, or you will be out of business very soon.
Best regards,
Jaka Racman
since it seems you are not able to do some power calculations, I will do that for you. You can use the same procedure in the future, just change the numbers and use calculator. But be aware that this is only valid for the discussed type of circuit.
So, we have the following conditions:
Vsupply = supply voltage It is 30V in our case, and for the purpose of this calculation it is perfectly stable. Not so in real life.
Vsat = output Darlington saturation voltage. For the purpose of this calculation we will set it to 1V which is a very benevolent estimation, since in real life you would have problems with storage time at such a deep saturation.
Rc = current limiting resistor, 1 Ohm in our case as shown in the schematics.
R = load resistor representing speaker load. This one is typically 8 Ohm when specifying amplifier output power. Sometimes 4 Ohm is used, and also some amplifiers are specified for even lower resistance.
Vpk = amplifier peak voltage. Now when specifying output power, amplifier is fed with 1kHz sinusoidal signal. Signal is increased, until specified level of distortion is reached, and output voltage is then measured. For our calculation we will disregard distortion and we will assume that amplifier is linear until it starts to clip. Clipping starts when amplifier's peak voltage reaches supply voltage minus Darlington saturation voltage. In our case this is:
Vpk = Vsupply-Vsat = 30V – 1V = 29V
Vrms= amplifier effective voltage. For power calculation we use term rms voltage. The rms value of an AC wave is often called the effective value or DC-equivalent value. For example, if an AC source of 100 volts rms is connected across a resistor, and the resulting current causes 50 watts of heat to be dissipated by the resistor, then 50 watts of heat will also be dissipated if a 100-volt DC source is connected to the resistor.
Now for sinusoidal signal rms value is peak value divided by square root of 2. So we have:
Vrms = Vpk/sqrt(2) = 29V/1.4142 = 20.506V.
Irms = amplifier effective output current. Since we have series connection of current limiting resistor and load resistor, equal current is flowing through them and total amplifier power will be shared between them. So:
Irms = Vrms/(R+Rc)
Pc = power dissipated on current limiting resistor.
P = power dissipated on load resistor. So:
P = Irms^2*R = Vrms^2*R/(R+Rc)^2
Now for 8Ohm load resistor:
P = 20.506^2*8/(8+1)^2 = 41,53W
For 4Ohm resistor:
P = 20.506^2*4/(4+1)^2 = 67.27W , still far cry from declared 100W.
For 2 Ohm resistor:
P=20.506^2*2/(2+1)^2 = 93.44W, less than desired
Now if we want to calculate required load resistance for 100W output power, quadratic equation has to be solved, which I will not post here. Suffice to say that required load resistance for 100W output power is 1.585 Ohm.
Now with that load resistance power dissipated on current limiting resistor is 63W. Since we have two of them, each one operating on one halfperiode, they would have to be rated 31.6W for 100W amplifier rated power.
That concludes the lesson.
Now this is only half of the story. As it has been demonstrated, for 100W rated power, amplifier must operate into 1.585 Ohm load and that produce 11.2 A peak output power. Since Darlingtons are driven with 10k base resistors, maximum base current available is 15V-3*Vbe/10k=1.29mA, which requires Darlington hfe to be approx 10k. Such Darlingtons are very rare, but in my amplifier I used MJ11032/33 pair which has typical hfe in the range of 10k in the region of 10 to 20A, so they can be used for example. So in the case of the short circuit, with fully driven output transistors, peak current through Darlingtons would be somewhere in 20 A range not accounting for hfe increase with temperature. Under worst case scenario, with DC at the input you have 400W dissipation on the current limiting resistor. Next time try fuses, if you know how to specify them.
At the end, all this was based on the premise that the proposed amplifier works, which is not the case, since it lacks at least grounding resistor. I do not have time or will to find all the flaws in your design, so be so kind and correct your mistakes
Bojan, design is more than swapping parts. If you put product on the market, it must conform to certain standards. We are in EU now and you must put CE mark on products you sell. CE mark means that product was made in accordance with relevant EU directives. For audio, these are Low Voltage Directive and EMC Directive. And harmonized standards are EN60950, EN60065, EN55103 and EN55104. You better start learning what terms Risk Analysis, Single Fault Condition, Hazard etc mean, or you will be out of business very soon.
Best regards,
Jaka Racman
