Hi krachkiste,
Thanks for clearing this up, you are of course correct. I always try and place my output close to the middle of the output devices, or at least in the centre of the emitter resisitors, then take the NFB from the output (before inductor).
DX Amplifier PCB – Bottom Layer
Rereading D. Self it seems this is not neccessary as NFB will take care of any distortion. This has got me thinking about the take off point of the bootstrap.
regards
Carlos do you know these Polyester Folie Greenies ?Are they any good to use into the BlameES?
Attachments
Last edited:
Yes, if I underood you correctly.
If the NFB take off is "right" - as it seems to be in the pcb you just posted - the NFB will take care of asymetrical lengths of the "emitter wires".
On the bootstrap take off point.
Here I would apply the same rules as for the NFB t.o.p. (no half-wave rectified current contamination) but I would try to route an extra wire that is independant from the NFB wire so that this (NFB wire) is kept clean of bootstrap current too.
But as the bootstrap lies inside the feedback loop anyway, this whole issue with take off point should be much less critical, because errors would still be corrected.
So I think for the bootstrap t.o.p. all this care would really be too much and the advantage doubtfull.
Still the (not) contamination of the feedback wire with bootstrap (or any other) current seems important to me, as any errors introduced by extra current running through this wire, cannot be corrected by the NFB, because these errors would kind of add to the original signal so the amp would try to reproduce signal + error.
I hope you can extract what i'm trying to say from this strange english.
Ok, the tests are going on 🙂
At this evening i think there is a kind of borderline at 8V adjusting the bias. Crossing this point the Multimeter will show numbers like a rolling coster, fixing the bias to 7,9V everything is stable...or seems to be so ;-)
I will have a look at this tomorrow, when the amp has his temperature ...
now i will lean back and enjoy the musik 🙂)
good night all together.....
At this evening i think there is a kind of borderline at 8V adjusting the bias. Crossing this point the Multimeter will show numbers like a rolling coster, fixing the bias to 7,9V everything is stable...or seems to be so ;-)
I will have a look at this tomorrow, when the amp has his temperature ...
now i will lean back and enjoy the musik 🙂)
good night all together.....
Do you have a scope available?
Strange behaviour of the quicient current (steady trimming but current is jumping at some points, hystheresis loops, ...) might be an indication of parasitic oscillation.
Parasitic oscilations, hystheresis?.... was tested in my home, at least
the original board, and no one had strange bias drift (no one has reported) 12 amplifier were built, several folks, brazilian and strangers, the amplifier is stable, has not oscilations, i have a scope.
Of course, each case is a different case, he is using another different board, with smaller distance from copper line to nearby others, also German boards are using delayed insertion relay and a circuit... a connection is made by copper line to the speaker in the case of the speaker delayed insertion, and also circuit protection has some connections too, do not know if they have grounded the heatsink the way i suggested.
When we advance bias and suddenly jumps to a high value, for sure is oscilations, and usually you cannot reduce without switch the amplifier off, then reduce adjusting trimpot and switching the amplifier on once again after some seconds to discharge condensers.
This amplifier is not oscilating (official Taj boards) even when you connect a capacitor in parallel with a resistive load and also in parallel with speaker, no signs of oscilations, also has not oscilations triggered by audio, even saturating level in the input, does not oscilate when you put your finger in the input, this is a sign of stability, only mains hum is present when we do this way.
Taj boards were tested to avoid surprises, this board, the German one, is beeing tested rigth now, the first amplifier made with these boards.
Meanman, better to use Taj boards for safety reasons, as strange things are happening in our friend home... till he find a bug that keep the board free of suspections, i do suggest you not to assemble using these boards.
I have asked several brazilians to build using the official boards to be sure it is fine, i also build by myself and i had no problems, i have built three in three different boards, pictures published, and no one presented problems...maybe his problems is his board, maybe not.... we cannot be sure before some research.
I can guarantee Taj boards, because tested, not this one... i have not tested and the board shows some technicall errors as 90 degrées angles in copper tracks (inductance) and smaller distance between copper lines (capacitances increased).
Also, and repeating, some bias drift is normal and depends on the heatsink temperature...even cold for our fingers means hotter than when at environment temperature, so, there are always fluctuation in degrees.... unless the amplifier is installed inside an Iceberg..maybe, even this way, we gonna have increase in temperature while the surrounding ice melts.
Boys, you are both making an audio amplifier terrorism, spreading panic in the thread.... first search for bugs, them scream something is wrong, this way people will be afraid to build, will think the amplifier is a time bomb..and it is not, i was very carefull to check this several times.
regards,
Carlos
the original board, and no one had strange bias drift (no one has reported) 12 amplifier were built, several folks, brazilian and strangers, the amplifier is stable, has not oscilations, i have a scope.
Of course, each case is a different case, he is using another different board, with smaller distance from copper line to nearby others, also German boards are using delayed insertion relay and a circuit... a connection is made by copper line to the speaker in the case of the speaker delayed insertion, and also circuit protection has some connections too, do not know if they have grounded the heatsink the way i suggested.
When we advance bias and suddenly jumps to a high value, for sure is oscilations, and usually you cannot reduce without switch the amplifier off, then reduce adjusting trimpot and switching the amplifier on once again after some seconds to discharge condensers.
This amplifier is not oscilating (official Taj boards) even when you connect a capacitor in parallel with a resistive load and also in parallel with speaker, no signs of oscilations, also has not oscilations triggered by audio, even saturating level in the input, does not oscilate when you put your finger in the input, this is a sign of stability, only mains hum is present when we do this way.
Taj boards were tested to avoid surprises, this board, the German one, is beeing tested rigth now, the first amplifier made with these boards.
Meanman, better to use Taj boards for safety reasons, as strange things are happening in our friend home... till he find a bug that keep the board free of suspections, i do suggest you not to assemble using these boards.
I have asked several brazilians to build using the official boards to be sure it is fine, i also build by myself and i had no problems, i have built three in three different boards, pictures published, and no one presented problems...maybe his problems is his board, maybe not.... we cannot be sure before some research.
I can guarantee Taj boards, because tested, not this one... i have not tested and the board shows some technicall errors as 90 degrées angles in copper tracks (inductance) and smaller distance between copper lines (capacitances increased).
Also, and repeating, some bias drift is normal and depends on the heatsink temperature...even cold for our fingers means hotter than when at environment temperature, so, there are always fluctuation in degrees.... unless the amplifier is installed inside an Iceberg..maybe, even this way, we gonna have increase in temperature while the surrounding ice melts.
Boys, you are both making an audio amplifier terrorism, spreading panic in the thread.... first search for bugs, them scream something is wrong, this way people will be afraid to build, will think the amplifier is a time bomb..and it is not, i was very carefull to check this several times.
regards,
Carlos
Last edited:
No, sorry, i haven´t...
remove c 12 without replacement? Must i build in a jumper? I will try out, but not this evening ;-)
Just remove them...from both boards, replace with nothing, let the holes there
or, if you cannot let the holes there, install 100n or any small value capacitor in the place..then check if you still have these strange things.
Run a wire, if have not made yet, from transformer center tape (both must be united, center tape from both transformers), run that wire and connect the free point into your heatsink, attach it tigth, with screw or something that guarantees low resistance connection to heatsink ground, to the heatsink plate, to the metal base.
One side connected to the transformers center tape, other side to the metal plate, the heatsink.
regards,
Carlos
or, if you cannot let the holes there, install 100n or any small value capacitor in the place..then check if you still have these strange things.
Run a wire, if have not made yet, from transformer center tape (both must be united, center tape from both transformers), run that wire and connect the free point into your heatsink, attach it tigth, with screw or something that guarantees low resistance connection to heatsink ground, to the heatsink plate, to the metal base.
One side connected to the transformers center tape, other side to the metal plate, the heatsink.
regards,
Carlos
I am not absolutelly sure Rudi boards can be problematic
But i am absolutelly sure Taj boards are fine, i have tested several times, local friends have built, also some strangers from our forum...so...it is guaranteed.
Rudi board looks great, they are interesting, creative and nice..but i could not test, and when oscilations or signs of oscilations, unstabilities happens, we blame the circuit or the board, the circuit was build in several ways, and i did to be absolutelly 10 times sure about, i have panic to offer time bombs to my friends.... no way to me to fail about that..if not 10 times absolutelly sure about something i will not even sleep because of that.
I have enormous respect and good feeling dedicated to the ones build my amplifiers, i am responsable about and no way to offer bad things..things to oscilate or explode.
Watch Rudi board, observe the small distance from track to track, observe 90 degrees angles...this is against the rules developed along those last 50 years of electronics..we do not do this way anymore...so, it is the main suspect in my point of view.
Also, variation in bias is normal, but i never have imagined someone to go measuring from time to time..really i never could imagine such kind of strange things...i think people go listening and not measuring in a such obsessive way.....if i has that imagination i would have prepared a chart, with temperature and bias current when adjusted cold.
Big jumps or current, enormous increase and when you cannot decrease back again..this means oscilations.
Friends, do your search and research in silence, if you publish step by step what goes happening during your search for bugs, the amplifier image will be burned, no one will build afraigthned..very harmfull for the Dx Corporation..... go to direct mail no to be destroying the amplifier image when the guilty one can be yourself.
regards,
Carlos
But i am absolutelly sure Taj boards are fine, i have tested several times, local friends have built, also some strangers from our forum...so...it is guaranteed.
Rudi board looks great, they are interesting, creative and nice..but i could not test, and when oscilations or signs of oscilations, unstabilities happens, we blame the circuit or the board, the circuit was build in several ways, and i did to be absolutelly 10 times sure about, i have panic to offer time bombs to my friends.... no way to me to fail about that..if not 10 times absolutelly sure about something i will not even sleep because of that.
I have enormous respect and good feeling dedicated to the ones build my amplifiers, i am responsable about and no way to offer bad things..things to oscilate or explode.
Watch Rudi board, observe the small distance from track to track, observe 90 degrees angles...this is against the rules developed along those last 50 years of electronics..we do not do this way anymore...so, it is the main suspect in my point of view.
Also, variation in bias is normal, but i never have imagined someone to go measuring from time to time..really i never could imagine such kind of strange things...i think people go listening and not measuring in a such obsessive way.....if i has that imagination i would have prepared a chart, with temperature and bias current when adjusted cold.
Big jumps or current, enormous increase and when you cannot decrease back again..this means oscilations.
Friends, do your search and research in silence, if you publish step by step what goes happening during your search for bugs, the amplifier image will be burned, no one will build afraigthned..very harmfull for the Dx Corporation..... go to direct mail no to be destroying the amplifier image when the guilty one can be yourself.
regards,
Carlos
Last edited:
Dear Carlos,
I apologize very much for the confusion we - Volker and I - contributed to this thread.
When I left Volker's home last Thursday evening I felt strongly impressed by the beautiful
sound the BlameES is able to reproduce.
Be sure: the BlameES is a mature product, a very outstanding amplifier.
Both of us are newcomers to the DIY AMP -world.
We have some "rough understanding" on electronic circuit design, not more.
Maybe we are too curious and tweak without knowing what we do.
And it may also be that my rectangular PCB-design is suspect as well.
The quality of etching is not as it should be and the distances between some of the tracks are indeed so small that they may cause some crosstalk.
I will not continue my design any longer.
I will change to Todd's design.
Best regards - go ahead with the BlameES - Rudi_Ratlos
I apologize very much for the confusion we - Volker and I - contributed to this thread.
When I left Volker's home last Thursday evening I felt strongly impressed by the beautiful
sound the BlameES is able to reproduce.
Be sure: the BlameES is a mature product, a very outstanding amplifier.
Both of us are newcomers to the DIY AMP -world.
We have some "rough understanding" on electronic circuit design, not more.
Maybe we are too curious and tweak without knowing what we do.
And it may also be that my rectangular PCB-design is suspect as well.
The quality of etching is not as it should be and the distances between some of the tracks are indeed so small that they may cause some crosstalk.
I will not continue my design any longer.
I will change to Todd's design.
Best regards - go ahead with the BlameES - Rudi_Ratlos
It is all rigth, i think Volker was desperated, not understanding what happened
and them audio terrorists came to put more fuel in the fire.
VBE multiplier, the stand by adjustment circuit is not more than a resistance, it is called multiplier because multiplies the 600mV from base to emitter by 4.... so, 0.6 multiplied by four represents the 2.4 volts needed to bias (force to work, force to conduct) our four output transistors, drivers and output power units.... as you see and fast concluded, 600mV to each one of them.
Imagine current starts from positive, these electrons are mine (to explain) and will flow from positive to negative, think in current.... starting the positive line, then crosses R14, and then R15 and then go to the VBE multiplier... base resistances in the VBE multiplier have a ratio of 4 to 1, the base to colector use to be 4 times bigger than base to emitter, from colector to emitter you will have current flowing, the transistor is on because energy flows from the coletor to base biasing the unit.
So, current crossed the VBE multiplier transistor, the bias adjustment circuit, also thermal sensor as you will soon understand (I hope so)
After the current enters the colector of Q8 it passes to the emitter, and there's a resistance from colector to emitter, and this is adjusted biasing the transistor, adjusting base to emitter trimpot to increase voltage to the base or to decrease, this will variates, will change, the colector to emitter resistance, and that variation will produce more or less voltage drop from colector to emitter..so, a resistance effect is there, to produce 2.4 volts from colector to emitter, and this will drive the drivers and output transistors to conduct.
Will conduct more if you increase this 2.4 volts, and will conduct less if you decrease this 2.4 volts (more or less, not exactly 2.4 volts)... the current will continue and will face another resistance, the colector to emitter junction from Q7, the second VAS... this unit is conducting, because it is connected to
R16 that colects the current crossing Q6 colector to emitter..when current crosses R16, a voltage appear there, a difference in potential, and this is enougth to drive Q7 on because of it's base to emitter voltage...so..current will cross Q7 because of Q6... and Q6 will be conducting because of Q1 colector current.
to continue....
regards,
Carlos
and them audio terrorists came to put more fuel in the fire.
VBE multiplier, the stand by adjustment circuit is not more than a resistance, it is called multiplier because multiplies the 600mV from base to emitter by 4.... so, 0.6 multiplied by four represents the 2.4 volts needed to bias (force to work, force to conduct) our four output transistors, drivers and output power units.... as you see and fast concluded, 600mV to each one of them.
Imagine current starts from positive, these electrons are mine (to explain) and will flow from positive to negative, think in current.... starting the positive line, then crosses R14, and then R15 and then go to the VBE multiplier... base resistances in the VBE multiplier have a ratio of 4 to 1, the base to colector use to be 4 times bigger than base to emitter, from colector to emitter you will have current flowing, the transistor is on because energy flows from the coletor to base biasing the unit.
So, current crossed the VBE multiplier transistor, the bias adjustment circuit, also thermal sensor as you will soon understand (I hope so)
After the current enters the colector of Q8 it passes to the emitter, and there's a resistance from colector to emitter, and this is adjusted biasing the transistor, adjusting base to emitter trimpot to increase voltage to the base or to decrease, this will variates, will change, the colector to emitter resistance, and that variation will produce more or less voltage drop from colector to emitter..so, a resistance effect is there, to produce 2.4 volts from colector to emitter, and this will drive the drivers and output transistors to conduct.
Will conduct more if you increase this 2.4 volts, and will conduct less if you decrease this 2.4 volts (more or less, not exactly 2.4 volts)... the current will continue and will face another resistance, the colector to emitter junction from Q7, the second VAS... this unit is conducting, because it is connected to
R16 that colects the current crossing Q6 colector to emitter..when current crosses R16, a voltage appear there, a difference in potential, and this is enougth to drive Q7 on because of it's base to emitter voltage...so..current will cross Q7 because of Q6... and Q6 will be conducting because of Q1 colector current.
to continue....
regards,
Carlos
About the VBE multiplier... the thermal or thermicall compensation
.... so, you see that you have a series of resistances..first R14, then R15, them the resistance represented by Q8 colector to emitter junction, then the resistance represented by Q7 colector to emitter junction.
Depending the current (around 7 miliamps...more or less folks, aproximatelly folks) you will have different voltage drops and will set the voltages you need.
But VBE multiplier is not a static fixed resistance....it is when you adjust the amplifier cold, when you heat the transistor, the voltage drop over the junctions drops down, fell down, reduces.
And this is what you use to protect your amplifier to be increasing the heat without stop till the self destruction.
Transistors when you overheat them, or heat them, they reduce internal resistance, this makes more current cross...when more current crosses, then you will have more resistance reduction, and this will make much more and more current cross...and this will increase more and more the heat.... till the destruction..something must be done...and this is done by the VBE multiplier transistor.
It is fixed in the heatsink, so, heat goes to Q8 case.... so, if heatsink increase temperature from 22 to 30 degrees, the transistor senses, the junction produces voltage drop, then the 2.4 volts is not 2.4 volts anymore, drop to 1.9 volts (for instance folks, please guys, no one wants to be precise here)... when you have drop of this voltage, then drives and power transistors receive less Base to emitter voltage, this means they will conduct less... this is the control we have.
This happens dinamically, with audio playing of course..if you stop to listen the audio and go measuring, 2.4 volts is not anymore there..you will have less volts there....if you decide to measure the protective resistance, the ones you use to read the current, dividing the voltage readed by the resistance value in ohms (7.5 divided by 100 results in 75 miliamperes each rail)... well, the voltage measured will be different, if hot, even with the VBE multiplier reducing the bias to the output, the units overheated will drain more current, so voltage will be higher, and the VBE multiplier voltage will be lower...then VBE multiplier will increase (cooling) and the 7.5 volts will decrease because of cooling.
This is dinamic, this is changing all time long..i have never imagine someone stopping to listen to check..really Mr Volker is afraid from this equipment, a pity that, because this will contaminate the forum thread.
Of course, if adjusting you have jumps of voltage, that goes from 7.5 to 20 volts, and you cannot reduce..then you have oscilations, and you can check measuring the output, you will measure AC voltage there..should be zero, but while oscilating you will measure several AC volts, sometimes more than rail voltage..sometimes rail to rail voltage....depends a lot how oscilates and because to what oscilates, depends supply and if loaded or not loaded.
Oscilating, this will be hot, very hot!...not the cool amplifier Volker has.
But we have another type of oscilations, the ones triggered by the sinal, by emphaty, let's say this way, some frequencies and levels triggers the circuit to oscilate, and this usually happens when you have peaks or high frequencies in the audio program..then oscilated for a small period of time, this oscilations turns treble bad, harshes sometimes, sometimes almost erase treble..this depends..usually harshes a lot, sounds alike cracked bamboo.
Amplifier is good, lovely, superior sonics, the best one i have ever listened..was checked, hardly tested and you have my word, my guarantee, a tripple guarantee that will not oscilate or present any kind of harmfull thing..check boards, construction or think about if the effect (voltage variation, iddle consumption variations) if can be normal or not
Really, i have never observed that, i use to check heasinks with my fingers and i trust in the VBE multiplier, the thermal sensor, if heatsink does not increase too much temperature (if heatsink is big enought naturally).
I have observed when creating the Dx Amplifier, the standard, but watch you will see the same VBE multiplier and the same VAS current..almost the same..so, circuit was tested hundreds of times.
regards,
Carlos
.... so, you see that you have a series of resistances..first R14, then R15, them the resistance represented by Q8 colector to emitter junction, then the resistance represented by Q7 colector to emitter junction.
Depending the current (around 7 miliamps...more or less folks, aproximatelly folks) you will have different voltage drops and will set the voltages you need.
But VBE multiplier is not a static fixed resistance....it is when you adjust the amplifier cold, when you heat the transistor, the voltage drop over the junctions drops down, fell down, reduces.
And this is what you use to protect your amplifier to be increasing the heat without stop till the self destruction.
Transistors when you overheat them, or heat them, they reduce internal resistance, this makes more current cross...when more current crosses, then you will have more resistance reduction, and this will make much more and more current cross...and this will increase more and more the heat.... till the destruction..something must be done...and this is done by the VBE multiplier transistor.
It is fixed in the heatsink, so, heat goes to Q8 case.... so, if heatsink increase temperature from 22 to 30 degrees, the transistor senses, the junction produces voltage drop, then the 2.4 volts is not 2.4 volts anymore, drop to 1.9 volts (for instance folks, please guys, no one wants to be precise here)... when you have drop of this voltage, then drives and power transistors receive less Base to emitter voltage, this means they will conduct less... this is the control we have.
This happens dinamically, with audio playing of course..if you stop to listen the audio and go measuring, 2.4 volts is not anymore there..you will have less volts there....if you decide to measure the protective resistance, the ones you use to read the current, dividing the voltage readed by the resistance value in ohms (7.5 divided by 100 results in 75 miliamperes each rail)... well, the voltage measured will be different, if hot, even with the VBE multiplier reducing the bias to the output, the units overheated will drain more current, so voltage will be higher, and the VBE multiplier voltage will be lower...then VBE multiplier will increase (cooling) and the 7.5 volts will decrease because of cooling.
This is dinamic, this is changing all time long..i have never imagine someone stopping to listen to check..really Mr Volker is afraid from this equipment, a pity that, because this will contaminate the forum thread.
Of course, if adjusting you have jumps of voltage, that goes from 7.5 to 20 volts, and you cannot reduce..then you have oscilations, and you can check measuring the output, you will measure AC voltage there..should be zero, but while oscilating you will measure several AC volts, sometimes more than rail voltage..sometimes rail to rail voltage....depends a lot how oscilates and because to what oscilates, depends supply and if loaded or not loaded.
Oscilating, this will be hot, very hot!...not the cool amplifier Volker has.
But we have another type of oscilations, the ones triggered by the sinal, by emphaty, let's say this way, some frequencies and levels triggers the circuit to oscilate, and this usually happens when you have peaks or high frequencies in the audio program..then oscilated for a small period of time, this oscilations turns treble bad, harshes sometimes, sometimes almost erase treble..this depends..usually harshes a lot, sounds alike cracked bamboo.
Amplifier is good, lovely, superior sonics, the best one i have ever listened..was checked, hardly tested and you have my word, my guarantee, a tripple guarantee that will not oscilate or present any kind of harmfull thing..check boards, construction or think about if the effect (voltage variation, iddle consumption variations) if can be normal or not
Really, i have never observed that, i use to check heasinks with my fingers and i trust in the VBE multiplier, the thermal sensor, if heatsink does not increase too much temperature (if heatsink is big enought naturally).
I have observed when creating the Dx Amplifier, the standard, but watch you will see the same VBE multiplier and the same VAS current..almost the same..so, circuit was tested hundreds of times.
regards,
Carlos
Well uncle charlie, you are talking about 2.4 volts..but this is not correct!
We have 1.2 volts positive and 1.2 volts negative..how this happens?
1.2 volts positive plus 1.2 volts negative means fatorial of 2.4 volts
The 0.6 volts in the positive power transistor, from base to emitter, happens because it is connected (stand by mode, iddle) to the output line...so, transistors develops 600 milivolts from base to emitter, the upper one will develop 600 milivolts positive, and the lower one, the PNP one, will develop 600 milivolts negative.
The drivers faces already 600 milivolts in the power output transistors base to emitter junctions, so, as they are in series, you have 600 milivolts plus 600 milivolts, if upper transistors (NPN) you will have positive 1.2 volts.
The same happens to the negative side.
The output line is connected, to DC, almost to ground, as speaker resistance is very small, as output line is adjusted (off set) to read some milivolts only, so, output line is almost the ground...the differencial pair controls the stuff to make this stable..without differential the voltage is not so precise..will be very crazy.
Well.... i suppose you novices, could understand...i do not know the one is novice or not, i am not a magic man to enter your brains (only sometimes i can do that), so i cannot evaluate you folks, this servers for beginners, Rudi and advanced amateurs should forgive me to talk about such a foolish things.
Yes, you can use a single resistance, calculated by ohms law.... 7 miliamperes (0.007) is the current (maybe, i do not remember exactly) and the voltage is 2.4 volts..so, a single resistance can substitute Q8 colector to emitter junctions (that were operating alike a resistance, a heat sensed resistance a NTC i think, negative thermistance, as reduce resistance when overheated)...but the resistance cannot reduce its own resistance when overheated, so, resistance will not protect your amplifier, but serves for prototypes, something for a while only.
A 330 ohms resistance may work fine...but do not let the resistance there, substitute by a series of 4 diodes pointing down or use a VBE multiplier stage..if diodes must touch heatsink to control the heat.
regards,
Carlos
We have 1.2 volts positive and 1.2 volts negative..how this happens?
1.2 volts positive plus 1.2 volts negative means fatorial of 2.4 volts
The 0.6 volts in the positive power transistor, from base to emitter, happens because it is connected (stand by mode, iddle) to the output line...so, transistors develops 600 milivolts from base to emitter, the upper one will develop 600 milivolts positive, and the lower one, the PNP one, will develop 600 milivolts negative.
The drivers faces already 600 milivolts in the power output transistors base to emitter junctions, so, as they are in series, you have 600 milivolts plus 600 milivolts, if upper transistors (NPN) you will have positive 1.2 volts.
The same happens to the negative side.
The output line is connected, to DC, almost to ground, as speaker resistance is very small, as output line is adjusted (off set) to read some milivolts only, so, output line is almost the ground...the differencial pair controls the stuff to make this stable..without differential the voltage is not so precise..will be very crazy.
Well.... i suppose you novices, could understand...i do not know the one is novice or not, i am not a magic man to enter your brains (only sometimes i can do that), so i cannot evaluate you folks, this servers for beginners, Rudi and advanced amateurs should forgive me to talk about such a foolish things.
Yes, you can use a single resistance, calculated by ohms law.... 7 miliamperes (0.007) is the current (maybe, i do not remember exactly) and the voltage is 2.4 volts..so, a single resistance can substitute Q8 colector to emitter junctions (that were operating alike a resistance, a heat sensed resistance a NTC i think, negative thermistance, as reduce resistance when overheated)...but the resistance cannot reduce its own resistance when overheated, so, resistance will not protect your amplifier, but serves for prototypes, something for a while only.
A 330 ohms resistance may work fine...but do not let the resistance there, substitute by a series of 4 diodes pointing down or use a VBE multiplier stage..if diodes must touch heatsink to control the heat.
regards,
Carlos
Last edited:
Why and how boards drives circuits to oscilate!
First, transistors oscilated because they can, modern transistors (our main tragedy) are high speed devices, this means they can work in frequencies of several megahertz (100 and 150 Megahertz is very normal and common and usual to find now a days)...if you offer the correct conditions to them to oscilate they will run into oscilations.
And prejudice forces the designers to avoid lower speed units, because if you do that, fast someone will come with prejudices and will say if he can substitute by a better transistor...you see.... high frequency means better in their minds.
In a matter of fact they are, they can work as transmitters and oscilators too, and they can be used in high power amplifeirs, when you need a very good slew rate (time of climbing in the square wave form reproduction, time to reach the maximum)... in a very high powered amplifier, when you may have 200 volts of voltage variation in microseconds, well, the faster transistor can do this better.
But Dx Blame ES and all my amplifier, the majority, has to climb to a much lower square wave voltage, because they are just 20 volts RMS output amplifiers..so, you have to increase not too much, not very needed to be super fast...even this way, because prejudices, i am using fast transistors too..i had to do this way..tired of criticisms about.
Board offer the conditions to oscilate, even if the circuit design is good or very good, a board can make the amplifier oscilate.
Straight lines are not straigth, the have some micro degrees bent, the universe rounded because of gravity, we have no straigth line, nowhere.
They are inductors, and variates the inductance because of length....bigger the length bigger the inductor value.as
Copper lines, if runs parallel, almost touching one each other, represents capacitor plates, and you have a lot of capacitors, they are bigger in capacitance when lines are long, they are bigger in capacitance when lines are too close one related the other..so, you have several capacitors in the circuit, a bunch of them.
If these ones are in the first transistor base, or another high gain device..then the trouble starts..depending the inductance value, associated with the capacitance value, the transistor base can "see", or feel, or sense..then you will have a tuned circuit and the stage will oscilate,and will send this oscilation to the following stages that will amplify the oscilations.
I hope i could be helpfull about that stuff.
regards,
Carlos
First, transistors oscilated because they can, modern transistors (our main tragedy) are high speed devices, this means they can work in frequencies of several megahertz (100 and 150 Megahertz is very normal and common and usual to find now a days)...if you offer the correct conditions to them to oscilate they will run into oscilations.
And prejudice forces the designers to avoid lower speed units, because if you do that, fast someone will come with prejudices and will say if he can substitute by a better transistor...you see.... high frequency means better in their minds.
In a matter of fact they are, they can work as transmitters and oscilators too, and they can be used in high power amplifeirs, when you need a very good slew rate (time of climbing in the square wave form reproduction, time to reach the maximum)... in a very high powered amplifier, when you may have 200 volts of voltage variation in microseconds, well, the faster transistor can do this better.
But Dx Blame ES and all my amplifier, the majority, has to climb to a much lower square wave voltage, because they are just 20 volts RMS output amplifiers..so, you have to increase not too much, not very needed to be super fast...even this way, because prejudices, i am using fast transistors too..i had to do this way..tired of criticisms about.
Board offer the conditions to oscilate, even if the circuit design is good or very good, a board can make the amplifier oscilate.
Straight lines are not straigth, the have some micro degrees bent, the universe rounded because of gravity, we have no straigth line, nowhere.
They are inductors, and variates the inductance because of length....bigger the length bigger the inductor value.as
Copper lines, if runs parallel, almost touching one each other, represents capacitor plates, and you have a lot of capacitors, they are bigger in capacitance when lines are long, they are bigger in capacitance when lines are too close one related the other..so, you have several capacitors in the circuit, a bunch of them.
If these ones are in the first transistor base, or another high gain device..then the trouble starts..depending the inductance value, associated with the capacitance value, the transistor base can "see", or feel, or sense..then you will have a tuned circuit and the stage will oscilate,and will send this oscilation to the following stages that will amplify the oscilations.
I hope i could be helpfull about that stuff.
regards,
Carlos
Oscilations happens because of pick up.... because output is beeing captures by an
input device.
If you have a coil, the output coil, and power is entering the coil, then you have a very big magnetic energy there, electro magnetic waves travells into the space, and can reach the input..then you will have a microphonic effect, the amplifier will oscilate.
Sensitive circuits wire must travel using shielded cables, to avoid pick up signal from surroundings.
Radio frequency transmitters also enters the amplifiers and force them to oscilate... and this means Broadcasting Radio Stations, Television or Radio, Cell phone towers, electronic baby watching machines (radio) and cordeless telephones.... well, and several other things.
Long run of copper is not good, copper line sin parallel is not good, better to use jumpers, as perpendicular is better than parallel to pick up things..perpendicular is much less sensitive.
Well... this is very big to talk about..i will stop here not to publish 100 pages about...well, i can publish three or four, but the subject is big, can he 100 pages without troubles, the fact i cannot write that because i have not the knowledge to do, does not means i cannot evaluate how big that thing can be.
Watch Radio Amateurs Handbook and you gonna see how big this chapter is..search in A.R.R.L. American Radio Relay League (or something alike).
Todd made the board, has followed the best theories to do the board... i have checked many times, i have assemble several times, to be sure, absolutelly sure it is safe.
Please guys, do not put all my work under risk with untested boards...build using TAJ board, and using my schematic, do not invent nothing, do not change, or substitute a single part or value.... well, after constructed and tested, if passed to you, then you should tweak to your taste..but first publish play fine and sounded good, then after is up to you.
regards,
Carlos
input device.
If you have a coil, the output coil, and power is entering the coil, then you have a very big magnetic energy there, electro magnetic waves travells into the space, and can reach the input..then you will have a microphonic effect, the amplifier will oscilate.
Sensitive circuits wire must travel using shielded cables, to avoid pick up signal from surroundings.
Radio frequency transmitters also enters the amplifiers and force them to oscilate... and this means Broadcasting Radio Stations, Television or Radio, Cell phone towers, electronic baby watching machines (radio) and cordeless telephones.... well, and several other things.
Long run of copper is not good, copper line sin parallel is not good, better to use jumpers, as perpendicular is better than parallel to pick up things..perpendicular is much less sensitive.
Well... this is very big to talk about..i will stop here not to publish 100 pages about...well, i can publish three or four, but the subject is big, can he 100 pages without troubles, the fact i cannot write that because i have not the knowledge to do, does not means i cannot evaluate how big that thing can be.
Watch Radio Amateurs Handbook and you gonna see how big this chapter is..search in A.R.R.L. American Radio Relay League (or something alike).
Todd made the board, has followed the best theories to do the board... i have checked many times, i have assemble several times, to be sure, absolutelly sure it is safe.
Please guys, do not put all my work under risk with untested boards...build using TAJ board, and using my schematic, do not invent nothing, do not change, or substitute a single part or value.... well, after constructed and tested, if passed to you, then you should tweak to your taste..but first publish play fine and sounded good, then after is up to you.
regards,
Carlos
Last edited:
This is a joke, right 😉
Like in Roman Empire:
"Here my people, I bring you the gift of the greatest Amp in the world!
Build it and be happy with it and don't question it. Obey or off with your head!"
Really funny 😀
Well don't bother too much about me, or my opinions.
I see guys like me are not welcome here. I won't bother you again. I know you will be better off without me.
http://www.youtube.com/watch?v=5EKyhpKTAm0
Enjoy.
- Status
- Not open for further replies.