I found out that the plain P3A, displays nice results at lower currents, LTP at about 1.1ma, VAS at 5ma drivers at 3ma, over than that IMD in the linear region gets ugly.
guys .. you are in a ghost chase here ...
From the entire forum there should be just a handful of people that may translate what you see in your simulator to a sonic signature to make a choice, work with and advance from ( i can actually think of just 2 guys that can do that )
Now what you are missing here as a general rule that the P3A sounds that well and its very popular around many listeners for two basic reasons
1) the specific content of harmonics that you are trying to play with and/or remove
2) the reaction or interaction if you want of the CFP with the load which works in a different way than a classic EF2 ( also cannot be accurately predicted or translated on a simulator )
Over simulated amplifiers will end up with no character and no soul ...Allow the design as is , built it well , be nice to it In the end of this there is not much of P3A left to work with ...
Seen guys that have 100 times my knowledge presenting amps with a singleton in the input in the year 2015 WHY? because it has a nice sonic signature from tech aspect LTP will be always better and sound different...
My very best regards
Sakis
From the entire forum there should be just a handful of people that may translate what you see in your simulator to a sonic signature to make a choice, work with and advance from ( i can actually think of just 2 guys that can do that )
Now what you are missing here as a general rule that the P3A sounds that well and its very popular around many listeners for two basic reasons
1) the specific content of harmonics that you are trying to play with and/or remove
2) the reaction or interaction if you want of the CFP with the load which works in a different way than a classic EF2 ( also cannot be accurately predicted or translated on a simulator )
Over simulated amplifiers will end up with no character and no soul ...Allow the design as is , built it well , be nice to it In the end of this there is not much of P3A left to work with ...
Seen guys that have 100 times my knowledge presenting amps with a singleton in the input in the year 2015 WHY? because it has a nice sonic signature from tech aspect LTP will be always better and sound different...
My very best regards
Sakis
Member
Joined 2009
Paid Member
I was thinking you knew it better than me,
Mikrocap does not seem to have a detailed reference with its IMD function. By default the injected tone was 13 & 14Khz (should be 19-20Khz in a full audioband?). I'm not so sure about the vertical axis reference but the horizontal axis is the span of frequencies, Now within the harmonic.content there are products of intermodulation produced seen in the waves not harmonically related in the fundamentals. How to quantify the distortion produced? That is something that I cannot explain as I am no expert, that is why I was showing the graphs so that others more knowledgeable than me will explain it better. I do think other simulation programs plot it differently, than what I have posted.Correct me if I am wrong.
LEDs glowing very dimm
I am facing problem with my P3a build. Everything seems working alright. Stable bias at 50mv, 0.2mv DC offest nice looking 2k Sine wave(8ohm load) . But green led is not glowing bright. Which was glowing bright when I tested the amp with mains bulb tester.
Power supply 36v rails.I also played music for half an hour without any issues. None of the components were hot.
Mjl21194 as outputs bc546 for inputs BD139 and Bd 140. It's Alex mm pcb with corrected Led alignment. Can anyone guide me where to look for problem.
Regards
Goutham
I am facing problem with my P3a build. Everything seems working alright. Stable bias at 50mv, 0.2mv DC offest nice looking 2k Sine wave(8ohm load) . But green led is not glowing bright. Which was glowing bright when I tested the amp with mains bulb tester.
Power supply 36v rails.I also played music for half an hour without any issues. None of the components were hot.
Mjl21194 as outputs bc546 for inputs BD139 and Bd 140. It's Alex mm pcb with corrected Led alignment. Can anyone guide me where to look for problem.
Regards
Goutham
Last edited:
If you read Rod's circuit description, the voltage across the LED should be 1.9-2.0V and stable in operation with a signal. However, LEDs now vary more in the voltage drop produced by the various colours when lit, than when P3A was first developed and voltage variation (or perhaps the soldering or any other changes you may have made during testing) could be causing a problem. If you are using new rather than old LEDs, they would be my first suspect, if the amplifier still works OK.
A stable voltage is probably more important than the exact voltage since the LED voltage is a reference for the current regulator, controlling the LTP bias current and hence the operating point of the input stage. This bias current can be calculated and checked for correctness by Ohm's law from the voltage across R7.
A stable voltage is probably more important than the exact voltage since the LED voltage is a reference for the current regulator, controlling the LTP bias current and hence the operating point of the input stage. This bias current can be calculated and checked for correctness by Ohm's law from the voltage across R7.
To be able to choose parts this can only be done through comparison only on a given bias and a given circuit more or less
Please notice that choice of parts and choice of bias can also be a matter of opinion and this is what makes the choice rather complicated .
Example
Listeners that go for piano and a voice will be more happy with plenty of bias while speed will not bother them in this case amplifier can be made with 2N3055
Hard rock listeners will be happy with almost class B operation and very low bias the packet of harmonics and distortions produced is similar to the distortions injected to electric guitars and many people love that ( ?????) (!!!!!!) Mje 340 MJE150XX semis there will sound superb
Listeners like me into soulful house that require a number of instruments inside the program , some of them natural , vocals , crisp highs ,tight and speedy low end will have to go for high speed semis obviously Japanese and a good amount of bias to a level of 70 ma but no more than that .....
PS there is no stability issues in the P3a the circuit is very forgiving to even poor choice of parts
Please notice that choice of parts and choice of bias can also be a matter of opinion and this is what makes the choice rather complicated .
Example
Listeners that go for piano and a voice will be more happy with plenty of bias while speed will not bother them in this case amplifier can be made with 2N3055
Hard rock listeners will be happy with almost class B operation and very low bias the packet of harmonics and distortions produced is similar to the distortions injected to electric guitars and many people love that ( ?????) (!!!!!!) Mje 340 MJE150XX semis there will sound superb
Listeners like me into soulful house that require a number of instruments inside the program , some of them natural , vocals , crisp highs ,tight and speedy low end will have to go for high speed semis obviously Japanese and a good amount of bias to a level of 70 ma but no more than that .....
PS there is no stability issues in the P3a the circuit is very forgiving to even poor choice of parts
Is that so? The push-pull topology is innately unstable and the CFP is innately unstable. The need for phase compensation capacitor is a sign of illness. The compensation capacitor further reduces an already poor frequency range. I find the two 100 pF capacitors in the original circuit huge. Jean Hiraga showed that the capacitor is avoidable with carefully chosen devices. In the light of that, should I be impressed by the P3A?
well ....miller caps exist in many amplifiers correctly said better choice of semis might be able to reduce the values, a more even gain distribution , and proper choice of bias per stage might also help
BUt here you are missing the point
The P3a as is offers a low part count and a specific combination of topologies in a general simplified circuit ...the combination of bootstrap and the CFP output stage will offer a specific package of harmonics and distortions which as in most cases is a given fact
Minor refinements could produce a rather spectacular improvement but the basic circuit can remain the same ...
MAke your self prototype use anything available then you will know if not impressed ....
Poor frequency range ???? what are you talking about .... a correctly made P3a will hit easily 40khz of a very well shaped square wave and more than 100k in sine wave ...
BUt here you are missing the point
The P3a as is offers a low part count and a specific combination of topologies in a general simplified circuit ...the combination of bootstrap and the CFP output stage will offer a specific package of harmonics and distortions which as in most cases is a given fact
Minor refinements could produce a rather spectacular improvement but the basic circuit can remain the same ...
MAke your self prototype use anything available then you will know if not impressed ....
Poor frequency range ???? what are you talking about .... a correctly made P3a will hit easily 40khz of a very well shaped square wave and more than 100k in sine wave ...
Last edited:
The high level of instability considerably lessens the advantage of driving the output transistors by a common-emitter voltage amplifier (in place of a dull common-collector amplifier). The compensation capacitor is an unmistakable indicator of insufficient frequency range, springing from a resonant, high impedance area being in scarce supply of excitable charges and exhibiting large phase shifts. Yes, many amplifiers are phase compensated, so their chance of producing low distortion at high frequencies is slim.
It is exceedingly difficult to find adequate complementary bipolar output transistors (with the right current gain and matched transition frequency) for this circuit.
Besides, I think that you are a down-to-earth man and agree with some of your statements.
It is exceedingly difficult to find adequate complementary bipolar output transistors (with the right current gain and matched transition frequency) for this circuit.
Besides, I think that you are a down-to-earth man and agree with some of your statements.
Last edited:
Truly now do you have any idea of how old is this design Not as presented or bit modified from Rod but when it was originally created
Its got to be something between 1969-1974
now lets get serious about that .....
In reality though,today there is well known amplifiers, successors also that have a sigleton in the input next to a conventional LTP or a diamond Would you like to wonder why ?
Try this :
A sigleton will be far less accurate next to an LTP but it produces a sonic signature that is more dear to the human ear
Alike happens with the bootstrap
Alike happens with the CFP
Now in reality there technical reasons like the content of harmonics and the package of distortions that makes one amplifier like that "Dear" to the human ear Obviously under this line will be choice of semis and level of bias
Like tube amplifiers ...they suffer from a number of problems but still there is ppl that love them
In reality yet again what makes the P3a a successor is : ...
For the most people the P3a is so simple to make , the amplifier is very forgiving to poor choices of semis , poor tuning/choice of bias and since the circuit is made out of a very few parts it will play far more better than many consumer amplifiers ( due to simplicity only though )
For some other people that spend some time with this circuit and its deep hidden secrets i can verify one thing :
The sonic signature produced by the specific amplifier is unbeatable few EF 2 amplifiers can just seat next to it at the same class, and perfection will require a proper choice of semis depending on the application, a wise choice of bias and a few other small but very important details ...The P3a will play well at most construction ....to achieve serious numbers with it will require some work on the given circuit ...
At east electronics we do consumer hifi ....we do a lot, average 1000 amplifiers per year ....Obviously name any amplifier you like i have been there more than once from accuphase to denon ,from electrocompaniet to Adcom , mosfet IGBT bipolar name it we have heard it ...Still the P3a is unbeatable .... Hegel sounded a bit better but let us not forget that it costs 3.000 euro ...
My 2 cents
Its got to be something between 1969-1974
now lets get serious about that .....
In reality though,today there is well known amplifiers, successors also that have a sigleton in the input next to a conventional LTP or a diamond Would you like to wonder why ?
Try this :
A sigleton will be far less accurate next to an LTP but it produces a sonic signature that is more dear to the human ear
Alike happens with the bootstrap
Alike happens with the CFP
Now in reality there technical reasons like the content of harmonics and the package of distortions that makes one amplifier like that "Dear" to the human ear Obviously under this line will be choice of semis and level of bias
Like tube amplifiers ...they suffer from a number of problems but still there is ppl that love them
In reality yet again what makes the P3a a successor is : ...
For the most people the P3a is so simple to make , the amplifier is very forgiving to poor choices of semis , poor tuning/choice of bias and since the circuit is made out of a very few parts it will play far more better than many consumer amplifiers ( due to simplicity only though )
For some other people that spend some time with this circuit and its deep hidden secrets i can verify one thing :
The sonic signature produced by the specific amplifier is unbeatable few EF 2 amplifiers can just seat next to it at the same class, and perfection will require a proper choice of semis depending on the application, a wise choice of bias and a few other small but very important details ...The P3a will play well at most construction ....to achieve serious numbers with it will require some work on the given circuit ...
At east electronics we do consumer hifi ....we do a lot, average 1000 amplifiers per year ....Obviously name any amplifier you like i have been there more than once from accuphase to denon ,from electrocompaniet to Adcom , mosfet IGBT bipolar name it we have heard it ...Still the P3a is unbeatable .... Hegel sounded a bit better but let us not forget that it costs 3.000 euro ...
My 2 cents
Last edited:
Member
Joined 2009
Paid Member