Hi ,Hugh
I did build and test serial differential amps in the 80s.
As is the case with simple differential like your AKSA55 ,
a shunt compensation doesn t work well if not at all
with such single ended amps.
Second pole is dominant well before the open loop*gain reach
unity, and as, the amp is easily unstable.
Stable it is only with the use of an RL output network.
Without it, it works badly even with a resistive load as
the amp is basically underdumped.
The least is to make a simulation to check the
corresponding open and closed loop gain and phase
responses.
For the rest, i don t give any importance to the sayings
about an amp , as this one is praised despite these
shortfalls. I have more confidence in a technical study
of the thing than in what ressemble marketing and
auto suggestion behaviour.
Cheers,
Wahab
Nonsense.
Please, don't embarrass yourself further by sim-poking the stuff you obviously know too little about.
Typical fanboism response...
Please, use technical arguments.
What is obvious is that you consider yourself competent
and myself uncompetent without any technical ground
to support your sayings.
Who is talking with non sense?..
This is a technical forum, and unless you have
some point to prove me wrong, i suggest you to
not comment anymore since you are briging nothing
to the technical debate..
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The extreme lentgh of the thread with a gazillion
modifications through the posts say it all.....😀
You where perhaps right after all : the amp is more stable
than its schematic...🙄
I have 2 stereo Symasym built and running (for well over a year now). No issues at all. Was checked at full power into resistive load before being put into service, output was clean and clipped cleanly. No oscillations present.
I would reccomend the design, I used the PCB detailed on the 5.3 web page, had them made for me. Sounds very clear 🙂
I would reccomend the design, I used the PCB detailed on the 5.3 web page, had them made for me. Sounds very clear 🙂
my dear learned frnds i dont have much of money to go around with if I had so much money i would have built and tested every amp on this forum ........... but my hands r tied i have to choose one & stick with it good or bad ,so I wanted help from u people so that I can invest my little amount of money in the best diy stuff ..........
Wat do u think about DX blames St how good is it ...........?????
regards
aniket
Wat do u think about DX blames St how good is it ...........?????
regards
aniket
Wahab,
You reveal rather too much of yourself.
You are smart, sure, I concede that, but you imagine yourself to be smarter than Michael Bittner, all based on your simulations and empirical experience with a similar but not identical circuit. You must realise simulations rely implicitly on accurate models - which we both know are not widely available.
Please leave me, my designs, and my implied marketing out of this, it's about YOU, and YOUR judgement of another's work, a man much respected here.
Technical arguments are certainly an important aspect of the equation, particularly specific aspects of stability. But they are not the only significant aspects of amp design. I notice you shy away from any subjective assessment, yet, subjective assessment is very important. Perhaps the amp is more than adequately stable for its intended function, AND sounds very, very good. That is certainly the observation of many here. Would you still pronounce it technically inferior? What does this prove?
In the land of the blind, the one eyed man is king......
Hugh
You reveal rather too much of yourself.
You are smart, sure, I concede that, but you imagine yourself to be smarter than Michael Bittner, all based on your simulations and empirical experience with a similar but not identical circuit. You must realise simulations rely implicitly on accurate models - which we both know are not widely available.
Please leave me, my designs, and my implied marketing out of this, it's about YOU, and YOUR judgement of another's work, a man much respected here.
Technical arguments are certainly an important aspect of the equation, particularly specific aspects of stability. But they are not the only significant aspects of amp design. I notice you shy away from any subjective assessment, yet, subjective assessment is very important. Perhaps the amp is more than adequately stable for its intended function, AND sounds very, very good. That is certainly the observation of many here. Would you still pronounce it technically inferior? What does this prove?
In the land of the blind, the one eyed man is king......
Hugh
Simulators are relevant when it comes to compute a bandwith
and phase responses.
This parameter is dependant on internal capacitances and
current capabilities of the components, and the said laws
are linear vs frequencies, meaning that the error margins
are low, moreover as this analysis is made in small signal
conditions, thus eliminating most of the currents capabilities
in the equation.
Of course, in large signal conditions , the figures will
dramatically increase in the bad direction.
This beg the next subject which is your amp
that i used as an exemple of simple differential (LIN) amp ,
not to trash it , but to expose the fact that it don t use
a shunt compensation , as these kind of topologies
don t work with these kind of compensation.No MORE.
As for the marketing behaviour , i was talking about the
praising of the symasym that goes through this forum,
not about your products.
To go back to the subject, i d like to add that stability, and
thus gain/phase response, is the first criterion of a
good amp amp , before THD.
An amp that ring too much provide no listening pleasure,
quite the contrary.
Does your subjective listenings experiences agree with that ?....
Wahab
Wahab,
TECHNICAL:
Bandwidth issues depend on accurate, non-linear rendition of depletion layers, Early effect, dielectric absorption, layout, all relevant to predict phase shift for a given layout. Models to encompass these parameters are very, very tricky to find. I do not place more than an approximation of accuracy on the ability of a simulator to set the lag comp capacitor, for example, unless you use a milspec simulator with factory researched models, and even then there is doubt because of layout issues. You are dealing with pF of capacitance, very easily corrupted by layout parasitics. Most HF poles are in the range 750KHz to 2MHz, so it's RF we are talking of here, and none of the commonly available, free PSpice programs can accommodate layout issues unless ALL parasitics are known.
Sure, Bode plots are important, however, once stability criteria are met, and loop gain is less than unity by the HF pole, stability is attained, further discussion does not relate to absolute stability, simply to phase margin with particular (read: reactive) loads.
SUBJECTIVE:
AB comparisons of amps, using identical source, music, speakers, do reveal differences between amps. Phase margin may indeed have something to do with it. However there is much more.
Once stability criteria are met, and building a stable amp is not rocket science and does not require exhaustive effort, other factors assume importance, such as harmonic distortion profile, to give one.
You wish to talk technical, well, answer this salient question: To what extent does the harmonic profile affect the subjective listening experiment? Care to comment on Jean Hiraga's proposition that a monotonic decrease is best? And BTW, is this really a full on technical forum?
I repeat: Unless you have privately discussed with the designer your criticisms of his amplifier and actually built and tested the amp, your criticisms of Michael Bittner's design is less than plausible, and bad manners besides. You should also have made observation of the subjective sound qualities, an issue important to those seeking to build it. Your comments about the Symasym show a strange arrogance, and I can't imagine what you would gain by making them so emphatically.
I know Michael, I know him to be extraordinarily smart, and judging by your unidimensional discussion of amp stability and complete denial of subjectivity, I'd say you would benefit from conversation with him. Try PMing him; he's a great guy.
Enough from me, have a great day.
Hugh
TECHNICAL:
Bandwidth issues depend on accurate, non-linear rendition of depletion layers, Early effect, dielectric absorption, layout, all relevant to predict phase shift for a given layout. Models to encompass these parameters are very, very tricky to find. I do not place more than an approximation of accuracy on the ability of a simulator to set the lag comp capacitor, for example, unless you use a milspec simulator with factory researched models, and even then there is doubt because of layout issues. You are dealing with pF of capacitance, very easily corrupted by layout parasitics. Most HF poles are in the range 750KHz to 2MHz, so it's RF we are talking of here, and none of the commonly available, free PSpice programs can accommodate layout issues unless ALL parasitics are known.
Sure, Bode plots are important, however, once stability criteria are met, and loop gain is less than unity by the HF pole, stability is attained, further discussion does not relate to absolute stability, simply to phase margin with particular (read: reactive) loads.
SUBJECTIVE:
AB comparisons of amps, using identical source, music, speakers, do reveal differences between amps. Phase margin may indeed have something to do with it. However there is much more.
Once stability criteria are met, and building a stable amp is not rocket science and does not require exhaustive effort, other factors assume importance, such as harmonic distortion profile, to give one.
You wish to talk technical, well, answer this salient question: To what extent does the harmonic profile affect the subjective listening experiment? Care to comment on Jean Hiraga's proposition that a monotonic decrease is best? And BTW, is this really a full on technical forum?
I repeat: Unless you have privately discussed with the designer your criticisms of his amplifier and actually built and tested the amp, your criticisms of Michael Bittner's design is less than plausible, and bad manners besides. You should also have made observation of the subjective sound qualities, an issue important to those seeking to build it. Your comments about the Symasym show a strange arrogance, and I can't imagine what you would gain by making them so emphatically.
I know Michael, I know him to be extraordinarily smart, and judging by your unidimensional discussion of amp stability and complete denial of subjectivity, I'd say you would benefit from conversation with him. Try PMing him; he's a great guy.
Enough from me, have a great day.
Hugh
The problem is that an amp that is underdamped see
a vast increase in loop gain at the second pole frequency
as soon that a capacitance is added to the load ,
and so , gain margin will be no more high enough...
Such an amp will be conditionaly stable , never a good thing
as it become then load dependant to produce a good sound,
i.e, all depend of the speakers in such a case.
And that s the case of this amp.
Anyway, this topology has been explored well before, and
the shortfalls i m talking about are surely well known
by the designers of the time , Kaneda among others...
I believe the thread starter asked for a power amp suggestion, not an analysis of an example.
How about an amp advice instead, such as the NE553* + darlington AWahaB ?
How about an amp advice instead, such as the NE553* + darlington AWahaB ?
NE5534 + Darlingtons can yield a good amp , no doubt ,
but unfortunately , it s surely too low power for the
builder that did open this thread, unless he wants
to make a 7.1 AV amp....
About 50 Watts RMS/8 ohm per channel is in the range
that would undoubtly bring him some satisfaction for a
stereo system...
i have dealt with cfp designs it is quite good but many learned forum members dont like it and say its nt stable ........... as i did nt have instruments to see wat actually happens i believed them ........... can any body truely tell wat is the best diy amp😕 .............as many had built them ........
regards
aniket
I think its sad that a simpler request for advise on which amp to build has resulted in this discussion. I didn't realise that this was supposed to be an exclusivly technical forum - if I had, I would not have bothered looking at it as I would not be qualified enough to participate. I built Symasym as a complete novice after finding it on this forum and found the thread and project page amswered every query that I had during building - Unfortunatly I'm unable to comment on its "technical" stability or "design flaws" as I don't have the technical knowledge, but I can say it has performed exactly as described on the project page, and sounds very very good - well done and thank you Michael
That's almost a paradoxial oxymoron.
The best diy amps are the ones built by the least, not the most.
Examples that can be found on this forum are the PGP (pretty good power amp) or the ExtremA.
Your definition should be the one that suits your requirements best ; with boards, common available parts, and plenty of support.
The SymAsym covers all of that.
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