Hi Eva,
I am glad to hear that you tried this out for yourself.
Far too much I read on the Internet is posted merely based on hearsay, or there is no 'reference' shown to indicate how the results have been arrived at.
The only difference between your trials on output inductors, and mine on Zobel networks, seems to be that although we both measured the results (or attempted to, in my case, but found no measurable differences, as I said!), you don't make any mention of what the effect (if any) was on the sound, whereas I did.
I cannot help wondering, when anyone asks about which of two choices is likely to give "the best most natural sound" as happened here, which style of reply would be the most useful to him
However, it may be that you know fab better than I do, and that really he meant "which would measure the best", in which case I have completely wasted a lot of my time!
Regards,
I am glad to hear that you tried this out for yourself.
Far too much I read on the Internet is posted merely based on hearsay, or there is no 'reference' shown to indicate how the results have been arrived at.
The only difference between your trials on output inductors, and mine on Zobel networks, seems to be that although we both measured the results (or attempted to, in my case, but found no measurable differences, as I said!), you don't make any mention of what the effect (if any) was on the sound, whereas I did.
I cannot help wondering, when anyone asks about which of two choices is likely to give "the best most natural sound" as happened here, which style of reply would be the most useful to him
However, it may be that you know fab better than I do, and that really he meant "which would measure the best", in which case I have completely wasted a lot of my time!
Regards,
Folks,
I have the gnawing feeling that we may be getting a little ahead of ourselves here.
Fab's original question was simply whether any 1 of the 2 displays on his scope was better than the other. Defining "better", I took it that he was concerned about amplifier stability under various conditions, as oscillatory effects were clearly way above the audio spectrum. Sonic effects came up only in post #5, and then not what they are, but rather whether there would be any - there is a difference! We did all appear to concentrate on the stability effects, not sonics.
Bobken, I think that in your post #8 you may have inadvertently brought sonics into the equation by stating that the only way to be sure about "such choices" as Fab had to make was to actually listen to the results. My perception of "the choices he had to make" was that it was all about supersonic to r.f. effects which could possibly cause instability and the ill consequences thereof, not how it might sound.
And in this region, with respect to whoever says what, one can only have success by measuring or analysing on a computer programme, as there is nothing to hear (as we all seem to agree) unless the circuits under discussion (series choke and Zobel) were extending into the audio spectrum, where they were never supposed to be working in the first place. In the case of an amplifier so poorly designed that this was required, essential attention has to be devoted elsewhere, e.g. the compensation as Bobken suggested. In this respect I am also confused as to the audible difference between components, employed as said in circuits that should not have effect in the audio spectrum in the first place.
I do not wish to enter a fray about the significance of the often touted listening tests, except to cite an example from a very well known audio magazine: Years ago some 6 internationally known critics were asked to make a short-list of the best amplifiers (amongst other components) in their view, as well as their personal choice. The personal best for some were not even on the list of others. And these were seasoned critics! For whose taste must I now design?
Design of several of the best-known amplifiers were completed before a single listening test was conducted. If the right things are measured correctly, it will sound right to most people (also said by both Douglas Self and JLH, not to mention Baxandall, Williamson and Walker - if a Hall-of-Fame is of any significance). Meaningful listening tests are a science in themselves to be of any statistical value, as illustrated by tests conducted a.o. in the Scandenavian countries, notably under Prof. Bengt Sorenson, to mention but one specialist. To each his own, but a wealth of documented test results has made it abundantly clear that there exists such diversion in listening test results as to be of limited value to a designer.
But I am a little off-thread - only the door was opened.
Best regards.
I have the gnawing feeling that we may be getting a little ahead of ourselves here.
Fab's original question was simply whether any 1 of the 2 displays on his scope was better than the other. Defining "better", I took it that he was concerned about amplifier stability under various conditions, as oscillatory effects were clearly way above the audio spectrum. Sonic effects came up only in post #5, and then not what they are, but rather whether there would be any - there is a difference! We did all appear to concentrate on the stability effects, not sonics.
Bobken, I think that in your post #8 you may have inadvertently brought sonics into the equation by stating that the only way to be sure about "such choices" as Fab had to make was to actually listen to the results. My perception of "the choices he had to make" was that it was all about supersonic to r.f. effects which could possibly cause instability and the ill consequences thereof, not how it might sound.
And in this region, with respect to whoever says what, one can only have success by measuring or analysing on a computer programme, as there is nothing to hear (as we all seem to agree) unless the circuits under discussion (series choke and Zobel) were extending into the audio spectrum, where they were never supposed to be working in the first place. In the case of an amplifier so poorly designed that this was required, essential attention has to be devoted elsewhere, e.g. the compensation as Bobken suggested. In this respect I am also confused as to the audible difference between components, employed as said in circuits that should not have effect in the audio spectrum in the first place.
I do not wish to enter a fray about the significance of the often touted listening tests, except to cite an example from a very well known audio magazine: Years ago some 6 internationally known critics were asked to make a short-list of the best amplifiers (amongst other components) in their view, as well as their personal choice. The personal best for some were not even on the list of others. And these were seasoned critics! For whose taste must I now design?
Design of several of the best-known amplifiers were completed before a single listening test was conducted. If the right things are measured correctly, it will sound right to most people (also said by both Douglas Self and JLH, not to mention Baxandall, Williamson and Walker - if a Hall-of-Fame is of any significance). Meaningful listening tests are a science in themselves to be of any statistical value, as illustrated by tests conducted a.o. in the Scandenavian countries, notably under Prof. Bengt Sorenson, to mention but one specialist. To each his own, but a wealth of documented test results has made it abundantly clear that there exists such diversion in listening test results as to be of limited value to a designer.
But I am a little off-thread - only the door was opened.
Best regards.
Hi Johan,
Sorry if I appear to cross swords with you here but I take strong exception to your comment :
"Bobken, I think that in your post #8 you may have inadvertently brought sonics into the equation" etc.
Johan, before I even saw this thead or posted any comments at all, the originator clearly stated the following in his (subsequent) post # 5.
"My question is then: what is the best way to get the best *more natural sound* into the speaker and desensibilising the amp circuit to load impedance". This is recounted word-for-word, and this was what I replied to.
Goodness only knows how anyone in their right mind can suggest that *I* "brought sonics into the equation" as you have just done, if this query from the thread's originator is read properly!
As the question of *best... sound* came first in this particular query, I simply dealt with that particular issue first in my subsequent reply.
I then went on to comment on some other issues including those relating to the stability of amps.
Similarly, although this is presumably not directed at me here, I don't know how you can also say in direct relation to the issue of sonics in post #5 :
"... and then not what they are, but rather whether there would be any - there is a difference!"
There is absolutely *nothing* in that post #5 you refer to which supports these comments of yours, whatsoever.
Please take the trouble to read that post again before any further 'misquotes' or misleading comments on your part relating to the substance of any previous posts.
My quote above, taken verbatim from post #5 makes it abundantly clear that the originator assumes there could be some sonic effects, or why would he start this question "what is the best way to get the best more natural sound"?
My comments may also be a little off thread, too, but they relate factually to what has been posted here, and not to any mis-readings nor erroneous assumptions, or whatever.
Sorry if I appear to cross swords with you here but I take strong exception to your comment :
"Bobken, I think that in your post #8 you may have inadvertently brought sonics into the equation" etc.
Johan, before I even saw this thead or posted any comments at all, the originator clearly stated the following in his (subsequent) post # 5.
"My question is then: what is the best way to get the best *more natural sound* into the speaker and desensibilising the amp circuit to load impedance". This is recounted word-for-word, and this was what I replied to.
Goodness only knows how anyone in their right mind can suggest that *I* "brought sonics into the equation" as you have just done, if this query from the thread's originator is read properly!
As the question of *best... sound* came first in this particular query, I simply dealt with that particular issue first in my subsequent reply.
I then went on to comment on some other issues including those relating to the stability of amps.
Similarly, although this is presumably not directed at me here, I don't know how you can also say in direct relation to the issue of sonics in post #5 :
"... and then not what they are, but rather whether there would be any - there is a difference!"
There is absolutely *nothing* in that post #5 you refer to which supports these comments of yours, whatsoever.
Please take the trouble to read that post again before any further 'misquotes' or misleading comments on your part relating to the substance of any previous posts.
My quote above, taken verbatim from post #5 makes it abundantly clear that the originator assumes there could be some sonic effects, or why would he start this question "what is the best way to get the best more natural sound"?
My comments may also be a little off thread, too, but they relate factually to what has been posted here, and not to any mis-readings nor erroneous assumptions, or whatever.
ok, I will try to write faster because I lost again (many times now) my reply because of time expiration !!! moderator please do something...
Thanks to all your comments. It seems that, based on some comments, both waveforms are acceptable...but the one with inductor is more safe to use?
My understanding is that the good electrical characteristics are the same goal as the good sound unless the characteristics are not the ones to look for. So the "best sound" or "best electrical characteristics" are the same since we all want good sound, right?
Simply, what do YOU do for your own diy amp?
Is the RC load test significant? or is there another test.
Thanks to all your comments. It seems that, based on some comments, both waveforms are acceptable...but the one with inductor is more safe to use?
My understanding is that the good electrical characteristics are the same goal as the good sound unless the characteristics are not the ones to look for. So the "best sound" or "best electrical characteristics" are the same since we all want good sound, right?
Simply, what do YOU do for your own diy amp?
Is the RC load test significant? or is there another test.
Hi fab,
Based on JLH's comments (and he should know), you are unlikely to *hear* any differences with these two square-waveforms, as I already posted. However, I have not carried out this particular direct listening comparison, myself, using similar waveforms.
Generally, good "electrical characteristics" as you put it should sound better, but as I have also tried to point out, this is not the whole story as far as the best sound goes. Using a *correctly designed and damped* output inductor should give you a better phase-margin of stability, and as this should not adversely affect the sonics, it would seem "safer" as you say.
I have found it best for 'sonics' to use the intended speakers and cables in any trials/tests wherever you can, and you could end up with a slightly different result using alternative speaker/cable combinations, as their complex impedances will vary somewhat.
It is more important to achieve the best stability (clean square-waves) before adding the output inductors, in my experience, by adjustments to any compensation caps etc. Adding the inductor will usually 'upset' the waveforms to some degree, as I have found and several notable commentators have also explained, but this should not be harmful to the sound.
One of the advantages which the DIYer has which is absent for manufacturers or designers (which JLH first drew my attention to)is that we only need to optimise the amp's stability for our own 'known' loads, whereas the others need to take into account a multitude of different set-ups which users might choose to use.
I have commented quite a lot recently in connection with one of "my own DIY amps" in posts #10, #13, #20, and #21 (stability issues are discussed here) in the "JLH Mosfet Amp - Modifying it" thread, and in posts #21, #24, #30, and #32 in the thread "Fuses Impacts on sonics of a supply" if, as you appear to be, you are seriously interested in some listening trials/conclusions/developments etc.
Hugh Dean of Axa Amplifiers has also written about 'voicing' amplifiers recently in another thread, but regrettably Eva has attempted (with her usual destructive and derisory comments) to destroy any credibillty here.
Actually, "good sound" is not well-defined and different listeners will not always agree on what is good or not. However, my own approach has been to get as close as I can to the real experience, and hence use live concerts as a yardstick here.
I am lucky in having several simple-miked recordings of an artist (male vocalist) whose concerts I have been attending for nearly 30 years, so I know quite well how he sounds in real life. The male voice covers a surprising amount of the audio spectrum, and these recordings are a great help in making decisions over various choices relating to the naturalness/expressiveness and the fine details to be heard in this voice.
It helps that these concerts were all in a very small and intimate venue, so it is not too dissimilar from my own listening environment.
Regards,
Based on JLH's comments (and he should know), you are unlikely to *hear* any differences with these two square-waveforms, as I already posted. However, I have not carried out this particular direct listening comparison, myself, using similar waveforms.
Generally, good "electrical characteristics" as you put it should sound better, but as I have also tried to point out, this is not the whole story as far as the best sound goes. Using a *correctly designed and damped* output inductor should give you a better phase-margin of stability, and as this should not adversely affect the sonics, it would seem "safer" as you say.
I have found it best for 'sonics' to use the intended speakers and cables in any trials/tests wherever you can, and you could end up with a slightly different result using alternative speaker/cable combinations, as their complex impedances will vary somewhat.
It is more important to achieve the best stability (clean square-waves) before adding the output inductors, in my experience, by adjustments to any compensation caps etc. Adding the inductor will usually 'upset' the waveforms to some degree, as I have found and several notable commentators have also explained, but this should not be harmful to the sound.
One of the advantages which the DIYer has which is absent for manufacturers or designers (which JLH first drew my attention to)is that we only need to optimise the amp's stability for our own 'known' loads, whereas the others need to take into account a multitude of different set-ups which users might choose to use.
I have commented quite a lot recently in connection with one of "my own DIY amps" in posts #10, #13, #20, and #21 (stability issues are discussed here) in the "JLH Mosfet Amp - Modifying it" thread, and in posts #21, #24, #30, and #32 in the thread "Fuses Impacts on sonics of a supply" if, as you appear to be, you are seriously interested in some listening trials/conclusions/developments etc.
Hugh Dean of Axa Amplifiers has also written about 'voicing' amplifiers recently in another thread, but regrettably Eva has attempted (with her usual destructive and derisory comments) to destroy any credibillty here.
Actually, "good sound" is not well-defined and different listeners will not always agree on what is good or not. However, my own approach has been to get as close as I can to the real experience, and hence use live concerts as a yardstick here.
I am lucky in having several simple-miked recordings of an artist (male vocalist) whose concerts I have been attending for nearly 30 years, so I know quite well how he sounds in real life. The male voice covers a surprising amount of the audio spectrum, and these recordings are a great help in making decisions over various choices relating to the naturalness/expressiveness and the fine details to be heard in this voice.
It helps that these concerts were all in a very small and intimate venue, so it is not too dissimilar from my own listening environment.
Regards,
Bobken:
I'm not destructive, I'm just scientific. This implies that I don't follow that obsolete middle-age thinking scheme in which statements have to be blindly taken as axioms or rejected depending on how famous was who is claimed to be the author.
I don't design my circuits following what is written on The Sacred Stone Tablets
I'm not destructive, I'm just scientific. This implies that I don't follow that obsolete middle-age thinking scheme in which statements have to be blindly taken as axioms or rejected depending on how famous was who is claimed to be the author.
I don't design my circuits following what is written on The Sacred Stone Tablets
Hi Eva,
Whether it is intended or not (and I happen to think it is) you are extremely destructive in the manner in which you join in on many posts on this Forum. Other posters have mentioned this to you before, and as they have suggested, it seems like all you are interested in is to show-off your self-declared superiority, rather than to carefully explain something to an enquirer.
We all know you are quite clever, but when you 'sweep all before you' in such a derisory manner, implying that everyone else is an idiot, or whatever, and doesn't know anything about audio electronics, this is not very encouraging to others.
You don't know *everything* quite yet, as your open disagreements over some of what I have said make apparent to me. I have not posted anything which I have not actually experienced myself through very many years of audio involvement, except where I make it clear by saying that this comes from someone else, and I have or have not (yet!) verified it myself.
There are times when I have also honestly said I am not absolutely certain why something I have discovered is the way it is, but since I know for myself that these are facts (whether I fully understand it, or like it, or not, and quite franky I don't care if you do or don't either) I would be an idiot to ignore them.
You appeared to cause a great deal of ill-feeling in several other posts I have seen recently, and I simply don't know why this should be necessary. You frequently jump in with a few scathing remarks, often not well-explained, and I don't know how you can be so arrogant and ignore the comments of many other posters when you do this. Their points can be valid too!
40 years ago, I felt similarly to yourself in that measurements showed everything related to audio, and that technical excellence was what was *entirely* responsible for good sound.
Since then, I learned the error of my ways.
If you wish to bury your head in the sand and ignore this, I don't mind one little bit, but kindly don't keep on destroying the attempts of others, some of whom do know a thing or two, and who are genuinely trying to share a few significant matters with other people who are not so bigoted as you clearly are.
Regards,
Whether it is intended or not (and I happen to think it is) you are extremely destructive in the manner in which you join in on many posts on this Forum. Other posters have mentioned this to you before, and as they have suggested, it seems like all you are interested in is to show-off your self-declared superiority, rather than to carefully explain something to an enquirer.
We all know you are quite clever, but when you 'sweep all before you' in such a derisory manner, implying that everyone else is an idiot, or whatever, and doesn't know anything about audio electronics, this is not very encouraging to others.
You don't know *everything* quite yet, as your open disagreements over some of what I have said make apparent to me. I have not posted anything which I have not actually experienced myself through very many years of audio involvement, except where I make it clear by saying that this comes from someone else, and I have or have not (yet!) verified it myself.
There are times when I have also honestly said I am not absolutely certain why something I have discovered is the way it is, but since I know for myself that these are facts (whether I fully understand it, or like it, or not, and quite franky I don't care if you do or don't either) I would be an idiot to ignore them.
You appeared to cause a great deal of ill-feeling in several other posts I have seen recently, and I simply don't know why this should be necessary. You frequently jump in with a few scathing remarks, often not well-explained, and I don't know how you can be so arrogant and ignore the comments of many other posters when you do this. Their points can be valid too!
40 years ago, I felt similarly to yourself in that measurements showed everything related to audio, and that technical excellence was what was *entirely* responsible for good sound.
Since then, I learned the error of my ways.
If you wish to bury your head in the sand and ignore this, I don't mind one little bit, but kindly don't keep on destroying the attempts of others, some of whom do know a thing or two, and who are genuinely trying to share a few significant matters with other people who are not so bigoted as you clearly are.
Regards,
Bobken said:
Just a comment here: the artists would almost invariably have been singing into a mike, the signal of which would have been mixed, amplified and fed to a loudspeaker. In my experience, even the equipment used for "small venues" is something that would make an audiophile cringe. Don't even get me started on the insides of mixing consoles and PA power amps, just suppose as a best case, the midrange used in the PA speakers was an Audax PR170M0. While this is a highly respectable driver as PA drivers go, and quite an acceptable driver as home midranges go, a look at its CSD and distortion spectrum will tell you that what you are hearing is as much the signature of the driver as that of the singer.
Yet it is also my experience that there is a special live atmosphere that is dificult to reproduce. But I guess this comes from being there and seeing the folks.
Your comment about you choice of components for the RC Zobel also puzzles me. If anything, the parasitic inductance of the resistor and capacitor would make a difference much more than any other parasitic effect in those components. The way to go there would be to use just about any thick film SMD resistor and a high quality MKP snubber cap. I just don't understand your choice of components. Have you done a blind test?
Greetings,
Eric
Hi Rune,
Regrettably, there is no mistake on my part and a good example is when Eva joined the discussion with post #263 in "Simple Killer Amp-Listening Impressions".
Just look at what happened for several pages following that, and how helpful was any of that to anyone on the Forum?
This is a thread which I didn't make any comment on, myself, mainly because (just like Eva, too!) I have never heard this particular amp, but I was not biased against her for any reason as I had not been involved there.
Unlike myself, though, Eva has made it abundantly clear that she doesn't believe in any *listening tests* anyway, a view which she is perfectly entitled to hold, of course.
Why then (as someone else later asked her) did she join in there with several contentious remarks/criticisms etc. in a thread which is entirely about *listening impressions*, unless there was some inflammatory intent, or simply to show off some self-proclaimed superiority?
Just some of the wording used like "disappointed"... "mess" and there are others too if you care to read this thread, are hardly constructive or encouraging, or whatever, are they?
This then spawned an entire thread of its own "Simple Killer Amp -Circuit Analysis" wherein another member posted the following quote, which indicates just how some other members feel about Eva's attitude in her posts.
" Well, Evas intentions with this tread are all wrong being very destructive and no good DIY spirit
I like to look at measurements too, but also know they can be interpreted in different ways, and I find that Eva is desperately clinging to every little bit there is to find
This is looking more and more like a personal vendetta
Eva, I think you as a professional has broken the rules as a professional being in this community
Very sad to see a talented person waste her skills like that."
I had no wish to post so much off-topic material here, nor to make any more of the issue than I had already done. I merely wish Eva would show others some respect for their opinions and experiences, even if she doesn't happen to share them.
Regards,
Regrettably, there is no mistake on my part and a good example is when Eva joined the discussion with post #263 in "Simple Killer Amp-Listening Impressions".
Just look at what happened for several pages following that, and how helpful was any of that to anyone on the Forum?
This is a thread which I didn't make any comment on, myself, mainly because (just like Eva, too!) I have never heard this particular amp, but I was not biased against her for any reason as I had not been involved there.
Unlike myself, though, Eva has made it abundantly clear that she doesn't believe in any *listening tests* anyway, a view which she is perfectly entitled to hold, of course.
Why then (as someone else later asked her) did she join in there with several contentious remarks/criticisms etc. in a thread which is entirely about *listening impressions*, unless there was some inflammatory intent, or simply to show off some self-proclaimed superiority?
Just some of the wording used like "disappointed"... "mess" and there are others too if you care to read this thread, are hardly constructive or encouraging, or whatever, are they?
This then spawned an entire thread of its own "Simple Killer Amp -Circuit Analysis" wherein another member posted the following quote, which indicates just how some other members feel about Eva's attitude in her posts.
" Well, Evas intentions with this tread are all wrong being very destructive and no good DIY spirit
I like to look at measurements too, but also know they can be interpreted in different ways, and I find that Eva is desperately clinging to every little bit there is to find
This is looking more and more like a personal vendetta
Eva, I think you as a professional has broken the rules as a professional being in this community
Very sad to see a talented person waste her skills like that."
I had no wish to post so much off-topic material here, nor to make any more of the issue than I had already done. I merely wish Eva would show others some respect for their opinions and experiences, even if she doesn't happen to share them.
Regards,
Hi Eric,
I note your comments here, and don't disagree with what you have said.
It is unfortunate that many recordings are not very well made and there is nothing we can do about this, afterwards.
This is why I consider myself fortunate to have these few carefully recorded compilations which are not commercial releases, but are much more 'revealing' than any other recordings I have. The miking was direct (i.e. un-amplified sound, and not through any speakers etc.) IIRC using a simple crossed pair a la Blumlein, with no correction/EQ and minimal interstage amplification merely sufficient to give adequate levels for the master tapes.
However, as you suggest, things are still a mile away from the 'real thing', regrettably, and for some of the reasons you mention.
I am not familiar with the mid-range drivers you comment upon, but I don't doubt what you say here. This is why I have used ATC dome mid-ranges in my own 'domestic' speakers, for over 20 yrs, as they are the most revealing and accurate-sounding mids I have ever heard.
Few people who have experienced these ATC units will argue that they are not amongst the finest (if not the very best) available in the world, and they have enabled me to make many substantial improvements elsewhere in my audio system.
Of course, the way they reveal even the finest nuances in the sound means that you can readily appreciate any recording and mixing artefacts/shortcomings, but similarly it does enable a careful and dedicated listener to appreciate very minor sonic changes in the replay equipment too. It is not by accident that ATC monitors are used in many of the worlds recording studios.
If you are interested in my experiments with 'listening' to components, I showed several references relating to some of my own (mainly relevant) posts above. I am sorry that you don't understand my conclusions or choices here, but this is what I found when listening to the parts concerned, although I was unable to *measure* any variations here at all.
Incidentally, I don't personally see any advantage to using an SMD resistive component in this location, and I will always choose polystyrene caps over polypropylene (all other things being equal), as they simply have less adverse effect on the sound in my experience. Similarly, where available, extended foil polystyrenes sound better (IMO) than the conventionally wound polystyrenes, probably due to the greater area of contact between the foil and the terminations.
Regards,
I note your comments here, and don't disagree with what you have said.
It is unfortunate that many recordings are not very well made and there is nothing we can do about this, afterwards.
This is why I consider myself fortunate to have these few carefully recorded compilations which are not commercial releases, but are much more 'revealing' than any other recordings I have. The miking was direct (i.e. un-amplified sound, and not through any speakers etc.) IIRC using a simple crossed pair a la Blumlein, with no correction/EQ and minimal interstage amplification merely sufficient to give adequate levels for the master tapes.
However, as you suggest, things are still a mile away from the 'real thing', regrettably, and for some of the reasons you mention.
I am not familiar with the mid-range drivers you comment upon, but I don't doubt what you say here. This is why I have used ATC dome mid-ranges in my own 'domestic' speakers, for over 20 yrs, as they are the most revealing and accurate-sounding mids I have ever heard.
Few people who have experienced these ATC units will argue that they are not amongst the finest (if not the very best) available in the world, and they have enabled me to make many substantial improvements elsewhere in my audio system.
Of course, the way they reveal even the finest nuances in the sound means that you can readily appreciate any recording and mixing artefacts/shortcomings, but similarly it does enable a careful and dedicated listener to appreciate very minor sonic changes in the replay equipment too. It is not by accident that ATC monitors are used in many of the worlds recording studios.
If you are interested in my experiments with 'listening' to components, I showed several references relating to some of my own (mainly relevant) posts above. I am sorry that you don't understand my conclusions or choices here, but this is what I found when listening to the parts concerned, although I was unable to *measure* any variations here at all.
Incidentally, I don't personally see any advantage to using an SMD resistive component in this location, and I will always choose polystyrene caps over polypropylene (all other things being equal), as they simply have less adverse effect on the sound in my experience. Similarly, where available, extended foil polystyrenes sound better (IMO) than the conventionally wound polystyrenes, probably due to the greater area of contact between the foil and the terminations.
Regards,
Some people taking part in the aforementioned thread were actually sent by the manufacturer to use the forum to advertise and sell a commercial product by employing the most unfair deceiving techniques. I believe that moderators have taken actions to control that, since that kind of threads have become less active now. I believe that the manufacturer of that comercial product also got banned from this site some weeks ago, and this is not particularly a sign of fairness.
Fab,
Early in this thread I promised some analysis on the serie L and Zobel networks. I have unfortunately been out of circulation for 2 weeks, but would like to post some figures now, if only to honour a promise, and since there were rather more qualitative discussion than quantative.
I regret not being able to post a circuit and graphs, but the following should be clear if you will picture the serie inductor as L, a usual damping resistor in parallel as Rl, and the Zobel as Cz and Rz. I have simulated a driver (8 ohm) with an internal impedance of 0,25 ohm representing a "damping factor" of 32 (it is usually higher), and as load a model of a reasonably good tweeter, and a cable capacitance of Cc.
The tweeter impedance is 8 ohm nominal, resonating at 1 KHz (15 ohm) and further rising from 8 ohm at 4,3 KHz, through about 10K at 10 KHz, 13.7K at 20 KHz to 19 ohm at 50 KHz and so on.
Starting with an unduly high L for this application of 20 uH, and furthermore Rl as open, no Zobel network and Cc of 47 nF - this must surely present a worst case - there is a 3 cycle damped oscillation over the tweeter at 132 KHz of 9% overshoot and 13% undershoot.
Going to L=20uH, Rl=22 ohm, Cz=400nF, Rz=10 ohm and Cc=47nF, renders a 1,5 cycle of oscillation at 66 KHz with a 0,5 dB pp amplitude.
As above but with Cz=100nF and Cc=4nF (a little more realistic), gave a 0,4 dB (amplitude) 1 cycle oscillation at about 85 KHz.
Finaly, using the fairly practical values of L=8uH, Rl=22 ohm, Cz=100nF, Rz=10 ohm and Cc=4nF, the result is an about 1,5 cycle of oscillation at about 200 KHz, of overshoot of 0,6 dB and undershoot of 0,2 dB.
I believe this should suffice to indicate that there can be no audible effect from these networks. The L and Cc is still on the high side; more normal are 2,5uH and 2-3 nF of cable capacitance. If any amplifier is so heroically misdesigned that substantially higher values are needed to calm matters down, investigation should begin with the amplifier design itself, as others have suggested. (By the way, nothing manifested at the amplifier output, before L.)
To sum up what has mostly been said, these networks are only intended to (a) isolate to a degree the effect of cable capacitance on amplifier stability and (b) to give a degree of load at supersonic frequencies (Zobels mostly come in at >80 KHz). These effects must be optimized with a signal generator and scope; regarding listening, possible occasional instability would mainly manifest as a sort of listener fatigue with no indication of what remedy to take, unless again there is something catastrophically wrong.
Although much of the above is a repetition of what others already remarked, I hope the figures will put you at rest.
Regards.
Early in this thread I promised some analysis on the serie L and Zobel networks. I have unfortunately been out of circulation for 2 weeks, but would like to post some figures now, if only to honour a promise, and since there were rather more qualitative discussion than quantative.
I regret not being able to post a circuit and graphs, but the following should be clear if you will picture the serie inductor as L, a usual damping resistor in parallel as Rl, and the Zobel as Cz and Rz. I have simulated a driver (8 ohm) with an internal impedance of 0,25 ohm representing a "damping factor" of 32 (it is usually higher), and as load a model of a reasonably good tweeter, and a cable capacitance of Cc.
The tweeter impedance is 8 ohm nominal, resonating at 1 KHz (15 ohm) and further rising from 8 ohm at 4,3 KHz, through about 10K at 10 KHz, 13.7K at 20 KHz to 19 ohm at 50 KHz and so on.
Starting with an unduly high L for this application of 20 uH, and furthermore Rl as open, no Zobel network and Cc of 47 nF - this must surely present a worst case - there is a 3 cycle damped oscillation over the tweeter at 132 KHz of 9% overshoot and 13% undershoot.
Going to L=20uH, Rl=22 ohm, Cz=400nF, Rz=10 ohm and Cc=47nF, renders a 1,5 cycle of oscillation at 66 KHz with a 0,5 dB pp amplitude.
As above but with Cz=100nF and Cc=4nF (a little more realistic), gave a 0,4 dB (amplitude) 1 cycle oscillation at about 85 KHz.
Finaly, using the fairly practical values of L=8uH, Rl=22 ohm, Cz=100nF, Rz=10 ohm and Cc=4nF, the result is an about 1,5 cycle of oscillation at about 200 KHz, of overshoot of 0,6 dB and undershoot of 0,2 dB.
I believe this should suffice to indicate that there can be no audible effect from these networks. The L and Cc is still on the high side; more normal are 2,5uH and 2-3 nF of cable capacitance. If any amplifier is so heroically misdesigned that substantially higher values are needed to calm matters down, investigation should begin with the amplifier design itself, as others have suggested. (By the way, nothing manifested at the amplifier output, before L.)
To sum up what has mostly been said, these networks are only intended to (a) isolate to a degree the effect of cable capacitance on amplifier stability and (b) to give a degree of load at supersonic frequencies (Zobels mostly come in at >80 KHz). These effects must be optimized with a signal generator and scope; regarding listening, possible occasional instability would mainly manifest as a sort of listener fatigue with no indication of what remedy to take, unless again there is something catastrophically wrong.
Although much of the above is a repetition of what others already remarked, I hope the figures will put you at rest.
Regards.
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