Re: Re: jcx
It is probably equally likely that people without adequate knowledge of control theories or understanding of the subject matter are trying to use ill-defined terms like "back EMF" to mystify a well understood subject (like the electro-mechnical interaction of a loudspeaker) so that they can sound sophisticated (or more sophisticated than they really are).
My free advise to the back EMF crowd is to read some books on control theories (undergrad level books will be fine for this purpose) and make sure they understand the subject before invoking the term "back EMF" ever in public.
On a related note, some people here are extremely well written in terminologies that only they themselves understood. and it is extremely hard to follow those folks in plain English, in spite of the fact that they are excellent native speakers of English. Those folks would invoke ("pile on" is a better phrase I guess) many unrelated technical terms that you have no clue what they are talking about. If we encourage the use of self-made terms like "back EMF" the situation can only get worse.
ingrast said:
It is probably equally likely that people without adequate knowledge of control theories or understanding of the subject matter are trying to use ill-defined terms like "back EMF" to mystify a well understood subject (like the electro-mechnical interaction of a loudspeaker) so that they can sound sophisticated (or more sophisticated than they really are).
My free advise to the back EMF crowd is to read some books on control theories (undergrad level books will be fine for this purpose) and make sure they understand the subject before invoking the term "back EMF" ever in public.
On a related note, some people here are extremely well written in terminologies that only they themselves understood. and it is extremely hard to follow those folks in plain English, in spite of the fact that they are excellent native speakers of English. Those folks would invoke ("pile on" is a better phrase I guess) many unrelated technical terms that you have no clue what they are talking about. If we encourage the use of self-made terms like "back EMF" the situation can only get worse.
OT
Has someone analysed the effects of the variable voice coil inductance (as shown on the link above) on Xover freq?
jcx said:
Has someone analysed the effects of the variable voice coil inductance (as shown on the link above) on Xover freq?
I'm confused about that last graphic, Jorge. In post #2 and post #3, it looks like when the loop was closed, the output node was renamed from n003 to n004 due to the different hookup.
But in the last two graphics, they are both n003 and look approximately the same before for the before and after feedback cases. I'd expect the waveform of the last graphic (post #22) to be much lower in amplitude than the one in post #21. Was there a mixup in the graphics files or am I misunderstanding what you're plotting here?
But in the last two graphics, they are both n003 and look approximately the same before for the before and after feedback cases. I'd expect the waveform of the last graphic (post #22) to be much lower in amplitude than the one in post #21. Was there a mixup in the graphics files or am I misunderstanding what you're plotting here?
Andy
Node 004 is where Zo connects to the speaker in the O.L. case.
Node 003 is the output of the current gain stage (U2) in the closed loop case.
Node 004 is where Zo connects to the speaker in the C.L. case.
In posts #2 and #3, I was showing the effect of feedback on damping, and in post #4 I was showing that U2 was outputing the same voltage as before (but with inverted phase) to increase damping.
Sorry if it wasn't clear.
Here's node 004 at 10 KHz - voltage is higher (compared to 110Hz) since there is less NFB due to U1's pole at 3 KHz..
Node 004 is where Zo connects to the speaker in the O.L. case.
Node 003 is the output of the current gain stage (U2) in the closed loop case.
Node 004 is where Zo connects to the speaker in the C.L. case.
In posts #2 and #3, I was showing the effect of feedback on damping, and in post #4 I was showing that U2 was outputing the same voltage as before (but with inverted phase) to increase damping.
Sorry if it wasn't clear.
Here's node 004 at 10 KHz - voltage is higher (compared to 110Hz) since there is less NFB due to U1's pole at 3 KHz..
Attachments
Hi tlf9999,
Nice post. I always try to communicate in lay terms where possible. Many years as a graduate tutor then lecturer taught me that it was far better to communicate at street level even complex concepts achieved the best results.
Cheers,
Greg
Nice post. I always try to communicate in lay terms where possible. Many years as a graduate tutor then lecturer taught me that it was far better to communicate at street level even complex concepts achieved the best results.
Cheers,
Greg
Hi Jorge,
You have started a thread to investigate back-EMF induced distortion but unfortunately you have simulated using *ideal* amplifiers that are incapable of producing the distortion generated by the *real-world* amplifiers we are investigating in Lumanauw's thread.
Good on you for trying though, but in uncovering nothing you then went on to state "that 'myths' are treated as 'truth' in a religious way", which more or less implies that some other individuals are as like anthropomorphic or talking rubbish.
Hi jcx,
You say that my discussion is "misleading" (your quotes) and even frustrating in the face of such a rich background of engineering history (that is personal). Whilst to me it is the likes of your's and Jorge's comments that are presently frustrating.
Just because you have not yet found anything does not give you the right to slag anyone.
If we all thought the same way - boy wouldn't the world lack innovation and be seriously boring.
Hi tlf9999,
What term do you suggest that we should be using in place of the back-EMF that you are criticising (my?) use of; ie. were all the teachers and lecturers who taught me, and are all the text books - wrong ?
Definition;
Back-EMF:
An EMF that opposes the normal flow of current in a circuit.
(Amplifier current - loudspeaker circuit)
Jan, you suggested that we try to get a little closer to real life, and Chocaholic you suggested that the circuit has no frequency dependency, then there were genuine attempts at applying same, to attain findings.
However, any of us could draw and simulate around these idealised triangular little boxes, but the results will still not include biased device non-linearities (illustrated by Andy in Lumanauw's thread), device capacitances, junction storages, early effects etc.
All that has been simulated so far is the build up of (loudspeaker system) back-EMF and effects due to a suddenly starting sinewave, though it is essential we do understand the genuine existence of these too, and not claim they go against established theory.
Can I suggest that as a minimum an entire amplifier schematic needs to be used when attempting simulated observations, with stabilisation components as used in real life.
My Post#174/5 in Lumanauw's thread already illustrates back-EMF induced errors: Errors that do not arise when the load is a resistor - because there is no back-EMF.
You could use this same circuit your self for illustrative purposes, or why not use JCX's amplifier circuit as previously appeared somewhere else in diyAudio (?), which had a gain defined IC stage followed by a transistor buffer and an auto-biased Mosfet output stage, all closed with a simple global loop.
Maybe JCX could volunteer the circuit, so that it could be slotted directly into your U1/U2 Post#1 investigation schematic, and then be additionally run at 1kHz and 10kHz as Jan has suggested !
Cheers ........... Graham.
You have started a thread to investigate back-EMF induced distortion but unfortunately you have simulated using *ideal* amplifiers that are incapable of producing the distortion generated by the *real-world* amplifiers we are investigating in Lumanauw's thread.
Good on you for trying though, but in uncovering nothing you then went on to state "that 'myths' are treated as 'truth' in a religious way", which more or less implies that some other individuals are as like anthropomorphic or talking rubbish.
Hi jcx,
You say that my discussion is "misleading" (your quotes) and even frustrating in the face of such a rich background of engineering history (that is personal). Whilst to me it is the likes of your's and Jorge's comments that are presently frustrating.
Just because you have not yet found anything does not give you the right to slag anyone.
If we all thought the same way - boy wouldn't the world lack innovation and be seriously boring.
Hi tlf9999,
What term do you suggest that we should be using in place of the back-EMF that you are criticising (my?) use of; ie. were all the teachers and lecturers who taught me, and are all the text books - wrong ?
Definition;
Back-EMF:
An EMF that opposes the normal flow of current in a circuit.
(Amplifier current - loudspeaker circuit)
Jan, you suggested that we try to get a little closer to real life, and Chocaholic you suggested that the circuit has no frequency dependency, then there were genuine attempts at applying same, to attain findings.
However, any of us could draw and simulate around these idealised triangular little boxes, but the results will still not include biased device non-linearities (illustrated by Andy in Lumanauw's thread), device capacitances, junction storages, early effects etc.
All that has been simulated so far is the build up of (loudspeaker system) back-EMF and effects due to a suddenly starting sinewave, though it is essential we do understand the genuine existence of these too, and not claim they go against established theory.
Can I suggest that as a minimum an entire amplifier schematic needs to be used when attempting simulated observations, with stabilisation components as used in real life.
My Post#174/5 in Lumanauw's thread already illustrates back-EMF induced errors: Errors that do not arise when the load is a resistor - because there is no back-EMF.
You could use this same circuit your self for illustrative purposes, or why not use JCX's amplifier circuit as previously appeared somewhere else in diyAudio (?), which had a gain defined IC stage followed by a transistor buffer and an auto-biased Mosfet output stage, all closed with a simple global loop.
Maybe JCX could volunteer the circuit, so that it could be slotted directly into your U1/U2 Post#1 investigation schematic, and then be additionally run at 1kHz and 10kHz as Jan has suggested !
Cheers ........... Graham.
Graham Maynard said:
Hello, Graham.
My statement that myths are treated as truth is a wide spanning one.
I'm not an audio designer - just an EE that by chance started working with audio about 45 yrs ago when tubes were all (but then left the field), met people with VERY good ears, heard VERY good and very expensive sound equipment (not the same) and met countless audio fanatics.
I've read the English magazine's review that was the reason for Quad (Peter Walker) taking the reviwer to court...
I always felt pity for the poor audio fanatics that are looking for the magic Graal that costs a bundle but is always out of reach, just because some golden eared reviwer in a magazine says A is better than B...
So, what I'm trying to do is to show to the ones that care that statements in audio shall always be placed in the contest 'this sounds good to my ear' and not absolute truth.
Because:
We have SS class A truth;
We have SS class AB truth;
We have closed loop truth;
We have no NFB truth;
We have SE tubes truth;
We have PP tubes truth;
We have analog front end truth;
We have digital front end truth.
And we have even the ABX truth!
Or, too many different truths to make any valid argument out of it!
And going back on topic, my very simple simulation was just to show that 'Back EMF' or whatever one names it will not increase an amp's stress be it an OL or a high FB one.
If you have better data - not opinion, I know ears are different from person to person - I will be pleased to see it and learn.
Regards,
Jorge
Hi Jorge,
Somewhere in diyAudio I have already posted changing output current due to back-EMF, but I do not keep info filed because I have my own things to get on with. I have however shown you a circuit and suggested how it can be examined in order to see how back-EMF can 'stress' an amplifier.
Cheers ........ Graham.
Somewhere in diyAudio I have already posted changing output current due to back-EMF, but I do not keep info filed because I have my own things to get on with. I have however shown you a circuit and suggested how it can be examined in order to see how back-EMF can 'stress' an amplifier.
Cheers ........ Graham.
Graham Maynard said:
Sorry, Graham, but I really don't remember such a circuit. Could you pls refresh my memory?
Thanks,
Jorge
Hallo guys
I would suggest a little experiment about real audibility of back EMF/feedback related stuff.
1.Take a low/non feedback amp like Pass or tube amp (called amp1), which you assume it has no problems with back EMF distortion. Speaker's connected between output of amp1 and ground.
2. Listen.
3.Take a high feedback (or amp being tested) amp (amp2 ) and make it 'amplify the ground', I mean input to zero potential. Than connect speaker between output of amp1 and amp2 creating a kind of bridge. (amp2 of higher power than amp1)
4. Listen and compare to point 2
Comments?
Anyone did it already?
best regards
I would suggest a little experiment about real audibility of back EMF/feedback related stuff.
1.Take a low/non feedback amp like Pass or tube amp (called amp1), which you assume it has no problems with back EMF distortion. Speaker's connected between output of amp1 and ground.
2. Listen.
3.Take a high feedback (or amp being tested) amp (amp2 ) and make it 'amplify the ground', I mean input to zero potential. Than connect speaker between output of amp1 and amp2 creating a kind of bridge. (amp2 of higher power than amp1)
4. Listen and compare to point 2
Comments?
Anyone did it already?
best regards
Attachments
darkfenriz
Nice suggestion, but to be a valid test one would have to make some more compares:
- The one you've suggested;
- Non Feedback - speaker - non feedback
- Feedback - speaker - feedback
Paying close attention to acoustic level output (use an SPL meter to calibrate before each test)
Any volunteers?
Nice suggestion, but to be a valid test one would have to make some more compares:
- The one you've suggested;
- Non Feedback - speaker - non feedback
- Feedback - speaker - feedback
Paying close attention to acoustic level output (use an SPL meter to calibrate before each test)
Any volunteers?
Thank you
I assumed, that if tested amp has damping factor of >200 and offset voltage <30mV and nothing like EMF-induced-distortion ever occurs, than both 'should' sound the same
about SPL level:
no meter needed, only a switch between 'real' ground and output of an amp 'amplifying' ground.
I assumed, that if tested amp has damping factor of >200 and offset voltage <30mV and nothing like EMF-induced-distortion ever occurs, than both 'should' sound the same
about SPL level:
no meter needed, only a switch between 'real' ground and output of an amp 'amplifying' ground.
Graham Maynard said:
whatever that has been in use for many years by well qualified engineers and scientifists. You can usually find them in well written highschool or college level textbooks.
Graham Maynard said:
they aren't wrong. It is those that invented self-made terms of "back EMF" that are wrong.
Graham Maynard said:
Just exactly what does the above mean?
darkfenriz said:
About the test:
If an amp sounds bad, how will one knows if it's due to NFB or not?
That's why I suggest more than one test.
About level
For the high NFB to ground case, you are right.
But quite likelly the non NFB amp will have a higher output impedance and level will be less.
It's known (and by salespersons...) that the higher volume amp 'sounds' better at first listen!
Jorge said:
I reckon the whole damping-ratio/back-EMF hoop-la falls in the category of identifying a non-existent problem, and then working long and hard to solve it.....
A notable example of such:
http://www.thekunderts.net/ken/docs/c&d2001-01.pdf
Hi Mikeks,
if speaks of amp in abstract sense, you are right.
If you speak from the point of view of the THDS and IMD of the amp ( induced by this problem ) you have ( nearly ) reason.
If you speak from the point of view of the " audio reproduction " with dynamic loudspeakers, don't taste of thing is speaking.
Hi All,
I continue to ask the critical "seniors" members, in the comparisons of this matters, of lists me the "truthes" problems to resolve and as resolve them, but lowers always the silence...
In this Thread read the comments of "pseudo-intellectuals" that explains that this problems have already be essays a lot of years will do ( is true, but the technologies evolve and the problems stay ), hypothesizes an improper use of the technical term, and the is been ironical about the opportunity to discuss this matters " at street level ". I believe that anyone goes into this deduces technician has an enough base to analyse it. Offend the intellectuals abilities of the members are not synonymous of brain power, and it is the only thing " street level" " that there is in the forum.
Ciao
Mauro
if speaks of amp in abstract sense, you are right.
If you speak from the point of view of the THDS and IMD of the amp ( induced by this problem ) you have ( nearly ) reason.
If you speak from the point of view of the " audio reproduction " with dynamic loudspeakers, don't taste of thing is speaking.
Hi All,
I continue to ask the critical "seniors" members, in the comparisons of this matters, of lists me the "truthes" problems to resolve and as resolve them, but lowers always the silence...
In this Thread read the comments of "pseudo-intellectuals" that explains that this problems have already be essays a lot of years will do ( is true, but the technologies evolve and the problems stay ), hypothesizes an improper use of the technical term, and the is been ironical about the opportunity to discuss this matters " at street level ". I believe that anyone goes into this deduces technician has an enough base to analyse it. Offend the intellectuals abilities of the members are not synonymous of brain power, and it is the only thing " street level" " that there is in the forum.
Ciao
Mauro
Hello, Mauro
Pls see my post #30.
Which of the truths there is the truer one?
That is why it becomes extremelly difficult to analyse (from a strictly technical viewpoint) the quality of audio equipment.
One have to be able to separate the real facts from personal tastes (and there is even vested commercial interest).
But I would really like to use more representative data to try to understand the whole process, and you are on a very interesting search.
Pls see my post #30.
Which of the truths there is the truer one?
That is why it becomes extremelly difficult to analyse (from a strictly technical viewpoint) the quality of audio equipment.
One have to be able to separate the real facts from personal tastes (and there is even vested commercial interest).
But I would really like to use more representative data to try to understand the whole process, and you are on a very interesting search.
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