there is even more and less than "can be audibly detected" to music reproduction - we actually swallow many absurdities from Stereo phantom center, multi-miced, amplitude panned mixes to $10k 1-2 liter "audiophile" bookshelf speakers
I have seen reports that hearing LR XO 180 degree, ms phase rotation in mid band can be trained for - but we have the example of many loudspeakers, even highly reviewed by audiophiles that have this "issue"
at least one "phase sensitivity of harmonics" paper I read summary conclusion was that altering harmonics of a instrument could be heard - when the modification changed the waveform envelope by ~ 1%
we have further evidence deeply based in DBT subjective evaluation from lossy codec design - again ~1% in 6-7 bits of information is coded for each critical band of human perception - not getting ns phase accuracy from that
compared to amplifier actual "phase errors" the psychoacoustic thresholds are ridiculously huge for an designed to the level of Bob's or Doug's books
it gets really annoying to have to listen to this chatter keep being passed around as "wisdom” about why some amplifiers “sound bad" when the numbers are easy to find, compare, and the psychoacoustic thresholds are orders of magnitude away from even basically competent amplifier performance in the audio band – CFA vs VFA doesn't' even enter into it at this level of innumeracy
I have seen reports that hearing LR XO 180 degree, ms phase rotation in mid band can be trained for - but we have the example of many loudspeakers, even highly reviewed by audiophiles that have this "issue"
at least one "phase sensitivity of harmonics" paper I read summary conclusion was that altering harmonics of a instrument could be heard - when the modification changed the waveform envelope by ~ 1%
we have further evidence deeply based in DBT subjective evaluation from lossy codec design - again ~1% in 6-7 bits of information is coded for each critical band of human perception - not getting ns phase accuracy from that
compared to amplifier actual "phase errors" the psychoacoustic thresholds are ridiculously huge for an designed to the level of Bob's or Doug's books
it gets really annoying to have to listen to this chatter keep being passed around as "wisdom” about why some amplifiers “sound bad" when the numbers are easy to find, compare, and the psychoacoustic thresholds are orders of magnitude away from even basically competent amplifier performance in the audio band – CFA vs VFA doesn't' even enter into it at this level of innumeracy
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JC does the best he knows how to. 🙂 As fussy as he is to details, just think of what he could do with a CFA?
-Richard
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Is that what you found from reading the entire works? I am not sure about that.
IMO - Esp interesting to me are digital processes and what they do to phase and its audible.
THx-RNMarsh
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TI - CFA Stability Analysis -
CFA stability analysis by Texas Instruments:
View attachment Stability Analysis.pdf
-THx-RNMarsh
CFA stability analysis by Texas Instruments:
View attachment Stability Analysis.pdf
-THx-RNMarsh
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A little harsh jcx I have to say.
I would however agree that the differences between competently designed amplifiers of either persuasion are not night and day and can be, for the most part explained due to specification differences.
We have a good technical discussion here (ok it's not at AES level) intertwined with a bit of subjective folklore, but I believe an undervalued and under represented topology has finally gotten some airtime within the DIY community.
That can only be a good thing . . .
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Bob,
Most designers just stick with what hey know, and they keep refining it.
Self - blameless (not my cup of coffee)
JC - folded cascode with JFET IP ditto
CH - balanced zero FB
NP - class A ultra simple
Etc
Etc
😉
1- Because he did not invented-it.
2- A CFA does not need to be handcrafted by virgins during full moon nights.
3- You don't need special components, that only one of your friends is able to provide.
4- Your special silver wire, burned during one month before to be cut and marked for its direction makes no difference in it.
5- Remember, feedback is EVIL.
6- Oh, poor, you don't even know the difference between hifi and midfi.
7- This line is just there because seven is a magical number.
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hehe...
It is very simple: just try to modify the 'nature' of an instrument with a digital tone corrector (like to give the feeling it is behind a door, in an other room): Nothing happens.
And, when you look to the numbers, you don't believe you have applied such a huge amount of correction.
Same thing if you want to add some distance between the instrument and you (scene depth), or change the weight or the size of an instrument.
On my side, i loved digital correctors to clean the sound and remove some unwanted frequencies (high pass filters, notch filters etc...), and used exclusively analog ones to 'create' the instrument's sound, size, distance, height.
Are-you joking ?
Did-you listen to music with your eyes ?
Now, you will have a real credibility problem, here.
Everybody have experienced that ALL amps, All preamps, all power supplies, all lytic caps etc. sound different, and even cables can make a difference (well we know why;-).
And that those differences are not always (or often) measurable.
There is still a lot of mysteries in the way our ears+brain work, in this hifi 'make believe' game.
Esperado, you have provided valuable input in several posts here, but #3807 was not one of those. Why attacking someone who's not participating in this thread ?
If feeding the servo/any from the same point as some of the audio feeding power sources (actually I would advice to do this always) make sure to decouple the op-amps strongly (see picture).
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That's what I do, but be sure to give the 'external' (to the servo) split (T filter) a higher Ft than the servo 🙂
Well, you're probably right. Bad humor.
I don't wanted to fire the man - i have a *deep* respect for this valuable engineer and his search for perfection -, but some commercial arguments he likes to push, that i consider like snake oil. (Am-i the only one ?).
The frontier between pure maths and audiophile's fairy tails is so acrobatic, sometimes ;-) and i'm unable to resist to make a bad joke about this.
ps: I believe he participated in this thread :http://www.diyaudio.com/forums/solid-state/240712-cfa-topology-audio-amplifiers-182.html#post3768503, so he is free to answer and fire-me for my grin.
So true, but life is so short ;-)
I believe Nelson had explored a lot of various countries, including CFAs, not ?
I'm not sure that his difficult search for "simple" is something we have to neglect.
It is one of the questions witch remain unanswered in this thread, as nobody had the occasion to compare some complicated/sophisticated CFA designs with simplest optimized ones, VSSA like.
One thing i would dream we can organize, at the end.
Some burning amp day, somewhere, sometimes, with our various realizations.
We should learn a lot of things.
My TL072 is fed from the cap multipliers , to the locally decoupled IPS board
.. then to the 12V zeners /47u caps with "to the pin" .1uf caps on the
IC. The 2-47u's and .1u's are within mm's of the IC.
As I am using a slower IC , this would not be enough ??
(PS components circled)
OS
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Opstripper, you did not answered my question: "Is the slope of this voltage error (or recovery) in the audio band ?"
And i have an other one: had-you made sure that your TL072 never enter in saturation (if i remember well, it don't appreciate-it and can produce a reversed output when overloaded ) ?
And i have an other one: had-you made sure that your TL072 never enter in saturation (if i remember well, it don't appreciate-it and can produce a reversed output when overloaded ) ?
Bob I hear and agree with you. However there is another factor that is being overlooked, I doubt that simulation will demonstrate the effect thoroughly. Shunt capacitance prevents the impedance seen at the vas collector from becoming inductive at high frequencies. For this reason not only a EF3 but also EF2 would benefit from it. Offcourse we talking of very small values here in the case of VFA. However a CFA already has this built in if one uses shunt compensation for the design which is the best method for CFA compensation. For this reason youll notice that with CFAs s ULGF can be pushed a little higher with no ill effects on stability. This is not possible with VFA if one doesnt use some shunt compensation on it which in turn will obviously have a detrimental effect on THD especially at high frequencies. However using shunt in a CFA doesnt affect THD as much as the diamond buffer can theoretically supply as much current as needed so the vas current is not constrained like in the case of VFA.
Further advantage that shunt compensation has is that the high frequency open loop gain after compensation is not fixed by the value of the compensation capacitor as is the case with the miller capacitor. The name of the game with feedback amplifiers is open loop gain, like Bruno Putzeys says, one can never have too much. All CFB opamps on the market use shunt compensation and this is prime reason.
The gain in the loop is very good criteria, with CFAs the shunt is best.
See my previous post.
Manso, I appreciate your opinion very much and I would like your comment on my compensation used in 200 W CFA here. http://www.diyaudio.com/forums/solid-state/243481-200w-mosfet-cfa-amp-47.html#post3773418
Thanks
Damir