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Old 15th November 2012, 06:42 PM   #5431
Julf is online now Julf  Europe
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Quote:
Originally Posted by Esperado View Post
Such a 5 pole calculation is affraying and require high mastery.
"One does not simply design a nc400"
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Old 15th November 2012, 06:51 PM   #5432
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Originally Posted by Esperado View Post
If i understand well, Bruno takes its feedback source AFTER the output switching frequency filter, witch is good to cancel the introduced non linearities of it but add at least 2 poles at the traditional 3 ones. That implies feedback high frequency phases have to be tuned in order to avoid oscillation when you want huge open loop gain and feedback. Such a 5 pole calculation is affraying and require high mastery.
it's been a while (8 years) since I studied control theory at the university so me going into the subject is not the best idea.
but yes, the feedback is taken post output filter.
only thing I can tell you is that Bruno mentioned a few times that his approach is not exactly textbook (he actually gave a few not so enthusiastic considerations about how control theory is taught in school). I would agree, the portion about non-linear systems was short and not even required for the exam. stupid if you ask me.

I know it's a very long thread but there are some technical portions with Bruno's involvement that concern the above (as far as I recall).

the Hypex website seems to be recovering. it contains a few general (not extremely technical) papers regarding the subject. and there's an AES paper by Bruno. I have it by since it's not downloadable free of charge I'm not sure I'm allowed to post it. if you're an AES member and feel it's worth the 5 bucks, it's called "GLOBALLY MODULATED SELF-OSCILLATING AMPLIFIER WITH IMPROVED LINEARITY".
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Last edited by mr_push_pull; 15th November 2012 at 06:55 PM.
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Old 15th November 2012, 07:29 PM   #5433
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Originally Posted by Esperado View Post
It would be useless to enter in this old sea snake, scientists against audiophiles...
(read my signature)
I'm neither the one neither the other, or, better, a little of the two.
I mean, maths are good to design and measurements to see what happens and understand more.
But our ears and brains are pretty complex interface in the make believe game of audio reproduction, and, during my life, i had several occasion to assist at the evolution of measurements practices, discovering new kind of distortions and to improve my listening accuracy etc...
So, as far i'm concerned, i lie on both, and use to listen a lot at the end of my design processes and always get some real improvements in this. That was the reason of my questions, answers will be taken with precautions, of course, i don't believe in marketing poetry ;-)
But each time you ask a single question in this forum(with something behind you mind), you get silly flame wars instead of simple responses to them.

To respond to your question, and on my point of view, yes "tons of theory" are applicable (when verified) but they NEVER cover the all story, reason why nothing, NEVER, is perfect.
My post contained a minimum of irony (which someone has taken), but also contains a truth.
I agree completely on the complexity in Human perception.
I do not agree however, to put science aside, which contains the actual facts. as cover so that they remain visible only things as convenience.
I often hear people say that ... the distortion in the time domain ... no, it has not been proven! .. So you do not have to worry...
but what they have to prove?...
The distortion in the time domain is the harmonic content of a musical instrument. I mean ... a set of "non-linearity" is the harmonic spectrum of an instrument and changes in relation to the frequencies of the musical note also. then, in the case of an amplifier, if we want that does not add or subtract, thus changing the harmonic content. we expect that with a very pure signal at 1kHz, the amplifier must not generate harmonics (still very low). this is in theory what you need.
obvious that there are many things that contribute to generate harmonics.
therefore, a sound is made ​​in its nature of what you say ... it was not tried.

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Old 15th November 2012, 07:41 PM   #5434
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Quote:
Originally Posted by Esperado View Post
If i understand well, Bruno takes its feedback source AFTER the output switching frequency filter, witch is good to cancel the introduced non linearities of it but add at least 2 poles at the traditional 3 ones. That implies feedback high frequency phases have to be tuned in order to avoid oscillation when you want huge open loop gain and feedback. Such a 5 pole calculation is affraying and require high mastery.
This was the subject of Bruno's presentation at the Burning Amp Festival in October. By including the filter, he gets a 5th order loop that, at a certain point, falls off at 100dB/oct.
Then he modifies the loop so that it only falls at a stable 6db/oct at the region where the ol gain goes through 0dB. Mastery indeed.

jan
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Old 15th November 2012, 08:04 PM   #5435
Omholt is online now Omholt  Norway
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Originally Posted by StigErik View Post
And what would that be? I think you will have a hard time finding any purely technical "matching" problems with any of the two amps, since they are both having extremely low output impedance and the same frequency response.
I don't know, but there has to be something than explains it. I asked someone about it and they mentioned either a difference in the SMPS or "reaktiv motklobling" (reactive feedback?).
Dipoles are normally an easy load, but you used EQ quite a bit and had low sensitivty maybe the they were pushed on the border with UcD and the SMPS made a difference.

I'm just throwing out some thoughts, but I believe there's a techincal explanation behind just the fact that nCore surpasses UcD in the bass. I doubt it's related to distortion since dipoles have more of that.
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Old 15th November 2012, 08:21 PM   #5436
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Originally Posted by jan.didden View Post
Then he modifies the loop so that it only falls at a stable 6db/oct at the region where the ol gain goes through 0dB.
Jan, did you mean Bruno is the son of mr Nyquist ? (Smiley here)
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if you're an AES member and feel it's worth the 5 bucks,
I paid the tax at a time, because i was obliged... No, i'm not any more ... in my barrel... ;-)
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Last edited by Esperado; 15th November 2012 at 08:31 PM.
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Old 15th November 2012, 09:21 PM   #5437
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Originally Posted by Omholt View Post
Dipoles are normally an easy load, but you used EQ quite a bit and had low sensitivty maybe the they were pushed on the border with UcD and the SMPS made a difference.
There is nothing in the nature of dipoles that makes them an easier load than any other speakers.

In my case I have a lot of EQ yes, but that does not make the load any different from the amp's perspective. The impedance curve remains. I never exceed 20W output either, so any decent amp should drive them with no power or current limiting problem. And as it happens the EQ maximum is also where the impedance of the speaker is highest (around Fs). A walk in the park really.
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Old 15th November 2012, 09:52 PM   #5438
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Quote:
Originally Posted by StigErik View Post
There is nothing in the nature of dipoles that makes them an easier load than any other speakers.
More than that, and if we do not compensate each loudspeaker for motional impedance and inductance (i recommend that), the pick of resonance will be much higher than the same loudspeaker in a correctly tuned vented box.
This said, please take in consideration that, like Gaston, i'm on the no dipole side of the force ;-)
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Last edited by Esperado; 15th November 2012 at 09:56 PM.
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Old 15th November 2012, 10:07 PM   #5439
fas42 is offline fas42  Australia
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Originally Posted by Esperado View Post
Not to forget than, often we can find an improvement somewhere, when it is elsewhere. I mean, increasing the slew rate of an analog amp give often the feeling of "faster" basses, while it is in the treble that there is less distortion/harshness.
I agree. People frequently talk of the bass improving, but it has absolutely nothing to do with the actual bass frequencies; it's actually the transients and higher harmonics being reproduced properly that creates the subjective impression of better bass. I have a system with bass reproduction capabilities that would be pathetic by most people's standards, but it is capable of creating the experience of extremely punchy, gutsy bass -- purely because everything above the lowest frequencies is done with pretty good accuracy ...

Frank
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Old 16th November 2012, 12:08 AM   #5440
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Thanks for answering the question regarding linear PSU.

Is there a reason to use the switching PSU instead of linear? As the linear would probably be cheaper, would it be better?
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