Actually, in my experience the converse is more often true. When reasoned argument is failing, the other person (losing the factual argument) says something like "what do you know about practical things - I bet you have a PhD". Thank you for demonstrating this technique for us. There was even one guy on here who tried to solve disputes (and gain sympathy?) by repeatedly declaring that he is a TV repair man!dvv said:
Neah, it is just "cool".
People sometimes will act different just to differentiate from the "crowd" that they live in. Some crave to show-off opposition to mainstream trends as their indentity, to state "I am special" (therefore better noticed from the rest of the group).
Any tool is good for that: tatoos, piercings, overpriced Apple products, LP collections, tubes amplifiers, NOS made with DAC's that are not in production anymore...
People sometimes will act different just to differentiate from the "crowd" that they live in. Some crave to show-off opposition to mainstream trends as their indentity, to state "I am special" (therefore better noticed from the rest of the group).
Any tool is good for that: tatoos, piercings, overpriced Apple products, LP collections, tubes amplifiers, NOS made with DAC's that are not in production anymore...
Ah, some here are goood at that kind of arguments. Will twist everything to their use... For example engineers for them are sometimes geinuses (when desing a DAC that is not in production anymore) or just deaf idiots (when specify the use of OS filters or OpAmps in final stage).
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Nulling
Any ideas
Abstract
A dominant distortion mechanism in audio power amplifiers results from nonlinearity in the voltage and current transfer functions within the power output stage. A technique is presented that uses a magnetic differential sensor to sense this distortion and to apply a supplementary error-correcting feedback path within the amplifier, in addition to overall negative feedback. Differential-current derived feedback is explored and the technique is shown to be applicable to both voltage and current transfer errors. Analysis reveals the system alignment for obtaining a distortion null and these results are confirmed using nonlinear transient analysis. Basic system topologies are presented using voltage transfer and transconductance gain cells as an aid to complete amplifier synthesis. Comparisons are made with feedforward-feedback error correction where the current-dumping amplifier is reconfigured using differential-current feedback. Generalisations are made to a multi-loop nest of amplifiers using individually aligned error correcting paths to achieve corresponding improvements in distortion reduction
Any ideas
Abstract
A dominant distortion mechanism in audio power amplifiers results from nonlinearity in the voltage and current transfer functions within the power output stage. A technique is presented that uses a magnetic differential sensor to sense this distortion and to apply a supplementary error-correcting feedback path within the amplifier, in addition to overall negative feedback. Differential-current derived feedback is explored and the technique is shown to be applicable to both voltage and current transfer errors. Analysis reveals the system alignment for obtaining a distortion null and these results are confirmed using nonlinear transient analysis. Basic system topologies are presented using voltage transfer and transconductance gain cells as an aid to complete amplifier synthesis. Comparisons are made with feedforward-feedback error correction where the current-dumping amplifier is reconfigured using differential-current feedback. Generalisations are made to a multi-loop nest of amplifiers using individually aligned error correcting paths to achieve corresponding improvements in distortion reduction
dvv, thanks for your active position in this discussion, but, at analogy with one saying, "chair" designers will never find common position with "practice" designers. I belong to the last group, since for me it became obvious quite a long time ago - models are still very far from reality in the field of audio. Designing audio is much more tricky and less grounded by "theory" than designing instrumentation and control equipment.
Open Loop Bandwidth and quality of parts used (especially capacitors) are of the major importance. Hope the efforts of John Curl will bring something new upon the table.
If finding of proper parts really matters to you, I could try to send you some laterals, we have them supplied mainly from Singapore (almost sure not fake).
At present, I find it grounded by practice to use only RF transistors at the output stage.
Such an approach sounds as a nonsense for those who designs for manufacturing companies, but among DIYers we concluded, that NFB designs definitely benefit from RF transistors at output stage, their sound comes close to that from NoNFB designs, with additional pluses remaining at the bottom end.
Such an approach sounds as a nonsense for those who designs for manufacturing companies, but among DIYers we concluded, that NFB designs definitely benefit from RF transistors at output stage, their sound comes close to that from NoNFB designs, with additional pluses remaining at the bottom end.
Dr Who ?
It's that man again Dr M H .
Looks interesting .
http://www.essex.ac.uk/csee/research/audio_lab/malcolmspubdocs/J27 DCDF IEE.pdf
It's that man again Dr M H .
Looks interesting .
http://www.essex.ac.uk/csee/research/audio_lab/malcolmspubdocs/J27 DCDF IEE.pdf
At a guess, probably by Bob Carver, related to his ill fated magnetic amp.
I understand he actually sold a licence for it Yamaha, who then applied it in theri current series at the time, but for some reason Bob was very unhappy with it, legal minds clashed, and the deal broke down.
Well, to me, engineers, PhDs and so on are simply people, like everyone else. They stand or fall on heir own merits, just like everybody else.
Coming from a family chock full of PhDs, and about evenly divided into teachers and professors and bankers, I have had an outstanding opportunity to closely observe both Aside from outward appearances, the only difference I could claim to be true is that the banking half, plus my dad (he was the odd man out, a mechanical engineer), tended to be more practical when it came to the execution of a plan. But that's about it, the other differences I would attribute more to the underlaying basic profession than anything else. My uncle and aunt had PhDs in sociology and philosophy respectively, so it was to be expected that they would a bit slow on execution, but long and sometimes tedious in planning.
I think just about any family anywhere has a specific composition, nothing wrong or unusual about it.
Ah, that'll be me.
May i add an excessive scar memorabilia collection, a large number of kitchen utensils, and an substantial audio book & paper storage to the list.
In the immortal words of Jack Lucas ;
i'll be sending you a thought today as i lie in my stretch limo, having sex with the teenager of my choice. And that thought will be : thank god i'm me !
http://www.youtube.com/watch?v=1MVwHzOYT9Q&feature=related
Aren't we all.
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You can't be serious, did you ever look at the service manual for a 7000 series TEK scope?
at 1st glance Malcom's DCDF paper ignores Bode's gain/phase integral constriants - their application to "debugging" non-physical claims for various "clever" feedback arrangements have been know since the late '50's
I've mentioned these control theory results, pointed to refs a few time now
http://www.diyaudio.com/forums/soli...terview-error-correction-112.html#post1070802
http://www.diyaudio.com/forums/soli...lls-power-amplifier-book-127.html#post2416974
I've mentioned these control theory results, pointed to refs a few time now
http://www.diyaudio.com/forums/soli...terview-error-correction-112.html#post1070802
http://www.diyaudio.com/forums/soli...lls-power-amplifier-book-127.html#post2416974
Magnetic amps
D V V brought up magnetic amps .
I wanted to get one made for a project at work . The usually obliging transformer manufacturer ran a mile . Anyone ever heard one ?
http://www.aes.org/aeshc/pdf/how.the.aes.began/vincent_magnetic-audio-fundamentals.pdf
D V V brought up magnetic amps .
I wanted to get one made for a project at work . The usually obliging transformer manufacturer ran a mile . Anyone ever heard one ?
http://www.aes.org/aeshc/pdf/how.the.aes.began/vincent_magnetic-audio-fundamentals.pdf
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