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Old 27th August 2012, 02:48 PM   #2791
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Quote:
Originally Posted by mikelm View Post
I would guess nearly all are non inverting
Because CFB is a bad definition (is poorly named), i think not all of us ;-) accord themselves on it.
There is no question of Voltage or Current in the matter, or, to be more accurate, and according to Mr Ohm, we always use both of them together.
All the matter is to avoid any additional pole in the feedback path.

I propose this definition:
"Current feedback (So called) is a global negative feedback where output signal is mixed to the input signal without active parts in the feedback path."

This means the amp itself is inverting and exclude differential input stage where signal is applied to the non inverting input and CR to the inverting one.

Just to demonstrate and fun, we discussed early in this thread a CF SSA with a differential stage for symetrical input.

I do not want to argue with homemodder and i'm certainly less hype than him on the market knowledge.
The only thing i know is how it was difficult to me to find a TRUE Solid state commercial or DIY CFB amps since (between 1970 and 2000), each time i was looking for one.

As it is difficult to find a more talented and nice printed circuit designer than sir Alex, or audio designer equal to L.C. ;-)
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Old 27th August 2012, 03:11 PM   #2792
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Esperado, tell you what Ill post the schematic of a commercially available design that led to the design of dartzeel just for fun. The designer of dartzeel claims it took him 16 (something like that) years to come up with it but he was or so he claims friends with the designer of this said commercial design. The commercial design is at least 30 years older than the dartzeel.

I can post Sony CFB from the 90s or perhaps a Pioneer or two from late 80s or early 90s.
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Old 27th August 2012, 03:24 PM   #2793
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Originally Posted by homemodder View Post
The designer of dartzeel claims it took him 16 (something like that) years to come up with it.
Did this guy was 16 years old when he wrote this ?
;-)
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Old 27th August 2012, 03:48 PM   #2794
mikelm is offline mikelm  England
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Quote:
Originally Posted by homemodder View Post
I can post Sony CFB from the 90s or perhaps a Pioneer or two from late 80s or early 90s.
we await with interest
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Old 27th August 2012, 04:38 PM   #2795
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Originally Posted by Esperado View Post
Did this guy was 16 years old when he wrote this ?
;-)
No thats what he claimed during an interview of the dartzeel amps. I think he is in his late 50s now. Just a marketing ploy to get very foolish people to pay 150 000 euros for stereo amp.
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Old 27th August 2012, 04:58 PM   #2796
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Originally Posted by homemodder View Post
No thats what he claimed during an interview of the dartzeel amps. I think he is in his late 50s now. Just a marketing ploy to get very foolish people to pay 150 000 euros for stereo amp.
Absolutely! Don't he realize he deserve-himself, looking as the worse engineer ever: i wonder which manager can afford an engineer witch take 16 years (or even 1) to design an amp.
I imagine.. when the amp is finished, parts are obsolete and no more available, back to the starting point. Loop...
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Last edited by Esperado; 27th August 2012 at 05:27 PM.
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Old 27th August 2012, 05:54 PM   #2797
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Thank you dear Shaan, but the link bites its tail and returns the same page

M.
Here it is!
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File Type: png SSA_SHAAN.png (5.1 KB, 329 views)
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Old 27th August 2012, 07:41 PM   #2798
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I noticed this version doesn't have a cap across the 2 feedback points?
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Old 27th August 2012, 07:53 PM   #2799
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Ah! Thank you, Shaan!

I would like to, if my first attempt is a success, make a modular amp and try different output sections...for example, I wonder how a Sziclai pair would work here, or if it would ruin the performance or if it is just impossible to use it...for that, I will have to study first what the *** is a Sziclai pair, to begin with
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Old 27th August 2012, 08:06 PM   #2800
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I noticed this version doesn't have a cap across the 2 feedback points?
When I first built it I had oscilation around 10 or so MHz and had samll caps <33p across NFB resistors. Others that built it did not have the oscillation (I think). Later found the reason for oscilation was due to stray capacitance between gate/source and heat sink.
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