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Old 1st January 2012, 07:14 PM   #471
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Of course, there is a typo under drawing 3. It should be read, "Parallel feedback", instead of "parallel input..."
As you may see, all feedbacks are around the single stage except the last one where feedback is both a degradation and a loop. Also, the same resistors represent load for the 2'nd transistor.
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Old 1st January 2012, 07:36 PM   #472
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Quote:
Originally Posted by Wolfsin View Post
@qusp made an interesting statement in another thread.

Electrical measurements can demonstrate that balanced is better than se but, it takes the human ear to detect the improvement that differential signals make on the transducer.
Envision a battery powered scope or DVM, there is no way to differentiate between the two, a mc transducer can't know the difference. I would think the amplifiers grounding, supply wiring, etc. would cause more of a difference between se/bal.
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Old 1st January 2012, 07:38 PM   #473
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Quote:
Originally Posted by Wavebourn View Post
Of course, there is a typo under drawing 3. It should be read, "Parallel feedback", instead of "parallel input..."
As you may see, all feedbacks are around the single stage except the last one where feedback is both a degradation and a loop. Also, the same resistors represent load for the 2'nd transistor.
No. 3 needs a source impedance for completeness.
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Old 1st January 2012, 07:43 PM   #474
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Everyone, if you really want to get down to the fundamental equations, then look at this IEEE article from 1966: Daugherty, D. Greiner,R.
'Some Design Objectives for Audio Power Amplifiers. pp. 43-48
10.1109/TAU.1966.1161838
IEEE TRANSACTIONS ON AUDIO AND ELECTROACOUSTICS VOL 14 issue 1
It is the LAST page that is most important and the ONLY one that I am missing. You might look at THEIR conclusions, before making any of your own.
If anyone has this article and could send me the last page, I would be grateful.
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Old 1st January 2012, 08:20 PM   #475
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Sy,

Quote:
Originally Posted by SY View Post
No, I didn't. I asked...
You constructed a case that has nothing to do with the topic. Hence my suggestion to stick to simple circuits so we are clear what is being debated.

Quote:
Originally Posted by SY View Post
Just to make sure there's no language barrier, do you understand the meaning of feedback derivation and application? For example, what one would mean by "series derived, parallel applied"?
Yes, I understand, however, such feedback would not be degeneration, but looped feedback, if it is derived like looped feedback.

So, let's go back to basic electronics, given is one stage, with one active device, inverting.

We can apply degeneration to the device or looped feedback.

If the looped feedback (miller or full range) if used to produce the same gain reduction as degeneration will produce different results regarding harmonic spectrum, output impedance, input impedance and bandwidth, can we conclude safely that applying degeneration to a device is not the same as looped feedback?

After that we can consider if the same still holds if we use multiple stages with degeneration applied or with global looped feedback applied...

Ciao T
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Old 1st January 2012, 08:26 PM   #476
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Quote:
Originally Posted by john curl View Post
Everyone, if you really want to get down to the fundamental equations, then look at this IEEE article from 1966: Daugherty, D. Greiner,R.
'Some Design Objectives for Audio Power Amplifiers. pp. 43-48
10.1109/TAU.1966.1161838
IEEE TRANSACTIONS ON AUDIO AND ELECTROACOUSTICS VOL 14 issue 1
It is the LAST page that is most important and the ONLY one that I am missing. You might look at THEIR conclusions, before making any of your own.
If anyone has this article and could send me the last page, I would be grateful.
Gladly when I am back at work.

See snip from Otala, why must we remain with our heads in the past? 50KHz follower bandwidths are long gone.
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Old 1st January 2012, 08:27 PM   #477
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Hi,

Quote:
Originally Posted by Wavebourn View Post
Thorsten;
let's start from basics:
here is the drawing I did for kids long time ago, when my English was even worse than now. I hope you are agree with this basics.

Click the image to open in full size.
Very nice and colourful. I am quite familiar with the issues, but it seems that there are some here in dire need of such a diagram.

As things are so nicely colour coded, Yellow is degeneration, orange is (incomplete) looped feedback and purple is a circuit that not only uses more than one stage, but also combines degeneration and looped feedback, but is so far not yet on the agenda for debate...

I note that you have commented on the relative impacts on the impedances, but alas, not on harmonic distortion...

Ciao T
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Old 1st January 2012, 08:48 PM   #478
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Well I must say that I was surprised when I won 'phonostage of the year' using 2 inexpensive IC's, (neither were ADI) to make it. However, I have also listened to my JC-3 phonostage, and compared it to my best Vendetta Research phono stage. I am still using the Vendetta research. AND I hope to make even better products in the future with both discrete and advanced IC designs (they are already in process).
Still, as there is no substitute for cubic inches in displacement in auto engines, there is no substitute for standing current, low noise jfets, and fully complementary circuits, for example. It is just that you can, most likely, keep most people happy without using every possible design technique, and that is what we do at Parasound, BUT we do not try to just 'cheapen' the product by using IC's when we can still use discretes.
We satisfy our customer base with pretty good products, much as Honda might.
However, some out there need, and are willing to pay for 'more' and they will get it through other sources, like Constellation Audio. You know, the folks who drive Porsches and Bentleys, etc. Trust me, a Bentley is more 'car' than a Honda. (at 10 times the price).
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Old 1st January 2012, 09:29 PM   #479
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Funny thing is nobody cares about passive components only active ones. However passive components are the key part of an OPAMP concept.
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Old 1st January 2012, 10:17 PM   #480
jcx is offline jcx  United States
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funny thing that all those major electronics manufacturers have made polystyrene extended foil caps, resistors to "audiophile flavors", carbon vs metal film, wire wound, TaN, bulk metal foil...

I never knew the high end audiophile market drove so much of the tech I use in precision industrial/scientific instrument circuits - clearly no engineer ever asked for them ever for any other reason than their sound - according to your mythology

Last edited by jcx; 1st January 2012 at 10:19 PM.
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