Is the CFB topology superior, and why? - Page 29 - diyAudio
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Old 4th November 2012, 09:21 AM   #281
Bonsai is offline Bonsai  Taiwan
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I don't think you can prescribe what is mandatory or not. There are too many Great sounding designs of all types and topologies to make generalizations like that.
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Old 4th November 2012, 09:26 AM   #282
MiiB is online now MiiB  Denmark
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Sorry... I did not say that the path i have chosen is my designs is the only way.. there may be numerous way the getting the desired result. what i have seen in my designs is that simple current feedback circuits with good housekeeping is at least for me and my ears a feasible path.
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Old 4th November 2012, 10:03 AM   #283
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Quote:
Originally Posted by Bonsai View Post
I don't think you can prescribe what is mandatory or not. There are too many Great sounding designs of all types and topologies to make generalizations like that.
In this thread the topic is feedback only, not other parts of the amps, topologies, etc.

Can someone explain why we need extra transistor in FB path if the output impedance from where FB is taken is low Z?
Any nonlinear element inserted in FB path makes the whole regulation process to deal with extra unnecessary corrections that wouldn't be needed if this element wouldn't be inserted. From that point of view CFB is superior to VFB because it deals with less anomalies in a regulation system, in other words regulation formulas are much simpler, considering all the physical laws from subatomic particles up.

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Sorry... I did not say that the path i have chosen is my designs is the only way.. there may be numerous way the getting the desired result. what i have seen in my designs is that simple current feedback circuits with good housekeeping is at least for me and my ears a feasible path.
CFB perfectly serves me as well.
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Old 4th November 2012, 10:29 AM   #284
MiiB is online now MiiB  Denmark
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The start in CFB designs for me was the thread that lineup started on the Fetizilla. That was a very eye opening design for me... later a found that it was kind of Old news as the Hiraga I so enjoyed when younger also had the CFB approach.

Later The SSA take on the Hiraga evolution took thing a step further, as this type of bridge suspension of the gain takes away some of the single ended circuits limitations. But at the cost of added complexity and further need for extensive housekeeping.

Lazy..one can argue if the non ideal current source of a resistor is better or worse than a extra transistor or Fet. Hence my quest for discussing the pro and cons of the supporting circuit... As in most in life it simply boils down to the execution.

Last edited by MiiB; 4th November 2012 at 10:32 AM.
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Old 4th November 2012, 11:05 AM   #285
dadod is offline dadod  Croatia
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Quote:
Originally Posted by Lazy Cat View Post
In this thread the topic is feedback only, not other parts of the amps, topologies, etc.

Can someone explain why we need extra transistor in FB path if the output impedance from where FB is taken is low Z?
Any nonlinear element inserted in FB path makes the whole regulation process to deal with extra unnecessary corrections that wouldn't be needed if this element wouldn't be inserted. From that point of view CFB is superior to VFB because it deals with less anomalies in a regulation system, in other words regulation formulas are much simpler, considering all the physical laws from subatomic particles up.
If you are so concern of extra transistor in FB path you can use inverted input in VFB amp as signal input.
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Old 4th November 2012, 11:36 AM   #286
MiiB is online now MiiB  Denmark
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can't do.. then you get a real low input impedance or very high impedance and noisy feedback chain
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Old 4th November 2012, 11:45 AM   #287
dadod is offline dadod  Croatia
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Originally Posted by MiiB View Post
can't do.. then you get a real low input impedance or very high impedance and noisy feedback chain
Yes you can, just put a buffer before input. There are simple and excellent buffers as from JLH.
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Old 4th November 2012, 12:08 PM   #288
MiiB is online now MiiB  Denmark
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Yet they are not sonically invisible... you just change one set of drawbacks for another.

But inverted shunt feedback circuits can sound good too.. as I said not one true path.
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Old 4th November 2012, 01:33 PM   #289
dadod is offline dadod  Croatia
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Originally Posted by MiiB View Post
Yet they are not sonically invisible... you just change one set of drawbacks for another.

But inverted shunt feedback circuits can sound good too.. as I said not one true path.
They could have lower distortion then the rest of the amp, so they could be sonically invisible.
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Old 4th November 2012, 01:46 PM   #290
MiiB is online now MiiB  Denmark
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theres no such thing as sonically invisible...

and why add more complexity when the answer is straightforward in the CFB..??

Last edited by MiiB; 4th November 2012 at 02:01 PM.
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