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Old 13th April 2008, 03:39 PM   #41
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In context, I would take it to mean feedback to a low impedance node as opposed to a high impedance one.

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Old 13th April 2008, 04:35 PM   #42
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Exactly. They should have called it "Super Happy Fun Feedback"

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Old 13th April 2008, 04:40 PM   #43
Blues is offline Blues  United States
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Sim of the simplified circuit gives out 800k of input Z and just 9dB of gain...

A pot on R4 adjusts output dc offset...

Such impatience!...Just playing with the circuit while waiting for the official one.
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Old 13th April 2008, 05:52 PM   #44
EUVL is offline EUVL  Europe
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The reason why I was confused was that I recently saw a circuit from Kaneda where he uses real output current (i.e. sensing resistor in series with load) as feedback.

Then I remebered seeing the term on the AD844 datasheet, and Google sorted the rest out for me.

But as Nelson said, the term as used by the chip companies is misleading. The way Kaneda is using it is true current feedback.

Being impatient, what about DC stability and noise performance in this implementation -- 2 well-known drawbacks of "current feedback" opamps ?


Patrick
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Old 13th April 2008, 07:02 PM   #45
zinsula is offline zinsula  Switzerland
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Quote:
Originally posted by EUVL
I am not sure which part of the circuit you are referring to is current feedback.

Anyone care to explain to me, Tino ?

Patrick
Hello Patrick, well I use this term (appropriately or not, I don't know) for feedback connections which go to emitter/source node of the input.

I see a unity gain CFP as 100% feedback ("current feedback"). But I don't want to start a semantic dispute, there is at least one big thread here from 2-3 years ago about this.

Tino
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Old 13th April 2008, 07:04 PM   #46
EUVL is offline EUVL  Europe
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Tino,

No dispute. I got it now.

Thanks,
Patrick
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Old 13th April 2008, 10:41 PM   #47
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Quote:
Originally posted by Blues
Sim of the simplified circuit gives out 800k of input Z and just 9dB of gain...
Don't get to excited by either the sim or the simplified circuit. The
actual gain is 15.2 dB or so into 8 ohms.
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Old 14th April 2008, 02:27 AM   #48
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Iím really interested in this F5 because the basis is quite similar with my BaboZen (Papaís Z5 with input JFETs), and particularly because Iím happy user of the excellent sound of BaboZen. It would be a very simple work for me to convert my BaboZen into this F5 if I count only the number of components I should replace.

Hmm . . .

Unfortunately, however, my BaboZen is at home while Iím away from home across the sea . . .




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Old 14th April 2008, 03:54 AM   #49
EUVL is offline EUVL  Europe
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> Being impatient, what about DC stability and noise performance in this implementation -- 2 well-known drawbacks of "current feedback" opamps ?

Nelson, any comments ?


Patrick
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Old 14th April 2008, 08:37 AM   #50
Vix is offline Vix  Yugoslavia
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Quote:
Originally posted by Nelson Pass
Now I've done it. The F5 isn't even out and some of you will
already be scrambling to build the two balanced versions.



To Steen: I guess you are already done with the chasis, heatsinks, PSU.....just waiting for the final schematic, and..we can expect the comment about F5 next weekend?

Nelson, thanks a lot. It is a joy to have something fresh.
I guess that the sound iof F5 is similar to that of SoZ, but with a lot lower distortion...
By the way, what is its output impedance?

Best wishes and get well soon...
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