F5 power amplifier - Page 5

GRollins · 13th April 2008, 03:39 PM

In context, I would take it to mean feedback to a low impedance node as opposed to a high impedance one.

Grey

Nelson Pass · 13th April 2008, 04:35 PM

Exactly. They should have called it "Super Happy Fun Feedback"

Blues · 13th April 2008, 04:40 PM

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.

EUVL · 13th April 2008, 05:52 PM

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

zinsula · 13th April 2008, 07:02 PM

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

EUVL · 13th April 2008, 07:04 PM

Tino,

No dispute. I got it now.

Thanks,
Patrick

Nelson Pass · 13th April 2008, 10:41 PM

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.

Babowana · 14th April 2008, 02:27 AM

I’m really interested in this F5 because the basis is quite similar with my BaboZen (Papa’s Z5 with input JFETs), and particularly because I’m 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 I’m away from home across the sea . . .

EUVL · 14th April 2008, 03:54 AM

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

Nelson, any comments ?

Patrick

Vix · 14th April 2008, 08:37 AM

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...

13th April 2008, 04:40 PM	#43
Blues Lightning In A Bottle diyAudio Member Join Date: Sep 2003 Location: The Milky Way	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. __________________ Leap into the Warpspeed wormhole... http://www.6moons.com/audioreviews/warpspeed/1.html

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13th April 2008, 03:39 PM	#41
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	In context, I would take it to mean feedback to a low impedance node as opposed to a high impedance one. Grey

13th April 2008, 04:35 PM	#42
Nelson Pass The one and only Join Date: Mar 2001	Exactly. They should have called it "Super Happy Fun Feedback"

13th April 2008, 05:52 PM	#44
EUVL diyAudio Member Join Date: Oct 2003	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

13th April 2008, 07:04 PM	#46
EUVL diyAudio Member Join Date: Oct 2003	Tino, No dispute. I got it now. Thanks, Patrick

14th April 2008, 02:27 AM	#48
Babowana Formerly "jh6you". R.I.P. Join Date: Jul 2006	I’m really interested in this F5 because the basis is quite similar with my BaboZen (Papa’s Z5 with input JFETs), and particularly because I’m 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 I’m away from home across the sea . . .

14th April 2008, 03:54 AM	#49
EUVL diyAudio Member Join Date: Oct 2003	> Being impatient, what about DC stability and noise performance in this implementation -- 2 well-known drawbacks of "current feedback" opamps ? Nelson, any comments ? Patrick