Schemes of no-feedback amps

raul_77 · 3rd June 2013, 07:37 PM

Please, if anyone has any scheme of amplifiers or preamps without feedback, preferably solid state, Can you put here?

Almost 100% of the schemes that can be achieved using feedback, but I'am more interested in designs without feedback.

I mean global feedback, may have some local feedback.

Anticipated thanks.

dadod · 3rd June 2013, 09:21 PM

Quote:

Originally Posted by raul_77

Please, if anyone has any scheme of amplifiers or preamps without feedback, preferably solid state, Can you put here?

Almost 100% of the schemes that can be achieved using feedback, but I'am more interested in designs without feedback.

I mean global feedback, may have some local feedback.

Anticipated thanks.

Preamp here No NFB line amp (GainWire mk2) and here Current conveyor as a voltage amplifier

akis · 3rd June 2013, 11:10 PM

I have designed a built an amp where the current amp stage (final stage) uses no global feedback, and the driver (voltage amp) stage has no sense of the output. Does that count?

raul_77 · 3rd June 2013, 11:36 PM

Hi dadod, very interesting, many thanks!

Hi akis, yes! Can you share your design? Please.

Happy days

padamiecki · 4th June 2013, 05:40 AM

great Krill: Krill - The little amp that might...
and http://www.diyaudio.ru/filestore/Mil...-_cookbook.pdf

knutn · 4th June 2013, 07:11 AM

Voltage Amplifier & Current Buffer DIY

forr · 4th June 2013, 10:34 AM

No NFB line amp (GainWire mk2)
post #4 dadod : there is no amp without any negative feedback.

Cant' we say : there is no amplifying device without negative feedback, even it has no degenerative resistor in its following electrode ?

I think that Bob Cordell, speaking about local negative feedback, tells something like that degenerative resistors has about the same effects on high compoments of harmonic distorsion as global negative feedback.

dadod · 4th June 2013, 10:49 AM

Quote:

Originally Posted by forr

No NFB line amp (GainWire mk2)
post #4 dadod : there is no amp without any negative feedback.

Cant' we say : there is no amplifying device without negative feedback, even it has no degenerative resistor in its following electrode ?

You are right!

VladimirK · 11:49 AM

Quote:

Originally Posted by raul_77

Please, if anyone has any scheme of amplifiers or preamps without feedback, preferably solid state, Can you put here?

Almost 100% of the schemes that can be achieved using feedback, but I'am more interested in designs without feedback.

I mean global feedback, may have some local feedback.

Anticipated thanks.

Hello, Raul
This is a very good sounding unity-gain NoGNFB preamp (buffer).
Input impedance 50kOhms, output impedance 6 Ohms. THD is a bit compensated by counter-polarity jfet-bjt stages, but not THD is the main ground for good sound. Output zero voltage (quite stable) is adjusted by corresponding paralleling of R2 resistor.
Greetings to Spain, I was working for some period at the University of Alicante.
Vladimir

00940 · 4th June 2013, 04:08 PM

This started as a low gnfb headphones amp (by Kevin Gilmore, see this ), morphed into a high impedance balanced to unbalanced converter (as suggested by jcx) and turned into a decent preamp (by lazyness, never bothered to turn it back to its original state).

Sims in ltspice give 0.02% thd for 2vrms into 600r. It could be improved a lot with cfp at the input.

3rd June 2013, 07:37 PM	#1
raul_77 diyAudio Member Join Date: May 2001 Location: Spain	Schemes of no-feedback amps Please, if anyone has any scheme of amplifiers or preamps without feedback, preferably solid state, Can you put here? Almost 100% of the schemes that can be achieved using feedback, but I'am more interested in designs without feedback. I mean global feedback, may have some local feedback. Anticipated thanks.

4th June 2013, 05:40 AM	#5
padamiecki diyAudio Member Join Date: Mar 2004 Location: Krakow	great Krill: Krill - The little amp that might... and http://www.diyaudio.ru/filestore/Mil...-_cookbook.pdf __________________ regards, Pawel

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3rd June 2013, 11:10 PM	#3
akis diyAudio Member Join Date: Jul 2008	I have designed a built an amp where the current amp stage (final stage) uses no global feedback, and the driver (voltage amp) stage has no sense of the output. Does that count?

3rd June 2013, 11:36 PM	#4
raul_77 diyAudio Member Join Date: May 2001 Location: Spain	Hi dadod, very interesting, many thanks! Hi akis, yes! Can you share your design? Please. Happy days

4th June 2013, 07:11 AM	#6
knutn diyAudio Member Join Date: Mar 2006 Location: Oslo	Voltage Amplifier & Current Buffer DIY

4th June 2013, 10:34 AM	#7
forr diyAudio Member Join Date: Dec 2004 Location: Next door	No NFB line amp (GainWire mk2) post #4 dadod : there is no amp without any negative feedback. Cant' we say : there is no amplifying device without negative feedback, even it has no degenerative resistor in its following electrode ? I think that Bob Cordell, speaking about local negative feedback, tells something like that degenerative resistors has about the same effects on high compoments of harmonic distorsion as global negative feedback.