NFB types

nironiro · 2nd December 2020, 12:44 PM

Hi,
Anybody knows what is the different in those two types of NFB?
What are the advantages of putting NFB ground capacitor in the position A?

I saw that NFB in some cassette decks playback amplifier and wonder why they put capacitor at that position.

Thanks in advance for answers!

MarsBravo · 3rd December 2020, 10:48 AM

NFB B is the usual circuit (with a small cap over the feedback resistor), a separate RC series branch controls the hf-feedback better. NFB A is to bypass the large groundcap (with lesser hf bandwidth) so the hf feedback works even better.

nironiro · 3rd December 2020, 04:44 PM

Tnx MarsBravo, that sounds reasonable.

There are even more variations of NFB, one Grundig phono preamp have output cap included in the feedback loop.

lcsaszar · 4th December 2020, 07:12 PM

Whatever you include in the feedback loop forward path, its nonlinearity will be reduced by the NFB. Whatever you include in the feedback loop feedback path, its nonlinearity will appear at the output.

MarcelvdG · 5th December 2020, 06:39 AM

There is less signal current flowing through the electrolytic capacitor in case A, so it will distort less (for a given capacitor type).

3rd December 2020, 10:48 AM	#2
MarsBravo diyAudio Member Join Date: Feb 2017	NFB B is the usual circuit (with a small cap over the feedback resistor), a separate RC series branch controls the hf-feedback better. NFB A is to bypass the large groundcap (with lesser hf bandwidth) so the hf feedback works even better. __________________ Y/Yo=(1-X/Xo)exp2 <> Y/Yo=(e)exp(X/Xo){Xo=kT/q}

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Commercial Solid State Amps with jumper controlled Modes "without NFB" and "with NFB"	tiefbassuebertr	Solid State	12	28th February 2014 05:27 PM
Source/emitter global NFB amp	jcarr	Solid State	48	19th December 2008 09:22 PM
NFB and Electron Propagation (from Blind Testing)	mikek	Everything Else	135	29th March 2003 09:31 PM
NFB volume control	Joel	Tubes / Valves	5	13th December 2002 04:24 PM

New To Site?	Need Help?
Register to Participate Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

3rd December 2020, 04:44 PM	#3
nironiro diyAudio Member Join Date: Jun 2013	Tnx MarsBravo, that sounds reasonable. There are even more variations of NFB, one Grundig phono preamp have output cap included in the feedback loop.

4th December 2020, 07:12 PM	#4
lcsaszar diyAudio Member Join Date: Mar 2004 Location: Budapest, Hungary	Whatever you include in the feedback loop forward path, its nonlinearity will be reduced by the NFB. Whatever you include in the feedback loop feedback path, its nonlinearity will appear at the output.

5th December 2020, 06:39 AM	#5
MarcelvdG diyAudio Member Join Date: Mar 2003 Location: Haarlem, the Netherlands	There is less signal current flowing through the electrolytic capacitor in case A, so it will distort less (for a given capacitor type).