Negative Feedback In Audio Amplifiers: Why Is It Used?

[@CleberHarrisonGuitar]

Great video! Thanks very much!

[@emmyokonkwo290]

Good explanation

[@DJDavo013]

Wow, I never understood what they ment with nfb You made it so easy to understand… Thanks for that! So to determine the best resistor value, i view the signal on a scope or bode plotter, add a pot and adjust it to get the lowest distortion… Or is it more easy to calculate it?

[@joeltunnah]

True, but you don't mention any of the downsides. In moderate amounts (below 15db), NFB actually increases harmonic distortion above 3rd order. So you need lots of NFB to reduce the higher order harmonics, which necessitates adding more gain stages... which increases open-loop distortion. And due to phase shift and gain of the NFB loop changing with frequency, you get intermodulation distortion (IMD) which is particularly nasty, and transient IMD on percussive sharp attack sounds. Also the NFB loop essentially doesn't work at very low and very high freq, causing instability at those extremes due to the high gain, unless compensated. These things were not well understood in the 1950s when guitar amp topologies were set in stone. You definitely don't get something for nothing. I've yet to hear an amp that sounds better designed with NFB. The average guitar player may not notice, but when you build your own amps and listen, you start to hear the differences.